Haven't post much lately, so heres a question.



I have a rotor pump, before I did any modification to it, at idle, I get about 10psi, 30-40 at cruise, I think thats within specs from the factory service manual, but I think its a little low, so I put a bunch of washers between the nut and the spring of the oil pressure regulator valve on the oil pump, now it idles at 25psi hot and 55-60 psi cruising.



but the thing is, with the washers in there, it limits travel of the regulator piston, I dont know if it will affact anything, but so far I haven;t have any problems.



what oil pressure you guys have in you Ys? do you guys think that 25psi at idle and 60 at cruise is overkill for these engine? is there any high pressure springs out there that will fit the rotor pump instead of putting shims and washer in it?

Shimming the spring isn’t expected to affect the hot oil pressure at idle speed providing the engine has normal clearances and no blockages.  The spring simply controls the pressure point at which the relief valve opens and thereby dictates the upper end oil pressure setpoint.  Shimming the spring will simply create more resistance for the relief valve and cause it to open at a higher pressure.  In your case, simply removing the pump, taking it apart, and replacing it would appear to have boosted your low end oil pressure regardless of what you did in the way of shimming the relief valve spring.  High on the list of possibilities is that the oil pump was pulling in some air at the inlet side and that issue was alleviated when the pump was reinstalled.

 

Too much shim can potentially limit the relief valve movement by inducing spring coil bind which then prevents the valve from fully exposing the internal hole in which it must dump oil to relieve the excess oil pressure.

 

The gear style pump in my ’55 with a 272 will bump 67-70 lbs oil pressure at a cold fast idle but will fall down to 20 lbs hot and idling.  It will still run 55 psi going down the road when hot and this is at 100K plus miles on the engine and using 10W-40 oil.

 

My roadster Y engine has its gerorotor style oil pump relief valve shimmed so that the stock spring is ~0.150” shorter which provides 90+ psi cold pressure.  Hot idle at about 1000 rpms sees the oil pressure drop to around 15 psi but immediately jumps up when the engine speed is brought up.  Going through the traps at temperature, it’s running 70+ psi pressure with 20W-50 racing oil.

Lorena, Texas (South of Waco)

Hi ted and guys, i drilled and tapped the relief spring screwin plug in oil pump and fitted bolt with locknut, washer and fibre washer. i can then externally adjust the relief pressure reading the oil guage. Aussie bill.

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia