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Thread: Everyday drivability of Triple carbs

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    Registered User 70 Cam Guy's Avatar
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    Default Everyday drivability of Triple carbs

    I just had a nice email conversation with Todd @ Wolf Creek Racing about a Mikuni PHH setup. Just want to say his good reputation on these message boards is well deserved.

    On to my question and curiosity. I have spent the last couple days searching here and hybridZ for threads on the Mikuni's. They run the gambit but I failed to notice anyone talking about how our cars are to drive with a set of triple sidedrafts. I've seen threads about bogs and needing help but not many come back with a resolution and review.

    When things are tuned and in good working order, what are these things like to drive? Say I want to to drive to work a couple days in mixed traffic. Will I be pulling my hair out in frustration for some reason that is car related? I am pretty aware that just stomping on the gas could (nearly) stall the engine. Do you triple owners have any major gripes? I would consider throttle response with my SU's to be very good, I hear throttle response is even better with triples?

    I have driven my friend's race Mango (Corolla) and it runs like a top (and it's a monster) with the Weber 45's. No bogs, idles forever without issue, and pulls like no tomorrow. Other guys that frequent his shop drive their 18-RG and 2TG Corrola's/Celica's all the time with the Mikuni's. They don't complain but they are die hard old skool Japanese car fans. Are they just thick skinned and tolerant?

    Cheers
    -Andy
    1973 HLS30-166105
    RB20DET swap, HKS GT2530 turbo, HKS Actuator, Hallman MBC, ebay intake manifold, ebay dump pipe, straight pipe, 14 psi boost

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    240Z Elec. Upgrade guy Zs-ondabrain's Avatar
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    Excellent question. When I had my triple Weber DCOE's on the 70', they were kick-ass after 2500 RPM. Awesome throttle responce, sucked air like a Hoover on Roids, and just sounded awesome. The car would idle, like you said, all day long and were adjusted to about 800 RPM.

    However. Daily driving was a pain because my E88 head has bad valve guides, my block has bad rings on 2 pistons and Webers are a bitch to properly tune if the motor isn't up to par. If the motor was rebuilt and the N42 I have on the shelf was installed, and I had an O2 Sensor on the header with a proper meter, they would probably a lot easier to tune and more worth having for daily driving.

    The problem with mine, on top of the bad motor, was between 1800 and 2500 RPM. Total flat spots, back-firing and low power. Those constant backfires filled my K&N filters with fuel, then the last time it ignited that fuel and scared the hell out of me with flames coming from the engine compartment. Beating the crap out of it with a towel then finally giving up and hitting the ignition sucked the flames back into the Webers and the fire was gone. That's when I decided to do the full polish and rebuild of the Original SU's and put the Webers on the shelf till the motor gets rebuilt, or I put them on the 260Z's rebuilt motor.

    So in closing, the Webers are fricken awesome over 3000 RPM's, for me, but others will obviously have better or different results. Learn about them and how o properly tune them before considering them. They work great on 2.8's or bored out L24's and L26's.

    By the way, when tuned right, I got over 27 MPG on the freeway.
    Hope that helps,
    Dave
    Last edited by Zs-ondabrain; 10-18-2009 at 12:10 AM.
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    My 40DCOEs were pretty well behaved. A little finicky below 2000 RPM ,couldn't snap the throttle wide open without a slight hesitation ,but perfectly driveable in Tucson weather. Idled well, got good mileage, stayed in tune. Keep in mind there is no choke but on a cold start a couple pumps of the throttle to get started and a minute or two warm up and all was good.


    Steve
    Last edited by doradox; 10-18-2009 at 01:13 PM.

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    Registered User conedodger's Avatar
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    Mine seem fine. I had them tuned on a dyno with EGT, CHT, and exhaust gas analyzer. Runs very nicely. With no chokes though, they can be a bit bitchy on cool mornings like today.
    Rob
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    I ran triple 44's with a stock compression motor, a medium cam, a light flywheel, 2.5 exhaust and an ACT clutch and it was a *****cat in traffic. No problems at all. It did have less power off of idle, but that was a sacrifice I was willing to live with. I also drove basically the same setup (stock clutch though) with SU's and that worked great too. I think the car was faster at autox with the SU's because my gearing was too tall for the Mikunis, but I couldn't get myself to give up the top end power of the Mikunis. They made quite a bit more power on the top end.
    Jon

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    The only issue I have with my 44mm Mikunis is that I failed to have them modified to handle hard left hand turns. The bowls need a baffle to keep fuel from moving away from the pick-up.

    For daily driving they are fine but a heat shield and coated or wrapped exhaust is required unless you want to boil off some gas.

    A non-modified engine will not see much improvement over say a set of rebuilt SUs. Two inch bored out SUs on a slightly modded L series engine is a very good way to go also.

    Mileage? From 25 to 8 mpg depending on my right foot. Average seems to be around 16 but then I drive my 3.2L hard.

    ITBs with a good air/fuel computer would give me 20-40 more hp but at a cost of another $2-3K.

    Triples aren't perfect but they are very very nice at what they do.
    if a little knowledge can make you dangerous, I'm a little dangerous

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    Quote Originally Posted by gnosez View Post
    The only issue I have with my 44mm Mikunis is that I failed to have them modified to handle hard left hand turns. The bowls need a baffle to keep fuel from moving away from the pick-up.
    You mean right handers, right? It's not a pickup issue, it's a sloshing over the jets issue. Tom Holt was nice enough to show pics of the simple solution here:
    http://www.classiczcars.com/forums/s...ad.php?t=18948
    Jon

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    True, I've always Loved the INSTANT throttle responce when driving over 3K RPM, as aposed to the slower responce of the SU's. Those and a lightened flywheel would make for a neck breaking reaction to my right foot.

    Dave
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    Yeah, I got my right vs left screwed up (likely by being out here on the Left Coast for too long). I'll try the simple solution this winter (it snowed back home today in Boston).
    if a little knowledge can make you dangerous, I'm a little dangerous

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    Another thing though to keep in mind is not to skimp on the linkages. The people that say triples never run right usually are the ones that have cheap linkage setups that fall out of adjustment. Flatspots though are just acc pump adjustments and a good tuner can get rid of any. Just my 2c worth...
    HS30-00121

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    Hi Andy:
    I have ran triple Weber 40 DCOE's on my 72 since 1975. Once they were properly set up - I never had an issue with them again. You can hook up the chokes on the DCOE's, although I never actually needed them here in Florida. I'm pretty sure I have 36's for actual choke size inside the 40 DCOE's on my L28.

    Want to enjoy driving your 240Z? Run the S.U.'s with electronic ignition.

    Want a "wow" factor under the hood - triple carb's man.

    Want to have a car that will start and run very well all the time - - get a modern Fuel Injection system.

    In all three cases, the induction system has to be set up and tuned/programmed to perfection. A few dyno runs with someone that knows what they are doing is worth every penny.

    Personally - today - I'd opt for a modern fuel injection system. If you want looks and performance perhaps fuel injection via the triple throttle bodies...

    Just my opinion...
    FWIW,
    Carl B.

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    Wow, I wasn't expecting this many responses! It gives me a fresh perspective and some more to think about

    I actually have the SU's tuned in really well in my opinion. I have a ZX distributor and header/exhaust already. Before calling for a tow on my way to JCCS (voltage regulator went kaput) I was getting 25 mpg mostly highway. The car is definitely a lot of fun to drive and either way I want to get a Fidanza flywheel because I love a quick revving NA engine. Adding a moderate street cam has always been on my mind as well.

    I like the idea of ITB fuel injection but I just don't realistically have the resources to support that idea. My friend's shop has a Dynapack 3000 (hub-mounted dyno). Tuning for max power would probably go fairly quickly but tuning for drivability takes a fair amount of time.

    Aside from that, I have a seemingly irrational desire keep it old school. Being around what is probably an abnormal amount of classic Japanese cars with Mikuni's and Weber's, I love the look, I love the sound, and as shallow as it may sound, you can't beat the wow factor of all those carb's.
    I've certainly had some biased influences
    http://performanceoptions.net/Gallery.html

    I assume the standard linkages from Wolf Creek are quality. The images Todd sent me look like very good quality actually. I do appreciate all the advice here as well. When little issues work together, you wind up with a big difficult-to-diagnose problem (as I experienced early on with a bum set of SU's). I will definitely also need a solution for the heat either homemade or other.

    Thanks Jon, the 44's have actually been what I've been leaning towards. I still have my 4 speed so the gearing doesn't seem too tall to me. Is that me hearing what I want to hear?
    -Andy
    1973 HLS30-166105
    RB20DET swap, HKS GT2530 turbo, HKS Actuator, Hallman MBC, ebay intake manifold, ebay dump pipe, straight pipe, 14 psi boost

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    Quote Originally Posted by 70 Cam Guy View Post
    I assume the standard linkages from Wolf Creek are quality. The images Todd sent me look like very good quality actually. I do appreciate all the advice here as well. When little issues work together, you wind up with a big difficult-to-diagnose problem (as I experienced early on with a bum set of SU's). I will definitely also need a solution for the heat either homemade or other.

    Thanks Jon, the 44's have actually been what I've been leaning towards. I still have my 4 speed so the gearing doesn't seem too tall to me. Is that me hearing what I want to hear?
    Todd has good linkage setups on his Mikunis. IIRC he puts a support rod end in the middle of the chrome linkage bar, from the factory the Mikunis only had rod ends on either end of the chrome linkage bar, and the middle would bend slightly under the weight of the return springs for the throttle plates.

    I would suggest with 44's that you get a ZX NA 5 speed and a 3.90 or 4.11 diff. I think the stock 4 speed and rear end would work, but you have such large gaps between the gears that you'll be out of the powerband on shifts. I had a friend with a pretty built 510 and he had the 280Z 5 speed which has similar gaps in the ratios. Our cars turned very similar lap times at autox but when we went to a big track he had to deal with the gap in the 2-3 shift and the one time I was behind him coming onto the front straight, as soon as he made that shift I was in front of him. Now a Z has more torque and a wider power band than a 510 in general, but after that incident he got a closer ratio 5 speed and we were neck and neck again.
    Jon

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    Registered User 70 Cam Guy's Avatar
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    I didn't realize the wider ratio from the 77-78 would be so pronounced. I was hoping to avoid swapping transmissions because the car is still pretty low mileage but it sounds like another thing to keep an eye out for. The R200 swap was another thing I haven't really tried to wrap my brain around besides needing the matching mustache bar.

    If you mean the rotating linkage bar, there looks to be a support rod end at each point on the Cannon manifold where a rod & lever connect to the carb (from the chrome bar). I don't know the proper names for some of these carb linkages. Maybe that is something he added? I haven't actually looked at my Cannon in a while. The pictures he sent look first rate, almost made me throw everything on my card right there.... have to curb my impulsive side for the moment
    -Andy
    1973 HLS30-166105
    RB20DET swap, HKS GT2530 turbo, HKS Actuator, Hallman MBC, ebay intake manifold, ebay dump pipe, straight pipe, 14 psi boost

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    The Cannon has 3 "towers" which are rod ends that hold the linkage bar. The Mikuni has 2, and the spring pressure from the carbs acting on the linkage will bend the bar in the middle.

    The ratio isn't a make or break deal, but if you're racing and you are next to a car with tighter ratios and a lower rear and all else is equal, you'll lose.

    I made a list of the parts you need for the R200 swap here:http://forums.hybridz.org/showthread.php?t=114798

    The parts list needed to bolt in a longnose R200 into a 240Z is as follows:

    1. mustache bar from 280Z with R200
    2. yoke (companion flange) from 280Z with R200
    3. rear cover from 280Z or ZX with R200
    4. side stub shafts from 280Z or ZX with R200 to bolt up to stock halfshafts
    FOR EARLY 70-71 Z's only, you need 5 -7.
    5. Longer 72-78 driveshaft
    6. Curved transverse link that sits right behind the diff from 72-78 Z
    7. Flip front diff mount around on crossmember

    5-7 are necessary because the early Z's had the diff mounted forward, and swapping to the R200 moves the diff rearward. Obviously if you buy a diff from a 280Z with an R200, it has everything you need except the mustache bar. If you buy the 300ZX diff, then you need the above pieces.
    Jon

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    Registered User 70 Cam Guy's Avatar
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    As long as the triple manifolds are forward-to-rear, it doesn't surprise me they flex in the middle without a middle support. I've been excited about my 240Z for a while now and happy with the improvements I've made. I thought that would subside after a little while but it still feels like the honeymoon of a cool new project. I love it

    I think the 5-speed and R200 are an "eventual" thing but it hasn't been anything I've thought about real seriously yet. I've always liked the idea of an LSD though. It's great to get some practical advice and opinions on this stuff.

    You know I'd completely forgotten about the FAQ section on Hybrid Z. Before my car was even running properly, I read a large amount of the strut thread and the strut sectioning thread. Also have read the suspension mods faq, and some of the adjustable LCA thread. That was probably about the same I asked you the coilover questions. I've even spent a week of lunches at work reading the Weber jets thread to learn more about the Webers. I started reading the R200 thread months ago but stopped after thinking "I'll never do this swap"...

    Thanks again everyone for your input on this thread, it's been a great eye opener and hopefully it will help others that are curious about life after SU's.
    -Andy
    1973 HLS30-166105
    RB20DET swap, HKS GT2530 turbo, HKS Actuator, Hallman MBC, ebay intake manifold, ebay dump pipe, straight pipe, 14 psi boost

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    Default linkage pics

    Here are some pics of the triple linkage I fabricated. Maybe you can use some ideas.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    72 240-- stock motor and drivetrain, 50,500 orig. miles

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    Registered User 70 Cam Guy's Avatar
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    Quote Originally Posted by george71z View Post
    Here are some pics of the triple linkage I fabricated. Maybe you can use some ideas.
    Nice, did you machine the levers or were those bought? Do they use a set screw? Does it thread into the rod or is there a clamp I didn't notice? I like the heim style rod ends, they are solid and precise.
    -Andy
    1973 HLS30-166105
    RB20DET swap, HKS GT2530 turbo, HKS Actuator, Hallman MBC, ebay intake manifold, ebay dump pipe, straight pipe, 14 psi boost

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    RedNeckZ redneckz II's Avatar
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    Cool drivability of triple carbs

    I have 45mm Weber DCOE's on the car now. The car came that way. It started with a L-24 engine and now has a L-28 in it. Both of them had a E-31 head on it, that had been modified a lot. In the L-24 engine we ran with 30mm main venturies tubes and never had any problems on the street. On the L-28 block we were looking for more power in the higher RPM range, so we went with 37mm main venturies tubes in it. With the cam we are now running, we lose a little in the lower RPM range and get a lot more in the higher range. We still get good gas milage out of it, (if we keep my lead foot out of it). What I like with this combination is the sounds it makes. I have a early Z-28 camero hood scope on it and when you put the peddle down, it surprises the people next to you with that sound that it makes. On the street I always got good gas milage with the car (drove it from NC to Colorado, a lot per year). How you peddle it will decide how much you will get. Overall driving wasn't that bad on the street with them on it.
    Last edited by redneckz II; 10-22-2009 at 02:54 PM. Reason: edit it again

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    Wow 45's with 37mm chokes, must be a hot motor
    I read most run with 32mm chokes on the Weber 40's. IIRC, the Weber book does say 30mm chokes for the triple kit. Do the 30mm chokes compensate since you were running 45s? Throttle response must have been out of sight.

    It's interesting everyone seems to be getting good gas mileage with these carbs. I never though I'd see 20 mpg with my car, let alone the 25 I got on a mostly freeway tank of gas. I'll be happy if I can keep it over 20, and will likely be beside myself if I get better than the SU's. It sounds like if you're smart with the skinny peddle you can make them work for you in any situation

    I forgot about the rallyX car had the Weber's on it (owned by a friend of the shop owner). It ran like a top, what a fun car!
    http://smg.photobucket.com/albums/v2...underCross.jpg

    Last edited by 70 Cam Guy; 10-22-2009 at 11:48 PM. Reason: proof reading is good :)
    -Andy
    1973 HLS30-166105
    RB20DET swap, HKS GT2530 turbo, HKS Actuator, Hallman MBC, ebay intake manifold, ebay dump pipe, straight pipe, 14 psi boost

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    I don't think 37's are that huge. That's what I ran on my 44s.
    Jon

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    Registered User 70 Cam Guy's Avatar
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    Quote Originally Posted by jmortensen View Post
    I don't think 37's are that huge. That's what I ran on my 44s.
    Oh I don't know, I'm still learning these sidedrafts. I figured if the 45s typically come with 34mm chokes, an L28 that needs 37mm chokes has some good mods to it.

    I still have a lot to learn
    -Andy
    1973 HLS30-166105
    RB20DET swap, HKS GT2530 turbo, HKS Actuator, Hallman MBC, ebay intake manifold, ebay dump pipe, straight pipe, 14 psi boost

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    Todd is straight shooter and does some really nice work up there. I got my 40's from him and they look excellent. But they are not on the car waiting for some work. He was very helpful and again the quality was tops.

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    Registered User 70 Cam Guy's Avatar
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    Quote Originally Posted by TexasRider260Z View Post
    Todd is straight shooter and does some really nice work up there. I got my 40's from him and they look excellent. But they are not on the car waiting for some work. He was very helpful and again the quality was tops.
    The local guys I spoken to also speak pretty highly of Todd and Wolf Creek. I heard Mikuni guru at the dyno day over the weekend. I didn't run my car but another guy with a '73 with round tops pulled 112.2 at the wheels (exhaust with turbo muffler, stock exhaust manifold). The AFR showed in the 12s so for fun, we pulled off the air cleaner top to see if we could lean it out a hair. It pulled 114.2 but it looked like lost a little on the lower rpm. It did lean it out in the mid-range but it went rich again up top. This was on a Dynapack, sorry I don't have the printouts.

    Seeing over 110 at the wheels gave me some hope
    -Andy
    1973 HLS30-166105
    RB20DET swap, HKS GT2530 turbo, HKS Actuator, Hallman MBC, ebay intake manifold, ebay dump pipe, straight pipe, 14 psi boost

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