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91chevyss 03-04-2013 08:40 PM

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

bjautos7 03-04-2013 09:54 PM

Quote:

Originally Posted by 91chevyss (Post 1653585)
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.

91chevyss 03-04-2013 10:05 PM

okay ill try that tomorrow. could a cracked head cause this or blown gasket?

bjautos7 03-04-2013 10:16 PM

Quote:

Originally Posted by 91chevyss (Post 1653609)
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.

T-bucket23 03-05-2013 03:19 PM

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

Mr. P-Body 03-05-2013 05:31 PM

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

GMC boogie 03-05-2013 05:43 PM

Good point P-body! Possible valves too tight on that side.

91chevyss 03-05-2013 06:52 PM

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? http://i1321.photobucket.com/albums/...psc31b1d57.jpg http://i1321.photobucket.com/albums/...ps35ab9b1e.jpg

T-bucket23 03-05-2013 07:00 PM

No question that is your issue. Improper torque is my guess

crownver 03-05-2013 07:04 PM

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?

91chevyss 03-05-2013 07:28 PM

Im hoping improper torque but head looked flat took a straight edge to it but havent checked block.

91chevyss 03-05-2013 07:30 PM

whats a good gasket to use?

PatM 03-05-2013 10:52 PM

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

91chevyss 03-05-2013 11:14 PM

yes it has more than once lol

PatM 03-05-2013 11:26 PM

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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