AMC 401 Oil Pressure low ?

74Bubblefender wrote: You said race engine...you should not expect the same oil pressure from higher clearances. But a quick spec of the pump will tell you a lot. I would also suspect different areas of that engine like the lifter bores, bearing clearances including the thrust bearing (which is often overlooked by engine builders. Often the biggest initial loss is the space between the gear top and bottom in the oil pump. Its the killer of a oil pump.

I agree 100% on the oil pump. I don't remember the pump gears end clearance specs off the top of my head. But I replaced the cover on a 360 once before that was out of spec. We used some wet grinding compound on a plate of glass and ran the pump housing mating surface over it for what felt like forever and took .001" off and then figuring gasket thickness were able to get the gear endplay within specs. I sometimes use Bulltear midplates between the pump casting and filter adapter to give the gears a harder wear surface to ride on. They include a slightly thinner gasket too, I believe. It was good for 10 psi at idle in one engine I used it in, if I recall correctly.

Sounds like the same thing I had with my 401. 10W-30 pressure was low, 20W-50 was good. I'd bet the main bearing clearances are excessive but if you're going to run the thicker oil it may be okay.

-Steve-

I run Amsoil Dominator Racing oil because of its high Zinc content.

I run .002 to .0023 main clearances and for oil I run straight 30W Valvoline or Rotella with rislone ZDDP in all the old cars and the lawn tractor as well

Most aftermarket lifters are smaller diameter then factory, complicate that with worn lifter bores.