71 GMC with 454 Burning Oil !! Can you help ??? Please ! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jeremy_phd · 01-16-2004, 04:55 PM

I have a 71 GMC 4x4 that I just put a 454 in. It later just started smoking and we thought we figured out that it was just one cylinder. It only smokes out of the passenger side tailpipe and it only smokes when you are ideling. If you hold the engine at say 2500 RPM at a dead stop it doesn't smoke but as soon as you let your foot off the gas and the engine returns to idle speed it comes out again. And when you drive it down the strett it doesn't smoke either. The only oil it uses is at startup sometimes and at idle all the time. We took the pass side valve cover off and found that one of the cylinders had a broken valve seal and we replaced it and all the other seals on all other cylinders were fine and unharmed but aftre this it still does the same thing and smokes only at idle and only out of the pass side. We thought it might a vacuum problem and that it might be suckin oil out of the intake valley or something but I'm lost and I need help please. Anybody have any sugesstions or help I can use ?????

Bram · 01-16-2004, 05:05 PM

Welcome aboard.
What is you're oil pressure gauge reading at idle?

jeremy_phd · 01-16-2004, 05:08 PM

My oil pressure is pretty high. The lowest it ever gets when the motor is thoroughly warmed up it still is past the halfway mark I'd say between half way and 3/4 of the way. When I'm driving it goes off the scale it's so high on the stock gauge. I don't know the exact pounds of pressure though it doesn't have that on those old gauges.

Bram · 01-16-2004, 05:13 PM

What color of smoke is it blowing?

Black smoke on full throttle acceleration.
Main jet is too rich.

Grey smoke on full throttle acceleration.
Bad valve guide seals, or bad rings. The engine was mis-assembled.

Grey smoke when you start the engine, particularly when cold.
Bad valve guide seals. The engine was mis-assembled.

**MJN** · 01-16-2004, 06:10 PM

stock oil pressure gauges only go up to 60 psi

jeremy_phd · 01-16-2004, 06:20 PM

It blows grey smoke. However, it does not blow any smoke at any acceleration point, half throttle, full throttle, 1/4 throttle. The only time it smokes is at idle speed and it's only out of the pass side pipe. I took off the valve cover and all of the springs on that side and only one valve guide seal looked bad to me cause it was broken, all the others looked fine so I replaced the one and it still smoked. But only at idle still out of the pass side pipe.

cdowns · 01-16-2004, 07:32 PM

do you have baffeled valve covers? if not get some

jeremy_phd · 01-16-2004, 07:38 PM

Yes I have baffled valve covers

jhow66 · 01-16-2004, 11:28 PM

New engine? how many miles?

jef5150 · 01-16-2004, 11:48 PM

im gonna bet youve got bad valve guides!!!! (it smokes at initial start up,and at low rpm only)!!! my .02. jeff

Blazer1970 · 01-17-2004, 09:57 AM

Since you already checked the valve seals, it is very likely that it is sucking oil from the valley through a bad intake gasket. I would replace the intake gaskets (since it is easy to do), and go from there.

jeremy_phd · 01-23-2004, 03:37 AM

Blazer 1970,
Thanks for the heads up on the intake gasket. We checked it and it did have a vacuum leak. I pulled out the breather and put a piece of paper over the hole and it quit smoking almost all together like barely. Then when you took it off and put the breather back in it started smoking again alot. So we pulled off the intake and it had oil in all the intake runners on the passenger side the only side it smokes on. Also, the only time it smokes is after the motor gets warmed up and only at idle. It doesn't smoke when I drive it, upshift, downshift, decellerate, accelerate, nothing. Only when the motor is warm and at idle at dead stop and only out of the pass side pipe. My brother thinks it is the #6 piston because that is the one that had the bad valve seal that we replaced. He thinks the oil ring might be messed up. I'm not so sure though we checked the compression and it was very high and had the exact same on all cylinders at 150 lbs. I figure if the oil ring was bad on that one cylinder it would have lower compression than the others if the ring was messed up. I would like it if you could give me a few more hints like maybe should I replace the Valve seals on that whole side and see if that helps at all since it's cheap to do ? Or maybe replace the valve guides or something on the pass side cylinder head ? PLEASE, ANY HELP WOULD BE GREAT !!! I'M LOST NOW I THOUGHT THE NEW INTAKE GASKET WAS THE END OF THE ROAD !!!

01-16-2004, 04:55 PM	#1
jeremy_phd Registered User Join Date: Jan 2004 Location: Tempe Posts: 5	71 GMC with 454 Burning Oil !! Can you help ??? Please ! I have a 71 GMC 4x4 that I just put a 454 in. It later just started smoking and we thought we figured out that it was just one cylinder. It only smokes out of the passenger side tailpipe and it only smokes when you are ideling. If you hold the engine at say 2500 RPM at a dead stop it doesn't smoke but as soon as you let your foot off the gas and the engine returns to idle speed it comes out again. And when you drive it down the strett it doesn't smoke either. The only oil it uses is at startup sometimes and at idle all the time. We took the pass side valve cover off and found that one of the cylinders had a broken valve seal and we replaced it and all the other seals on all other cylinders were fine and unharmed but aftre this it still does the same thing and smokes only at idle and only out of the pass side. We thought it might a vacuum problem and that it might be suckin oil out of the intake valley or something but I'm lost and I need help please. Anybody have any sugesstions or help I can use ?????

01-16-2004, 05:05 PM	#2
Bram Broke Join Date: Aug 2001 Location: West Plains,MO Posts: 385	Welcome aboard. What is you're oil pressure gauge reading at idle? __________________ 72CheyenneSuper1ton4x4BigBlock

01-16-2004, 05:08 PM	#3
jeremy_phd Registered User Join Date: Jan 2004 Location: Tempe Posts: 5	reply My oil pressure is pretty high. The lowest it ever gets when the motor is thoroughly warmed up it still is past the halfway mark I'd say between half way and 3/4 of the way. When I'm driving it goes off the scale it's so high on the stock gauge. I don't know the exact pounds of pressure though it doesn't have that on those old gauges.

01-16-2004, 05:13 PM	#4
Bram Broke Join Date: Aug 2001 Location: West Plains,MO Posts: 385	What color of smoke is it blowing? Black smoke on full throttle acceleration. Main jet is too rich. Grey smoke on full throttle acceleration. Bad valve guide seals, or bad rings. The engine was mis-assembled. Grey smoke when you start the engine, particularly when cold. Bad valve guide seals. The engine was mis-assembled. __________________ 72CheyenneSuper1ton4x4BigBlock

01-16-2004, 06:10 PM	#5
MJN Registered User Join Date: Feb 2000 Location: Maquoketa, Ia/ Orr, Mn Posts: 2,988	stock oil pressure gauges only go up to 60 psi __________________ '51 South Bend Model "9A" '56 Chevy 3600 NAPCO '74 Chevy Cheyenne Super K20-restored on 37's '72 GMC Sierra Custom K2500- in progress '08 GMC Envoy Denali '12 GMC Sierra 2500HD Denali '17 GMC Yukon XL VCCA member #58596 http://www.nohrco.com

01-16-2004, 06:20 PM	#6
jeremy_phd Registered User Join Date: Jan 2004 Location: Tempe Posts: 5	It blows grey smoke. However, it does not blow any smoke at any acceleration point, half throttle, full throttle, 1/4 throttle. The only time it smokes is at idle speed and it's only out of the pass side pipe. I took off the valve cover and all of the springs on that side and only one valve guide seal looked bad to me cause it was broken, all the others looked fine so I replaced the one and it still smoked. But only at idle still out of the pass side pipe.

01-16-2004, 07:32 PM	#7
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	do you have baffeled valve covers? if not get some __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

01-16-2004, 07:38 PM	#8
jeremy_phd Registered User Join Date: Jan 2004 Location: Tempe Posts: 5	Yes I have baffled valve covers

01-16-2004, 11:28 PM	#9
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	New engine? how many miles? __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

01-16-2004, 11:48 PM	#10
jef5150 Inline 69 Join Date: Apr 2003 Location: valleysprings,california Posts: 1,018	im gonna bet youve got bad valve guides!!!! (it smokes at initial start up,and at low rpm only)!!! my .02. jeff

01-17-2004, 09:57 AM	#11
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,510	Since you already checked the valve seals, it is very likely that it is sucking oil from the valley through a bad intake gasket. I would replace the intake gaskets (since it is easy to do), and go from there. __________________ Tim

01-23-2004, 03:37 AM	#12
jeremy_phd Registered User Join Date: Jan 2004 Location: Tempe Posts: 5	Blazer 1970, Thanks for the heads up on the intake gasket. We checked it and it did have a vacuum leak. I pulled out the breather and put a piece of paper over the hole and it quit smoking almost all together like barely. Then when you took it off and put the breather back in it started smoking again alot. So we pulled off the intake and it had oil in all the intake runners on the passenger side the only side it smokes on. Also, the only time it smokes is after the motor gets warmed up and only at idle. It doesn't smoke when I drive it, upshift, downshift, decellerate, accelerate, nothing. Only when the motor is warm and at idle at dead stop and only out of the pass side pipe. My brother thinks it is the #6 piston because that is the one that had the bad valve seal that we replaced. He thinks the oil ring might be messed up. I'm not so sure though we checked the compression and it was very high and had the exact same on all cylinders at 150 lbs. I figure if the oil ring was bad on that one cylinder it would have lower compression than the others if the ring was messed up. I would like it if you could give me a few more hints like maybe should I replace the Valve seals on that whole side and see if that helps at all since it's cheap to do ? Or maybe replace the valve guides or something on the pass side cylinder head ? PLEASE, ANY HELP WOULD BE GREAT !!! I'M LOST NOW I THOUGHT THE NEW INTAKE GASKET WAS THE END OF THE ROAD !!!



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