[Dick Boneske]

I've turned the wheel lock to lock dozens of times with and without the engine running. The system works fine when cold, never overflows, does not leak at all.

After about 15 minutes, it whines, assist is jerky like a loose belt, and the hoses are too hot to touch.

I have a '70's Pontiac pump also. Today, I checked the high pressure outlet fitting and noted it has a oil inlet hole (.140" vs. .130") and different design (large tapered oil inlet) than the '64 fitting. the newer outlet fitting has two holes on its outside diameter which the '64 fitting does not have. In addition, the hole at the flared pipe connection is .250" on the '64 pump and .182" on the newer pump. The spring in the rear of the pressure regulating valve appears to be the same for the '64 and newer pump.

In the newer pump, the pressure regulating valve that bears against the spring has two shim washers instead of one on the '64 valve.

Those are the differences I can see between the two pumps. I understand the '70's series pumps operated at 1400 psi vs 900 psi for the older pumps. This must be established by the spring in side the pressure regulating valve.

[Kell]

Originally Posted by Dick Boneske

After about 15 minutes, it whines, assist is jerky like a loose belt, and the hoses are too hot to touch.

This sounds exactly like air in the system, that is what mine did, took a long time to bleed all the air out.

However, it sounds like you can change out the valve easily to test as well. They (the PS expert I talked to on the phone) say it has little to no effect on steering effort but something to do with pressure like you said. I put an IROC box on mine as well, steering effort is pretty high but is way better than the station wagon feel of the old one. I put a newer style pump and valve on mine at the same time so I can't say on the valve part.