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Discussion Starter · #1 ·
I have a '32 ford w/a 350 GM performance parts crate motor. The builder put on a Offy tri-power package but it's only running on the center carb. There's a plate on the 1st and 3rd carb base plus the fuel line is blocked off. I want to run all three but the idle drops down while in gear at a stop and I want to get that fixed before dealing with the other carbs. Everything is fairly new. I've replaced and tested all hoses for vacumn leaks, tried adjusting the fast idle and air/fuel mix screws. Even tested with starter fluid on all possible places for a leak. Carbs look brand new so I don't think they need to be rebuilt. The carbs are rochester GM 2 Jet, center carb is a manual choke. Any other suggestions?
 

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Discussion Starter · #5 ·
I don't know the cam size but my understanding is that it's a bone stock GM Mr Goodwrench replacement crate motor. All he added was the Offy intake for show. I'll have to check the timing. I was thinking it was a vacumn leak or carb adjustment, but after eliminating most of the carb related possibilities, I'm now thinking I should check the timing- I'm no expert so I didn't think that was a possibility but this was noted in related bulletin board discussions.
 

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Jason, If the engine is 'bone stock', then I guess your cam isn't big enough to work with the triple deuces. Depending on the cam degrees for a stock engine, you're looking at about 6 degrees BTDC. I have my 327 set @ 8 degrees so I can get some type of gas mileage. Orignally, I assembled the engine for multi carbs, but changed my mind and now run a 750cfm Q-Jet. To really run right I have to bump the timing to around 12 degrees. Jim
 

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Discussion Starter · #7 ·
BimmE, thanks for the response. Here's my question... If I'm only running off the center carb (the dumpers are blocked-see my 1st post), then shouldn't it run the same as if I only have a 2 barrell on it? I'm thinking your reason is why they are blocked off. I was told it was for fuel mileage, but it has progressive linkage, so it shouldn't matter. I'm running the car with no hood and it looks great, but I may have to take it off or do some cam work.
 

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Jason34, Lets observe your 3X2's on your engine. How are they isolated from the holes in the manifold? If they are 2G's they should have 4 nut/washer combos holding they down. Are they tight to the manifold? Use a feeler gage to test. If the isolation device is metal, are there gaskets top and bottom for the 2 end slaves? If not metal have you changed the isolation devices? If you remove the carbs, check for any obstruction on the bottom of the throttle plate, also the mounting surface & look at the areas around the studs that hold the carbs down, to insure the immediate surface around the studs isn't pulled up slightly. Now that you have both end carbs off look at the base plate; try and wiggle the throttle rod on both sides. There will be some movement but NOT very much. If excessive it has to be repaired. Are the 2 throttle plates installed? If so, when Wide Open(W/O) they will contact what ever is used to block the throttle plate from the manifold. Next box.
 

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Pg2- Next lets look at the throttle plate assembly as a unit. Does it have needle adjusting valves installed? If so, they need to be removed and the 2 holes tightly plugged. Lead shot or a small fishing sinker can be used. Any openings, top, bottom, outsides, and inside in this plate should be plugged. On an original 3X2 setup these cards are there, doing nothing, till called on by jamming your hip into the carbs for more power. Plug the fuel inlet to keep any trash out of the space. I'd remove the progressive linkage from the 2 ends carbs too. It may look nice, but it isn't helping anything. The center 2G is the life blood for the engine. Try and perform the above checks to this also. Here the throttle shaft needs to be really unmovable. Anyone else - can you think of anything else? - Jim
 

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Discussion Starter · #10 ·
Thanks again! Someone machined a real nice block off plate that isn't too thin/flimsy and it's shaped to the base of the carb so well that you have to look real good to see it. There is a gasket between the plate and manifold, not one on top- between the plate and carb. I didnt see that as necessary of the manifold is blocked off. I sprayed starter fluid around it good to see if there were any leaks but I agree this could be a problem and should test again. As for the dumpers, yes, they have throttle base plate without the screws and choke. I also have the progressive linkage arm which connects the center to the other carbs removed right now while I'm trying to figure this out. This weekend my plan is to check the block off plates again, and adjust the timing.
 

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Jason34 said:
Thanks again! Someone machined a real nice block off plate that isn't too thin/flimsy and it's shaped to the base of the carb so well that you have to look real good to see it. There is a gasket between the plate and manifold, not one on top- between the plate and carb. I didnt see that as necessary of the manifold is blocked off. I sprayed starter fluid around it good to see if there were any leaks but I agree this could be a problem and should test again. As for the dumpers, yes, they have throttle base plate without the screws and choke. I also have the progressive linkage arm which connects the center to the other carbs removed right now while I'm trying to figure this out. This weekend my plan is to check the block off plates again, and adjust the timing.
i know this may have nothing to do with your situation but on my catalina its a single 2 set up and i was having the same problem it idled at 1000 netural/park droped to 500-600 in gear some times would die couldnt cut ac on either my points were very far out of adjustment and when strain was put on the engine i had weak spark and it wouldnt idle right ran great at high rpm untill one day it wouldnt run at all check those points if it has them they can cause lots of problems.
 

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Discussion Starter · #12 · (Edited)
ALL! Thanks for your help! It's running strong now, so I wanted to document what i did for future viewers;

First I bought a vacuum gage and set to max vac on the center carb- it's at 11. Next, I checked the timing. To my surprise it was set at 12 deg BTDC. I set it to 8 (I may try 10 this weekend), removed the block-off plates on the 1st and 3rd carb, hooked up the progressive linkage and it's running strong! Starts easier and idles just fine in gear.
 

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Tri-power carburators require special secondary carburators that are designed without an idle system. That is why those carburators are difficult to find and are expensive when you find a pair. If you don't have the correct secondary carburators, you will be chasing idle problems all the time.

There is a company that converts standard Rochester 2GC carburators to Rochester 2G carburators so they can be used as secondary carburators on a tri-power. Hot Rod Tri-Power Carburetors - Rochester Carburetor Service
 
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