Ran compression test today

[Athrawn17]

Cylinder #1 - 90
Cylinder #2 - 98
Cylinder #3 - 110
Cylinder #4 - 100

Did this by just hitting the starter and doing one cylinder at a time. That's the way to do it right?

Looking at the manual, I'm at 900 feet above sea level. So min pressure should be 90. Just double checking these numbers with the experts on the board.

 

[asphelt]

I presume you did the test with a cold engine and did not squirt oil into the cylinders.

In any case, you should be doing cart wheels right now!

 

[David G]

You will want throttle wide open.

Those numbers look good to me, not exceptional, but nowhere
near needing work.

 

[Athrawn17]

Right, no oil or ATF in the cylinders. Just took out the plug, put in the tester, cranked starter a few times.

 

[David G]

I personally would not run a compression test unless I was willing
to work on it. I have a little OCD, so it would bug me knowing
about the issues without fixing them.

 

[Bruce (VA)]

Minimum acceptable pressure is 90 lbs w/ the lowest pressure reading w/in 75% of the highest reading. Run the engine to operating temp, turn it off, remove all 4 plugs, remove the breather hose & make sure the choke and throttle are both open. Crank it at least 5 compression strokes or until the gauge stops moving. Write down the first compression reading (that is the valves seating) then write down the reading after 5 strokes or when it stops increasing. You should have two numbers for each cylinder. Then, add a tablespoon of oil to each cylinder & repeat the process, but you only need the final reading for each cylinder. Write down the results & post back for help figuring out what it all means.
50 Tips

 

[Hobo,NC]

(quoted from post at 05:18:29 05/28/12) Cylinder #1 - 90
Cylinder #2 - 98
Cylinder #3 - 110
Cylinder #4 - 100

Did this by just hitting the starter and doing one cylinder at a time. That's the way to do it right?

Looking at the manual, I'm at 900 feet above sea level. So min pressure should be 90. Just double checking these numbers with the experts on the board.

If the engine runs good no need to go any farther... If the valve adjustment is correct You are good to go,,, a lower # on the front cylinder on a inline engine is not unusual cuzz it runs a tad cooler than the rest and normally will have more ware/carbon deposits....

If you want to play you can do a wet test then a leak down test... If the test show loss at the rings you have a dissension to make do I soak them in a good carbon buster,,, its possible things could get worst if the rings are worn the carbon is helping seal the rings and by removing it you loose the seal its rare but happens... Its a warring shot I use just in-case things go down hill and get hit with the blame of fudgen up a good running engine..

I had it happen one time on a Ford 292,,, The complaint was oil usage,,, after a good carbon cleaning it huffed and puffed oil worst,,, It went from it ran great when I brought it to ya to you fudged up my engine...

It took years for the customer to get over it then he came back and I worked on his stuff till he passed away... Why folks don't want to hear the truth I dunno so I always fire a warring shot just in case...

 

[Athrawn17]

(quoted from post at 05:37:15 05/28/12)


If the engine runs good no need to go any farther... If the valve adjustment is correct You are good to go,,, a lower # on the front cylinder on a inline engine is not unusual cuzz it runs a tad cooler than the rest and normally will have more ware/carbon deposits....

If you want to play you can do a wet test then a leak down test.

Engine runs fine. My oil pump needs a rebuild though as after 30 min or so I get very low (4-5 psi) pressure on the gauge. So I was trying to decide if anything else needed some "assistance". This was all done with the hood on, so I don't think I'll be doing a wet test yet.

Thanks for everyone's input.