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Thread: Tuning 40 DCOE Weber 151 on an L24

  1. #101
    Registered User conedodger's Avatar
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    Quote Originally Posted by Zedyone_kenobi View Post
    I was looking into those, but the prices get big quick.
    Rob, can you tell us what you were running prior to the hypojets?
    Stephan,
    I already did. Go back a few pages and you will see my initial post in this thread. I called Peirce Manifold and did some changes and those are listed too.
    Rob
    2000 BMW R1100 RT-SE (for sale)
    1999 Toyota 4Runner Supercharged
    1975 Porsche 914 stroker motor autoX car
    1973 Datsun 240Z Restoration project. New paint in original white. E31 head on 2.4 block. Nissan Motorsports header. R200 with Nissan motorsports LSD.

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    Okay you Weber guys, besides the specifics slated for your carbs, was there some general wisdoms discussed for triple carb operators??
    Would have been there but couldn't make the 16 hour drive!
    Things of interest to me would be Venturi sizing in relation to engine size, intake length?
    Last edited by madkaw; 10-15-2012 at 12:31 PM.
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
    3.90 Subaru STI LSD

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    Quote Originally Posted by madkaw View Post
    Okay you Weber guys, besides the specifics slated for your carbs, was there some general wisdoms discussed for triple carb operators??
    Would have been there but couldn't make the 16 hour drive!
    Things of interest to me would be Venturi sizing in relation to engine size, intake length?
    Oh man, this discussion could go on for a loooong time!

    A good start would probably be buying Obert's book.

    But to sum it up, of course there is the precautionary warning of making sure all other systems on the car are functional, ignition, charging, etc. A dysfunctional engine will make it impossible to tune and will frustrate you to no end.

    Once you're ready to tackle the carbs, the fuel levels must be set accordingly. Keith has found that to be 2mm below the brim of the passageway to the aux venturi. Then make sure your carbs are in order: no leaks, barrels flow equally, throttle returns correctly, linkage set up properly. Once that is set, you're ready to "tune". Ensure throttles are positioned correctly to the progression holes, sync at idle and high rpm, play with the jetting...

    Keith is working on a paper to detail all of this, hopefully he'll have it up soon. We had some very interesting discussions on the physics of what is really going on inside those carbs, and I'm sure he will be covering that in the paper as well.

    As far as venturi-to-engine size question, that is a good one and not simple to answer. Venturi size would be best determined empirically. The goal would be to go as big as you can without sacrificing driveability, and this depends on parts availability and the skill (moreso patience) of the tuner.

    Intake length sizing is its own discussion, and I've made some fairly detailed posts on it on HybridZ. In a nutshell:

    1. Use air horns, or at least have some sort of radiused opening at the inlet of the carb
    2. Longer intake valve-to-carb inlet length is more efficient at lower rpm
    3. Shorter intake valve-to-carb inlet length is more efficient at higher rpm
    4. Have as few bends as possible and try to make it a straight shot into the cylinder

    I've designed a spreadsheet that is supposed to predict intake and exhaust lengths according to RPM but I've yet to test it.

    I'm sure Obert's book has the details on it. Internal Combustion Engine Fundamentals by Heywood has some very good sections on intake and exhaust design. I've recently bought Obert's book, and in some respects it's outdated (which makes it cheap ), but most if not all of the information will be very relevant to the L-series engine.
    2/74 260Z

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    Registered User conedodger's Avatar
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    Here is one of the things I took from the discussion;

    Most problems in cars that run ok, are covered up by running the carbs rich. When you back off pig-rich, you may uncover some other problems you need to take care of.

    When you drive with these carbs on the street, you are likely running on your idle jets. Even possibly the highway.

    Leon got the tuning sequence according to Franck down in his post above. I think Leon's car came out better than mine yesterday because he has a rock-solid ignition system and mine is 40 years old but in good repair. His O2 readings were rock solid. I also think Leon wants to get his so close to perfect that he will be the guy to watch with his next moves... 8)
    Rob
    2000 BMW R1100 RT-SE (for sale)
    1999 Toyota 4Runner Supercharged
    1975 Porsche 914 stroker motor autoX car
    1973 Datsun 240Z Restoration project. New paint in original white. E31 head on 2.4 block. Nissan Motorsports header. R200 with Nissan motorsports LSD.

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    Quote Originally Posted by conedodger View Post
    Here is one of the things I took from the discussion;

    Most problems in cars that run ok, are covered up by running the carbs rich. When you back off pig-rich, you may uncover some other problems you need to take care of.

    When you drive with these carbs on the street, you are likely running on your idle jets. Even possibly the highway.

    Leon got the tuning sequence according to Franck down in his post above. I think Leon's car came out better than mine yesterday because he has a rock-solid ignition system and mine is 40 years old but in good repair. His O2 readings were rock solid. I also think Leon wants to get his so close to perfect that he will be the guy to watch with his next moves... 8)
    I definitely agree with the rich-running sentiments. Getting a carb to run an engine is one thing, getting it optimized is the challenge. You're definitely on the idles at low-speed cruise and I remember Keith saying that you're about 50/50 on the idles and mains at high-speed cruise, say 75mph.

    Mine came out running a lot better than it was but there is definitely work to be done! I'll be getting some 110 mains and a set of internal throttle return springs (mine are dead) soon. Keith's Elan (400cc cylinders, 30mm chokes, same as my Z) runs the O3 tubes and only needs 110 mains.

    Besides Rob, my Z hasn't seen a track yet. My goal is for someone else to be able to drive the car and not tell it's carburetted. Your Z is almost exclusively a track car, so as long as tip-in and WOT are set, you're ready to roll! Of course getting better mpg on the way to the track is always a good thing as well. I need to get my Z out there with you guys.
    2/74 260Z

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    Very interesting thread for sure! I am very tempted to try the hypojets, but the cost is so scary. Seems Keith still uses the weber idle jet for the most part. I have had great luck with the 55F9 idle jet. But my mileage is not stellar. But here is the kicker. I pulled my plugs after a long drive on the free way and I am running a beautiful shade of light brown. I mean spot on perfect. It would seem his fancy etube is something to strongly consider. Just the price of entry is daunting especially since I probably have 300 dollars in jets as is.
    1971 240Z HLS30-38691
    93.9% done and getting better every day
    Now with 100% more DATSUN SPIRIT L28 Power
    1968 Datsun 2000 SRL311-03416

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    Quote Originally Posted by Zedyone_kenobi View Post
    Very interesting thread for sure! I am very tempted to try the hypojets, but the cost is so scary. Seems Keith still uses the weber idle jet for the most part. I have had great luck with the 55F9 idle jet. But my mileage is not stellar. But here is the kicker. I pulled my plugs after a long drive on the free way and I am running a beautiful shade of light brown. I mean spot on perfect. It would seem his fancy etube is something to strongly consider. Just the price of entry is daunting especially since I probably have 300 dollars in jets as is.
    I'll report back with my findings once I get things dialed in. You can see first hand whether it's worth it or not!
    2/74 260Z

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    Thanks Leon~!
    1971 240Z HLS30-38691
    93.9% done and getting better every day
    Now with 100% more DATSUN SPIRIT L28 Power
    1968 Datsun 2000 SRL311-03416

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    I would agree with everything Leon said but one thing... My Z is about 90% street use. If I could, I would reverse that number but alas, I still have a 15 year old at home so I have to keep working...

    Stephan, I suspect there is a market for your slightly used jets? I have some 50F9's in my box of used jets...
    Rob
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    I got a set of those as well.
    They were way too lean at steady cruise
    1971 240Z HLS30-38691
    93.9% done and getting better every day
    Now with 100% more DATSUN SPIRIT L28 Power
    1968 Datsun 2000 SRL311-03416

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    Quote Originally Posted by conedodger View Post
    I would agree with everything Leon said but one thing... My Z is about 90% street use. If I could, I would reverse that number but alas, I still have a 15 year old at home so I have to keep working...

    Stephan, I suspect there is a market for your slightly used jets? I have some 50F9's in my box of used jets...
    Ah, that's right! It was Bill that said he exclusively tracks his Z. Ooops!
    2/74 260Z

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    Any of you Mikuni guys who have been following this thread, Silverstreak (Bill) dropped off his Mikunis at Keith Franck's place today and his initial comment on Sidedraft-Central is that it appears that Mikuni just copied the Weber design on tubing and jets and such. What I take from that comment is that he believes he can improve them... Exciting news for you guys!
    Rob
    2000 BMW R1100 RT-SE (for sale)
    1999 Toyota 4Runner Supercharged
    1975 Porsche 914 stroker motor autoX car
    1973 Datsun 240Z Restoration project. New paint in original white. E31 head on 2.4 block. Nissan Motorsports header. R200 with Nissan motorsports LSD.

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    Keep the info flowing - my setup is dead on with no problems. My rpm band is solid as far as I want to go - fuel pump is a little loud but once you get to rockn' around 4-6000 rpm who can hear the fuel pump. I did just install a 5 speed a few weeks ago and man did the rpm's drop in crusing speed - I did install a R180 diff 3.90 - great for my set up and tons of get up and go!
    Unless I see some earth shattering news I'm leaving my set up where she is - AF gauge is spot on...........don't want to goof it up now! I could see selling my SU's sometime in the future.......gotta think about that one...........
    Life's a journey; enjoy the ride!

    Mitchell
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    R180 3.9 Diff - Close Ratio 5 Speed - Toyota Vented Brake Upgrade w/ Porterfield High Performance Pads & Shoes

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    Quote Originally Posted by Travel'n Man View Post
    Keep the info flowing - my setup is dead on with no problems. My rpm band is solid as far as I want to go - fuel pump is a little loud but once you get to rockn' around 4-6000 rpm who can hear the fuel pump. I did just install a 5 speed a few weeks ago and man did the rpm's drop in crusing speed - I did install a R180 diff 3.90 - great for my set up and tons of get up and go!
    Unless I see some earth shattering news I'm leaving my set up where she is - AF gauge is spot on...........don't want to goof it up now! I could see selling my SU's sometime in the future.......gotta think about that one...........
    Mitchell,
    When you get tired of gazing out over those beautiful mountains in your backyard and you want to work in the garage, try that RX-7 pump. Quiet as can be. You can't even hear it with the key on and the engine off. Cheap too. Only $45 IIRC.

    On a Mikuni note, Keith Franck has really dove into the carbs Silverstreak dropped off. He has pointed out weaknesses, found where they tried to improve on the Weber design, and I think started to gather ideas to improve them. Silverstreak does about 90% track with his car, though he does drive it to events. If Keith comes up with some prototype e-tubes, Silverstreak will be testing them at Laguna Seca this Fall... Stay tuned. I will open a new thread on Mikuni improvements when that happens...
    Rob
    2000 BMW R1100 RT-SE (for sale)
    1999 Toyota 4Runner Supercharged
    1975 Porsche 914 stroker motor autoX car
    1973 Datsun 240Z Restoration project. New paint in original white. E31 head on 2.4 block. Nissan Motorsports header. R200 with Nissan motorsports LSD.

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    Registered User conedodger's Avatar
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    Here's an interesting tidbit... I just found out my Triple Webers are rare as hell! I have 42DCOE 8 triples. They apparently were commissioned by Maserati in the 1960's and were also used on Morgans and Triumph's...

    The reason I was researching them is I was thinking of selling them and going with 40DCOE 151's for the idle adjust-ability.
    Rob
    2000 BMW R1100 RT-SE (for sale)
    1999 Toyota 4Runner Supercharged
    1975 Porsche 914 stroker motor autoX car
    1973 Datsun 240Z Restoration project. New paint in original white. E31 head on 2.4 block. Nissan Motorsports header. R200 with Nissan motorsports LSD.

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    molto bello

    Just enjoying all this Weber talk. I am going to replace my RX7 fuel pump with a new mr Gasket pump. I am still seeking to run about 3.5 psi.

    Did Keith Frank mention what fuel pressure you guys should be running.. it would be interesting to know what he thinks.
    1971 240Z HLS30-38691
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    Now with 100% more DATSUN SPIRIT L28 Power
    1968 Datsun 2000 SRL311-03416

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    Quote Originally Posted by Zedyone_kenobi View Post
    molto bello

    Just enjoying all this Weber talk. I am going to replace my RX7 fuel pump with a new mr Gasket pump. I am still seeking to run about 3.5 psi.

    Did Keith Frank mention what fuel pressure you guys should be running.. it would be interesting to know what he thinks.
    He did. 'Adequate' to paraphrase. You don't have a problem if you aren't starving... I believe it was Leon who asked the question though. Maybe he could elaborate...
    Rob
    2000 BMW R1100 RT-SE (for sale)
    1999 Toyota 4Runner Supercharged
    1975 Porsche 914 stroker motor autoX car
    1973 Datsun 240Z Restoration project. New paint in original white. E31 head on 2.4 block. Nissan Motorsports header. R200 with Nissan motorsports LSD.

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    Quote Originally Posted by conedodger View Post
    He did. 'Adequate' to paraphrase. You don't have a problem if you aren't starving... I believe it was Leon who asked the question though. Maybe he could elaborate...
    That about sums it up. Enough flow as to keep the floats filled and enough pressure to get the fuel there. I agree that if you don't have starving issues, you're likely ok. I would put a fuel pressure gauge either after the carbs or between the 2nd and 3rd carb and make sure there is some pressure there, if you're really curious. I've taped a fuel pressure gauge to my windshield to test this. Not my fault if your car burns down.

    I'm still using the stock mechanical pump, but I did block the return line when I was tracking starvation issues. Turns out it was a bad fuel filter, but I never got around to unplugging the return line since it was running well. I should unplug it one of these days for curiosity's sake.
    2/74 260Z

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    Registered User LeonV's Avatar
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    BTW,

    I played with the Z a bit last weekend. Switched the hypojets from H223 to H221, meaning the smallest air bleed hole. H22 denotes a .022" orifice, the third number is air bleed size with 1 being smallest and 4 largest. A smaller air bleed enriches idle while leaning transition. You can look at the hypojet as a "teeter-totter", which balances out idle and transition mixtures. It's an awesome tuning feature of the hypojet, essentially making 1 idle jet into 4 (e.g. 50F8, 50F9, etc).

    Therefore, moving to the smallest air bleed enriched my idle while simultaneously leaning out transition/cruise. The Z ran even better! Idle was rock solid at ~14.5:1 at about 1 1/4 turns of the mixture screw and cruise mixtures were leaner, in the 13:1 range. Testing was done on a relatively cool day so I'd like to lean out cruise mixtures further. Keith recommended blocking off a hole in the e-tube to see if cruise mixtures get leaner (part-throttle AFR is controlled by a combination of the idle jet and e-tube), although it may have an adverse effect on transition. If this experiment doesn't give good results, going to a smaller hypojet should do the trick.

    The only real issues I still have are my carbs not always going back to idle (mechanical issue), hesitation when suddenly jumping on the pedal at low rpm, and going too rich at WOT. New internal throttle return springs and 110 mains are on order from Pierce Manifolds which should help the throttle return and going rich issues. I'm working with Keith to solve the sudden WOT hesitation and will be putting in stiffer accel pump springs as soon as he gets them in. That should strengthen the pump shot. I checked and have size 40 pump jets, but did not check bleed back. Keith believes that the springs will have a bigger effect than changing either the pump jet or bleed back jet.

    One other benefit I noticed last weekend, the car starts much easier when it's warm. I no longer have to crack the pedal to start it. Cold starts require pumping since I don't have my cold-start units connected, which I never needed before since I was running so rich.
    2/74 260Z

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    Quote Originally Posted by conedodger View Post
    He did. 'Adequate' to paraphrase. You don't have a problem if you aren't starving.
    Agreed, when I was running the RX7 pump in my Mikuni powered L30 track car I did not see any adverse effects of the undersized pump other than very low fuel pressure until I changed to 37mm chokes. When I moved up to the bigger chokes I started going lean at WOT near red line in 4th so I switched to a bigger pump and solved the problem. I can see no downside to the occasional 0psi reading on the fuel pressure gauge as long as AFR's don't go lean. If fuel supply is an issue the lean spot will generally occur after long periods of sustained WOT operation I don't see this being an issue with a street car unless the fuel system is badly undersized. Just my $0.02.
    Steve

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    1971 240Z (track car)

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    Quote Originally Posted by LeonV View Post
    BTW,

    I played with the Z a bit last weekend. Switched the hypojets from H223 to H221, meaning the smallest air bleed hole. H22 denotes a .022" orifice, the third number is air bleed size with 1 being smallest and 4 largest. A smaller air bleed enriches idle while leaning transition. You can look at the hypojet as a "teeter-totter", which balances out idle and transition mixtures. It's an awesome tuning feature of the hypojet, essentially making 1 idle jet into 4 (e.g. 50F8, 50F9, etc).

    Therefore, moving to the smallest air bleed enriched my idle while simultaneously leaning out transition/cruise. The Z ran even better! Idle was rock solid at ~14.5:1 at about 1 1/4 turns of the mixture screw and cruise mixtures were leaner, in the 13:1 range. Testing was done on a relatively cool day so I'd like to lean out cruise mixtures further. Keith recommended blocking off a hole in the e-tube to see if cruise mixtures get leaner (part-throttle AFR is controlled by a combination of the idle jet and e-tube), although it may have an adverse effect on transition. If this experiment doesn't give good results, going to a smaller hypojet should do the trick.

    The only real issues I still have are my carbs not always going back to idle (mechanical issue), hesitation when suddenly jumping on the pedal at low rpm, and going too rich at WOT. New internal throttle return springs and 110 mains are on order from Pierce Manifolds which should help the throttle return and going rich issues. I'm working with Keith to solve the sudden WOT hesitation and will be putting in stiffer accel pump springs as soon as he gets them in. That should strengthen the pump shot. I checked and have size 40 pump jets, but did not check bleed back. Keith believes that the springs will have a bigger effect than changing either the pump jet or bleed back jet.

    One other benefit I noticed last weekend, the car starts much easier when it's warm. I no longer have to crack the pedal to start it. Cold starts require pumping since I don't have my cold-start units connected, which I never needed before since I was running so rich.
    Tried 110 mains today and they're way too lean. Car doesn't want to accelerate at WOT and AFR reads 15-17. Ordering 120 mains today, those should be close to what I need. Haven't put in the new return springs or pump springs since Keith accidentally sent 2 springs instead of 3. Silly Lotus guys!
    2/74 260Z

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    Nova Scotia,Canada,Earth Blue's Avatar
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    I just ordered some 115's for an L24 that had 125's and ran rich. The owner now has 120's that Stephen loaned me and just reported it ran better and less exhaust smell so The 120's will prbably be great for your L24 Leon.

    The car is ~400km from me and my O2 sensor so I'll measure the 120 A/F in the spring and also run the 115's and plot.

    Please measure A/F with the 120s between 3k and 6k
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    Just a note no fuel pressure, I have found the holy grail of fuel pumps for high volume good preset pressure and dead quiet.

    THe RX7 pump was great, but I was only getting 2 psi out of it at anytime. I was having issues in 3rd and 4th gear as my air fuel ratios were raising under sustained load. Not sure if it was the pump or not, but I upgraded to this little jewel.

    It is a Mallory 4070LP electric fuel pump. It is preset to put out between 3 and 4 psi without the need for regulation. I fired mine up and sure enough, I could not even barely hear it. I leaned over to the engine and it was dead on 3 psi. This pump has a bypass screen that allows you to up the pressure further if you need to. But I think I will be just dandy at 3 psia. It was the last thing I wanted to do before my rally. I am bringing the RX7 pump as a back up.

    I think I am currently running 130 mains in my L28. I still need to do some data logging. Or get a reliable copilot to pay attention while I drive. The roads around here are not conducive to high rpm 3rd and 4th gear runs.
    1971 240Z HLS30-38691
    93.9% done and getting better every day
    Now with 100% more DATSUN SPIRIT L28 Power
    1968 Datsun 2000 SRL311-03416

  25. #125
    Registered User conedodger's Avatar
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    Quote Originally Posted by LeonV View Post
    Tried 110 mains today and they're way too lean. Car doesn't want to accelerate at WOT and AFR reads 15-17. Ordering 120 mains today, those should be close to what I need. Haven't put in the new return springs or pump springs since Keith accidentally sent 2 springs instead of 3. Silly Lotus guys!
    Leon,
    It just so happens that I have two pump springs and two carbs worth of O5 tubes. Maybe you could send me one set of yours? 8O Lotus guy, Senna did pretty well today (last night) in India though...
    Rob
    2000 BMW R1100 RT-SE (for sale)
    1999 Toyota 4Runner Supercharged
    1975 Porsche 914 stroker motor autoX car
    1973 Datsun 240Z Restoration project. New paint in original white. E31 head on 2.4 block. Nissan Motorsports header. R200 with Nissan motorsports LSD.

  26. #126
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    Quote Originally Posted by Blue View Post
    I just ordered some 115's for an L24 that had 125's and ran rich. The owner now has 120's that Stephen loaned me and just reported it ran better and less exhaust smell so The 120's will prbably be great for your L24 Leon.

    The car is ~400km from me and my O2 sensor so I'll measure the 120 A/F in the spring and also run the 115's and plot.

    Please measure A/F with the 120s between 3k and 6k
    Good to hear, Blue. Will do!

    Quote Originally Posted by Zedyone_kenobi View Post
    Just a note no fuel pressure, I have found the holy grail of fuel pumps for high volume good preset pressure and dead quiet.

    THe RX7 pump was great, but I was only getting 2 psi out of it at anytime. I was having issues in 3rd and 4th gear as my air fuel ratios were raising under sustained load. Not sure if it was the pump or not, but I upgraded to this little jewel.

    It is a Mallory 4070LP electric fuel pump. It is preset to put out between 3 and 4 psi without the need for regulation. I fired mine up and sure enough, I could not even barely hear it. I leaned over to the engine and it was dead on 3 psi. This pump has a bypass screen that allows you to up the pressure further if you need to. But I think I will be just dandy at 3 psia. It was the last thing I wanted to do before my rally. I am bringing the RX7 pump as a back up.

    I think I am currently running 130 mains in my L28. I still need to do some data logging. Or get a reliable copilot to pay attention while I drive. The roads around here are not conducive to high rpm 3rd and 4th gear runs.
    I hope you mean psig!

    Good find, although it may be out of the budget for some. Looks like a good (better?) alternative for the RX7 pump. I've got an RX7 pump sitting around as well, I'll put it to use eventually and see what happens.

    Quote Originally Posted by conedodger View Post
    Leon,
    It just so happens that I have two pump springs and two carbs worth of O5 tubes. Maybe you could send me one set of yours? 8O Lotus guy, Senna did pretty well today (last night) in India though...
    Yeah, I suppose Lotus guys are OK.

    Hopefully Keith sent out the missing links today. I'm expecting the mains and Keith's final spring to come in at some point in the week and then I can do some more tests, as long as it isn't wet out.
    2/74 260Z

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    Dry as a bone here. Literally I think. I hooked up my fuel pump differently. I ran a 12 gauge wire directly to the coil with a 20amp fuse just before it connects to the coil. Increased my fuel pressure to 3psi. I took it for a spin and it acts differently. I would imagine partly because I eliminated the MSD box. It probably was covering for some problem. I have to do that EDIS! By the way, Leon, why did you do two different mounts for your EDIS stuff? You have the box on one aluminum plate and the coil pack on another. Are you avoiding interference? It seems everything would fit on that one mount...

    Waiting on the package from Keith to start tearing in to things. I suppose I could do two carbs but...
    Rob
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    Quote Originally Posted by conedodger View Post
    Dry as a bone here. Literally I think. I hooked up my fuel pump differently. I ran a 12 gauge wire directly to the coil with a 20amp fuse just before it connects to the coil. Increased my fuel pressure to 3psi. I took it for a spin and it acts differently. I would imagine partly because I eliminated the MSD box. It probably was covering for some problem. I have to do that EDIS! By the way, Leon, why did you do two different mounts for your EDIS stuff? You have the box on one aluminum plate and the coil pack on another. Are you avoiding interference? It seems everything would fit on that one mount...
    I wanted a cleaner look and I like that the EDIS module is somewhat hidden underneath the fender. Interference issues are a good point to consider as well.

    Frankly, the placement was really dictated by available holes already in the body (didn't want to drill new holes). The right fender had perfect holes in it already for a coil bracket and as a bonus, it places the coil pack such that the plug wires stay short. The battery tray area had plenty of space (and holes) after removing the 260Z's emergency start button for a relay/module bracket.

    Quote Originally Posted by conedodger View Post
    Waiting on the package from Keith to start tearing in to things. I suppose I could do two carbs but...
    Same here.

    120 mains shipped from Pierce today, they should arrive tomorrow.
    2/74 260Z

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    Well, it wouldn't run with the O5 tubes. It would start and run badly but no coaxing of the throttle would get me moving at all. But when I put the original tuning-day configuration back in with the new accelerator pump springs things went back to running like it did at the tuning day and on the way home, with one strong exception. When I jump into the throttle from anywhere, the A:F ratio goes to 12.5:1 and stays put. It loves the springs! In fact, if I do go with my plan, to sell these rare beasts to some Maserati, Ferrari, Morgan restoration guy, I will buy 45DCOE 152's and replace the springs!
    Rob
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    Quote Originally Posted by conedodger View Post
    Well, it wouldn't run with the O5 tubes. It would start and run badly but no coaxing of the throttle would get me moving at all. But when I put the original tuning-day configuration back in with the new accelerator pump springs things went back to running like it did at the tuning day and on the way home, with one strong exception. When I jump into the throttle from anywhere, the A:F ratio goes to 12.5:1 and stays put. It loves the springs! In fact, if I do go with my plan, to sell these rare beasts to some Maserati, Ferrari, Morgan restoration guy, I will buy 45DCOE 152's and replace the springs!
    Rob, that is great to hear, now I really want to get home and try them out! The stumbling at sudden throttle input (e.g. quick, rev-matched downshifts) has been my biggest gripe.
    2/74 260Z

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    Leon,
    What is this? It looks like a pump jet but shorter. Keith put them in my package and I would imagine yours but all he mentioned was the O5 tube.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Rob
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    Quote Originally Posted by conedodger View Post
    Leon,
    What is this? It looks like a pump jet but shorter. Keith put them in my package and I would imagine yours but all he mentioned was the O5 tube.
    I'm not sure exactly, I didn't get one in the package since I only got springs from Keith. He may have put it in accidentally.

    Does it have any holes when looking at it straight-on?
    2/74 260Z

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    Only a hole down the bore. I wonder if it replaces the hypojet but without the hypo?
    Rob
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    I'm very curious about your new springs.
    I've understood they are stiffer but to which extend? It looks like it could be something to try out also on my side.
    Matt - 72' 240z

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    Quote Originally Posted by Lazeum View Post
    I'm very curious about your new springs.
    I've understood they are stiffer but to which extend? It looks like it could be something to try out also on my side.
    Matt,
    Dimensionally they look identical. My understanding is that the spring rate is doubled. Keith gave us a part number and his source, the problem was that you had to have a minimum order of $40. He bought 30 of the springs and I suspect is selling them on his Yahoo store. They were about $1.40 each I want to say?

    Pretty lively difference I'd say.
    Rob
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    Quote Originally Posted by Lazeum View Post
    I'm very curious about your new springs.
    I've understood they are stiffer but to which extend? It looks like it could be something to try out also on my side.
    Quote Originally Posted by conedodger View Post
    Matt,
    Dimensionally they look identical. My understanding is that the spring rate is doubled. Keith gave us a part number and his source, the problem was that you had to have a minimum order of $40. He bought 30 of the springs and I suspect is selling them on his Yahoo store. They were about $1.40 each I want to say?

    Pretty lively difference I'd say.
    To corroborate Rob, Keith said they're double the spring rate. This should activate the accel pump sooner and give it a stronger shot.
    2/74 260Z

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    Default Weber Accelerator Pump Parts

    Weber DCOE Pump Springs:
    Weaker

    • 47600.064
    • 47600.068
    • 47600.034
    • 47600.055

    Stronger




    Weber DCOE Throttle Return Springs:
    Weaker

    • 47605.012
    • 47605.027
    • 47605.009

    Stronger




    Weber DCOE Pump Rods:
    Stroke mm
    Overall length mm
    Part Number
    10
    59.5
    10410.02
    14
    63.5
    10410.02
    16
    65.5
    10410.01
    18
    67.5
    10410.024
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    I guess my next move would be to measure mine and fine some stiffer. I'll keep this on top of my head for the future. My carbs are really well tuned for now.
    Matt - 72' 240z

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    Matt, I will look up the manufacturer and spring number for you. It is total order with shipping = $40 USD so you might be ok if you have them shipped some fancy way... 8)
    Rob
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    Quote Originally Posted by conedodger View Post
    Leon,
    What is this? It looks like a pump jet but shorter. Keith put them in my package and I would imagine yours but all he mentioned was the O5 tube.
    To clear this up, as Keith already told you on SDC, that is the dry jet. It goes on top of the e-tube and underneath the holder.
    2/74 260Z

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    Quote Originally Posted by LeonV View Post
    To clear this up, as Keith already told you on SDC, that is the dry jet. It goes on top of the e-tube and underneath the holder.
    Yes, I did install these after Keith cleared that up and I might have installed them wrong, I didn't notice any difference in the diameter of the top/bottom shaft. In short, it ran much worse. Exaggerated tip in lean condition. I have to go get my calipers and check them to see if there is a difference top to bottom.
    Rob
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    Quote Originally Posted by conedodger View Post
    Yes, I did install these after Keith cleared that up and I might have installed them wrong, I didn't notice any difference in the diameter of the top/bottom shaft. In short, it ran much worse. Exaggerated tip in lean condition. I have to go get my calipers and check them to see if there is a difference top to bottom.
    Did you install the e-tube with the air-holes towards the bottom?
    2/74 260Z

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    Ok, so here is a question for you 151/152 guys. Having discovered that my 42DCOE 8's are rare, having been only OEM on Ferrari, Maserati, and Morgans, I trolled around the internet until I found a couple guys looking for these to do correct restorations on a Maserati 3500. One of them has made an offer of $1000 for my three. I think I can get more than that but that is another conversation.

    If you were going to pick a carb set for an L28 bottom end with flat top pistons and an E31 big valve ported and polished, would you pick 151's or 152's and why?
    Rob
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    Quote Originally Posted by conedodger View Post
    Ok, so here is a question for you 151/152 guys. Having discovered that my 42DCOE 8's are rare, having been only OEM on Ferrari, Maserati, and Morgans, I trolled around the internet until I found a couple guys looking for these to do correct restorations on a Maserati 3500. One of them has made an offer of $1000 for my three. I think I can get more than that but that is another conversation.

    If you were going to pick a carb set for an L28 bottom end with flat top pistons and an E31 big valve ported and polished, would you pick 151's or 152's and why?
    Rob,

    I may be picking up some new triples in the future as well. For the L28 I plan to build, I plan to go with the 45DCOE152.

    Why? 'Cause they're bigger!
    2/74 260Z

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    I would say bigger isn't always better but I would also agree.
    With my current setup: F54, flat top, p79 ported/polished, Rebello Cam, I'm a little bit short with my 40DCOE. Some 45DCOE with small chokes would probably work better.
    Matt - 72' 240z

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    To recap the last week or two of my quest to rid myself of the sudden-open-throttle hesitation:

    1. Tried stiffer pump springs. They seemed to help my hesitation but they were so stiff that they overwhelmed the throttle return springs (new ones) and didn't let it drop back to idle.

    2. I replaced the pump springs with my old ones but soldered up my bleed back jets. The setup was 40 pumps and 55 bleeds, and was now 4- pumps and zero bleed. It drove better with less hesitation, but it was still there when suddenly going WOT and sometimes when rev-matching.

    3. Keith sent me some .53mm pump jets and a drill bit to upsize to .61mm if necessary, as well as some slightly stiffer springs. Holy cow, what a difference!!! The rev-matching and WOT at low rpm hesitation is gone! Once in a while I'll get a short lag in power output because of AFR going lean, but no more bucking-bronco take-offs. Not only that, but my idle is at 14:1 and cruise is 13-13.5:1 (I want this leaner). It feels so much better to drive this car now. My current accel pump setup is stock springs, 53 pumps and zero bleed.

    I'm thinking I may need some leaner hypojets to get the cruise AFR where I want it. It's close but I want it leaner, at 14.5:1 or higher. I might as well try the slightly stiffer accel pump springs to see if they eliminate some mixture lag, but I won't want to use them if they mess with the throttles returning. I'd rather upsize the pump jets.

    All in all, you can barely tell this thing is carburetted now (especially if you don't look at the AFR meter )!
    2/74 260Z

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    Quote Originally Posted by Lazeum View Post
    I would say bigger isn't always better but I would also agree.
    With my current setup: F54, flat top, p79 ported/polished, Rebello Cam, I'm a little bit short with my 40DCOE. Some 45DCOE with small chokes would probably work better.
    Bigger is better, if your engine can support it. An L28 with an aggressive cam can easily run 45s.

    Basically, if (when) I decide to get some new carbs and I have the option between 40 and 45, I'm going with 45.
    2/74 260Z

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    Thanks guys. Leon, don't burn valves. I wouldn't go that lean at cruise with today's pump gas. 13.5:1 is the leanest I would go.
    Rob
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    Quote Originally Posted by conedodger View Post
    Thanks guys. Leon, don't burn valves. I wouldn't go that lean at cruise with today's pump gas. 13.5:1 is the leanest I would go.
    I should be ok. The stoichiometric point of E10 is around 14.1:1 but the AFR meter normalizes what it measures to the stoich point of pure gasoline (14.7:1) since it calculates based on lambda (measured AFR = pure gas AFR * lambda). If I can lean it out a bit more, I'll be happy, and so will my wallet!
    2/74 260Z

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    Quote Originally Posted by LeonV View Post
    I should be ok. The stoichiometric point of E10 is around 14.1:1 but the AFR meter normalizes what it measures to the stoich point of pure gasoline (14.7:1) since it calculates based on lambda (measured AFR = pure gas AFR * lambda). If I can lean it out a bit more, I'll be happy, and so will my wallet!
    Oh yes, I forget that you are paying Bay Area gas prices. We are about 25cents under Sacramento...
    Rob
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    Quote Originally Posted by conedodger View Post
    Oh yes, I forget that you are paying Bay Area gas prices. We are about 25cents under Sacramento...
    Lucky bastard...

    We finally dipped under $4/gal recently.
    2/74 260Z

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    Guys,
    still following this thread-even if I'm a Mikuni guy-
    I have contacted mr. Franck and he responded. I have never been able to get into Sidedraft Central Yahoo group-which was mandatory if I was going to be part of this experiment. I have resorted to getting a Yahoo e-mail account to see if that helps.
    keith wrote me saying that I might benefit from the tubes if my car did not pass the F.I. test-you guys might have touched on this in this thread. I'd say I am border line in that aspect. I have been reading the last few posts and it sounds like I am where you are as far as a slight hesistation during hard tip-in at lower rpms. No coughing, sputtering, spitting-just a millisecond of hesistaion, so maybe i'm at a pretty good point. At higher RPMS, above 3500, there is no hesitation.
    I have tried quite a few things, but don't know if I have ever completely gotten rid of that slight studder. Other than that, these carbs have really been wonderful. I am going to put some fresh needle&seats in the floats so I know everything is good, and i am going to take to the dyno!
    This weekend I even played with valve timing to see if that would change anything concerning hard tip-in at lower rpms-it didn't. I did quite a swing on the cam timing and basically put it back where it was-slightly advanced.

    I have noticed watching my AFR's that WOT AFR is dictated by when hard tip-in occurs. If I stomp it at 2500rpm the AFR's look super rich for a while thru the rpms before getting to the 13 range. If I start out at a higher rpm the AFR's look much more optimum thru the remaing rpm range.
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
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    Just to add another data point to this thread:

    My good friend has a 510 with rebuild L16 motor and dual DCOE40 side drafts with 32mm chokes. It came with 135 main jets.... and fuel-fouls the plugs. I have not had a chance to run with the O2 sniffer.

    The L16 per chamber volume is the same and an L24 so carb sizing/jetting should be similar.

    To recap:

    L16 DCOE40 32mm Choke 135main Pig Rich ~ 7-8 AFR (Estimated)
    L24 DCOE40 30mm Choke 125main Rich ~ 10-11 AFR (Measured)
    L24 DCOE40 30mm Choke 120main Rich ~ 11-12 AFR (Estimated.. will be measured Spring 2013)
    L24 DCOE40 30mm Choke 115main TBA ~ 12-13 AFR (Planned for Spring 2013)
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
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    Quote Originally Posted by Blue View Post
    Just to add another data point to this thread:

    My good friend has a 510 with rebuild L16 motor and dual DCOE40 side drafts with 32mm chokes. It came with 135 main jets.... and fuel-fouls the plugs. I have not had a chance to run with the O2 sniffer.

    The L16 per chamber volume is the same and an L24 so carb sizing/jetting should be similar.

    To recap:

    L16 DCOE40 32mm Choke 135main Pig Rich ~ 7-8 AFR (Estimated)
    L24 DCOE40 30mm Choke 125main Rich ~ 10-11 AFR (Measured)
    L24 DCOE40 30mm Choke 120main Rich ~ 11-12 AFR (Estimated.. will be measured Spring 2013)
    L24 DCOE40 30mm Choke 115main TBA ~ 12-13 AFR (Planned for Spring 2013)
    Phil,

    I just ran my L24 today with 120 mains (40DCOE with 30mm choke). Saw about 12:1 on AFR meter when I was looking. It was fairly cold out though, so it will be richer in warmer temps. I may go with 115s but it runs so well, I'm not in a hurry.

    I'd imagine at 7-8AFR, that 510 would be billowing black smoke out the exhaust pipe.
    2/74 260Z

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    yup... the plugs would foul after ~ 25km and black smoke. I had to give my friend new plugs to get home. He lives ~ 25km from my place and decided to take a drive over on Sunday. He barely made it home.
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


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    Registered User conedodger's Avatar
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    Well, I'm doing it. I found a guy in England who is restoring a Maserati 3500 which uses a pair of 42DCOE 8, which I have three of. We agreed on a price that will give him three of his original carburetors and will get me three brand new 45DCOE 152's. So my tuning will begin anew. I would imagine, I can just transfer over the jetting I have and if my chokes (32mm) are the same, I should be running pretty close to the same.
    Rob
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    Quote Originally Posted by conedodger View Post
    Well, I'm doing it. I found a guy in England who is restoring a Maserati 3500 which uses a pair of 42DCOE 8, which I have three of. We agreed on a price that will give him three of his original carburetors and will get me three brand new 45DCOE 152's. So my tuning will begin anew. I would imagine, I can just transfer over the jetting I have and if my chokes (32mm) are the same, I should be running pretty close to the same.
    Nice, Rob! Keep us updated.
    2/74 260Z

  58. #158
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    Not sure about the equivalence of choke size with different carb sizes.
    Check the file attached below, given by Duragg on HBZ.
    The only exception would be at 32mm according to this chart so your comment may still apply

    Click image for larger version. 

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    Matt - 72' 240z

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    Great data Matt! Thanks
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


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  60. #160
    Formerly known as Koalia Reverend's Avatar
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    Quote Originally Posted by LeonV View Post
    Lucky bastard...

    We finally dipped under $4/gal recently.


    Lucky indeed...8.5$ dollar per gallon here...
    -72 240Z "Goldie"

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    Last week, I replaced the custom 100 air jets from the O3 etube with 140s. This flatlined my AFR trace at WOT! No more getting richer as rpms climb. This did make low-rpm transition a bit leaner but I'll be tuning that out with the hypojets, which control low-speed, low-throttle opening operation.

    Next plan:
    - Smaller hypojets, either the H20 or H18 should do the trick.
    - Drilling out my pump jets to .62mm, I still need a slightly fatter shot when I get on it. By optimizing (leaning out, in my case) all the other circuits in the carburetor, the pump shot needs to do more work to keep the mixture proper now that everything isn't masked by running overly rich..
    - Re-sync and re-tune idle
    2/74 260Z

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    Quote Originally Posted by Blue View Post
    Idle Mixture Screw Pitch on 40DCOE2 is 0.8mm

    I'll measure it on the 40DCOE151's when I get close to them(100km away presently)

    The other important part to measure is the taper of the screw. I'll measure that optically.


    For the record the 40DCOE151's thread is also 0.8mm. I'll measure the taper.
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


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  63. #163
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    Where are you sourcing (for purchase) the Keith Frank optical float gauge?

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    Quote Originally Posted by AdreView View Post
    Where are you sourcing (for purchase) the Keith Frank optical float gauge?
    Optical Fuel Level Measuring Tool Indexed at 25mm for DCOEs - Buy @ Webstore item#30564448
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


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    Oh, there she is. Thanks for the link.

    So I'm new to the tuning of Weber carbs, actually just bought a set of triple 40 dcoe with Cannon manifold. I just happened to catch a episode of Wheeler Dealers where they tuned a carb'd Lambo with this at idle to match airflow:

    Air Flow Meter Synchrometer - Dune Buggy Parts, Sandrail Parts, VW Parts - MooreParts.com

    Has anyone used this unit or similar?

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    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


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    I just want to thank you guys for posting all this great info.

    Just finished the resto on my series 1 and after a shake out drive this weekend discovered the notorious flat spot at about 2200-2500rpm. I'd set the floats to 8.5mm but know the actual fuel level is about 32-34mm below the jet well surface.

    Btw, my carbs are 40DCOE-18's.

    This thread gives me hope that the fuel level is the main culprit. Now if I can just stay clear-headed while digesting all the data!

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    Good stuff Chuck! Try the fuel height at ~ 27-29mm and report back if you can.

    Also let us know what the jets, tubes, chokes, and motor details are. Data is king.
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


    John Ruskin (1819 - 1900)



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  69. #169
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    Great thread here guys, thanks for the information.

    I have a situation with mine that I'm hoping someone can shed some light on.

    Dcoe 40's, stock cam l26 f55 idle jets, float level on all set correctly, synced perfectly, timing at 18degrees initial with a recurved dizzy.

    Cruise afr is 12.5 to 13 but my idle needs to be very rich (9.5) or I get popping through the carbs when transitioning to cruise rpm.

    Any ideas? Car runs great otherwise. Just a little baffled as to my my idle need to be so rich.

    Thanks,
    Dean

  70. #170
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    A few more questions...Need more data...

    Which F55 jet are you running?
    55f8
    55F9
    55F11

    Also, what Etube are you running and what air corrector and main jet

    What do you consider cruise RPM.

    So when your idle is at 9.5:1 your cruise rpm is pretty good. You could actually afford to lean it out a bit more in the cruise afr.

    More info would be nice though before just guessing.
    1971 240Z HLS30-38691
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  71. #171
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    Quote Originally Posted by Zedyone_kenobi View Post
    A few more questions...Need more data...

    Which F55 jet are you running?
    55f8
    55F9
    55F11

    Also, what Etube are you running and what air corrector and main jet

    What do you consider cruise RPM.

    So when your idle is at 9.5:1 your cruise rpm is pretty good. You could actually afford to lean it out a bit more in the cruise afr.

    More info would be nice though before just guessing.
    Idle55f9
    170 air corrector
    F11 emulsion
    130 mains(way too rich,have ordered 120's
    Cruise is around 2200 rpm

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    What is your fuel level set to.
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
    The person who buys on price alone is this man's lawful prey.


    John Ruskin (1819 - 1900)



    ZCars in Eastern Canada seaport ready for shipment to Europe

    http://ZSportCanada.com


  73. #173
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    Quote Originally Posted by Blue View Post
    What is your fuel level set to.
    26mm from the base.

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