Compression test..good or bad or? (1 Viewer)

[Rat Patrol]

Getting ready to pull this engine and get rid of it but wanted to know what you folks thought of these numbers.



1976 FJ55/stock. Unknown miles.


#6..... 5..... 4........ 3...... 2..... 1.....
149* 150* 135* 135* 141* 143


Number 1 cylinder is near the radiator. Test was done with a brand new tester that screws into the spark plug hole.

 

[Renoron]

Looks pretty good to me. Ratio of 135 and 150 maybe too great though.

Anybody else?

 

[Ian Rogers]

run it

 

[65swb45]

run it

x2

 

[Degnol]

Getting ready to pull this engine and get rid of it but wanted to know what you folks thought of these numbers.



1976 FJ55/stock. Unknown miles.


#6..... 5..... 4........ 3...... 2..... 1.....
149* 150* 135* 135* 141* 143


Number 1 cylinder is near the radiator. Test was done with a brand new tester that screws into the spark plug hole.

Did you perform the test with the engine warmed up? Throttle plate blocked open? I would also follow with a wet test to distinguish between valves and rings. There are many cruisers running with much lower numbers than that.


Ed

 

[IDave]

There are many cruisers running with much lower numbers than that.


Ed

Dang, my F135 sits with 114-120 on a good day. It zips along at 75mph up and down mountain passes.

Just wait until I rering it and have the valves ground!

 

[Rat Patrol]

Yep, engine was warm but would like to try again with throttle plate blocked open....Just to make sure, is the throttle plate the butterfly flap inside the throat of the carb? Also, how do you do a wet test?

 

[IDave]

Yep, engine was warm but would like to try again with throttle plate blocked open....Just to make sure, is the throttle plate the butterfly flap inside the throat of the carb? Also, how do you do a wet test?

The throttle plate is the thing that opens in the carb when you pull on the accellerator linkage or cable.

A wet test consists of testing the compression with the cylinder dry, then dribbling a teaspoon or two of engine oil into the cylinder through the spark plug hole and retesting.

If the low compression is due to ring leakage only, the compression should come up to normal as the oil temporarily seals off the rings.

If oil fixes it partly or not at all, then that implies an upper end of the cylinder leak, either valve stem seals or valves.

Be careful not to put in a lot of oil, because you can always put in enough to make the numbers look really good.

 

[Pete]

You're well within factory spec of minimum 114. I'd do nothing if I were you except drive it. Like the other guys said, the factory spec is with engine warm and throttle open. I prop a stick on my acclerator pedal to hold it open while I crank it with my remote starter.

Pete

 

[n2666s]

those numbers look good......just drive change the oil and drive it; from the pix it looks like it hasn't been in a long time;

Lou