Overheating Intake Manifold - Help !! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

68dontneedanewone · 03-28-2007, 09:47 PM

Here's the deal......... 72 V8, either 350 or 400 small block ('new' truck, haven't checked casting numbers).

Son took a rock in the radiator and severely overheated it.
Got it home and had water droplets out of both (duals) tailpipes, but with 150lbs +/- compression in all cylinders, so figured it blew the intake manifold gasket.

Replaced the manifold gasket and sandblasted/painted the manifold while I had it off. Should have taped off all the openings, but didn't. Used 100lb air nozzle to blow out all passages afterward.

Now the truck is 1) hard to start when hot, 2) diesels after shutting off, 3) expels gas/air mixture or other smoke-like substance through carb/air filter housing, and 4) manifold has turned black over both sides of center water channels (between #2-4 and #3-5 intake channels).
Timing and dwell are spot on the specs.

Any ideas on what I've done, or what might be the problem/fix?

Thanks for any ideas,
Earle

GREASEMONKEY72 · 03-28-2007, 09:52 PM

check the timing it could be the deiseling problem and also the carb could need a rebuild and also sounds like its got to much fuel going into the carb, that would be the white smoke coming out of the carb and i dont know about it turning black on the sides but it could be that it wasnt cleaned and preped good enough before you painted it and now the paints coming off, i hope any of that helped and goodluck

Sammy · 03-28-2007, 10:12 PM

If you were puting on aftermarket intake, with older engines you have to cut the intake gasket or you will block a water passage. Thats a warning with the gasket set. ???

68dontneedanewone · 03-28-2007, 11:42 PM

No, it's the original manifold. I'm sure there aren't any passages blocked by the gasket - double checked one last time before setting the manifold back in place.

CrashEd · 03-29-2007, 12:23 AM

If it wasn't a high heat paint then it would burn on the air passages that heats the carb up. The passage between 3-5 and 2-4 is exhusat.
Ed

cameeks · 03-29-2007, 03:45 AM

Quote:

Originally Posted by CrashEd

If it wasn't a high heat paint then it would burn on the air passages that heats the carb up. The passage between 3-5 and 2-4 is exhusat.
Ed

Also try to do the compression test with the radiator cap off could have blown the head gasket and the closed coolant system could be keeping the pressure up.

The last Idea was me thinking too much. Might not affect anything.

03-28-2007, 09:47 PM	#1
68dontneedanewone Registered User Join Date: Nov 2001 Location: Covington, GA USA Posts: 67	Overheating Intake Manifold - Help !! Here's the deal......... 72 V8, either 350 or 400 small block ('new' truck, haven't checked casting numbers). Son took a rock in the radiator and severely overheated it. Got it home and had water droplets out of both (duals) tailpipes, but with 150lbs +/- compression in all cylinders, so figured it blew the intake manifold gasket. Replaced the manifold gasket and sandblasted/painted the manifold while I had it off. Should have taped off all the openings, but didn't. Used 100lb air nozzle to blow out all passages afterward. Now the truck is 1) hard to start when hot, 2) diesels after shutting off, 3) expels gas/air mixture or other smoke-like substance through carb/air filter housing, and 4) manifold has turned black over both sides of center water channels (between #2-4 and #3-5 intake channels). Timing and dwell are spot on the specs. Any ideas on what I've done, or what might be the problem/fix? Thanks for any ideas, Earle __________________ Earle - Covington GA 68 Chev SS/SWB: 350-Edelbrock intake/carb, 'built'700R4(kevlar bands etc), front disc, A/C 2002 Silverado CrewCab LongBed 8.1 Vortec Allison Tranny Last edited by 68dontneedanewone; 03-28-2007 at 09:49 PM. Reason: Additional info.

03-28-2007, 11:42 PM	#4
68dontneedanewone Registered User Join Date: Nov 2001 Location: Covington, GA USA Posts: 67	Re: Overheating Intake Manifold - Help !! No, it's the original manifold. I'm sure there aren't any passages blocked by the gasket - double checked one last time before setting the manifold back in place. __________________ Earle - Covington GA 68 Chev SS/SWB: 350-Edelbrock intake/carb, 'built'700R4(kevlar bands etc), front disc, A/C 2002 Silverado CrewCab LongBed 8.1 Vortec Allison Tranny

03-29-2007, 12:23 AM	#5
CrashEd 72 chevy Join Date: Jan 2007 Location: Central Il Posts: 725	Re: Overheating Intake Manifold - Help !! If it wasn't a high heat paint then it would burn on the air passages that heats the carb up. The passage between 3-5 and 2-4 is exhusat. Ed

03-28-2007, 09:52 PM	#2
GREASEMONKEY72 Registered User Join Date: Aug 2006 Location: Bakersfield,CA Posts: 7,893	Re: Overheating Intake Manifold - Help !! check the timing it could be the deiseling problem and also the carb could need a rebuild and also sounds like its got to much fuel going into the carb, that would be the white smoke coming out of the carb and i dont know about it turning black on the sides but it could be that it wasnt cleaned and preped good enough before you painted it and now the paints coming off, i hope any of that helped and goodluck __________________ -steven Alte Seele S.S. "Allison" '72 C/10 LWB 350SB/TH350 - DD PITBULL IS NOT A CRIME

03-28-2007, 10:12 PM	#3
Sammy Registered User Join Date: Apr 2000 Location: Bonne Terre, Mo Posts: 3,005	Re: Overheating Intake Manifold - Help !! If you were puting on aftermarket intake, with older engines you have to cut the intake gasket or you will block a water passage. Thats a warning with the gasket set. ??? __________________ '69 Chevy Long Fleet & '71 GMC Short Step & Project "ODD BALL" "You can wash a pig, soak it in most expensive perfume. In the end it is still just a pig." ODD BALL build thread http://67-72chevytrucks.com/vboard/s...d.php?t=478629"



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