Rocker shaft oil restrictor.... how small is too small

[64PI]

I have another gauge to try I can pull from my truck that I believe is accurate.  Is it possible that the gauge could be accurate on the higher end of the PSI and off on the low?? Now you’ve got me wondering about the copper supply line too.

[blykins]

It's possible that it's off on the entire scale......like maybe it's showing 20 at idle and really 85 at wide open song.   

[Thumperbird]

Ah, some fun Thursday afternoon banter, but no beer.

Just the fact that it is low in and of itself is not proof of a problem but certainly and indicator of something different as Brent states.

If it were for sure 5psi everywhere within the engine then maybe 5 is ok at idle, the lower it is at idle though the less room you have for variability throughout the engine.  Oil has some tortuous pathes to navigate, the highly tortuous pathes may see very little if any oil at that pressure where you want it, just like water, takes the path of least resistance.  Also, low pressure means that even if the oil is getting to location there may be no oil ingress for tight bearing locations as the pressure can not overcome other forces. 

I also do not buy into the low load argument.  At low loads things are bouncing around within the given clearances, sure they may not have the load of higher rpm but I for one for sure would not want to thin or no lube on a bearing rotating just fast enough to clank back and forth across the clearance gap, different kind of wear probably but not good.

The oil is the bearing and the bearing is the oil distributor/retainer across any given surface.

I also look at these things this way, what are the limits and how bad is it if you get there?
Well we all know 0psi is the lower limit and it is very very bad, so 1 or 2 psi is likely very bad, 3 or 4 psi is likely bad, you get the idea.

[My427stang]

Okay, I'm not surprised you don't see it as normal.  But is it harmful?  You write what normal idle oil pressure is.  What establishes a norm?  What happens if it's 40psi or 50psi at idle?  I've seen that plenty of times.  I mean, the  often stated rule is that you need 10psi/1000rpm and that gets thrown around as though it were gospel.  Is that always the target pressure?  If you had a customer engine with great oil pressure all the way around but with 5psi at hot idle, what would be your remedy?

If the gauge and oil were known to be correct, I'd probably be tearing it down to see what's wrong.

Me too, something isn’t right.  If 5 psi at the gauge they back of the motor is likely lower.

Maybe cam bearing clearance, maybe oil galley plug, maybe clearances aren’t what you think, maybe pickup sucking air, maybe oil mods gone wrong.  Harmful, who knows, but there is a reason and that reason won’t get better

[cammerfe]

For what it may be worth, all the FE engines I've ever owned, (Except a '63 390-300 for a couple of months during a somewhat complex trade situation) have been performance oriented. I find that an idle of much over 1K is a little bit wearing on me as the driver. A thousand is OK and I usually try for about 850. The rise in oil pressure at that part of the rev curve is almost vertical.

What does your gauge say at 1000? 900?

At one point, I put a new set of rod bearings in a worn '64 390-330 that also had a somewhat 'lumpy' cam of unknown origin. That otherwise 80K miles-on-the-speedo engine jumped up to 25 at idle and 60+ past 3000.

Can you get to a livable level just by up-ing the idle a bit?

KS

[winr1]

Rebuilt the 352 in my F100 25 years an 40,000 miles ago just to move it around till I built new mill

Still driving it .. lol ..... main and rod journals looked had been turned with a cats claw

Inserts were worn past the copper, had to rat tail file the top ridge off to use a ridge reamer

All top rings were broken into 2 or 3 parts

5 of the second rings the same

Mill had around 350,xxx miles on it, the oil filled air cleaner was usually low on oil
.......................................................................................
New full groove mains, rods, cast rings.... original small body oil pump

Cold, 40 idle ..... 70 psi on freeway

Hot, 25 idle ..... 60 psi on freeway  ( Texas weather )

Puffs a bit at start, idles nice and runs smooth



Ricky.

[64PI]

I guess the thing that I don't understand is that IF there were excess clearance or a internal oil leak somewhere, wouldn't I be seeing a drop in pressure across the board? Like I said the only time it dips to 5psi is after the engine is hot and at idle in gear(900rpm). How much volume is getting to the bearings at 5psi, I don't know... Initial start up the gauge goes to 75.... after I get heat in the engine (160-180) and back out of the shop and it will idle on its own at 900 rpm the oil pressure is still reading in the 40-50 psi range. Seems normal enough there. The drop is only after I run the car and get the water up to 190-200 (who knows where my oil temps are at this point). 

If a galley plug was missing, or the pump was sucking air or the clearances are 2X the size I measured.... Would it still be able to get 75psi at WOT and hold steady and not fluctuate? You would think you would see some sort of fluctuation.

I have 3 different gauges to try. I'm going to hook them all directly to the oil filter housing. Spin the pump with a drill while the engine is cold and see what each of them read. RPM will be a constant. Oil temp will be a constant. The only variable will be the gauges.

This engine used to have 10 psi hot at idle when my mains were @ .0025".. The only thing different during the rebuild is using cleveland mains to open up the clearance to .003"... The engine DID take out the cam bearings but I do not believe that was a oil related issue due to the fact that there were no signs of oil starvation to the cam bearings, the main bearings looked as good as the day I put them in and the rod bearings also looked beautiful. You would think if I had a oil delivery issue the rod bearings would be the first to go.. Especially when I was spinning the engine to 7500 rpm..

[wowens]

A internal oil leak can be large enough at low rpm to show a big drop on the guage, but your HV pump can overcome it and show steady pressure at higher rpm. 5 psi is problematic. I've had FE's for 50 + years, had some at 13 at idle, never 5.

[john a]

I switched to Brad penn oil and my idle oil psi dropped about 8-10 psi. I would try a different oil.

[My427stang]

I guess the thing that I don't understand is that IF there were excess clearance or a internal oil leak somewhere, wouldn't I be seeing a drop in pressure across the board? Like I said the only time it dips to 5psi is after the engine is hot and at idle in gear(900rpm). How much volume is getting to the bearings at 5psi, I don't know... Initial start up the gauge goes to 75.... after I get heat in the engine (160-180) and back out of the shop and it will idle on its own at 900 rpm the oil pressure is still reading in the 40-50 psi range. Seems normal enough there. The drop is only after I run the car and get the water up to 190-200 (who knows where my oil temps are at this point). 

If a galley plug was missing, or the pump was sucking air or the clearances are 2X the size I measured.... Would it still be able to get 75psi at WOT and hold steady and not fluctuate? You would think you would see some sort of fluctuation.

I have 3 different gauges to try. I'm going to hook them all directly to the oil filter housing. Spin the pump with a drill while the engine is cold and see what each of them read. RPM will be a constant. Oil temp will be a constant. The only variable will be the gauges.

This engine used to have 10 psi hot at idle when my mains were @ .0025".. The only thing different during the rebuild is using cleveland mains to open up the clearance to .003"... The engine DID take out the cam bearings but I do not believe that was a oil related issue due to the fact that there were no signs of oil starvation to the cam bearings, the main bearings looked as good as the day I put them in and the rod bearings also looked beautiful. You would think if I had a oil delivery issue the rod bearings would be the first to go.. Especially when I was spinning the engine to 7500 rpm..

Pressure is indeed the measurement of resistance, so you are correct that if it had a big dump, you should not have cold pressure, or any pressure later

However, think about how an FE measures oil pressure, it is essentially (except for a short run) right after the pump and just before all the galleys that go everywhere

Based on that, there is always going to be some resistance to flow from the galleys and intersections themselves, to include the filter mount itself as it exits a round about pattern. 

5 psi is low hot, real low, silly low...so I do understand that you are trying to work through this logically, but it takes something real loose, wrong oil, real loose oil pump....when it's cold, that resistance enroute to the moving parts is greater, when the oil thins it's less, but it isn't right

I'd be sure a second gauge says the same thing, I'd likely swap out the oil and filter to something different, but if it didn't change, I'd be looking inside.

I do like your plan, it also allows you to listen through the distributor hole, a plug leaking will usually gurgle

[Barry_R]

Short answer is yes - you can go lower on restriction - we go to .060 pretty often with no real visible or documented ill results.  You'd be amazed to see how much oil can flow through a .060 diameter hole.

Given that the pressure gets normal pretty quickly you are probably OK, but that 5 reading is awfully low.

You are already planning to go through the normal stuff - oil, filter, gauge.

On an older block it could be lifter to lifter bore clearances - hard one to fix in the car (like impossible...)

On really problematic ones we have pre-oiled with the pan off to "see" the big leaks.  Use a big Home Depot masonry tray, a cut off oil pump pickup, and a few feet of 5/8 heater hose to make a remote pan.  Spin the pump with a drill and watch the waterfall.

[64PI]

How about using compressed air with a regulator to try and identify the source of a leak? Or would you just hear air pissing out from every bearing surface? Would you be able to hear air passing through a "loose" oil pump?

IF I do not see any improvements with putting the oil cooler on and keeping the engine at a manageable temperature with my new cooling set up, I'm going to start looking deeper. I'm very confident in my bearing clearances and measurements. So I would like to think I can take that out of the equation. All the galley plugs were put in with sealer.. The cam retaining bolts with loc tite. The only thing I could think to question are the oil pump, It is used but I cleaned it and everything looked fine. I also question the canton pickup tube.. all the welds looked fine and I did not see any cracks.. But so did their oil pan I put on 4 years ago that started leaking after I put heat in the engine.. So maybe there is something leaking there.

I appreciate everyone's input and help on this and I hope to resolve the issue hopefully without destroying anything or having to completely tear down the engine.

Fred

[My427stang]

Let me give you an example of a recent SBC I had a chance to play with

Without the proper collar to block off an oil passage where the distributor goes, oil pressure shot up as the huge passage dumped oil.  As it did so, it made a hell of a lot of noise like a gurgling sewer pipe, it was very clear.

Depending on which galley, it could be blatantly obvious when you spin the primer tool.  Behind the distributor or the angled ones you see through the distributor hole will be obvious.  The rear ones under the intake, not as much, and we know the rear of the block isn't leaking because it would pee on the floor LOL

You may find the culprit immediately in the distributor hole or near it

[chris401]

I had an oil galley come out behind the distributor. It was at the 22 psi range at idle with hydraulic lifters but dropped to 3 with dumbbell lifters. You have all the same pressure ranges I had with that engine and an HV oil pump.

[67428GT500]

I put the restrictions in my heads, .075 restriction. The restriction is drilled at the rear upper galley that feeds #5 main, the feed hole from the pump to the adapter is drilled to 7/16" and the pump mounting area on the block is drilled to 5/8 and blended. I have screw in plugs in all locations. I am running Precision Oil Pump's blueprinted HV pump.
I have the mechanical gauge in my '67 Shelby. 80 LB cold. ( Penn 30WT) hot idle is 35-40 and cruise is about 70LB at 3200 RPM.
Plenty of oil up top as well.
                                                                                          -Keith