Dry compression test of 1981 Spider 2000 Cylinders

[Kevin Bischel]

What is the optimal pressure value for dry compression tests of the cylinders in a 1981 Spider 2000? What would be good, so-so, and oh-oh values or ranges? How about the difference in measurements from cylinder to cylinder. My owner's manual says that the compression ratio is 8.8 to 1 but my Fiat Spider Shop Manual says 8.1 to 1?! Both list the same stroke and bore.

Background
I just changed the belts, sparkplugs, and coolant in my 1981 Spider 2000. While the spark plugs were out I did a dry compression test. Two cylinders tested just above 115 psig and the two other cylinders were just below 120 psig. The motor was cold when I did the test. I don't remember which values correspond with which cylinder, I have the values recorded but not with me. I haven't had the car very long and it has about 52K on the motor.

Thanks in advance for any information.
Kevin Bischel

[Jim DeShon]

First of all I believe the compression on the 2.0 motor is 8.1 not 8.8. That compression seems O.K. to me. Certainly not over about 130 with 8.1 compression. This varies from make to make and car to car due to valve timing, carbon buildup, as well as engine condition. You might want to adjust it's valves and try it again. I would not want to see much more than 10% difference between cylinders. ...J.D.

[spiderrey]

u believe correctly. it is a low compression unit

[Jim DeShon]

I also like to do compression tests on warm engines. This allows for piston expansion, proper valve train expansion and a normal amount of oil on the cylinder walls. ...J.D.

[So Cal Mark]

those compression numbers are okay and very uniform. Shouldn't be more than 10% variance between cyls. The first pump on the gauge when cranking should be about 75psi