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Answer to no compression and blowby

Posted: Wed Jan 12, 2005 8:56 am
by ytt105
To recap. 1987 RR. 3.9 short block, 3.5 heads. On gas. Purchased 3 weeks ago. No compression on one cylinder and blowby gas very oily.

I removed the offending head last night, will take the other one off tonight.

I found about an inch of tin head gasket laying on the pushrods, under the valley gasket.

My assumption is that this massive leak caused the no compression reading as all the compression was going into the vally area and forcing oil out the breather.

Sound plausable.

This motor was rebuilt in 1999 by Grahem Cooper so I assume everything was done correctly. But, the amount of crud over all the parts shows what can happen when you have a compression leak into the oil and probably not too many oil changes done over the years.

It also shows how forgiving these engines are.

OK, I'm going to clean everything up, skim the heads and bolt her back together.

Anything I should know?

Posted: Sat Jan 15, 2005 7:30 am
by Bush65
Does the 3.9 have torque to yield head bolts? If yes, you should replace the head bolts.

Posted: Sat Jan 15, 2005 5:35 pm
by J Top
The shim gaskets are the highest compression but are the least forgiving,
If it has been blown for a while it would be sensible to check the block deck for true.
J Top