Nailhead Oil pressure

[Guest]

Hello,<BR>This is my first post since registering with this fine group. I have a recently rebuilt 401 in a 65 Riviera. I recently installed aftermarket mechanical gauges, including an oil pressure gauge. With engine cold, oil pressure at idle and at speed is 40+ psi. But, when engine warms up, pressure at speed is still in this same range, but drops to almost nil (5 psi) at idle. I hear no clacking noises, and know the engine was rebuilt right (by me, grew up in a shop and have rebuilt literally hundreds of engines, but this is my first Buick Nailhead, our clientele was almost exclusively Ford and Chevy people.) I know this pressure cannot be normal. I am running 10W-40 oil, should I go back to straight 30 weight? I can't think this would make a significant difference. Engine has a new stock oil pump, I tried to find a high volume pump, just because that is what I always liked to use, machine shops around here (South Carolina) couldn't find a listing on one. Does anyone have any experience with shimming the relief valve spring on oil pumps to get higher pressure, or something else that could be done. I don't want to waste the over $1100 worth of new parts in this engine due to lack of oiling. Educate me if there is something special about this engine, please.<P>------------------<BR>

[palbuick]

I had the same problem with my 425, when rebuilt, cold oil pressure was 40 lbs, soon as it warmed up dropped to about 8 lbs. Tried every suggestion, blocked oil gallerys,<BR>plugs in front of block in too far, spun front cam bering??. Finally I ordered a high volume oil pump from Carmen Faso, and went to a heavier oil. Now pressure is a steady<BR>20-24 lbs hot and 45 lbs cold. Old phone # for Carmen Faso 716-693-4090, N.Y. He has many Buick Goodies and his REBUILDS are excellent, carbs, distributors, oil pumps.<P>Jim Schilf /palbuick@aol.com

[The Old Guy]

5 to 8 lbs. is scary, but it is all that is necessary. Most idiot lights go on at 7or8 lbs. As long as you have 10 lbs. per 1000 rpm you are in good shspe. Gm even makes some of their gages non=linear so they show higher than what they are at low RPM

[The Old Guy]

I forgot to add that shimming the spring will have no effect on idle pressure. it will only raise running pressure. I had a 58 Pontiac that carried 5 or 6 lbs, at idle and I worried for the first50,000 miles and when I sold it with 122,000 it still carried the same pressure<BR> Joe T<BR>

[Guest]

The only thing that I would add is, I would never assume that any new part meets quality spec. Check it before you use it. Your new oil pump may have excessive internal clearances. I have done a couple 401 engines. On both of those the original pumps were excellent, but the rod bearings were going and bleeding off the oil pressure.

[Guest]

I have a 401 from a 65 Riviera with 10,000 miles on the rebuild. When the engine is cold it will be about 40 lb pressure. After the engine has run at temperature for a few miles and you come to a stop the pressure drops to around 10 lb. The pressure goes back to 30-35 lbs when driving.I have a 1972 motors repair manual and it states 'Normal'oil pressure is 33 lbs.Slightly above idle maybe 1500 RPM the pressure will move up to 20-25 pounds.