Start by testing the compression. It should be consistent within a few PSI on each cylinder. Any cylinders that have little or no compression probably have a burned valve. If all cylinders are up, check the plugs, wiring and distributor.
WILL IT STLL RUN ?OR IS IT DEAD ?
Compression ratio on a 1974 Chevy 350 in a Nova was 8.5:1.
The compression ratio of a 350 Chevy engine usually ranges from 8.0 and 9.0 to 1. This provides a good balance of fuel economy and power.
8.5 to 1 compression is factory stock.
The 1990 Chevy G20 has a 5.7L Small block 350 v8. So It has 8 cylinders :)
150 psi should not vary by more than 10 psi between cylinders
10.5-1
About 8.5 to 1
Chevy 305=5.0 Chevy 350=5.7 Chevy 4.3=350-minus two cylinders making it a V6
then youre running about 8.5:1 compression
150 LBS. per cylinder. If you hace more then 15 LBS. difference between any cylinders the engine will idle rough and not run good.