* Engine condition: A brand new, perfectly rebuilt engine will have higher compression than one with significant wear.
* Cam specifications: A higher-performance camshaft will often result in lower compression readings.
* Head gasket condition: A blown or leaking head gasket will dramatically lower compression.
* Altitude: Compression readings will be slightly lower at higher altitudes.
* Engine modifications: Modifications like different pistons, heads, or a different compression ratio will significantly alter the expected compression.
Generally, a healthy 350 Chevy engine will have individual cylinder compression readings between 140 and 170 PSI. However, it's crucial that the readings are *consistent* across all cylinders. A significant variation (more than 10-15 PSI difference between the highest and lowest cylinder) indicates a problem that needs attention.
To get an accurate assessment, you need to perform a compression test using a reliable compression gauge and following the proper procedure. Comparing your readings to the manufacturer's specifications for your specific engine build is also recommended. Don't rely solely on a general range; consult a repair manual or a professional mechanic for the most accurate information.
