Believe it or not I am having problems with my yardsale intake. Damn it! I bought this intake and all three carbs at a yardsale I came across. The carbs were on a sbc intake, so I was hoping that it was settup to run, proper jetting etc. I just put the 3 dueces on tonight, and I am having a problem. Fires right up, but is idleing at 2k and I can't get it to come down. I rebuilt all three carbs before putting them on, but don't know about the jet size. I am running them all simultaneously, not progressive, but since they are all shut, this shouldn't affect it right? I was also wondering about the gasket between the carb and the metering plate, as the rebuild kits had 4 or 5 I matched what was on it but their are definitely some deferences here. Anybody got some suggestions, this is my first multi carb settup. Thanks
if your carbs are all shut it should not even run, i havent worked on multi carb cars but have had years working on bikes with 4 carbs, can you remove your linkage and try running it off one carb first? your jets shouldnt make a different at idle.
sounds like maybe a vacuum leak. make sure the outter two either don't have idle circuts or are screwed all the way in (not too hard though, just slightly bottom them out).
I have removed the linkage, no change I screwed in the outside then all idle screws, no difference possible vacuum leak, I just rebuilt em, don't know where it might be, any common spots to check?
have you removed your scoops and looked right down inside to make double sure the butterflies are totaly closed? you probly have, do the butterflies have holes in them? the later egr carbs have holes and larger jets, maybe this could have an effect, i`m guessing
I have the scoops off now so I can see whats going on. I have pulled the linkage and checked each one individually to make sure it is closed and when I rebuilt them putting the plates back in the cross bar I made sure everything closed up completely, no holes. This is one of the reasons I am wondering about the gasket at the metering plate. Some of hte gaskets I didn't use looked like they may block a few holes I am wondering if it is sucking air/fuel through there? I appreciate everyone's help.
cool car by the way, i`m building the same frame front end setup on my 28 chevy, your running the rad in the back someplace?, with your butterflies all completly closed the car should not even start, i think you must be sucking air someplace and have a carb flooding, just so i`m clear, your front and rear carb have the idle screws removed and there idle mixture screws turned all the way in?
The idle scres are all the way in. what do you mean removed and all the way in? can't be both can it? I might misunderstand
Did you check to see how much slop is in your throttle shafts? You could spray some carb. or brake cleaner around the bases where the shafts come through.Or you could use propane. If the idle speed changes, that's where your leak is. Just make sure there's no spark jumping anywhere.
your idle speed screws are located next to your throtle linkage on the drivers side, one per carb. your idle mixture screws are located down at the base of your carbs, two per carb. i`m sure you know this. your front and rear carbs can have the idle speed screws removed as you will not be useing them anyway. the front and rear carbs can have the idle mixture screws turned all the way in for now. with the linkage conecting all 3 carbs togather removed you should be running just off the center carb. i think thats the best place to start. once you have it running good then i`d start adding the front and rear carbs and they will have to be synchronized.
Did a set one time. Used the center carb for the primary, filled the idle circuits on the other two with JBweld. If you totally remove the idle STOP screws, the butterflies will get stuck closed, so they are needed to let them close but not jam when they slam. I called Hot Rod Carbueration for tech advise, had them send the corect metering parts(think it was just jets). They also sell base plates made for the secondaries. Try blocking off the front and rear(sheet metal under carb?) in order to determine the health of at least one of the carbs. I personally had no problems with our's, ran them progressive, 350 w/crane 350horse cam, had a great kick when called on! LEE
Thanks, I was jsut looking at the different basses for teh secondarys, kinda spendy to go that route considering I only have 300 bucks into the intake and carbs. I was already thinking along the lines of blocking of the secondarys to verify the main was working. I through this on last night and it was getting late, so I thought I would get everyone's thoughts before I tinker again tonight.
I am thinking about changing the gaskets, I should be able to block the idle circuits with one of the other gaskets.
A couple things..be absolutely sure you put the throttle plates back into the bores the right way as they are bevel cut to seal when closed. If that is correct and am assuming you checked your throttle shaft for leakage, let it idle, and one at a time cover the air horn on the front or rear one at a time with your hand, if the idle gets more respectable it is one of those carbs and you will need to do some readjusting. Actually, when I setup 3 in a row with straight linkage I don't turn the air needles on the front and rears in all the way, as it will then make it easier to sync the three.
so with those screws removed and the idle mixture screws all the way in on the 2 outside carbs and your linkage removed you should be able to run it off the center carb, my rochester carburetor manual says that your idle mixture screws on your center carb should be set at 2-1/2 to 3 turns out.
Your carb to manifold gaskets are probably the culprits.i had the same problem and that was the cause.
Did you put the butterflies back in in their correct orientation? They have beveled edges and the bevels have to be parralel to the bores.If the sharp edge faces the bores they will not idle down because they cannot close properly.If one is oriented correctly and one not,they will not idle down. Also when they are reinstalled you have to do it with the idle stop backed all the way off and the butterfly screws loose,tamp the butterflies shut gently with the screwdriver handle and then tighten the butterfly screws.Then run the idle stop in until you hear the butterflies crack open (if they are tamped properly they should be slightly stuck and there will be an audible noise when they open)and stop right there on the 2 end carbs.On the primary go an additional 1 turn from crackopen.(you may have to go more or backit down this is just a jumping off spot) Most 3 deuce set ups have thicker butterflies on the 2 end carbs (to insure closure without being so "stick" sensitive) and blocked Idle circuits(closing the air bleeds should do to stop the fuel flow on idle). Those look like big bore Rochesters,if this is the case you prolly will have trouble with them "stumbling" without progressive linkage.(you really should buy or make progressive linkage) Once you get it to idle you may also find that you have to dissconect acc. pumps on end carbs or slow their "action" way down so it doesn't stumble from too much enrichment when you whack it. I wouldn't change the gaskets to block the idle circuits.
Fast idle is frequently caused by a vacuum leak as stated before. Fill a squirt bottle with water and squirt a little water around suspect places(throttle shafts,carb base,intake to head gaskets,and any vacuum lines) with it at idle speed. When you squirt water on the vacuum leak,you will hear the engine stumble as it sucks water in. I have found many vacuum leaks this way. Water is much safer to use than petrol products.
Thanks guys, I appreciate all the good advice on this. I started with the center carb screws out 2 1/2 outside carbs in all the way. I am fairly sure the butterflys are in proper, although I didn't check the bevel, the screw holes are just slightly off center so I don't think i could have them in backwards, although I may not have them set just right. Something to check. I bought a progressive throttle settup, but can't make it work. I figured I may need to disconnect the extra two acc. pumps. I like the water idea.
I should be able to follow a fairly methodical process to check stuff after all the advice. Beets the hell out of "I don't know lets try this?!"
im running a vintage speed y adapter on my sbc in my model a sedan we had alot of problems with vacuum leak around the carb bases because the vintage speed adapter has such a small base it wouldnt cover the entire base of the carb like say your intake probabley does make sure all your vacuum ports are blocked off too (sure you already did that) and i dont mean to hijack here but im running str8 linkage and when i jump down on it it stumbles from reading above posts im thinking progressive linkage will fix this correct or incorrect
Some 2GC's have screw in the back of the carb between the bores about halfway up. It's an air bypass for setting idle (The 2GC on my Buick 350 has one). Yours might be open and letting too much air through. I don't know the procedure for adjusting these screws, my carb works well so I didn't mess with it. When you rebuilt the carbs did you remove the throttle shafts? If so, the blades might not be aligned properly and causing the throttles to stick open. Might be worn throttle shaft bores too. Good luck Shawn
Double check everything for a vacume leak. Could be an unplugged vacume takeoff from a base, a warped base, too thin carb to manifold gasket, missaligned butterflies, worn shafts, or maybe missing screw between the barrels on the back as noted in the post above. Also the distributor, brake, cruise control or any other vacume lines. Look for any other vacume takeoffs that may be on the intake or carb bases. If all that checks out the next logical progression is to get it to run on 1 carb. Block off/remove the outer 2 and try to run it on just the center one. Don't just assume the butterflies, shafts, vacume takeoffs and bases on them are not leaking. Get it down to 1 possible carb problem in stead of 3. If that doesn't work try one of the others in the center position if you haven't modified them or figure out why that carb isn't running right. Once you have the engine running as a 2 barrel, make the end carbs into secondaries only and add them in. The reason people use the HRC bases is they have new non leaking shafts, non warped bases and thicker tapered butterflies that seal better than the old worn stock ones. I used them on the last 3X2 setup I did and I'd do it again. Expensive tho. Depends on just how worn out your stuff is. As for the gasket in the carb, it could very well be that you got the wrong one in one of the carbs. Double check the kit instructions if it came with any or you can find some pretty good breakdown pictures on the internet. Make sure you have the right gasket on the right way and you didn't forget to put in any small parts or mis-adjust the floats. Three deuces scares a lot of people with all the bull about synchronizing the carbs using magic/special synchronizers and special lost knowledge etc. but for the most part if you're running progressive you're running a center carb as your primary and the outer carbs are just secondaries. They aren't used at all till around 1/2 throttle or later. Think of it as a 3 piece Holley double pumper. It's not rocket science and no arcane spells or potions are needed.
Success! It was a combination of several things. 2 of the accelerator pump rods were bent and not allowing the butterflys to close all the way. The front carb float was a little off and that carb was flooding, I also put heavier springs on it to keep everything closed tighter. Idle is completely controlable now. I still need another hour to finish tuning, I had it pretty good then I drove around for a few and now I have a flat spot right off idle. But when you open it up it screams! 840 cfm = just right apparently. I'll let you know how it works out. Thanks again
So true! Usually first comment about 3x2 is something like "whoa, that looks so good!" And second comment is "But that is not easy to tune it up". Yeah, right... They are not so complicated systems as people usually think.
The tri-power definately didn't scare me. Just was looking for pointers, as there is no subsitute for experience. I ended up opening all the outside idle circuits about 1/2 turn, it smoothed out the idle. Tonight I will try doing a semi-progressive settup where the center will open just enough to get past the rpms up before the other two hit.
The Jalopy Journal
