* Engine RPM: Oil pressure is higher at higher RPMs.
* Oil temperature: Oil pressure decreases as oil temperature increases. Hotter oil is thinner.
* Oil viscosity: The weight of the oil (e.g., 10W-30, 20W-50) significantly impacts pressure. Thicker oil provides higher pressure.
* Engine wear: Worn engine components (bearings, etc.) will result in lower oil pressure.
A general guideline for a warmed-up 1979 350 Chevy small-block at idle is 10-20 PSI. At higher RPMs (e.g., 2000-2500), you'd expect significantly higher pressure, perhaps in the 30-50 PSI range. However, these are just estimates.
Consult your owner's manual: The best source for the ideal oil pressure range for your specific 1979 350 engine is the owner's manual. It will specify the acceptable pressure ranges at various engine speeds and operating temperatures.
Low oil pressure is a serious problem that can lead to engine damage. If you're concerned about your oil pressure, have it checked by a qualified mechanic.
