Compression check, what normal?

[Skoobie]

Finally broke down and had the local shop do a compression check on my 188K shortblock just to guage how much time I had left on the motor. All cylindars checked in at 160-165 psi. I asked him what that ment and he said it wasent really important what the #'s were, but more so that they all read the same. It showed that all my valves were ok. He also said that there is no set "good" psi as it can vary widely depending on your cam choice. I currently have an E cam in with 1.6 RR. How does my compression compare to a new motor? Am I still in the black, or should I start saving for a rebuild?

 

[1EVIL88VERT]

those are good numbers, as long as they are all within 10%. My 3000 mile shortblock only has 155psi.

 

[Daggar]

The shop manual shows a 25% difference to be acceptable. If you're within 10 then you're golden!

 

[double drop top]

The second test you need to do is a leak down test. This will give you a better read on the condition of your rings and valves then a compression test.

 

[Skoobie]

The second test you need to do is a leak down test. This will give you a better read on the condition of your rings and valves then a compression test.

The leakdown was an hours labor by itself...that can wait

 

[HISSIN50]

Or just buy yourself a compression gauge (20-40 bucks at parts stores) and do it yourself.

I would have done a wet compression test afterwards, but I would not have paid someone to do the test, esp after the numbers you put up (very very good, IMHO).

Good luck.

 

[90mustangGT]

The compression test, like said before, the numbers really don't matter unless they are really low becuase you need at least 70psi for combustion. It's evenness that your are looking for.

The leakdown was an hours labor by itself...that can wait

Actually, this is the really important test to check engine performance condition.

My old motor, read between 155-165 across all cylinders. Great right?
Wrong, when I did a leakdown test I was getting 26% leakdown on #3 but all the rest werein the hight 30's low 40's, and #6 was at 50%.

10% or less = Excellent
Under 20% = Good
Under 30% = Acceptable
31% or more you have problems.

 

[Skoobie]

I would have done a wet compression test afterwards, but I would not have paid someone to do the test

What kind of equipment do you need for the test? Cost Vs. having a shop do the test?

 

[Vipersix]

You might be able to rent one from Advance or Auto Zone, otherwise you can buy one from Summit for $70.