Engine Problem Opinions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

73737373 · 12-22-2005, 05:27 PM

Situation: Big block from a 72 GMC rebuilt many years ago, has about 150 miles on it. Runs and drives OK, but idles rough when stopped and in gear. No rough idle when stopped and in park or neutral. Have had plugs and wire replaced, but to no avail. I'm not an engine guy....stuck valve? Bent rod?

FRENCHBLUE72 · 12-22-2005, 05:39 PM

Sounds like the carb may need to be adjusted hows the choke???

73737373 · 12-22-2005, 05:42 PM

Not sure, but that would be a preferred solution. JC

franko72 · 12-22-2005, 06:06 PM

carb. adjustment would be my next thought.be sure timing is correct.check all plugs for firing properly.check for intake or carb. gasket leaks, vac. lines also.
install a new dist. cap and button. Basic checks and tune up.

blazerparts · 12-22-2005, 06:31 PM

Depends on your definition of rough. My 396 runs smooth as silk, but in gear at idle, it bounces a little.

Rally Nova · 12-22-2005, 06:50 PM

It could possibly be a vacuum leak on the intake manifold or the carburetor somewhere. I've taken carburetor cleaner & sprayed around the intake while it's running. If the engine speeds up or bogs down, you have found the leak. Does it have a stock cam or an aftermarket?

73737373 · 12-23-2005, 10:43 AM

We got her running...smoothly. Might have had some junk in one of the idle jets. Thanks to all. JC

12-22-2005, 05:27 PM	#1
73737373 Registered User Join Date: Sep 2005 Location: Oklahoma USA Posts: 1,000	Engine Problem Opinions Situation: Big block from a 72 GMC rebuilt many years ago, has about 150 miles on it. Runs and drives OK, but idles rough when stopped and in gear. No rough idle when stopped and in park or neutral. Have had plugs and wire replaced, but to no avail. I'm not an engine guy....stuck valve? Bent rod? __________________ 1968 Custom SWB, 327/3 speed OTC 1969 CST LWB, 402/400 1970 CST LWB, 402/400 1970 Sierra Grande LWB, 350/350 1971 Cheyenne LWB, 350/350 1972 Cheyenne Super LWB, 402/400 1972 Sierra Grande LWB, 402/400 1979 Silverado LWB, 350/350 1984 Suburban 1990 454 SS 1991 Silverado, X-cab, 4.3/5 speed Getrag 2005 Silverado Crew Cab Corvettes: 75, 77, 78, 93, 96

12-22-2005, 05:39 PM	#2
FRENCHBLUE72 PROJECT 7DEUCE Join Date: Dec 2002 Location: GRANTS PASS OR Posts: 21,606	Re: Engine Problem Opinions Sounds like the carb may need to be adjusted hows the choke??? __________________ GO BIG GREEN GO DUCKS MEMBER #6377 72 k-5 daily driver 6'' lift 35'' 350-350-205 slowly getting rust free. Project "7DEUCE" check out my build http://67-72chevytrucks.com/vboard/s...d.php?t=267665 Tim Powell..R.I.P EastSideLowlife..... R.I.P..

12-22-2005, 05:42 PM	#3
73737373 Registered User Join Date: Sep 2005 Location: Oklahoma USA Posts: 1,000	Re: Engine Problem Opinions Not sure, but that would be a preferred solution. JC __________________ 1968 Custom SWB, 327/3 speed OTC 1969 CST LWB, 402/400 1970 CST LWB, 402/400 1970 Sierra Grande LWB, 350/350 1971 Cheyenne LWB, 350/350 1972 Cheyenne Super LWB, 402/400 1972 Sierra Grande LWB, 402/400 1979 Silverado LWB, 350/350 1984 Suburban 1990 454 SS 1991 Silverado, X-cab, 4.3/5 speed Getrag 2005 Silverado Crew Cab Corvettes: 75, 77, 78, 93, 96

12-22-2005, 06:06 PM	#4
franko72 Franko72 Join Date: May 2004 Location: Cincinnati,Ohio Posts: 471	Re: Engine Problem Opinions carb. adjustment would be my next thought.be sure timing is correct.check all plugs for firing properly.check for intake or carb. gasket leaks, vac. lines also. install a new dist. cap and button. Basic checks and tune up. __________________ 1972 C20 cheyenne Super 402 BB/400 turbo LWB A/C Tilt, Cruise Control, Saddle tanks, Tach My Home Page Better to burn out than it is to rust

12-22-2005, 06:31 PM	#5
blazerparts No,I DON'T have Tourett's Join Date: Mar 2005 Location: Reno, NV Posts: 556	Re: Engine Problem Opinions Depends on your definition of rough. My 396 runs smooth as silk, but in gear at idle, it bounces a little. __________________ '72 K5 CST 350/350 Daily Driver '69 GMC3500 Camper Special CST Flatbed 396/400 Upgraded to show truck '69 GMC 2500 L6292, 3spd beater

12-22-2005, 06:50 PM	#6
Rally Nova Registered User Join Date: May 2005 Location: Brazoria, Texas Posts: 60	Re: Engine Problem Opinions It could possibly be a vacuum leak on the intake manifold or the carburetor somewhere. I've taken carburetor cleaner & sprayed around the intake while it's running. If the engine speeds up or bogs down, you have found the leak. Does it have a stock cam or an aftermarket? __________________ 1969 GMC C-1500 1972 Rally Nova 1988 Monte Carlo SS 2004 GMC 2500 Crew Cab

12-23-2005, 10:43 AM	#7
73737373 Registered User Join Date: Sep 2005 Location: Oklahoma USA Posts: 1,000	Re: Engine Problem Opinions We got her running...smoothly. Might have had some junk in one of the idle jets. Thanks to all. JC __________________ 1968 Custom SWB, 327/3 speed OTC 1969 CST LWB, 402/400 1970 CST LWB, 402/400 1970 Sierra Grande LWB, 350/350 1971 Cheyenne LWB, 350/350 1972 Cheyenne Super LWB, 402/400 1972 Sierra Grande LWB, 402/400 1979 Silverado LWB, 350/350 1984 Suburban 1990 454 SS 1991 Silverado, X-cab, 4.3/5 speed Getrag 2005 Silverado Crew Cab Corvettes: 75, 77, 78, 93, 96



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