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how much oil pressure to expect

2066 Views 31 Replies 10 Participants Last post by  jopes
I built a 400 and I am in the process of putting a manual oil gauge in today. What should I expect? The entire engine was done to spec and a high volume pump I run 10-40 in it. Let me know as I am wondering. Before rebuild it had 20 lbs hot no matter what RPM.
I have searched and can't really find any specs. This is going into a 79 bronco by the way. ANy help appriciated. Thanks Lucas
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On mine with a similar built 408 runs anywhere from ~55 at idle to ~75 at part throttle and ~80+ at WOT.
is that cold? Those sound like great numbers. Did you do anything else to it? Please let me know. Thanks
Thats at operating temp. Cold it usually idles around ~75-80. Not sure if it affects pressure much but I also have an external oil line setup to feed the rear main.
My oil pressure is about the same that highhorse said he has, mine is a 351M without external line.
Thats at operating temp. Cold it usually idles around ~75-80. Not sure if it affects pressure much but I also have an external oil line setup to feed the rear main.
Got a pic and a link to a write up on the external line set up. My 400 dosnt seem to have much oil pressure and im going to be adding a cam and maybe some aussie heads I found. Thanx
Got a pic and a link to a write up on the external line set up. My 400 dosnt seem to have much oil pressure and im going to be adding a cam and maybe some aussie heads I found. Thanx
Here ya go-http://www.fullsizebronco.com/forum/showthread.php?t=122933&highlight=external+line
I set mine up so that they run 35-40 hot idle and 50-60 off-idle with the HV pump. Had too many issues with busted dizzys running anything higher.

I buy my pumps from Precision..blueprinted..and they set the pressure relief where I want it. 75 psi from stock volume pump would be fine..but for a HV..yr asking for trouble IMHO.

Oh..and FWIW..all my engines have the reverse oiling (external line) setup too..some through an oil cooler and some just direct.
mine from day one has pretty much always ran 25-30 psi hot @ idle and 50+ just off idle with 20w50 and a stock melling pump. After reading everything on HV pumps I decided to stick with a stocker.

edited: Engine was built like 5 years ago, and well has lived a abused life, just like my sheep do. :toothless
thanks guys now I know what kind of pressure to expect...why not the high volume pump??
a well machined engine and a well assembled engine should not need extra oil. plus it puts more strain on the dizzy gear.
Mines quite a bit lower then everyone else's numbers...but my bottom end is all original, and has never been rebuilt. I run about 50 at cold idle, and about 12 or so at hot idle. Under throttle while warm, it runs about 20-30psi. I suspect cam bearings to be at fault as well...but, I think it's sufficient for now. That's with a high volume pump.
Mine runs 80psi cold, 60 idle and about 70 at cruise when warm. Pressure that high is hard on dist gears and pump driveshafts, stock pressures make for better reliability. I'll be changing my pump back to one with stock output. HV/HP pumps are for racing where the oil plays a much larger role in cooling the rotating assembly.
I got 45 at cold idle.
60 reved up cold
20 hot idle
30-35 hot reved up.
I am disappointed.
Those dont sound like that bad of numbers. 20 hot at idle is a little lower than I prefer though. Im not sure it matters that much but I have a Melling H/V pump. What are you running?
same. I got my stuff from summit racing here in ohio.
I got 45 at cold idle.
60 reved up cold
20 hot idle
30-35 hot reved up.
I am disappointed.
what weight oil?
who built the engine?
was the bottom end balanced?
were the holes on the rods within specs or re honed?
crank turned and polished?
well its 15-40 I wanted to run thinnner but won't now
I bought it with the pistons, mains, rods installed...I had to put the timing set, oil pump, heads, etc together.
The bottom end I thought the guy said was balanced, but only to run 6,000 rpm tops
Good question on the holes in the crank...I don't know
The guy that did the bottom end I believe just polished it as it was in spec.

I think I am going to pull the engine and check the bearings as I really wanted more...This is for my trail ride/wheeler only and it will see some rpms and abuse.
did they put in new cam bearings as well? but since everything was already done, you truely have no idea because it is just his word.

as for the holes in the crank, they only need to be rechamfered (how ever the heck it is spelled) if the crank it turned like .020 under.


I am talking about the big hole on the rod where the rod bearings go. They can get stretched out and become ovaled, thus causing oil pressure to bleed off.
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