I have read many responses to oil pump and low pressure;

My situation is this: 76 chev pickup, Chev. 350, recently rebuilt, flat top pistons, mild cam. Oil pressure at 40 PSI when cold, then drops to 0 after warm-up. Pressure increases to about 15-25 PSI when I give it gas.

So I am going to put in a high vol. Mellings pump to see what happens....Is there a gasket between the pump and the block?

Also, from the pan, what should I look at as far as main bearing wear, etc? 5000 miles on rebuild, hopefully bearings OK.

Any other suggestions will be greatly appreciated...

You wont be able to see the conditions of the bearings until you pull a main cap off. Better to just leave it alone if you dont hear any noises or and slapping sounds.

Never run the engine when it says 0! If it says that, something is VERY wrong, either with the gauge, or the oil pump assembly.

yeah, no BAD noises; I hear the lifters when i crank it up, just for a split second; she purrs fine until the oil thins, then it sounds like the lifters bleed. I am gonna put that pump in and drive her till I do hear a knock. Its just a beater.

Thanks for the reply.
CF

I have heard certain oil filters can cause this, especially FRAM. Try running some 20-50 oil and see what happens.

I know it sounds stupid, but my current oil filter is a K&N model with 20w-50 (Castrol GTX oil) my current pressure is 60psi cold 45-50 psi hot @idle

my last oil filter was a Fram model with 10w-30 (Castrol GTX oil) running 50psi cold and 40 psi hot @idle.

I know its both oil weight and brand of filter change, but the difference was quite drastic.

(you *almost* always need to take into account the weather in your area when choosing oil weight, in So-Cal that doesn't often factor in though)

there's my $.02

i live in mississippi, hardly ever below 30.

running 10W30 right now, and a Fram filter. Am going to go ahead and put a new pump on, as well as a Napa filter and castrol GTX 20W50.

What type of guage are you using? Manual or electric.....manuals are more accurate.

If you are hearing your lifters when it warms up, sounds like you are not getting enough oil to the top of the engine.

When you rebuilt, were the cam bearings replaced?. If there is too much clearance in the cam bearings, oil pressure will suffer.

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seems 10w30 is way too thin to run. I live in North Idaho and here we usually change the oil to 10w30 so vehicles will start in the winter in temps of 0-10 degrees Farenheit or lower. I am no professional but i usually run at least 10w40 when it is warmer out.

All bearings were replaced; I don't recall any boring being done; mains and cam journals were OK; went back with std. size bearings.
What are the odds of a cheapo Elgin type oil pump going bad, or
the pickup coming loose, or the like?

Again, thanks for the input..

If you don't feel good about the quality of the pump, replace it.

Remember, "you only get what you pay for"

They don't call me "Mr Cliche'" for nothing.........lol.

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No gasket between the pump and the rear main.

If your gauge is right you might want to keep an eye on the oil tempature for a while. If you are overheating the oil it can lose it's viscosity. You may want to try synthetic oil as well.

You want to have 10psi per 1000RPM, that is the general rule of thumb.

Well since Melling is the only pump mfg left in the USA I would say you have a re-boxed melling. If you put STD bearings in it and the crank was reused, polished or not polished I would say you have excessive bearing clearance. I would put the HV pump in it with the HIGH pressure spring and run 20w50w and run it till she knocks... being a chevy she will probly only go another 200K miles.

Chris

Thats what I wanted to hear, Chris....

***, if need be, I'll pull her and throw in some new bearings along with a more radical cam...heh heh...

CF

Get that Fram off there ASAP!

I just went through this BS with my 305 Chevy replaced the Fram with Purolator gained quite a bit of pressure. My engine has a hv moroso pump on it. Has 70+ psi cold at speed, drops down to about 45 psi once its warm Im using 10w30 too.

After reading all the posts on last oil filter thread I cut open a few filters that were laying around Fram was the smallest filter area that I found.

will do....