Inliners International Forums General Discussion Engines Rochester 2G

I have a 78 Chevy G-20 with a 292, Jegs 50,000 volt coil with adjustable vacuum advance, stock manifolds, 2 1/2 " exhaust, Saginaw 3 speed and 273 rear. I have replaced just about everything in this van in an effort to get it to run well. My latest effort has been the addition of a TransDapt 2 to 1 BBL adaptor and a Rochester 2G carb. I have to say that this latest addition has boosted my power considerably BUT I am having problems tuning.
1: Stalls when I come to a stop(in neuteral).Idle is to low? Refer to #2
2: Runs on when I turn it off. Butterfly ofen to far?
3: The throttle is VERY touchy. I get great responce off the line and to about 1/4 throttle and then it goes flat.
4: Backfiring (more like popping) when I let off the gas. Is this indicitave of a rich condition?
5: I still haven't figured out how to hook up an electric choke.
Any help or sugestions Please

Brien

How's the timing look? Have you checked for any vacuum leaks?

Timing is right on and I don't think that there are any vacuum leaks. I rebuilt the carb before I put it in and ran new vacuum lines.

Can anybody give me some tuning ideas?
I need all the help that I can get.

Thanks

Try a different carb & see what happens.

Good luck, John M......

beware the transdapt adapter. i used the same one on a jeep 258. couldnt get the thing to run right. sprayed some carb cleaner around the base and huge rpm fluctuation. i took a little mirror and looked and there was actually a gap between adapter and manifold. vintage speed sells a really nice adapter - well machined and no leaks i could tell..
be sure to check initial timing with the vacum hose to the distrib clamped and after the engine was warmed up.
sounds like could also be a mixture problem. set mixture with vacum gauge to manifold vacum, adjusting idle as needed. mixture - idle - mixture - idle until get highest vacum at correct idle speed.
be sure the carb settings are on the money - the rebuild kit should have how to adjust linkages, blade to body adjustments, etc.
just my 2 cents

I'd like to try another carb but I don't have one.
The TransDapt adapter is not all that. I had to do some extensive modifications in order to get the butterflies to open all the way without them rubbing on the sides. I'm not happy with this part.
There is something going on with this because I adjusted the mixture and idle so that it ran decent and now it is stalling on me again. I think that it is leaking. Either the adapter or the carb itself.
How much vacuum should I have at the manifold? 14lbs?
About how many turns out should the mixture screws be for a basic setting?

Thanks for the suggestions.

Brien

Well after some investigation and a good suggestion by hotrodsbyray I found that this TRANSDAPT adapter will NOT work with a large base Rochester.
The 2bbl end is not large enough to cover the entire base of the carb leaving a small sliver of the constant vacuum port exposed.
After several hours of modification I have to throw this part in the trash. I will not buy any other parts from TRANSDAPT.
Thanks all for the help. I will keep all informed on the search for a sutable replacement.

Brien