Hello,

I am buying a built engine it has been used previously approx 2000kms.

Note the engine also has aftermarket camshafts, pistons rods ect.

Compression was 150 140 145 145 150 150

This was on a cold start, the engine was also out of the car and the engine had been sitting around a few weeks unstarted without oil, so we filled it with oil and turned it over just via the starter engine to get the compression readings.

I am a bit worried about the piston showing 140, what do you guys think?

Do you need any other info to comment?

 

bump any one had experience with this?

 

Patience brother... we are all either asleep, hung over or at church on Sunday mornings.

What is the compression ratio of the pistons in the built motor you are buying? If they are 9:1 or 8.5:1 you should be OK based on some threads I researched.

Use the advanced search feature and search "compression test".

 

you should be ok, those readings are not amazing as far as variance is concerned but it shouldnt be too bad. typically you dont want more then 5% variance which with a high compression of 150 would put the lowest one at 142.5 so its not to far off. also you dont really need to be too concerned unless they are below 130 or above 160 or larger variances so again the compression check shows it should be ok. might want to double check the compression of the pistons but alot of things will effect the compression test including cams it all has to do with static and dynamic compression ratios so its hard, if not impossible to detemine compression ratios based off the compression test. more tomarrow if you need more help and if i get off work earlyer all this damn work is killing me >.<

 

ya, That doesn't seem bad for a compression test on a cold engine.

Get a leakdown tester and check that. It's much easier on an engine pulled out of the car and it's a little more accurate than a compression check to diagnose stuff. Also, it's never good to just crank over an engine that has been sitting out of a car like that so leakdown is best.

That being said, like others stated, the numbers aren't bad. Once warmed they will probably all equal out.

 

thanks guys, i did read as long as the none of the pistons were out by 10% it should be ok. I though there may have been a few users on here that have had their engines tested and had similar readings. I am also thinking like binder said once the engine warms up i will test it again and hopefully they all equal out a little more.

 

ya, that variance isn't enough to worry about. I also don't worry too much on cold tests since the engine will be hot during use. They will probably equal out more when it's warm.

 

+1 for leakdown test

 

Probably going to be fine since the difference in minimal, and like Binder mentioned once it warms up, probably won't be too bad.