oil fouled spark plugs

[ranch67]

what is the acceptable compression for the cylinders?

i'm going to do a compression test first, then figure if i need to have the head rebuilt/refreshed with new valve seals.

thanks

 

[wsa111]

15-20# at the most.
Once you run your compression test & you have a weak cylinder put 100# of air pressure & see if the leak is valves or rings.
Air from crankcase-rings-piston, air from exhaust-exhaust valve & air out the intake-intake valve. Wish you the best of luck.

 

[Gene Fiore]

15-20# at the most.

Bill...you mean 15 to 20psi differential between cylinders right? The average cylinder would be anywhere from 100 to 120 or so depending on compression ratio I would think. My cylinders are at 155 to 160 but my compression is over 10 to 1.

 

[wsa111]

Run your compression test with carburetor at full throttle, engine warm & all spark plugs removed.
Lets see what you have. Bill

 

[rbohm]

8) gene and bill are both right. you should have about 120psi per cylinder, and the difference should be less than 20psi from the highest to the lowest. as bill said, run the compression check and give us the numbers.

and dont forget that it isnt just worn rings that can lead to oil fouling, bad valve guides and valve guide seals also contribute to the issue.

 

[fmartin_gila]

Bill was referring to a leakdown test to determine where the compression was going after a compression test has determined there is low compression in a cylinder.

Fred

 

[ranch67]

well i replaced spark plugs, wires, cap and rotor and the fouling seemed to disappear. which is good, but the issue of low stumbling rpm persists.
i started checking for possible vacuum leaks. pcv etc. i pulled the outlet tube for the transmission modulator at the carb base and the rpms suddenly went up.?

i pulled the carb and replaced the base gasket it seemed to help but stumbling still persists. its been about 2 years since last rebuild.

any input,

thanks!

 

[ranch67]

carb is a carter YF.

 

[rbohm]

well i replaced spark plugs, wires, cap and rotor and the fouling seemed to disappear. which is good, but the issue of low stumbling rpm persists.
i started checking for possible vacuum leaks. pcv etc. i pulled the outlet tube for the transmission modulator at the carb base and the rpms suddenly went up.?

i pulled the carb and replaced the base gasket it seemed to help but stumbling still persists. its been about 2 years since last rebuild.

any input,

thanks!

8) sounds like you are on the trail. bad modulator perhaps? they are cheap enough, just go ahead and replace it.

 

[ranch67]

how to test for a bad modulator?

seems kinda lame for me to ask. but are they easy to install?

is this related to my removing the tube/vac hose from carb base that would go to the modulator?

thanks.

 

[rbohm]

8) the modulator is easy to replace. as to testing it, like i say they are cheap so just replace it.