Hi, Im new to this forum and in need of some help with my corvette. I have a 69 with a 427 in it, I've had it for 32 years, but have not driven it much as I have had this problem since I've owned it. The oil pressure when started is around 40-45 psi, but as the engine temp. Goes up the oil pressure goes down, to zero at temp. 200 deg. range. I have replaced main, rod, cam bearings twice, had the crank cked. At a machine shop for trueness, plastic gauged mains and rods, .001-.0025" tried thicker oil 10-40' 20-50. 2 different oil pressure gauges, 2 different oil pumps with different pick-ups, currently has a mellings m77hv high volume pump, pick up is 3/8 to 1/2 inch from the bottom of the oil pan (7 qt.)
And still has the same issues, has anyone ever encountered this ? Any help would be greatly appreciated. Thanks

 

I don't think anything that early had an oil cooler. Does the pressure vary at all at temp with rpm? Those clearances you state are very tight.

 

Yes, when I raise the engine speed when at temp. the oil pressure will go up, aprox 20 psi @ 2500 rpms

 

I know I read two new guages, if you don't have any "noise" from the engine, place an independant oil pressure guage just to verify.

 

Are you using an electric or mechanical oil pressure gauge?

 

I'm using a mechanical oil guage, and one of the 2 gauges that have been connected was an external guage, still have the same results.

 

So, you are not loosing oil, external or internal?

 

No not loosing oil externally, and I haven't run the engine long enough to see if oil level goes down, but I have no signs of burning oil.