help with compression test results

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Oct 7, 2005 | 02:38 AM

cheetha94607

Thread Starter

New User

Joined: Jan 2005

Posts: 21

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help with compression test results

ok i have a 302 and recently did a compression test
the results are:

#1-135
#2-120
#3-45
#4-130
#5-120
#6-120
#7-120
#8-120

with number 3 i have place oil inside of the cylinder and it
didnt have no affect. dont know where to go from here can anyone offer some help.if so thanks alot.

Oct 7, 2005 | 02:48 AM

ford390gashog

Fleet Owner

Joined: Jan 2004

Posts: 26,007

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From: Brentwood,CA

were all the plugs out when this was done? i would lean towards a bad valve or bad piston.

Oct 7, 2005 | 03:10 AM

aurgathor

Cargo Master

Joined: Aug 2004

Posts: 2,899

Likes: 2

From: Lynnwood, WA

I can think of either:
a) bad valves
b) blown head gasket
c) blown piston

You still got seven fair cylinders, so assuming you only have a problem with the valves, you may be able to use it for quite a while. I'd check for a blown head gasket first since that's fairly cheap to replace and diagnose. A blown piston can let gasoline get into the oil and thin it, and in that case you really don't want to drive it. In any case, sell it (

) or start saving for a rebuild if it's not the head gasket.

Oct 7, 2005 | 03:57 AM

adamk1974

Senior User

Joined: Nov 2002

Posts: 146

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From: Kelso,WA

Hopefully you have a sticky vavle. A quick cheap thing to try that is also safe is to flush your motor. Motor flush can be purchased at any auto parts store. Try it then recheck that cylinder. I always say try the least expensive things first even though it may be unlikely it's worth a shot. I knew somone who had a similiar problem but he missed a gear and sucked a vavle big $. Hopefully not the case with you. Good luck!

Oct 7, 2005 | 07:53 AM

MichSandSquid

Senior User

Joined: Oct 2005

Posts: 140

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I have a 96 with the 302 in it. I bought it used from a co-worker and it was running kind of rough. We didn't do the compression check because i bought it for a snow plow truck with my boys. When they tore the engine down, one of the pistons had a burn hole thru the top side. I hope this isn't your problem too.

Oct 7, 2005 | 11:03 AM

460srule

Junior User

Joined: Sep 2005

Posts: 95

Likes: 0

compression check

One more quick test is to hold a piece of tissue over the exhaust while the engine is running.If it tries to suck the tissue into the pipe then you have a leaking exhaust valve.The tissue is sucked in only as the bad cylinder is being filled.