I had the heads redone on my '91 L03 at 90,000mi., oil pressure showed great. shortly after (500-1000 mi.) the ESC went bad and I drove for several weeks with engine running hot and ignition rattle before I fixed it. 4-5 thousand miles later I started getting a fouled plug in the #4 cylinder. I was thinking a valve might have gotten burned from earlier, or the engine has just had enough (95000). Tonight I ran a compression test on #4 cylinder. read 135psi., squirted appx. 1/4 oz of 30w oil in plug hole, then read 155psi.

Did I use to much oil? Is it a safe bet the rings are gone? Has any one replaced the rings on one cylinder with engine in car? Yes it would be nice to drop a 350 in, but with four kids and a big mortgage this is not an option.

Thanks,

Mark

 

20 psi increase in compresion with oil in the hole isn't much. 135 isn't that bad. what's the other holes compression? as for rebuilding just one hole, i ithnk i'd save myself a lot of time and effort and just buy a new plug when it fouls.

 

Thanks,

Its also using a lot of oil, appx. 1qt per 500-600 mi., if thats helps with anything. smoking on acceleration.

Also can I go two heat ranges up on the plug? or just one?

Thanks again,

Mark

 

i'd go 2 steps in heat range.

 

The rest of the cylinders read in the 145 area. if the bad cly. reads 135 before the oil and 155 after is it the rings or valves?

 

rings... a 10psi drop is not horrid, butnot goodeither. i'm assuming those are done with the engine cold? i would just replace the fouling plug...

Anyways, rings will cause smoke during accel and puff hard when you let off from wot... usually..

if you let it detonate there could have have been some damage done to the piston or ring...

 

you don't have a problem. if the readings are within 10% of each other you're good.

 

thats the rule of thumb here...