Compression/blowby question
Thread Starter
Cruising
Joined: Jan 2004
Posts: 10
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From: Kansas City Mo
Compression/blowby question
Im installing the GM hot cam kit on my 95 LT1. Had the heads redone and am in the process of putting it all back together. Oil pans off drivers side head is back on without rockers. Installed new time chain and gears and while rotating to TDC I can hear air escaping from the, I assume bottom of the cylinders as the crank rotates aroud. Car has 60K on it cylinder walls look fine there was some carbon build up on the tops of them. New rings?
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Re: Compression/blowby question (THEVETTEINMYGARAGE)
Well there is always some blow by, even with a complete rebuild.
Did you run a compression check before breakdown? Was it burning oil before the breakdwon?
Did you run a compression check before breakdown? Was it burning oil before the breakdwon?
Safety Car
Joined: Feb 1999
Posts: 3,504
Likes: 4
From: Mexico Beach FL
Re: Compression/blowby question (THEVETTEINMYGARAGE)
If you have concerns, the best thing to do is a leak-down test of the cylinders.
The percentage of leakage will tell you if there are any problems. After break-in, anything above about 10% is considered too high for a racing engine, but I think 15% is considered the line for a street car.
Since the rings are not perfect seals, my guess is what you are hearing is normal.
Tom Piper
The percentage of leakage will tell you if there are any problems. After break-in, anything above about 10% is considered too high for a racing engine, but I think 15% is considered the line for a street car.
Since the rings are not perfect seals, my guess is what you are hearing is normal.
Tom Piper
Thread Starter
Cruising
Joined: Jan 2004
Posts: 10
Likes: 0
From: Kansas City Mo
Re: Compression/blowby question (65Z01)
It wasnt burning oil brfore I torn it down and I didnt do a compression test. I thought after hearing the air escaping I might need new rings
