1966 401 Nailhead Power Steering pump pressure?

I have a 1966 Nailhead engine with the original cylindrical cannister type power steering pump installed in my 57 Buick project (not on road yet) I have a Mustang 2 power steering rack installed as well. The Mustang 2 racks are 600-800 PSI and the newer GM pumps are considerably higher pressure but I'm not sure about these older style. On the newer style GM pumps shimms can be used to reduce pressure but I don't see anything similar in this pump.
Can anyone tell me if there is anything on the pump that can be adjusted, or do I need to go to an external pressure regulating block? Thanks

The pump has an internal pressure relief valve that is set to open at 1100-1200 psi. There is no adjustment on this, but you should be able to lower the pressure by replacing the relief valve spring. This spring is inside the flow control valve and you can get to it by removing the ball seat.

Since reproductions of the Mustang II rack are commonly used on Chevy powered rods (basically the same pump as Buick) I would start by asking the aftermarket rack vendors what spring to use.

Ray



Quote:

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Originally Posted by raycow

The pump has an internal pressure relief valve that is set to open at 1100-1200 psi. There is no adjustment on this, but you should be able to lower the pressure by replacing the relief valve spring. This spring is inside the flow control valve and you can get to it by removing the ball seat.

Since reproductions of the Mustang II rack are commonly used on Chevy powered rods (basically the same pump as Buick) I would start by asking the aftermarket rack vendors what spring to use.

Ray



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Thanks for your reply. If I can get the proper spring it will save the hassle and extra fitting involved with an external pressure regulator.

If you come up with a spring that works, please post back with a vendor name and part number. This will be of help to any other members who run into the same problem.

Ray

Spammer is outta here!

I resolved the problem by purchasing a shim kit that installs under the relief spring, the same shim kit as the newer style pumps use, several manufacturers make these shim kits for GM pumps.

You kinda lost me here. If you put a shim under the relief valve spring, wouldn't that increase the pressure rather than reduce it?

Ray

The shims actually go above the spring (allowing spring to extend) so reduce the relief pressure. Several manufactureres make these shim kits to reduce GM PS pump pressure for the Mustang racks.