Oil pressure is too high.
 

I got my bird back on the road after being down way to long.

The motor was swapped. One of the mods I did to the M54DS pump was change the check ball from .625 to the .5625 and shim the spring. I also used one the 1/4" spacer plates on the pump.

I think I used the VR1 racing oil. I believe its 20W-50 weight. Not completely sure.

The pressure is at 80psi most all the time. Around 60 at idle.

I wouldn't think the mods or the thicker oil, would cause the pressure to be that high.

I was going to change the oil to a much lighter weight and see what that does. This is a roller cam and lifters, so I wouldn't think I would have to be concerned with zinc additive. I was considering like a 5W-30 Mobile 1.

Thoughts?

Even a straight weight 50 once warmed up to normal engine temp ( above 200f for oil ) wound not keep you at 60 psi at hot idle.

You issue is pump related and maybe to a lesser extent it maybe filter restricted related depending on where you reading the pressure at/ from.

I would keep a close eye on the condition of the dizzy gear until you do what’s needed to get your pressure down to a hot idle of 25 psi.

Clearances? The idle pressure should not have anything to do with the relief spring pressure. It`s a relief after all.

Look at it this way , unless where talking about the extra main and rod clearance’s used on the RAII and RA4 motors the clearance’s where no more then .002” with more of a average of .0015”.

With these clearance’s even the motors that used the 60 psi pump would never hold even 50 psi at hot idle, no less 60.

Your issue is something to do with your check ball and or shim/ spring set up.

How does a relief staying closed cause a high idle pressure?

Or, why would the relief need to open at idle?:confused:

I don't see it as an issue. I've been running pressures like that in my bird for almost 30 years and over 100k miles and I've never worn out a distributor gear or any of those other horror stories you read about.

Mine pegs the 80 lbs. gauge on start up, after warm it's 60 at idle, goes to 80 when I touch the gas, and if I run the highway for a good distance and get the oil pretty warm it comes down around 40 at idle, but will immediately jump up near 80 when I touch the gas. Been that way for decades. That's with 20-50 and 110+ outside.

Technically you could put thinner oil in it and it would likely come down 5-10 psi if that makes ya feel better. That's been my experience anyway when changing oil viscosities. Otherwise you'll have to dive back into it. Personally, I'd run thinner oil and drive it a while, see how it does.

What you don't want is oil pressures at idle coming down to 10-15 psi that you read a lot about and how people tell everyone that's okay. That's not normal for a healthy engine. Will it survive? Sure, for a while I'd guess, if you don't mind clackety lifters. I'd bet an engine like that would drop even lower after a highway cruise in Arizona heat. No thanks. An engine like that would be coming back apart if it were mine.

have you confirmed with another known to be good gauge?

My bird has done this for years and my previous engines did it also, my only issues I’ve ever seen from it was that if I romped on it cold it would brow the seal out of the oil filter which always made me let it warm up appropriately. W the turbo on it it warms the oil fairly quickly but I’ve raced it like this for many years without a tear down I built it in 2005 still going strong. And it’ll clock
Off 9s just be careful w cold oil .or go to a lighter weight.

I’ve always used the SD pump w the thicker base plate IDK if that’s why it has always done it because I build my engines to RAIV looser tolerances. If I romped on mine cold I’d see over 100psi .

I ran my old 455 for 30 years with a SD oil pump on 20w50 also. It would wrap the oil gauge all the way around to the peg on 0 when cold. Sold that engine that way. Front gallery plugs NOT tapped. Every now and then, in winter, it got straight 30w.

You got used to warming it up. At a few oil changes, I had ballooned up filters, but no leaks.

I'm running a Wix 51258 filter. Sending unit is stock setup off the filter housing. I'm with the filter adapter for long branch manifolds.

I had all this on my previous 455.
Gauges seemed very normal before. Always around 60 psi. The old motor also had a SD pump but with no mods.

The motor is used, I bought from a member here that drove it for many years. So I have no clue on the clearances.

It's a stock sending unit with factory gauge?

Couple things to consider. A fresh engine with stock clearances and a 60 PSI pump should not make 50 PSI at idle speed. If the oil is 20W-50, that is too heavy IMO. I would change to 10W-30 and re-check the pressure. If you changed your oil pump around by switching relief ball sizes, shimming the relief spring and other things, I don't know what pressure the ball pushes off the seat at now for maximum pressure. I think people say on here 70 PSI with those. I kinda go with what has worked for me the last 50 years. I use a stock M54DS for most street builds. And a M54F for high performance builds. Never had an issue. I do install the thick plate on the 80 lb. pump. The ball and spring limit the maximum pressure to the flow rate it can pass, nothing more. In other words, it will try to limit a 60 lb. pump to 60 psi unless the ball, seat, passage can't bypass enough of that 50Wt goo and then pressure will go higher. I would verify your actual pressure with a mechanical gauge as well.
My personal street car with 10W-30 oil and a M54F pump starts and runs at 110-120 PSI cold for 1-2 minutes. Then drops to around 50 PSI during warm-up. Once the thermostat is open and up to operating temperature, it runs around 20 PSI, hot idle, 50 PSI at 3000 cruise, 78-82 PSI @ 6000 RPM on the dyno. Melling stock Pontiac pumps do a very good job of regulating pressure in stock form. IMO.

Curious why 20/50 race oil is used on a roller cam engine thats not a race engine? What is the benefit to using a thick race oil on a street car? In iowa weather? In a month it will be highs in the 60s-70s with morning lows in the lower 50s or upper 40's, yes we had a heat spell and hit 100 a couple days, but even then a good quality non race oil is perfectly fine in those temps, especially a synthetic if you plan to use mobil 1.

Everyone uses the brand & weight they like, but for the most part ive read & been told to use a thinner oil with hyd roller lifters, SD performance said to use a 10/30 with the comp hyd rollers in my engine so did comp & my engine builder. Nobody suggested a race oil or to use 20/50 for a engine built with common street clearances.

I did the bigger ball & shim on a melling pump, using 10/30 i get about 80psi on cold start, drops to around 50-60 normal cruising, idle is about 30 fully hot. I usually use valvoline or other normal brand synthetic oil, lifters are all but silent, pressure is good & i feel a lot better not using overly thick 20/50 in iowa weather.

There is no benefit to using too thick of oil, most guys go with the 10psi for every 1000rpm rule, yes a little more at idle makes you feel good but a street engine will live a long life at ~10/15/20psi at idle. 60psi at idle is very excessive IMO.

Just my .02 but yeah I definitely agree with the folks suggesting a lighter weight oil. I’d try a quality 5w-30 or other practical lighter street weight oil and save the quarts of 20/50 for track days.


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I changed the oil last night to Mobile1 5w-20. I have not taken it out yet for a drive. I will report back. I read that there is a 4psi drop per 10 of oil weight.

I honestly don't remember what oil I used in my Bird. I just know I had one bottle of 20-50 laying around. I don't know If I put 1qt in or 6qt in. But the oil did seem pretty darn thick.

I don't know why I would have used a thick oil. Must have made sense at the time.

I don`t mind the 20w-50 with 3.25 mains, cross drilled crank, in hotter weather, or making a few passes.

In fact, it will be your friend.

I wouldn’t get overly concerned until you confirm the oil pressure with a good gauge and not the factory set up - they are notoriously inaccurate.

A little bit of physics:

At a given engine speed and a given size of pump gears, the pump is trying to put out a fixed total amount of flow.

If you shim or change the pump spring to higher pressure and leave the viscosity alone, you'll get more flow to the engine and less over the relief valve.

If you leave the pump spring alone and switch to a higher viscosity oil, the higher pressure is because of higher resistance to flow thru the engine and you will have less flow to the engine and more flow dumping over the relief.

A few years ago, we were talking to the chief scientist at Valvoline and he mentioned that he was custom blending oil for some of the NHRA Pro Stock teams. I asked what viscosity it was and his response..."If I had to put a number to it, probably 0W-5."

Draw your own conclusions.

Eric

Not sure on 1st gens but I have found 2nd gen gauges are very accurate if the sender is in good condition, I have compared both water temp & oil psi stock gauges to known good mechanical gauges, they are within a few degrees or psi.

But being he said the gauges worked OK before the engine change, its a safe bet they are close to accurate or at least working good enough to know the new engine/pump set up is reading way higher than before. Always a good idea to confirm with mechanical gauges for issues like this though.

Waiting to see if the lighter weight oil changes the psi readings...

I can see that.
Given pump size and gears. Pro stock.
One has to keep a separation between the crank and bearing during the “ lean times”.

Does pro stock run a stock pontiac pump and 3.25 mains?