I hope I have not sold myself short on my oil pump. I have a Melling M 55 oil pump in my engine, also my oil pressure guage shows around 45 lbs of pressure when cold and drops to 30 when the engine is at operating temp. I have switched guages many times but the pressure is the same. Should I give up on hoping that it is an electrical problem and get a higher pressure pump?

 

30psi @ an idle on a SBC is pretty damn good. all you need is 10 psi for every thousand RPM your going to turn. mine holds about 40 psi cold and 20 @ idle and it's only got 36K miles on it.

 

yea its just that this engine has maybe 15-20 hours on it. it doesn't even have a full mile added on the odometer. My 82 had 48k miles on it and I put a new pump on and it ran 60 psi.

 

40 psi cold and 20 hot at idle is great, a high pressure pump is needed if your winding the thing to the moon. like i said before , you need 10 psi per 1,000 rpm . so if you turn the engine 6,000 rpm , you need 60 psi @ 6,000 rpm....otherwise don't worry about it. and NEVER get a high volume pump unless you add a larger capacity oil pan (like a 7 qt pan) because it pumps all the oil to the top of the engine faster than it can drain back . seen it done, wasnt pretty. $8K engine spun two bearings and stacked one bearing @ 3500 rpm.

 

If you are that worried about it and want to go into it again, Remove the roll pin and put a couple of small washers inside there in between the spring and the pin for the relief valve. That is giving the spring more preload and not alowing the vlave to open until it has higher pressure.
That high volume taking all the oil seems a little far fetched since newer 4.3s' now have high volume pumps and still have 5 quart pans.
But those figures are right about how much pressure you need. If you go too high you are not getting lubrication. Your getting a jet wash!

 

i have seen with my own two eyes a high volume pump suck the pan dry.so it's not far fetched. if you put a high volume pump on an engine, it needs a higher capacity pan. a guy i work with has a 84 Camaro that runs 6.9's off the bottle (1/8th). on the first engine that was in the car he had just finished breaking in the camshaft and was checking the total timing, @ 3500 rpm the pan sucked dry and he spun 2 bearings and stacked one...so no it's not at all far fetched. the 4.3 has a 5 qt pan and a high volume oil pump, but they also have 4 less lifters , 2 less connectings rods , shorter oil galleys and 3/4 the lifter valley of a V8 so not as much stays in the top of the engine.

 

Cold start up 60 PSI and normal operation 40PSI and at idle 20PSI. I use a 2qt filter to give a six qt oil capacity to my 350 TPI crate motor..

 

well I appreciate everyones opinion on this I will just leave it alone and go on to the next thing I am wondering about. thanks everyone

 

Perhaps there was a problem with the pressure or the build but I have seen high volume pumps with stock capacity pans on them work just fine. So I have seen them work and you have seen an instance where it failed and figured its all the pans fault. I can't argue with what you have seen. But I can't agree with it when I have seen different.

 

the engine was put back together after having a new crank , 3 new rods and a 7 qt oil pan put on with 0 failures for 2 yrs untill a valve spring failed and caused catastophic failure. the oil pressure gauge hit 0 at 3500 rpm right before the engine seized (never knocked , never made any noise until it stopped, violently) the pan simply ran dry because all the oil was at the top of the engine. i had never seen that happen until then, and ever since then if i run a stock pan, i run a stock pump. not much need in a high volume pump anyway as long as the bottom end of the engine is built right, it's not needed unless it's a all out race engine that sustains high rpmfor extended times.