Rochester 2GCV Carb problems. --> Buick 231 -
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post #1 of 5 Old 01-19-2011, 12:29 PM Thread Starter
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1946 CJ2A 
Join Date: Jan 2008
Location: Massachusetts
Posts: 573
Rochester 2GCV Carb problems. --> Buick 231

hello people!

I just got a reman'd carb for my 66 cj5, with a 1980 (79-81) Buick 3.8L 231 CI. So the old carb, which was a rochester dualjet, crapped out on me..... i got another carb, which is a rochester 2 Jet (2GCV) not to be mistaken for the dualjet.

Anyways, after yanking the plugs, determining TDC on the piston, i set the distributor @ 13 degrees before.

so i now know the timing's right.

problem: carb will not idle, only around 1100 rpm. also, when i give it a very crisp shot of throttle, it pops through the carb. this, if im correct means she's too advanced? so attempting to fix this problem, i retard it more towards tdc. once this is done, it now runs worse, and pops through the exhaust.

anyone have any magical numbers that would work on this carb. the idle jets are 2 turns out from full lean, the choke is manual, and the idle screw is in very far to just keep it running.

1946 CJ-2A 225/T90/D18
1966 CJ-5 231/T86/D18
1986 CJ-7 258/TF999/D300
1984 C-10 6.2/SM465
Yeah it's a Diesel
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post #2 of 5 Old 01-19-2011, 02:03 PM
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1970 CJ5 
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Location: Colorado Springs CO
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A dualjet and a 2 jet are 2 very different carbs. Dual jet is basically the front two barrels of a Quadrajet, and has a triangular air horn. IIRC it would've been the stock carb for 1980. The 2jet would have a small round air horn opening (2 5/8 or 3 1/8 IIRC) this would be the stock carb for a CJ5 V6. Did you swap intakes? Adapter plate? It sounds like you might have a vacuum leak.
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post #3 of 5 Old 01-19-2011, 02:57 PM Thread Starter
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Location: Massachusetts
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i made my own adapter plate, 1/4" metal with the 2 wider holes in it, and the other carb has studs threaded into the adapter. doesnt seem like vacuum leak, because it has a hell of a suction on the carb at this time.

1946 CJ-2A 225/T90/D18
1966 CJ-5 231/T86/D18
1986 CJ-7 258/TF999/D300
1984 C-10 6.2/SM465
Yeah it's a Diesel
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post #4 of 5 Old 01-19-2011, 04:13 PM
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1967 CJ5 
Join Date: Apr 2010
Location: Yuba City
Posts: 144
If I was having this problem I would:

a) make absolutely sure there was not a vacuum leak.
b) adjust the mixture screws for slightly rich of peak RPM.
c) adjust the idle speed to specification (or as slow as it will run).
d) repeat b and c until either everything is correct or no additional improvement can be gained.

The timing will probably need to be re-set after you have reduced the idle speed.

"Peace is that brief glorious moment in history when everybody stands around reloading" Thomas Jefferson

"Nearly all men can stand adversity, but if you want to test a man's character, give him power" Abraham Lincoln
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post #5 of 5 Old 02-24-2011, 01:12 PM
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1969 C101 
Join Date: Jun 2004
Location: Little Rock, AR
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Remanufactured does NOT equal other good poop

I'm happy for you that you got a 231 - it is a sweet engine. I have the same one in my '69 Jeepster Commando.

OK, just want to throw in the ol' adage about remanufactured carbs - they're mostly junk.

They pay very low wages to people to pull them apart, throw 'em in a vat, and then start assembling them from a generic parts bin. if it fits, it goes get the picture.

Unless you got it from a reputable re-manufacturer, like "carburetorsandmore" that tests all carbs on a running engine, you are throwing the dice on whether or not the thing will work right. Unless you know the parts by heart, there's a good chance that the jets, needles and accelerator pump are not the correct ones.

As far as what you're experiencing - did you set the timing 13 BTDC with the vacuum disconnected from the carb? (sorry, don't mean to insult - just checking the bases) If not, reset it with the vacuum disconnected. Somewhere around 79-80, Buick changed the specs from 12 BTDC to 15 BTDC. Don't know if that makes a difference for getting it started and running, but I'll throw those specs at you anyway - you can try it out.

The really important thing is TOTAL advance (initial plus spring weights plus vacuum)

At 2500 rpm, your total advance should not exceed 35 degrees. 32 is what worked best for me (I have a dualjet 210).

What type of ignition do you have? is it HEI?

If it is HEI, please read Rich Motts EXPERT diagnosis of vacuum advance and timing issues with the HEI on a Buick 225.

Bottom line is that the vacuum from a 2GV is WAYYYYY to strong for the sensitive springs in the vacuum diaphragm on the HEI, and it puts in about 45 degrees total advance...bad juju.

If it is the stock HEI, you WILL NEED TO get an adjustable vacuum diaphragm (about $20) and adjust it to the LEAST sensitivity - read Richard Motts' explanation, how-to and write-up (handle is Rrich on the above forum - do a search for 225 HEI and you will find all of them, and you'll be smarter by the time you finish reading).

The point is, even though you have a 231, you have an HEI distributor... 225's that swap in an HEI from a later-model Buick 231 have had MAJOR problems with vacuum advance, because the 2GV carbs suck so much (no pun intended)

Also, there is a problem with the 2GV carbs with vacuum leaks next to the EGR ports underneath. If you used the FELPRO 6000 gasket, you will probably have an internal vacuum leak. (you can see the very thin gasket portion between teh main holes and the egr port.

There are other gaskets that cover up the egr ports underneath - the best one I have seen is the thick carb gasket from partsdude4x4 (a Jeepster parts site) Here's a link: (I am not affiliated)

I really think, now that I put all that down, that you have way too much vacuum advance. Hope that helps

1969 Jeepster Commando w/Buick 231. T14/D20. D30/D44, 4.10 Locked/Spooled. 4x disc brakes, Saginaw PS. 32" x 9.5" Super Swampers.
1970 Jeepster Commando, in pieces. Buick 350 / SM 465 / D20.
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