Compression Test

This evening, I performed a compression test on the engine.  I did the test with the engine cold without an intake installed so there was no air restriction.  The results were as follows:

1 - 160 

2 - 143

3 - 156

4 - 162

5 - 160

6 - 145

7 - 158

8 - 150

The best is number 4 with 162 psi and the worse was number 2 with 143.  That is a difference of 19 psi which is a 11.7% difference between the best and worst performing cylinder.  Ideally, you would have a 10% difference between them.  The average of the one side is 155.3 vs 153.3 on the other so the two sides of the engine are very similar in compression.

I decided to test the number 2 and 6 cylinders again a little later.  They tested as follows:

2 - 145

6 - 143

After researching a little, I decided to put some oil in a few cylinders and test again.  When I did number 2, it went to 180 psi.  When I did number 1, it went to 180 psi.  When I did 6, I must have put a little more oil in because it went to 225.  I cranked it over without the tester in number 6 and tried again and it went to 210.  I suspect the oil is raising compression due to displacing oil.  It would have been better to add oil with a syringe to know you are adding the exact amount to each cylinder but this test has essentially told me well enough the condition of the engine.