What are normal compression test values? Options

[Barry Brisco]

I've run a search for posts talking about "compression test values" but can't find an answer to my question, and my Owner's Manual and Haynes repair manual don't seem to tell me either: what are normal compression test values in a 914?

These numbers are for a 1.7 engine with an unknown number of miles, it's in a 914 that is for sale:

#1 130
#2 150
#3 140
#4 150

I am concerned about the #1 cylinder. That is a 13% drop from the highest cylinders.

Here are some online references about how much of a difference is acceptable between cylinders, and what indicates a potential problem:

http://www.automedia.com/Engine_Compressio...ccr20050801cc/2

If all the cylinders check out within 10 or so PSI of each other, and those numbers sync up with the factory specifications, then you're good to go.
If one or more of the cylinders show a difference of 15 or more PSI, then there are problems inside

http://www.freeengineinfo.com/compression-test.htm

The cylinders should all read within 5-10 psi of each other.

http://www.aa1car.com/library/compression.htm

As a rule, most engines should have 140 to 160 lbs. of cranking compression with no more than 10% difference between any of the cylinders.

So, at this point I'm thinking that this 1.7 engine is a bit tired and in the near future it will likely need some major attention: maybe a bad exhaust valve, maybe worse.

And yes, a leakdown test would be helpful.

Comments?

Thanks,

Barry

[tod914]

One time back in band camp, I had a shop do a compression check on my 75 2.0. They gave me numbers in the 60's for compression. I was wondering how the car even moved with those low numbers. Low and behold, they didn't have the buttler fly open when they did the test. I redid the test and it was up in the high 150's. Listen to Jake.. he's da man.

[Barry Brisco]

I certainly agree that Jake is an expert on 914 engines. But the fact that the compression test numbers I described ranged from 130 to 150 makes it seem likely that the test was done with the throttle open. Of course it is possible that it was not fully open. I don't know, I wasn't there when it was done.

Whether the seller of the car I am looking at is willing to do another compression test, and a leakdown test, I don't know yet.

Thanks,

Barry

One time back in band camp, I had a shop do a compression check on my 75 2.0. They gave me numbers in the 60's for compression. I was wondering how the car even moved with those low numbers. Low and behold, they didn't have the buttler fly open when they did the test. I redid the test and it was up in the high 150's. Listen to Jake.. he's da man.