GN and T-Type Performance Enthusiasts (GNTTYPE) Forums

GN and T-Type Performance Enthusiasts (GNTTYPE) Forums (http://gnttype.org/forums/index.php)
-   Fuel Systems (http://gnttype.org/forums/forumdisplay.php?f=35)
-   -   Rochester Carb Adjustment (http://gnttype.org/forums/showthread.php?t=14773)

jjurva 12-03-2011 11:28 PM

Rochester Carb Adjustment
 
I have an old rochester 2 jet on a buick v6. I see there are two fuel adjustment screws. Is one air and one fuel? Which is which? What is a good starting point as far as adjustment? Do these engines usually need vac advance?. As it stands now it will only run with the choke in a specific place and idles very high. won't run off choke if i don't have my foot on the peddle. Any way it sounds like a carb problem to me. Thanks for any help!

chrisjkruse 12-04-2011 12:06 PM

Re: Rochester Carb Adjustment
 
I'm no expert whatsoever, but in my experience.... if it's not a vacuum leak..then its probably clogged jets in the carb. Not enough fuel. Try this, but be careful: It's and oldtimers trick..

Place a rag in one hand...rev the engine pretty high with the other hand..then choke the engine out with the rag over the carb till it just about stalls..then do this again several times. The choking effect directs all of the vacuum to the jets..and often sucks out the dirt..
It has a pretty good success rate believe it or not.
As far as info on the screw setting..I have no idea.

chrisjkruse 12-04-2011 12:44 PM

Re: Rochester Carb Adjustment
 
uhh? is this a turbo car? because my method previously mentioned is for a non turbo.

Keller 12-04-2011 01:34 PM

Re: Rochester Carb Adjustment
 
What year carb and motor? Is it a E2M DualJet / VariJet, or an older 2GV, etc.?

I don't believe any of the carbed Buick turbos were 2BBL, only 4BBL. Not in the 80s at least.

If it has one of the E2M DualJet carbs, take a look at http://www.tocmp.com/manuals/Carbs/R...vice/index.htm

If it is one of the earlier 2G* carbs, see http://www.oldcarmanualproject.com/m...ual/index.html

Note that the newer ones have an internal TPS to signal the ECM, as well as a plate with an electronic grid below the carb that I believe was used to heat the carb and aid with idle and emissions.

Also see http://www.oldcarmanualproject.com/m...0-86/index.htm

charlief1 12-04-2011 06:59 PM

Re: Rochester Carb Adjustment
 
78 was the first year of the Buick V6 turbo cars and they came in 2 and 4 barrel designs. If your car is a turbo powered car or an NA from 78 to 80 then you have several adjustments you can do to them. After 80 they have computer controls and have different adjustments. The electric chokes were put on them between 79 and 80 and adjust differently from the earlier design.

Pics and a year will help to know what your dealinbg with as far as the design so please post some.:)

jjurva 12-04-2011 09:43 PM

Re: Rochester Carb Adjustment
 
It's an older 2g carb i guess, In the link you sent, Keller, the carb i have looks very simmilar to the two in the manual but not the same. The motor is from the 60's it is or looks very simmilar to the fireball v6. The carb is now spraying fuel out of the vent on the top of the bowl and has a small tube on the carb that i cannot figure out. You can see it in this picture http://www.oldcarmanualproject.com/m...3__2G_0007.htm
the picture on the top. It is a small tube on the lower left of the carb. what is it? To be honest I'm feeling discouraged with this carb. Would a new carb be a good option. If so what is a good cheap carb to go with.

charlief1 12-05-2011 12:31 AM

Re: Rochester Carb Adjustment
 
That's a 2GC carb and they're pretty easy to work on. If fuel is coming out of the top then the float and or needle are needing replacemment. My guess is that it's a 225 or 231 oddfire engine. The 231 was made of about 3 years as an oddfire then changed to even fire in 77 & 1/2. Does it have points or electronic ignition?

As far as the adjustments, my guess is that it has a heat pipe going to the choke. If that's the case you can replace the plastic choke thermostat with an electric one. It will work much better than the original one and they aren't that expensive.

To adjust the idle speed/mixture you need to have the engine at operating temp first. Then see what idle speed you have. If you have to reduce spring pressure on the choke thermostat do it. Then adjust the timing first. Then on the side of the carb adjust the idle speed. Once you get the speed to about 600 RPM then you need to adjust the mixture screws. A tach is the best way to do it. You're watching for a change in the RPM level, either up or down. You want the speed to go up as high as you can get it as you screw the screws out, then look for about a 50 to 100 RPM drop. Do one first and then the other. At this point I usually go sniff the tail pipe and see if it smells rich or clean. If it's rich screw the adjusters in very slightly on both sides and check the tail pipe again.

If this is clear as mud, sorry, but this is the basic procedure to do it.:)

Keller 12-05-2011 03:14 AM

Re: Rochester Carb Adjustment
 
Quote:

Originally Posted by charlief1 (Post 60742)
As far as the adjustments, my guess is that it has a heat pipe going to the choke. If that's the case you can replace the plastic choke thermostat with an electric one. It will work much better than the original one and they aren't that expensive.

Agreed. I have one of those pipes from one exhaust manifold to the choke housing on the Carter AFB that is on my '67 California GS with the Buick 340. I don't want to convert in order to preserve originality, but the electric setup is MUCH better. And the swap is simple.

jjurva 12-12-2011 11:57 PM

Re: Rochester Carb Adjustment
 
What was that tube for? It's in the top picture on the right side. It's the only unmarked tube. Or is that what you were saying was for exhaust manifold to the carb. Either way could you either tell me what it is or restate. Once again it is the top picture on this page , only unmarked tube, right side of carb http://www.oldcarmanualproject.com/m...3__2G_0007.htm whatever it is it sucks air pretty good while the motor is running

charlief1 12-13-2011 02:09 AM

Re: Rochester Carb Adjustment
 
The link didn't work for some reason. Now on a side note, I do have a Holley street dominator that will fit the 78 and earlier heads. That would allow you to put a 4 barrel on it and get rid of the 2 barrel.:)


All times are GMT -4. The time now is 02:19 PM.

Powered by vBulletin® Version 3.7.3
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.