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Old March 22nd, 2014, 02:45 AM
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GMCDAC GMCDAC is offline
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Join Date: Jan 2013
Location: Green Valley, east of Rapid City,SD
Truck: I have 4 GMCs, none with a V-6 - YET! Have had 2 in the family.
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Default Re: Blown head gasket vs. cracked block

Quote:
Originally Posted by Vern View Post
What you say pretty much covers what I heard. The idea was that you shouldn't fix "the top (head)" without fixing "the bottom (piston rings, bearings, crankshaft)". The guy I talked to was a racer. I just have to think about the trade off of putting money into an I6 vs the cost of buying and possibly rebuilding a V6. Might be worth the time to try the gasket fix and see what happens.

"driveshaft" was a typo for "crank shaft". The thought being that you should replace the bearings on the pistons, but not on an old crankshaft.
Yeah it is tough to make decisions on guesses, but that's all trouble shooting is anyway with experience mixed in. There is a cylinder leak down test that can be done also but that will still not tell the difference between cylinder wall or head cracks or a head gasket problem.

A used crank doesn't always mean it has to be turned either. In 1986 I built a 350 with a used, un-machined crank, new standard size bearings on mains and rods. I did check clearances and they were on the loose side of acceptable. Long story short, that engine is still running in my '72 GMC. It is getting tired again but it's only been 28 years!

DAC
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Doug Crawford
Rapid City, SD

1970 GMC K5 Jimmy Mom drove 30 years
1972 GMC C2500 owned since 1979
1955 GMC 100 driver-project
2006 GMC Yukon Denali---wife's truck

Hope to have a '60 GMC Suburban again someday
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