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Thread: dual carb conversion?

  1. #26
    3Geez Veteran MessyHonda's Avatar
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    Re: dual carb conversion?

    Quote Originally Posted by civic accord honda
    whay not do a EFI SAwp wouldent efi = more powe then a carb ?

    a weber carb conversion is easyer than taring apart the car just to put a silly EFI swap plus its only like 20 extra hp....the weber you can get rid of your old carnd and just bolt in on and tune it...and you should have at least the same power

    1989 Honda Accord LX-i
    B18c1 swap since 7/2011
    175whp and 132tq
    Redzone tuned



  2. #27

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    Re: dual carb conversion?

    actually properly tuned DCOE carbs with headers, full exaust and mild cam can make more power than EFI with the same mods.
    Alex.

  3. #28
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    Re: dual carb conversion?

    so sometims carbs are beter
    i like crabs beter thay are easyer to work on

    1988 Honda Accord LX-i Coupe 123k miles.

  4. #29
    3Geez Veteran lostforawhile's Avatar
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    Re: dual carb conversion?

    plus a nice set of sidedraft carbs is just so much nicer to look at then a fuel injection system. I guess I'm just old school. I think the tuning possibilities on this car would be a lot greater with good carbs then trying to modify the factory fuel injection system. the other possibility I'm looking at is a possible set of sidedraft SU carbs off of an mgb. these were almost as famous as webber carbs and they have many parts available for tuning. there were many roadraces and rallys won running SU carbs. they would need to be rebuilt of course,but it's one of those enjoyable projects you work on a bit at a time. from what I can see looking at this picture, it looks like I could just mill the factory inlet flanges off and tig the webber flanges on or the flanges I would have to make for the SU carbs. if I run into a water passage problem I'll tig it off and not run a heated manifold. I already installed an extra temp sensor in the thermostat housing anyway. it's pretty easy to make aluminum pieces to get rid of the egr valve etc. the other thing i might run are OER carbs,these are basically japanese webbers,they use all internal webber parts and are tuned exactly the same. the only real difference is price talking 600 bucks for a set vs 1000. the tech guy at Pierce said they would even tune them the way i wanted.

  5. #30
    3Geez Veteran lostforawhile's Avatar
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    Re: dual carb conversion?

    I have an extra carb intake in my junk,so what I'm thinking of doing is where the two runners on each side meet up into one,I may cut it straight across then mill it square and tig the webber mounting plates on to the runners. one barrel for each runner. that way I can cut off the excess aluminum around the egr valve etc. and grind it all smooth and make it look nice. what I need to do first is put the manifold in the bridgport and make a block that fits under one side of the flange while the intake flange for the carb is straight up and down vertical and lined up with the quill. this way after all that mess is cut off, the block will act as a reference for milling the intake nice and square and the carbs will be level with the manifold bolted to the head. after I get the carb mount flanges from pierce,I may have to mill more of the intake off,all I will have to do is put that block back under the intake flange mounted in the mill,and the manifold will be at the right angle.

  6. #31

    cygnus x-1's Avatar
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    Re: dual carb conversion?

    Ok, yeah. You mean an extra A20 intake right? I was thinking the same thing. Cut it just before the 4 runners combine into 2. That sounds a lot more feasible, and accord intakes are everywhere so you can afford to trash the first try if it doesn't work.

  7. #32

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    Re: dual carb conversion?

    you'd have to reshape the runners if you were going DCOE. the carbs are round and the ports on the head are oval. it's nothing some machining couldn't fix, but it's certainly something to think about. i'd personally not use much more than the flange from the stock IM.

  8. #33
    3Geez Veteran lostforawhile's Avatar
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    Re: dual carb conversion?

    Quote Originally Posted by Vanilla Sky
    you'd have to reshape the runners if you were going DCOE. the carbs are round and the ports on the head are oval. it's nothing some machining couldn't fix, but it's certainly something to think about. i'd personally not use much more than the flange from the stock IM.
    thats exactly what I did.hehe took a band saw to it. I'm going to keep some of the runners but not much. If I measured right the angle difference between the flange and the original carb mounting pad is 15 degree. in other words if I machine off the edges of the runners at 15 degrees and weld the flanges from pierce to them the carbs will sit level when the flange is mounted to the head. other question for those who are running dual sidedrafts,where did you mount your vaccume point for your booster? and where did you pull vaccume for the pcv valve? it's important to keep the pcv valve as it helps keep sludge out of the engine. also does anyone know the thread for the vaccume sensor on the back of the manifold? thats actually not for emissions,it retards your timing when the engine is cold to help start eaisier. it's pretty easy to set that back up. I thought instead of the heated manifold I would run an aluminum block on the firewall to hook the bypass hoses together. that way i can hook up that vaccume piece and the temp sensor and they will still function normally.

  9. #34

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    Re: dual carb conversion?

    Quote Originally Posted by shepherd79
    boy you have a lot of researching to do.
    where should i start.
    well, 86-87 prelude has two keihin carbs. They are like bike carbs but only two. the stock ones are very small. i hope you upgrade them with something better.
    the cylinder head from A18 will bolt up to A20 block without any problems. You may want to check on the size of the valves and the size of the ports. the reason i am saying that is because they may be a little smaller than A20 head, but i could be wrong.
    You can use regular A20 manifold. It will bolt up without any problems. they are no other options for headers since A18 and A20 share the same header bolt pattern.
    If you are going to upgrade the carbs go with 45mm at least. get the biggest you can find. Remember, they are going to be working twice as hard as if you had 4 bike carbs.
    PS. there are pictures of people running 4 bike carbs on A20 montors without any problems. you will make intake manifold the same way as if you had 4 individual throttle bodies.
    very well farmed info Shep, say Lost, Ive seen that motor before in a prelude se-i. at the jy. Tim really got the attention of the real motorheads here, R&D threads are a good place to browse about. Do you have access to C&C machine ??? computerized setup? you can draw out and design your own manifold or adaptor blocks to make anything fit. Depends on how much access to jy parts your have and are you willing to cross the Honda line and get fuel delivery system from another make ????carbed of course. Bike jy are hard and few and far between keep that in mind when your planning, ever break a jet or something when serviceing carbs your screwed. I say use a weber set up, can you find some vw bug dune buggy parts.. lol Intrigued RooDooToo

  10. #35

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    Re: dual carb conversion?

    my favorite way to pull vacumm is to tap all of the runners and build a vacuum manifold for everything to run off of.

  11. #36
    3Geez Veteran lostforawhile's Avatar
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    Re: dual carb conversion?

    Quote Originally Posted by roodoo2
    very well farmed info Shep, say Lost, Ive seen that motor before in a prelude se-i. at the jy. Tim really got the attention of the real motorheads here, R&D threads are a good place to browse about. Do you have access to C&C machine ??? computerized setup? you can draw out and design your own manifold or adaptor blocks to make anything fit. Depends on how much access to jy parts your have and are you willing to cross the Honda line and get fuel delivery system from another make ????carbed of course. Bike jy are hard and few and far between keep that in mind when your planning, ever break a jet or something when serviceing carbs your screwed. I say use a weber set up, can you find some vw bug dune buggy parts.. lol Intrigued RooDooToo
    well I'm going to modify a factory manifold and get the plates for making the manifold from pierce. I'll probably get the oer carbs from them too,they are the same thing as webber 45s but are japanese and use webber parts so tuning is easy. about half the price for a set also. 500 vs 1000. don't have a cnc machine available so it's done the old fashioned way. most of what you need for making the sidedraft manifold already exists by simply cutting them off and machineing them at the junction where the tubes come together. piece sells the plates that match the webber carb base the OER uses the same pattern. you simply tig them on to your manifold. and blend in the plates.

  12. #37
    3Geez Veteran lostforawhile's Avatar
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    Re: dual carb conversion?

    ok who has done dual carbs on here before and what problems have you run into while doing the setup? I like the idea of doing the vaccume manifold,I'm going to make the aluminum block that mounts to the firewall for the bypass hose and temp sensor vaccume control for the dis. if I could find some small liquid filled vaccume gauges,I thought of running one on top of each port, not just for looks,but for help in tuning the carbs. I'm going to kep my air cleaner assembly due to the time and trouble to make it. I will build a manifold that fits across both sidedrafts and duct air from my air cleaner. all I need to do is find another couple of bracing points to mount the back of it to on the block.

  13. #38
    3Geez Veteran lostforawhile's Avatar
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    Re: dual carb conversion?

    well it looks like I'm going to go with the 2 single barrel SU carbs,I found a ton of info on the internet and I never realized how many different kinds of cars people have installed them on,brittish,german,and japanese alike. I also never realized they were made until 88. I remember working on them as a kid and they are fantastic carbs,and so simple. yet they have survived all these years due to the fact they work so well. heres a little bit of info and a funny article as well on them. http://sw-em.com/su_carbs.htm

  14. #39

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    Re: dual carb conversion?

    Holy sausages butchman!

    "Sausage Skinners Union"





    wow, beautiful exhaust display...
    reminds me of the bike in the "AKIRA" movie

    - llia


  15. #40

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    Re: dual carb conversion?

    Quote Originally Posted by lostforawhile
    well it looks like I'm going to go with the 2 single barrel SU carbs,I found a ton of info on the internet and I never realized how many different kinds of cars people have installed them on,brittish,german,and japanese alike. I also never realized they were made until 88. I remember working on them as a kid and they are fantastic carbs,and so simple. yet they have survived all these years due to the fact they work so well. heres a little bit of info and a funny article as well on them. http://sw-em.com/su_carbs.htm
    there is a car at the junk yard that has simular carbs. it is MG with very small engine, but the carbs look just like it.
    Alex.

  16. #41
    3Geez Veteran lostforawhile's Avatar
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    Re: dual carb conversion?

    Quote Originally Posted by shepherd79
    there is a car at the junk yard that has simular carbs. it is MG with very small engine, but the carbs look just like it.
    they came in different sizes,if you get a chance see how much he wants for them and the linkages of course. also if you see any numbers on them let me know. the sizes are the sizes of the throttle bore,like 1 1/4 1 1/2 etc. I would need two of them at least 1 3/4 size bore or larger. it was common to put the bigger su's on smaller displacmment blocks for racing.

  17. #42
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    Re: dual carb conversion?

    what about opening up the carb A20 manifold and putting a edlebrock 650 on there..................

  18. #43
    3Geez Veteran lostforawhile's Avatar
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    Re: dual carb conversion?

    Quote Originally Posted by reliantkcar
    what about opening up the carb A20 manifold and putting a edlebrock 650 on there..................
    no comment

  19. #44

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    Re: dual carb conversion?

    650 cfm would be too big of a carb.
    I had 350 holley 2 barrel carb on my old accord and it ran rich on low rpm but high rpm it was great. it was pulling like crazy on high rpm.
    I still have carbed manifold that i ported for holley. all you have to do is drill and tap new wholes for the bolts that hold the adapter. i think i even have adapter somewhere too.
    it is easy to do since it is aluminum.
    Alex.

  20. #45

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    Re: dual carb conversion?

    Quote Originally Posted by reliantkcar
    what about opening up the carb A20 manifold and putting a edlebrock 650 on there..................
    650/919 CFM , no ways

    a 390, maybe 450, or 480 4bbl but you should divide the manifold to help the low end.

    https://www.3geez.com/forum/showthrea...t=37554&page=2


    Thing is even with the larger carb there are points in the stock manifold you can't open up, so you'll be limited not by the carb but by the restriction in the manifold. Eventually if you want to make more power you will have to go the custom manifold route.

    - llia


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    Re: dual carb conversion?

    Only reason I asked is because my friends dad has a 48 dodge with a chevy 350 in it if I put a new carb into it I get the old one. So I was just throwing an idea out there . BTW the biggest engine I currently own is a B20A5.............

  22. #47

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    Re: dual carb conversion?

    Maybe you could make the 650 a 3bbl.


    Close up one of the primary throttle ports might give you low rpm back.

    The next big challenge will be working on when the secondaries will open.

    Is it a vacuum secondary?

    How large are the chokes? Primary/Secondary

    How large are the throttle plates? Primary/Secondary.


    This is the AVS series... this one allows you to adjust when the secondaries kick in...
    The manifold would have to have a 3bbl plate inbetween the carb and plenum to help keep primary fuel delivery a little more equal to both sides of the manifold.

    - llia


  23. #48

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    Re: dual carb conversion?

    This guy is funny.
    http://www.moparchat.com/forums/showthread.php?t=56571



    Hey shep, was your carb progressive or synchronous.
    - llia


  24. #49

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    Re: dual carb conversion?

    Quote Originally Posted by lostforawhile
    ok who has done dual carbs on here before and what problems have you run into while doing the setup? I like the idea of doing the vaccume manifold,I'm going to make the aluminum block that mounts to the firewall for the bypass hose and temp sensor vaccume control for the dis. if I could find some small liquid filled vaccume gauges,I thought of running one on top of each port, not just for looks,but for help in tuning the carbs. I'm going to kep my air cleaner assembly due to the time and trouble to make it. I will build a manifold that fits across both sidedrafts and duct air from my air cleaner. all I need to do is find another couple of bracing points to mount the back of it to on the block.
    boy am I loving this thread, and I am totally intrigued Tim by your creative think tank plus 'counterforming' foresight ability, also I will mention Im glad A20A1 chimed in there are so many motorhead unstoppable engineers in this threadm Vanilla Sky, Shep, all of yaas. Thanks for the links too, I was not aware of the 'japan webers' , and A20A1 that bike is you bro, raging bull, never saw a three barrel carb quite like that one either.
    OK regarding the dual carb setups, my 2 cents worth from working on corvairs and vw's is yes you need a set of very good vacuum guages Small aircraft tool specialty vendors is a good place to look. A lot of what your working with here is old school, remarkable shitzit Lost... The carbs, when you build them, ensure they are identacle as possible regarding specs and settings you can not get to once installed, attention to detail will really come into play. Porting &polish of the intake mani. under them will need to be presice as possible too I figure. I use to have a trio setup of vacuum guages to sych carbs with. Just like you expect with weber style carbs, you are constantly trying find the best of both worlds to get it tuned, thus having mulitlples haveing them be perfect matched sets really helps. LIving in Ga. will be a little headache since we get several months of extreme temp changes throughout one day, that trend is moving further south so know you have seen some 40+ degrees changes inside one 24 hour period.
    your really motivated dude, this is awesome R & D , and what year is the mg under the fallen barn? restorable mg and mg minis are hot right now, I would not mind running across some deal on one, esp a mini mg.

  25. #50

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    Re: dual carb conversion?

    Quote Originally Posted by A20A1
    This guy is funny.
    http://www.moparchat.com/forums/showthread.php?t=56571



    Hey shep, was your carb progressive or synchronous.
    my carb was synchronous. it was motorcraft 350 or 375 cfm (not sure what exactly it was). i was told it was 350cfm. like this one. http://www.carburetorfactory.com/expvw07.html

    If you are not sure which carb you want to run look here and find the one you like. i had my hands on Rochester 2gv. It was nice a small carb. it was smaller than motorcraft one but just a little bigger than stock keihin.
    Probably close to weber. i was going to use it, but that is when my car got some rear damage.
    Alex.

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