69 350/300 oil pressure drop

[Vin Moretti #40969]

I am the second owner of a 69 350/300 since 1976. Car was bought new by a friend of mine. About 7 years ago I rebuilt the motor. Upgraded the internals but reused the heads/intake/carb/oil pan. Against my better judgment I was talked into a high volume oil pump. I have the typical problem of loosing oil pressure during hard acceleration. I didn’t notice it for a few seasons. Recently pulled out the high volume and replaced it with a standard volume/high pressure pump. It got a bit better but is still doing it. This only happens under acceleration, not when I rev it. Tried running a quart over fill but no difference. I think the pickup is being uncovered. The pan is 7 inches deep and seems to be well baffled and the pickup is 1/2 inch off the pan bottom. I'm 99% sure the pan is original to the car. I'm about ready to again replace the pump with a standard volume/pressure one. The pickup (suggested by Melling) seems to be positioned quite a bit forward in the pan.
I think an aftermarket pan (Moroso maybe) would cure the problem but I would like to keep the original pan.

[Duke W.]

Re: 69 350/300 oil pressure drop

If you have a standard volume pump you can just replace the spring with the standard 40-45 psi relief spring.

My suspicion is that you have the wrong pickup. Joe Lucia can probably give you a GM part number if it is still available, however, you could also try NAPA for a Clevite OE replacement pump or Sealed Power. You can check both online.

I believe the Corvette pickup is unique to the Corvette application. Pickups are normally at the very rear of the pan, and the baffling keeps the pickup covered under heavy brakig and most cornering loads.

Duke

[Joe L.]

Re: 69 350/300 oil pressure drop

Duke and Vin-----

The correct pick-up tube/screen is GM #3830080. It's still available from GM for about 18 bucks. It's also available in the aftermarket cross-referenced from the number I provided.

I can tell you as an original owner of a 1969 300/350 that put 200,000 miles on that engine configuration, with a standard pan and standard oil pump I never, ever experienced anything like what you described. So, I would highly recommend that you install a standard volume, standard pressure pump as was originally installed. As Duke mentioned, you can convert the standard volume, high pressure pump by installing pressure relief spring GM #3814903.

[Don Y.]

Re: 69 350/300 oil pressure drop

The only times I ever saw an engine lose oil pressure upon acceleration was on some of the "other" manufacturers vehicles that had two part sumps. Some Ford engines had a well on either side of the front suspension and the front well would get loaded with crud that would migrate to the pick-up screen and cause a high speed restriction. Since you had the screen out and would have probably noticed the blockage this cause seems to be ruled out. Have you removed the valve covers and checked for a restriction in the drain back holes at each end of the cylinder heads?