jimbob65

One more thing to check is your pick up tube size.....I hate to admit it...but I was using the smaller pickup tube for years and had a pressure drop like your, every time I gave it a little throttle. My bearing clearances are in 2.5mains/rods. I had Bought a new pump and pickup tube, installed a 70psi spring and checked clearances. Never noting that the actual pickup tube and pump end was smaller. Some rebuilds back (been racing this combo for 9 years now) we swapped ends from a different pump (bigger size pickup inlet) and larger pick up tube. Problem solved...

shannons86

NO I dont. A Race motor you want looser tolerances. A street motor that is going to be around and driven you want to be tighter. I am using a standard oil pump cause a street motor does not need a high volume or a high pressure!!! If it is built right. If I was building a race motor I would run tolerances about like what you are recomending...RACE ONLY. Not half and half. Adn how come oil weight dosent effect this??? How come when the motor is cold everything is fine??? The pressure will go to 70-80 psi... if the relief valve is bypassing and lettign oil around then how come it does it only when the oil is hot???? The pickup tube on the pump is a 5/8 inch. Plenty for the application. And it sets about a little over a 1/2 inch off the bottome of the pan, w/ gasket.Great thought though.

mourningyou

I couldn't tell you exactly why, but the oil pressure is always high on startup, until the oil heats up. The oil pump doesn't relieve the pressure when it is cold.

1racerdude

The OP when cold probably already has the relief open and the thickness of the oil is keeping the OP up. When it warms up ya get to see the relief open on the guage.
That's your oppinion on the clearances but the mains are to TIGHT.

shannons86

How come in an old sbc the oil pressure dosent drop like this motor?? I know a lot of guys that have built motors that have never checked clearence on rods or mains and there motors work fine!!!! Have any of yall ever checked a pump on a test stand???? The spring that comes in the pump factory normally starts to relieve at about 65-80 lbs. So I am going to say that the brg. clearence cant be the problem....

1racerdude

OK--- have it your way.

67RSSS6SPD

And I thought some real good advice was given in response to this question.

MachinistOne

LR is correct in his assesment IMO. Believe what you what, you came on here with the questions, and answers that you didn't want to hear made you upset...your clearances are TOO TIGHT(.) end of story, until you correct that problem you cannot accuratly point to problem somewhere else..........it is called the "problem solution by method of elimination"

shannons86

I just want yall to answer my question. How many people build a motor with not checking clearence?? How come factory sets theres up so tight? So if bearing clearnce was too tight... wouldnt I see some kind of indication in the filters?? Some type of material after 1000 miles?? I'm not complaning about the advise I just want some explaning...why. I've set motors up completly stock to run for a hundred thousand miles and never had a problem like this. And why does it happen at 3200 rpm's all the time.. wouldnt diffrent oil weight cause it to change a little?

shannons86

OK one more question... When the relief valve starts to break seat. The spring is going to hold pressure correct. So instance on my race car it has 70lbs. of pressure at 5000 rpm's thats when the relief valve starts to break at 8000 rpm's the pressure is still 70lbs. So when the valve starts to move it floats in the bore that it is in while oil pressure is on one side and spring pressure on the other...Correct???? So when I ease into this motor when the valve starts to bypass it should stay up at the psi stated by the spring right???

Mkos1980

HAHA This is the same problem I am having on both my motors. I knoticed this only on the dyno and track. I'll get on it through 1st and as I'm coming ot the top of second the pressure will drop and as soon as I hit 3rd the PSI pegs again and starts to come down as I approach the top of 3rd. 5K miles later I am still clueless. It never drops below 30 though when it goes through its cycles.

Mkos1980

My clearances are 2.3 rods and 2.4 on the mains. I am running a Melling 55 pump with a #26 spring in each motor.

shannons86

See this one drops as soon as you ease into it in first then never comes back untill the motor drops below 3400 rpm.

SStrokerAce

The mains are tight at .00175 but the rods are fine.

Your issue is related to the pan. What windage tray and pan do you have in there?

Bret

shannons86

Everything on the bottom end is stock...