engine compression

[Guest]

I cam acrossed a problem yesterday with the compression in my 350 7 cylinders had a compression reading of 120 and the number 4 cylinder read 30 I am pretty new to the head game but i am thinking it is the exhaust valve. can someone give me some input on how to check for problem being the problem is isolated to one cylinder<P>thanks <BR>john

[Guest]

my one thought, have you tried the low-weight oil test? Drop a few drops down the plug hole and retest. Getting a higher value is an easier (i think) repair then not.<P>2 shillings from a webbie.<BR>

[GSMAG]

Wow, 30 is REALLY low! If you didn't read the thread on pouring water through your carb while the engine is running, please do (I think is was titled "engine decoking".) IF you have a carbon buildup problem, this will help. If it's mechanical, no chance. Squirt some oil in the hole and recheck compression. If it comes up, a lot, it's rings, if not, valves or head gasket.

[Guest]

you can also have your mechanic do a leak down test. this comprises pressurising the cylinder and listening for where the leaking occurs. try the dekoking thing first though if your carefull it may help bring it up.

[Guest]

You can do all the tests you want, but if you have 30 lbs. on one of your cylinders you WILL be pulling at least the Heads.<BR>Then you can see for sure where the problem lies and go from there.