Weird oil pressure reading

[95 Drop top snake]

Ok since I replaced my heads after my car warms up every time I am cruising like in fith or any gear running low rpms if I barely or even put my foot in the gas I will loose like 10 psi of oil pressure and it will rise after the rpms increase a considerable amount I've had 2 different kinds of oil pressure guages electric and mechanical mechanical is what's on there now so I'm stumped on this one I'm thinking pushrods their not to long because I put 20 thousands shims and their and the rocker wasn't even tight against the valve tip but it is without it so mabey it's not enough lifter preload or what help please

 

[RichV]

Were the lifters pumped up when you shimmed?

Just thinking out loud, weird issue.

 

[95 Drop top snake]

Yes pulled distributed and primed with a drill

 

[Magic]

It might sound silly, but what brand oil filter are you using? Hate to say it, but if it is an Orange can Fram, these oil filters have made grown men cry about oil pressure issues.

Case in point a customer where I worked called in said, I just did an oil change on my Mustang (built 408) and now the oil pressure is reading 10 psi lower everywhere, is my engine toast? I said what did you use for oil and filter? He said the oil and weight and then mentioned Fram filter. I said, take that filter off and get something else or go to the dealer and get an FL1A and then call back. Instead he drove over to the shop, since we stocked the Motorcraft filters, swapped out the filters, topped up the oil, took it for a test drive and what do you know? His oil pressure was back to where it should have been!

Now I know millions of these filters have been used, but Ive never been a fan of them or their internal construction. Long debate, another barrel of monkeys, but just a thought.

 

[95 Drop top snake]

Don't think that's it have a k&n oil filter and royal purple 10w 30 full synthetic in it

 

[toyman]

Ok since I replaced my heads after my car warms up every time I am cruising like in fith or any gear running low rpms if I barely or even put my foot in the gas I will loose like 10 psi of oil pressure and it will rise after the rpms increase a considerable amount I've had 2 different kinds of oil pressure guages electric and mechanical mechanical is what's on there now so I'm stumped on this one I'm thinking pushrods their not to long because I put 20 thousands shims and their and the rocker wasn't even tight against the valve tip but it is without it so mabey it's not enough lifter preload or what help please

What is the pressure dropping to? A drop of 10 psi without a reference point doesn't mean much.

 

[RichV]

Ya, what pressure do you normaly run at startup? Once it warms up? And driving?

 

[95 Drop top snake]

Ok on start up it runs 80 psi and stays there at idle cruisin until the car warms up after that it runs 60 cruising and 40 at idle and like when I'm crusing and its at 60 and I'm like not in the throttle at the time them I barley put my foot in it it drops to 50 almost like a vaccuum guage does when I get on the gas

 

[rz5.0]

Not sure why it would do that.. Maybe a clogged pushrod. 50 is still good for oil pressure tho..

 

[toyman]

Ford spec is 40-60 psi @2000 rpm hot. 80 psi seems on the high side. Where is the gauge mounted or taking it's reading from?

 

[RichV]

Ok on start up it runs 80 psi and stays there at idle cruisin until the car warms up after that it runs 60 cruising and 40 at idle and like when I'm crusing and its at 60 and I'm like not in the throttle at the time them I barley put my foot in it it drops to 50 almost like a vaccuum guage does when I get on the gas

80 psi is when the pump bypasses. Way too high. I sheared my distributor gear with pressures like that.

Don't think that's your issue, but just FYI. High volume oil pump?

 

[95 Drop top snake]

i dont know about the pump havent messed with the bottom end since i bought the car the guage is hooked up were the factory guage sending unit was installed and it only runs 80psi when the car is cold it goes to 60psi max when the car is warm

 

[ratio411]

I had a similar issue on a 302 once, it would decrease oil pressure with rpm when hot, then raise pressure back up on the way back down.
It was the thrust main bearing gone bad. I have no idea why it did it, but that is what it did.

Edit:
This was 25 years ago, and after thinking about it, I want to say it was the front main bearing, not the thrust. Fact is that I am old, and just don't remember... pretty sure it was the front main.