IcemanG17

Test engine is a 1979 4.5L 16V USA model with approximately 175k miles...it sat without running for about 2 years. I was told it ran fine when it was removed.

tested on a COLD engine, well probably around 90F since it was hot in the shop...we tested the engine in firing order, here are the results

1: 5% 5: 5%
2: 6% 6: 7%
3: 9% 7: 9%
4: 8% 8: 6%

Since the variance between cylinders is at most 4%, I think thats pretty good and none showed significant leakage... 3-7 showed the most leak down, but also were the 2-3rd cylinder we tested?

I read some articles online that say 3% leakdown is about the lowest you can expect...& up to 20% is fine for street engines....what are your thoughts? Still I'm impressed for a 30 year old motor...but the bores I could see-feel from underneath were VERY smooth....

Mike B

IMHO, for cold numbers, those are very acceptable. Your homework is the same as I've read,
You may have other issues with a motor that hasn't run in two years but I like your compression numbers.

Lizard928

20% is too high imo.

Your numbers are very acceptable.

IcemanG17

Great.....I was quite surprised!!! I would imagine the numbers would improve a bit once warm too...since I've seen compression jump 20+psi cold to hot...

docmirror

Run it. did you put oil in the jugs before the test? anything like that on a cold engine is perfect. Change fluids and go drive.

IcemanG17

no.....waiting on a new oil pan gasket.....

Stylemobile

Lots of things that are easy to do while it is out and @#$%^&* when it is installed.
You know what they are......