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Old 03-04-2013, 09:40 PM
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compression test numbers on 350

did a compression test on my chevy 350
cyl# pressure
1 155
3 152
5 143
7 145
2 50
4 42
6 35
8 49
What could be wrong. I went back and check driver side to see if I messed on the pass. side and still got 155 on #1. Engine is a 350 bored .060 with stock tbi heads, edelbrock torker intake, edelbrock 750, edelbrock shorty headers, .488/.488 lift cam, and true dual flowmasters. Thanks

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Old 03-04-2013, 10:54 PM
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Quote:
Originally Posted by 91chevyss View Post
did a compression test on my chevy 350
cyl# pressure
1 155
3 152
5 143
7 145
2 50
4 42
6 35
8 49
What could be wrong. I went back and check driver side to see if I messed on the pass. side and still got 155 on #1. Engine is a 350 bored .060 with stock tbi heads, edelbrock torker intake, edelbrock 750, edelbrock shorty headers, .488/.488 lift cam, and true dual flowmasters. Thanks
sqirt some oil in 2 4 6 8 cylinders , re-do comperssion if it gets better its the rings , if still the same then it will be vavles.
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Old 03-04-2013, 11:05 PM
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okay ill try that tomorrow. could a cracked head cause this or blown gasket?
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Old 03-04-2013, 11:16 PM
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okay ill try that tomorrow. could a cracked head cause this or blown gasket?
if the head was cracked or a blown gasket there will be signs of water in the oil and making the oil milky white.
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Old 03-05-2013, 04:19 PM
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Even side could have been torqued wrong. I would also check to see if the exhaust is somehow plugged on that side. It would be unusual for the head gasket to blow on all 4 cylinders unless it wasnt torqued properly. It would also be unusual for the rings to wear just on that side.
I have also seen loose spark plugs cause valves to burn. Were they all tight. I was thinking maybe someone changed them and never tightened that side.
Also more history would be helpful. Was this a new build, were you driving it and it started running bad. Poor valve adjustment could also be causing your issue
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Old 03-05-2013, 06:31 PM
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If the gasket were "blown" that badly in all four cylinders, surely there would be a "hissing" noise very obvious.

I suspect the rockers are too tight on that side. You can put an air fitting on the end of your compression tester hose and plug air into the cylinder. Listen to where it comes out (carb or throttle body, exhaust or up through the pushrod area). If it's the cabr/TB, loosen the intake rocker and see if it lessens. Same with exhaust. If you hear it plainly but loosening doesn't "help", pull the head....

WIth numbers that "low", I would believe if rings, the wrong size rings were installed. That WILL "come up" significantly when you squirt oil in it (use heavier engine oil, "liberally").

Numbers on the other side are pretty normal for a "hot" cam. The lift number is nice to know, but the duration tells us a lot more about the cam. The "@.050" numbers are the best to use for general comparison. LSA (Lobe Separation Angle) is also important.

Jim
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Old 03-05-2013, 06:43 PM
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Good point P-body! Possible valves too tight on that side.
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Old 03-05-2013, 07:52 PM
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Putting oil in the cylinders didnt help and I loosened the rockers a little and that didnt help either so I pulled the head and didnt see any cracks in the head or piston or valves and I pulled one valve out to see if it was seating properely, it was ok but not great. The only thing I found was a break in the head gasket between 2-4 and 6-8 but not 4-6 so Im guessing this is my problem. what do yall think?
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Old 03-05-2013, 08:00 PM
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No question that is your issue. Improper torque is my guess
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Old 03-05-2013, 08:04 PM
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That's definitely your problem. Now you have to find out why it blew like that. Incorrectly torqued head bolts, warped head, block deck not flat?
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Old 03-05-2013, 08:28 PM
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Im hoping improper torque but head looked flat took a straight edge to it but havent checked block.
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Old 03-05-2013, 08:30 PM
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whats a good gasket to use?
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Old 03-05-2013, 11:52 PM
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I once severly overheated an engine (a 350) and both head gaskets blew in two places as your one gasket has. Was the engine running hot?

Pat
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Old 03-06-2013, 12:14 AM
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yes it has more than once lol
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Old 03-06-2013, 12:26 AM
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You might want to look for a cause of that overheating. Perhaps some sort of debris in yhe passenger side head? I don't know enough about the cooling system to "guess" what might be happening. But if you have it torn down, and it overheats again, you might blow out another gasket. You might want to investigate around a bit while it's opened up.

Pat
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