Quote:
Originally Posted by sdbob
Thanks Frank. Hmm I wasnt where of pumping problem. My all original SD still has the 80 psi pump. When I built my other SD, I used the 60 psi spring in an original SD pump. I had a 421 in a 63 GP in the 70s. I pumped enough oil in the valve covers,about 5800rpm, it came out on headers,scary.
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Turns out, in stock form, the 80 lb. pump was overkill - rule of thumb is 10 pounds per 1000 rpm. 60 lb. pump is perfect for these high torque Pontiac engines, in stock configuration. The 80 lb. pump was most likely supplied because engineers expected this engine to be modified for racing applications. Remember the motor had ports for installing an external oiling system, among other features.
The 60 lb. spring was good choice for a stock rebuild.
What year is your all-original SD? If 73, you might want to pull distributor and check wear on teeth of the distributor gear. Quite a few of the 73's seem to have suffered oil starvation at the gear, with resulting gear failure. It seems that the 74's improved the oil supply to the distributor (larger port) , as gear failure was not as common on the 74's.