* Engine condition: Worn rings, valves, or a cracked head will significantly lower cylinder pressure.
* Compression ratio: Different 350 engines had different compression ratios, affecting the pressure.
* Engine speed: Cylinder pressure increases with engine RPM.
* Spark timing: Incorrect timing will alter cylinder pressure.
* Fuel/air mixture: A lean or rich mixture will influence pressure.
* Altitude: Higher altitudes mean lower atmospheric pressure and therefore lower cylinder pressure.
A healthy 1979 350 Chevy small-block engine should ideally have a compression pressure reading in the range of 140-160 PSI for each cylinder, with no more than a 10-15 PSI variation between cylinders. However, this is just a guideline.
To find the actual cylinder pressure for *your* specific engine, you need a compression tester and perform a compression test. This is a relatively simple DIY project, or a mechanic can easily do it. The results from your test will tell you the real cylinder pressure.
