Have a 1971 Cutlass with a 1970 455 new build. Comp 270 cam 42-308-4 olds magnum new lifters, all new valve train. All new bearings & oil pump.New radiator, hoses etc. At start up oil pressure is about 55+ lbs. The engine has a 180 degree thermostat but temp usually settles at about 195-205 degrees. Once the engine is hot the oil pressure drops considerably. Idle 4-5 lbs 1500-2000 RPM 25 lbs. Any thoughts? Checked rear galley plug, it seems fine. Noticed oil pump drive shaft had a broken piece of washer or snap ring on the shaft and laying next to the shaft. Used a magnet to pick up the pieces and ended up picking the whole shaft up and out out. Looks like the shaft was installed upside down! The manual says service shaft and washers as a unit. Is it not possible to just install proper washers/retainer? Don't think this would have affected my oil pressure? Will it harm anything to drive it this way for a couple of days? Thanks

 

Not what you want to hear but sounds like too much bearing or rod side clearance.

 

I dont think a front oil galley pug is missing either because you would not have 55psi when the engine is started. Are you sure your gauge is accurate?..55 psi at startup and when cold is kinda high for a stock oil pump. Maybe you need to try a straight 30 weight oil. The 4 to 5 psi at idle would scare me but with an idiot light on the dash, thats just about enough to keep it off. If a machine shop built the engine I would ask them Why?...Make sure your gauge and line and engine port is free of gunk so it can read accurate. If all else fails swap the oil pump or shim it for more pressure. I wouldnt let the engine idle long with that low oil pressure.

 

Thanks for the advise. I'll give it a go.

 

The washer parts that you found were probably from the oil pump drive. This washer is pressed onto the shaft and the shaft was probably installed upside down, ( it should be installed with the end nearest the washer toward the oil pump)

 

Ok, I'm installing a new shaft and oil pump this weekend. Hope it will make a difference in oil pressure. (new pump)

 

Did you get the crank ground down at all ? and are the bearings oversized ? you dont have a plug problem otherwise you wouldnt have pressure. Your pressure should drop considerably after its warm, but that is just a little low

 

One problem is I bought this motor from someone else. The story is, it came out of a 1970 442 which was wrecked @ 35,000. The engine sat in a garage for years. Cylinders were honed, no boring needed. All new bearings. I'd guess all standard OEM size. Going to try another gauge too.

 

Here is the wrap up. Found neither the bearings or oil pump had been replaced! Back in business this weekend with good oil pressure, 22lbs @ idle hot.

 

thats some good oil pressure lol. My 350 i just rebuilt has 55 when its cold and around 22 when its warm. Full rebuild, didnt get the crank machined, didnt need it, oddly enough it had 127,000 on it. Must have been well taken care of. Glad you found out your problem.

 

I have a 70 455 with low presure as well . Has for 35 years . I could show you in the manual where it states 4 to 5 psi at idle.I found it years ago .

 

When the car is on psi level is around 20 cold or hot but when I accelerate it goes up to 60 psi or same when running is that normal?