Hot Rods Flathead oil pressure question

I,m curious what is normal oil pressure for a flathead Ford.
I recently built a 59A with a mellings high volume oil pump and have a persistent rear main leak.
I,m wondering if I have too much oil pressure(65 psi at highway speed) and I,m curious if I have to shim the pressure bypass in the valley and if so by how much.
I have already changed the rear main seal once and I,m wondering if i,m doing a shitty job or if it is something else
Thanks

 

That's a lot of oil pressure. I have 40 psi @ 2500 rpm and 20 psi @ 800 rpm

 

The spec is 55 psi at speed. I generally see 25 psi warm idle and 55 psi on the road on a properly built engine.

BTW, I have had nothing but trouble with high pressure/high volume oil pumps in stock rebuilds; they are only needed in racing engines with larger than stock clearances. This is one case where my signature line does not apply.

 

Having oil leak from the rear seal of the pan indicates it's flathead.

 

I’m with Tubman. Rule of thumb is 10 lbs pressure for every 1000 rpm.

 

When I first got my car I asked a buddy what kind of oil to use. He said "in a flathead? Something that matches the floor of your garage...", lol. Mine doesn't leak tho, maybe a drip now and then.

I'm also at 15-20 at idle, 45-55 flyin down the road. It was higher when I ran Rotella in it like some idiot told me to do, and this idiot listened to him. Switched back to 10/30 and the oil pressure got right again....

 

I,m running 20/50 Valvoline VR1.
Maybe I,ll try a different oil.
The thing is that I have another engine with the same oil pump and it,s oil pressure isn,t as high

 

I'm running an 8BA with a high volume oil pump, 20/50 VR1 oil and when it's warmed up it's about 20 at idle and 40-45 psi at highway speeds. I also have a slight drip at the rear of the pan but didn't RTV the rear gasket where the pan sits. Only about 600 miles on it so far but happy with the oil pressure.

 

I’m a fan of the VR 1. I use it in a lot of older vehicles I maintain. They do make it in 10-30 if you wanted to try it. As far as the other engine running lower pressure with the HVpump,it may have looser bearing clearance. 65 psi with a HV pump sounds about right with proper clearance.

 

Oil pressure has no effect on a properly installed rear seal.

 

^^^^^^^^^^ I agree!
6sally6

 

When the flathead stops dripping ,you know your down a quart !!

 

I thought the higher pressure might be pushing the oil past the seal

 

Oil leaks will slowdown or stop with the installation of a PCV system even on an old style engine that never had one. Personally I believe today no engine needs 20-50 oil built to drive on the street or should be built to need it.

 

I really hate to suggest modern updates to classic (flatheads, of course, are) but in the case of the later (8BA) engines, I will suggest going to a PVC system (properly done) rather than the traditional "draft tube. I will create a slight vacuum in the crankcase, (rather than a slight amount of pressure), which will solve a lot of leak problems.

(Ooops; great minds run in the same channels.)

 

I didn't think so. The seal is sealing against crankcase pressure, not oil pressure.

 

I don't think so, the seal is not sealing the oil into the bearings, it's sealing against pressure in the crankcase; that's why the other guys mentioned adding a pcv system, to alleviate the crankcase pressure.

 

Pressure release spring in oil valley not opening . anyone else thinking along those line

 

Jimmie said it - that was what I was going to ask if it still has the stock tube breather on it ?

 

yes it does

 

I'm with you; that's the limiting factor. If the proper spring is installed, there should be no way the pressure can be too high.

Of course, it's hard to predict the properties of an "extra capacity" oil pump.