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Thread: SU's or Weber/mikuni

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    Registered User grannyknot's Avatar
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    Default SU's or Weber/mikuni

    I am planning my build of an L28 3.07 stroker with most of the bells and whistles and I will have to decide soon on either SU's or Weber/Mikuni's. This will be a street driven car with some track/autocross.
    I have read a lot of the archived threads and basically it comes down to the SU camp saying that SU's can handle all the air needs of an L28 and therefore triple weber/mikuni's aren't needed. The Weber/Mikuni guys saying there is lots more HP hidden that the triples bring out. So who is right?
    I am not in either camp at the moment but I would like to see the numbers, SU's are simple and easily maintained, triples look good and sound AWESOME but I don't want to spend $1500 - 1800 for great induction sound.
    Can anyone point me to a thread or site that can help me decide?
    Thanks,
    Chris

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    Registered User 5thhorsemann's Avatar
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    If you are going to drive the car on the street, I would stick with the side draft options. I know that the Weber guys are going to pitch a bitch, but when was looking to rid myself of the flat tops I did a bunch of searching and based my decision this way.

    Finding #1, My motors specs, stock 240, would be a cool looking waste of $1500 to $2000 bucks.

    Finding #2, There were like 3 to 1 people out there with Webers looking for technical advice VS the SU owners.

    Finding #3, There are like 10 to 1 people out there running SU's on street cars over webers, and that means SU parts and advice were plentiful and cheap.

    I went with the round tops, and aside from a vapor lock issue that I recently solved, I have had zero serious issues that I couldn't solve on my own. In my OPINION, the $1000 I saved over the Mikuni's gave much more bang for the buck when looking at the overall performance of the car. But I would still love to have a set on my Lil Girl....................

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    Registered User tlorber's Avatar
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    Unless you are racing the car regularly, you are probably better of with round tops. There is no question that you will get more power from the triples (not just from air flow but from fuel delivery as well) but from what I have read there seems to be endless fiddling with jets and adjustments to get them set up.

    Also, that performance comes at a price- like going from 20 mpg to 13.

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    Registered User 5thhorsemann's Avatar
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    I was having a conversation last night with an MG owner friend of mine who is running a set of Mikunis on his car, and long story short, he is scared to death about the 15% ethanol mandate coming down the pike, He thinks that it will make the car unstreetable, i.e. race fuel only.

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    Registered User Walter Moore's Avatar
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    Is 15% ethanol going to work any better in SUs? I don't know that it isn't possible to set them up for E15, but it seems like they would need bigger jets. E10 is already a pain.

    Anyway, back to the original subject: I am convinced that if you are going to go to the trouble of building or buying a stroker you may as well go "whole hog" as the locals say and go to a crank sensor ignition system and modern fuel injection. Triples were the hot ticket back in the day, but there are a lot better ways to make power now.

    Having two SUs to balance and setup is already a pain. Why would you want to make life even harder? I also strongly suspect that SUs aren't going to have all the power you want on a 3L+ stroker. (just a subjective guess...)
    '71 240Z, Because any fool can drive fast in a straight line.

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    Registered User Travel'n Man's Avatar
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    What head and block are you planning on stroking? Give us some details on your plan so we can assist in guiding you a little better. Get ready to spend some $$! This is going to leave a mark on your wallet!

    Oh yea - almost forgot - tell us how you drive your car currently - are you tracking it - weekend mountain cruiser - race car? That's going to be a lot of engine.........
    Last edited by Travel'n Man; 07-22-2012 at 05:43 PM.
    Life's a journey; enjoy the ride!

    Mitchell
    L28 - N42 Block w/Flat tops - N42 Rebello Head & Cam - Triple 40 PHH Mikuni's - Headers - Recaro Seats -
    R180 3.9 Diff - Close Ratio 5 Speed - Toyota Vented Brake Upgrade w/ Porterfield High Performance Pads & Shoes

    1972 Datsun 240z
    HLS30-75040


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    Registered User cbuczesk's Avatar
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    Why not go with fuel injection?

    Chuck
    East Coast Z Nationals held at the Carlisle Import & Kit Nationals - May 16-18, 2014 Carlisle, PA
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    1969 240Z #390
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  8. #8
    Supporting Member Diseazd's Avatar
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    I'm an SU fan.......plenty of power throughout the power band....."0" problems. Everyone I know that owns sidedraft carbs are constantly changing this or that....fuel leaks etc. My SU's in my modified L28's run to redline in every gear.....w/o the constant attention to linkage, air/fuel ratios etc. Believe me, the SU's are very exhilarating! Sorry Mitchell.....
    http://www.flickr.com/photos/1404980...7600346077563/
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    Registered User rocketdog's Avatar
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    I just put Webers on my 260. Read my write up under S30 carburetors: Triple Weber Install. They are pricey but no where near the monsterous finicky things some have made them out to be. You just need to understand how they work and what needs adjusting...once. They will add considerable HP to your engine. I've run round tops SU's for years and these triples blow them away. The Webers offer way more tuning capabilities if you want to "track/autocross". There are other threads on this subject. Lots of good writeups with problems and solutions.
    Late 260Z; 2005 Daytona Blue paint; Triple Webers 40DCOE; competition springs w/Tokico HP shocks; Koenig 17x7 Crosshairs w/ Yokohama AVS 215/45 WR 17; Original owner; Show car w/ many awards

  10. #10
    Registered User Travel'n Man's Avatar
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    I've got to agree with Rocket Dog - install them - set them - forget them. Triples are a blast and not near the PITA that folks have made them out to be. I'll bet that most folks that have challenges either are not using a high quality refurbished units or they have not taken the correct setup installs, or some goofball sandblasted them. I will not go back to SU's (I've got them on a shelf in my garage - cause that is the best place for them).

    The main thing that you will miss with SU's is the true torque and horsepower of your engine (however you build it) - I've had both in the exact same car with the exact same engine build - my Mikuni set up wins every time hands down. Not a doubt in my mind at all - sorry Guy......
    Life's a journey; enjoy the ride!

    Mitchell
    L28 - N42 Block w/Flat tops - N42 Rebello Head & Cam - Triple 40 PHH Mikuni's - Headers - Recaro Seats -
    R180 3.9 Diff - Close Ratio 5 Speed - Toyota Vented Brake Upgrade w/ Porterfield High Performance Pads & Shoes

    1972 Datsun 240z
    HLS30-75040


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    Supporting Member Zedyone_kenobi's Avatar
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    I think Travelnman asked the single more important question here.

    How are you going to use the car? That is the key. Also, there is another option not listed..in terms of expense... they go:

    SU's refurbed

    SU's bored and modified for more flow

    Triple Webers/Mikunis

    If you do not want to go with the 1600 dollar triple setup, you can spend more than the 680 dollar SU setup and get a modified SU from Ztherapy that can flow a HECK of a lot more than standard SU's.

    Give that a thought.
    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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    Registered User steve91tt's Avatar
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    I have been running Mikuni's on a 1971 240Z for the past year or so. Once I got them tuned they have stayed tuned. They fire right up and run smoothly every time. The only issue I have is a fuel smell in my garage if I shut the car down hot without opening the hood. I like triples enough that I'm in the process of refurbishing an old set of Webbers for my 1973 240Z. SU's are great. Very reliable and simple. Triples can be just as reliable but not as simple...just more fun.
    Steve

    1973 240Z (daily driver)
    1971 240Z (track car)

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    Steve,
    you haven't tried the shut-off switch yet for the fuel smell?

    I think just breaking in a motor and and getting bugs worked out in your new engine is a great place for SUs. Though the Mikuni's and or Webers can be made to run better than the SU's, the SU's being more simplistic are a better way to get started. It's important to break in a motor properly and I wouldn't want to be dialing in triples on the fly with a new motor.
    Now Todd at Wolfcreek could get you close with a rebuilt set and you might get lucky to dial it in fast, but the SU's are almost full proof and cheaper to rebuild and maintain. Oncce you get the motor where you want, someone will gladly buy your SU's so you can upgrade.
    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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    Registered User cbuczesk's Avatar
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    Quote Originally Posted by madkaw View Post
    Steve,
    you haven't tried the shut-off switch yet for the fuel smell?

    I think just breaking in a motor and and getting bugs worked out in your new engine is a great place for SUs. Though the Mikuni's and or Webers can be made to run better than the SU's, the SU's being more simplistic are a better way to get started. It's important to break in a motor properly and I wouldn't want to be dialing in triples on the fly with a new motor.
    Now Todd at Wolfcreek could get you close with a rebuilt set and you might get lucky to dial it in fast, but the SU's are almost full proof and cheaper to rebuild and maintain. Oncce you get the motor where you want, someone will gladly buy your SU's so you can upgrade.
    I agree. I rebuilt the 440 6bbl for my Road Runner but used a working Holley 4bbl to break in the engine.

    Chuck
    East Coast Z Nationals held at the Carlisle Import & Kit Nationals - May 16-18, 2014 Carlisle, PA
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    1969 240Z #390
    1971 Fairlady Z
    1971 240Z parts car
    1972 240Z ITS race car
    1972 240Z turbo
    1974 260Z turbo
    1975 280Z my first car
    1978 620 King Cab

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    Registered User MotoManMike's Avatar
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    I've been running 15% here for about 2 years in SU round tops with no issues. Be weary if any of your carbs you want to run have rubber parts with ethanol, it will shrink the rubber up and cause problems tuning. I've rebuilt more ATV carburetors than I ever have since they introduced this ethanol mess. they use a rubber tipped float valve and the rubber shrinks up and cracks due to the ethanol. SU carbs are old school so they have been unaffected as none of the rubber parts are exposed to fuel. Cork and brass, they did it right .

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    Registered User Lazeum's Avatar
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    I haven't run SU's so I can really compare them.

    Fact is I love my DCOE, I barely have to touch them, they stay tuned and the sound!!!! You need however to understand how they work & find a way to tune them: Jets library ($$$) + wideband were my tools.

    Driveability with DCOE could be great, MPG could also be reasonable but you need to have carbs AND timing setup correctly. I made a 200mi trip at 21 mpg average.
    Don't forget you can set your side draft with bigger or smaller chokes, you don't have to get super large carbs & chokes to enjoy your engine (it's actually quite the opposite). Smaller carbs would provide a good torque at low rpm. This choice will also depend on our head setup (comp ratio, cam profile, etc.)

    So think also about what would have to go around with side-drafts: recurved dizzy or fully adjustable, timing light, jets library, wideband, books, etc. That would add up some hundreds of $$$ more.
    Last edited by Lazeum; 07-23-2012 at 01:44 PM.

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    You know, this thread is an exact reason I have no problem sending guys with questions here to find some real information rather than some of the nonesense I see elsewhere. Whatever side of an issue you think you are on, you can generally find intelligent discussion here.
    Bruce Palmer
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    Quote Originally Posted by Bruce Palmer View Post
    You know, this thread is an exact reason I have no problem sending guys with questions here to find some real information rather than some of the nonesense I see elsewhere. Whatever side of an issue you think you are on, you can generally find intelligent discussion here.
    Agreed, but grannyknot hasn't come back, I think we may have added to his dilemma. Unfortunately there is no hard and fast answer to his question, these are all good intakes, and all will perform well on his new motor. I guess the summary reply is, it all depends on his expertise, his willingness to study the chosen design and his ability to shell out the bucks necessary to make it happen.

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    Registered User grannyknot's Avatar
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    Quote Originally Posted by 5thhorsemann View Post
    Agreed, but grannyknot hasn't come back, I think we may have added to his dilemma. Unfortunately there is no hard and fast answer to his question, these are all good intakes, and all will perform well on his new motor. I guess the summary reply is, it all depends on his expertise, his willingness to study the chosen design and his ability to shell out the bucks necessary to make it happen.
    5thhorsemann hits the nail on the head twice in a row!
    Dilemma is the word, I thank everyone for their advice but it's all like the archives. I was hoping someone had done a back to back dyno with SU's and tripples that could end the debate but I guess not, maybe I'll do it!
    I will start with the SU's and go from there,
    Chris

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    Quote Originally Posted by grannyknot View Post
    5thhorsemann hits the nail on the head twice in a row!
    Dilemma is the word, I thank everyone for their advice but it's all like the archives. I was hoping someone had done a back to back dyno with SU's and tripples that could end the debate but I guess not, maybe I'll do it!
    I will start with the SU's and go from there,
    Chris
    Properly tuned, triples will always make more power than SUs. It has been done, thousands of times. If you're looking for dyno results, search hybridz.org.
    2/74 260Z

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    Known Zitus carrier! hls30.com's Avatar
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    In the not to distant past one of the Magazines(I believe it was either ClassicMotorsports or GrassRoots Motorsports) did a head to head contest between Webbers and Sus on a given engine, I have it somewhere, and I believe the result was six of one half a dozen of the other-meaning only marginal differences when both are tuned properly. If my memory serves that article correctly, that means there are more effective ways to spend that money. I'll hunt the article and post it when I find it. On the other side of the coin, Nissan did choose Mikunis for the performace sports versions for a reason.
    Will
    A Z is beautiful from any angle, I just happen to prefer to view from the drivers' seat!

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    Registered User madkaw's Avatar
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    Quote Originally Posted by grannyknot View Post
    5thhorsemann hits the nail on the head twice in a row!
    Dilemma is the word, I thank everyone for their advice but it's all like the archives. I was hoping someone had done a back to back dyno with SU's and tripples that could end the debate but I guess not, maybe I'll do it!
    I will start with the SU's and go from there,
    Chris
    Well hopefully I will have your back to back results soon. I ran 155 RWHP with my SU's and now have installed the triples with no changes to the engine. My goal has been to be systematic about upgrades because I want to be sure I am moving foward and not being decieved by the butt dyno. It will atleast a month, but I will be back at the dyno when I think I have my jetting really close.
    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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    Registered User Stanley's Avatar
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    No experience with the trips but just looking at it the triples manifold has 6 short, equal runners. Could that have as much to do with performance as the carbs? BTW since I'm not much of a mechanic I love it that I've got SU's - really simple for a performance carb. And all the help: yesterday found a sticking nozzle and wondered if I should grease it or not - found 5 threads here about exactly that.

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    Known Zitus carrier! hls30.com's Avatar
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    The article is in issue 146 (September 2010) of Classic MotorSports Magazine

    Nothing to scan it with at the moment.
    Last edited by hls30.com; 07-29-2012 at 12:50 PM.
    A Z is beautiful from any angle, I just happen to prefer to view from the drivers' seat!

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    Madkaw, we'll probably forget about this by the time you get to the dyno but please DO resurrect this thread and post your results.

    Thanks.

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    Quote Originally Posted by Stanley View Post
    No experience with the trips but just looking at it the triples manifold has 6 short, equal runners.
    EXACTLY! Triples have dedicated runners to each cylinder. This is an inherent advantage over SUs because of better mixture distribution between cylinders and a stronger signal for resonance (harmonic) intake tuning.

    There are also less pumping losses because of the fixed venturi design, so there are performance benefits to Webers outside of WOT operation. Correctly tuned, they will get better fuel mileage as well.
    2/74 260Z

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