howdy I'm having a low oil pressure problem when I first fire it up cold I have lower than 5 psi if I rev up abit not much I get about 5-7, it's a brand new pump and bearings except the cam bearings are the orignal I believe, and thier is no oil going to the top end

Fresh turned crankshaft?  Could any wear be felt or observed on the journals?  Checked the oil pressure gauge for accuracy? But if you’re not getting oil to the topend then you very likely do have low oil pressure.  Does the oil pressure go completely away as the engine warms up?  And of course the old cam bearings could be part of the problem but likely not all of it.

Lorena, Texas (South of Waco)

Crank was micrometered and within specs, and haven't ran the engine to temp since the took the old pump out, I noticed the bone dry top end after I had ran it to temp and was about to adjust valves, which only had some mild scoring and was a rotor type pump I figured the spring was tired since everything was within spec and didnt have a tool for checking the spring thats when I bought this pump, and something import as well when I first put the new pump on I had 20 psi cold at idle but it was leaking from a bolt being too long and a bolt failed too so I have to dissamebly the pump inside the truck in order to repair the problem which was fixed in which after I had the 5 psi problem and zero leaks and I assembled the pump correctly as well and tried two different gauages both brand new. Thiers no knocks or sqeaking and it is pumping it was sucking abit of air but I fixed that problem. And the sump is clean not clogged with anything. Thiers no oil plugs I could of missed anywhere I rebuilt it using a shop service manual I'm new to y blocks I've rebuilt many small block chevrolets. And it's a 1957 272 y block in a mercury m-100 pickup truck numbers confirm it.

Not sure I understand your paragraph of problems.. but did you mean that a bolt to long was installed in the pump? If it was the bolt that installs from the top, you may have tightened it into the pump housing & damaged the pump. And sorry, some qualification rebuilding SBC engines won't cut it when dealing with a Ford Y-block. There are many differences..

Paul

You might try resealing the oil pump inlet seal (rubber o-ring) with white grease and insuring you’re not pulling in air at that point.

Lorena, Texas (South of Waco)

ah well thats how I got 5 psi I telfon tape on the inlet fitting

Teflon tape on the fitting?  That's not where the seal is.  There is a rubber seal that goes over the inlet tube after the nut is put on the tube.  When the nut is tightnened into the pump, it compresses the seal on the tube.  I'm guessing that seal is not in there.

John - "The Hoosier Hurricane"

What John said or a crushed inlet tube due to over tightening...

BOB