Question on oil pressure effects in a 426 hemi. Street motor with stock parts except Crank/Rods/Piston. 478 Ci motor. Does have a cam so idle is about 1100. Main/rod are standard and clearances on tight side. Rod side clearance is on loose side. Lifter are on loose side. Using 15-50 break in oil and no name filter, stock volume pump with hemi spring. No restrictor in the oil port to the heads with stock hemi rocker assembly. Did have minor oil leak around short rock shaft and stand. Not at plug, when priming. No issue getting 65 psi hand priming (not drill) pump before closing up.

Engine runs and sounds great with headers on run stand set up. Using mechanical oil gauge.

Start up cold get about 65 psi running at about 2200rpm. Once warm in the 40 range above 2000 RPM. Once down to idle it is in the 20 psi range. When RPM is raised pressure rises. The issue I see is that after initial cam break in at 2200 to 2500 rpm with rises to 3000 rpm. While oil pressure was about 40-45psi. It might start to flutter down. As low as 30 and back up. If I run at 2500 for a minute or two then pulse it up to 3500 to 4000 oil pressure flutters down and wants to keep dropping. I go to idle for a while with pressure at 20psi, go back and raise rpm it climbs again but really never above 45 psi. Granted I have not gone above 4000 rpm. But once sustained at that higher 3000 to 4000 range oil flutters down.

So I have about 6 qts in the stock 70 pan set up for break in.

I changed to another stock pump that had tighter clearances, changed relief valve and spring. Do have a .060 thick washer on relieve for the break in. No change.

Have checked oil via dip stick, no water or foaming that can be seen, when filter off looked fine, small amount of oil coming out when changing parts looked good.

So now I need to figure out what's up.

One concern may be pickup too close to the pan? Recommendation is 3/8" or so, what is funny is the manual say to make sure pickup touches pan???? It is not, but clearance may be low. Can a pu too close to pan really do his. I hate to have to drop the pan, but seems odd to me since pickup design has a relieve so that even if on the pan, it should not inhibit flow to cause a loss of pressure?


Can it be an excess loss at the lifter bores? Was thinking of shifting to a higher volume pump to see if that resolved this. Of course if it is a suction problem hate to make it worse with a hv pump.

Could a filter cause this?

No evidence that too much oil getting to the heads. The baffle when pulling the filters off the valve cover have no signs of oil at all.

Just looking for some insight and any indicators of what can be the most likely causes on these symptom. Would love to rule out dropping the pan if possible, but may have to. Thanks.

Add another quart of oil and see what happens. Seems to me like the pan level may be to low and pulling air.
More RPM, more flow, less reserve capacity.
Doug

I would look at the relief valve first - I had an engine do the same thing and it was the oil pump relief hanging up once it warmed up - try another pump. If you are using the stock pick-up having it close to the bottom should not make a difference and yes a filter can cause the same issue - what filter?

First off.. change the filter.. I have seen this on SB changed the filter and all was good

No NAME oil filter, I always change the oil and filter after breaking in the cam and cut the oil filter apart to inspect the pleats in the filter, I suggest you do that to the filter now and maybe remove the drain plug and use the oil dipstick or some other thin narrow piece of steel or aluminum to check how close the oil pickup is to the bottom of the oil pan, if it fits in on the thin side and not sideways on the wide side your good If it fits in on the wide side that is to far away according to the drag race engineers at the old Mopar drag seminars
What color is the spring in the bypass your using now?

Good advice, heading over to shop. Was thinking more about this and the filter does make sense along with possibly the cover of oil pump. Not changed because it is original with cast number. But it is possible the relieve valve port is too worn and maybe pushing too much oil by relieve valve when not meant to.
Spring is hemi black. Correct length and compress to 22lb using service manual spec. Plus .060 lock washer in cap. Did add one qt extra on the last run, and it did seem to improve somewhat, but did not resolve issue.

Maybe you have a defective oil pressure gauge
All the stock and high volume oil pumps I've used with the black spring had 80 lbs. cold, no matter what weight oil (from 5W20 to straight 50 W) I used
EDITED: I like to see 10 lbs. per 1000 RPM with hot oil, IE 70 lbs. at 7000 RPM
I've built and raced a bunch of different stock blocks, 361,383, 426W and 426 Street Hemi as well as 413 and 440, most of them had loose liftrs bores and most of them would make 80lbs cold with a high volume oil pump, I've built them with .004+ main bearing clearances with the old Clevite full wide groove race main bearings with .003+ on the rod clearances.
I now use the Seal Power narrow full groove truck H.D main bearings that usually have a liittle less than .004 clearances with rod bearing clearances having between .0027 to .0035 oil clearance, I cut the bypass spring down, if needed, to get the 10 Lbs. per 1000 RPM with hot oil also if it has more than that after breaking the motor in

Gives me the eebeejeebee's.....That's how my aluminum Hemi was. Very inconsistent with oil pressure, then it blew up. Could be any of the things you mentioned, or it could be a whole list you didn't. Best way to look for it is with the engine on the stand and a drill motor thru the distributor hole to prime it. Try all your ideas out one at a time from the simplest to the more complicated. Make a list and start crossing things off you tried. I spent a season trying to find my issue.

Never like how little oil there is in a Stock Oil Factory Pan. Even a stock pump can empty a Hemi pan of 6 quarts and put it in the valve covers and lifter gallery. The Hemi I have in my Challenger all factory iron 426 has around 100 lbs of oil pressure at start up, 40 lbs at idle. I run around 12 quarts of 40 weight oil. In one motor on start up it pegs the gauge to well over100 lbs to about 150 lbs but dont go by that it is big cube Hemi all aluminum with a Barton spray system and all kind of good stuff. I am a big believer in oil pressure as long as you have an oil pan that has 10 or more quarts. One motor that we had built by another Hemi Builder that ran a Funny car for a family member had low oil pressure at start up and break in. It was like 11 lbs at hot Idle. 70 lbs at start up. Changed the pump and other stuff no change. Looked at everything and finally pulled the hemi and took off the oil pan and saw some numbers on the pan rail the we thought would answer all the problems. Stamped on the rail was 1.5 M. So out comes the crank and measure it and the mains were down 1.5 from the factory. Back then and likely now you could not find an over size main by 1.5 or 1. So we get out one of the spare stock cranks 10 under and put it in the motor and that solved the low oil pressure problems.We just got luck noticing that stamp on the oil pan rail or the complete fresh motor would of been torn down to bare bolts. Motor is still in the car for the last 35 years.

This is exactly what we have learned over the last 20 years of building and blowing up Hemi's. 6-quarts is just not enough.....Oil pressure is king, but these also need a lot of volume.. Gots to have lots of it, and 10 quarts for us is the min we will run on even a mild one. Then there is all of the discussions around restricting the flow to the heads, priority oiling, push rod oiling, spray bar oiling, etc.....So many different variables, there isn't one right answer, but its what ever works for you. I have not been able to make a 7 quart pan work, mine are built to hold 12 typically.

And if it pegs the gauge when cold, so be it...I want to see +15psi at an idle hot in gear, and none of this fluttering stuff. I do not care what it is when cold. These engines are finicky with oiling, and frankly so much so, I do not always like owning them. I have never had oiling issues with a wedge. Then again, you can't fit 6 quarts of oil up in the heads like you can a Hemi..

Wait until you step up to a set of B1 heads

How much lifter clearance is there?

What kind of cam and if roller, what lifters and lift.

I will probably never go that route.

Most of the stock blocks with 30,000 + miles on them that I have measure all had at least .0025 + clearances, with stock type replacement flat lifters or roller lifters
I have ordered and use the BB Chevy race .904 roller lifters for pushrod oiling and they do end up with a little tighter clearance on stock blocks
If your wanting to make a stock block as good as you can get it on the lifter bores have them bushed and size to fit your lifters

The description "Flutter" just freaks me out.

If it means what I think it means, and it's doing it with more than one gauge, then one place think I would look is....
I would be trying to examine possible
areas for the oil to become aerated/filled with air bubbles or simply leak internally.

Definitely chase the easier stuff first. More oil, different filter, relief valve etc

I have seen RB blocks where someone with good intentions tried to improve the main oil feeds by drilling or reaming them to 5/16",
which caused the bit to break through the side of the webbing/huge internal leak. This begs the question....if the bearing has
a 1/4" hole in it, and the upstream feed is 5/16" or even 1"..............will it ever flow more than the 1/4" hole?
I repaired the block by reaming/press fit tubing.

If there is a loss due to an internal leak, it may be possible to observe it while using a priming shaft.
priming with the intake and valve covers off to observe flow is good advice you have probably seen before.
I would probably start there.

Less often discussed.....if there is something weird going on in the lower end, you might be able to find it by priming and observing
flow and leakage with the oil pan off also. This can be messy but is sometimes educational......make a stub oil pickup without a screen, clamp
a hose to the stub, drop it in a bucket of oil. Place the bucket of oil in a large, clean pan under the engine, prime away
and observe from underneath with the best lighting possible. If one pair of rods leaks a whole lot more oil than all the rest, definitely
wonder why. If a leak comes from seemingly nowhere, zoom in on it...could be a hole somewhere there isn't supposed to be.

Of course, this is cold.
If the issue only happens when warm, like a porosity hole that opens enough to leak only when it warms up.....it can be next
to impossible to find.

Been a good read. I built this motor under the guidance of a master builder (hemi) but on a budget and as a practice motor. Unfortunately he is only available with occasional call because of illness. Hence some of the out loud thinking I am doing and asking on the forum. It was prior windowed block. But I had all the proper machine work done, test etc... Built to be a stock motor stroked to 4.15, but just under 10.25 to 1. While I have all the clearance data, the one exception is lifter bore. I know the lifters are stock size, just did not measure all the bores. Though I know that they are loose because of the honing required to clean them up. I am thinking more oil is the solution but will go step by step. I also think this post can be very helpful to the other building motors on their own.

So yesterday I swapped filter. Moved to a more traditional PH-8 size. Noticed the inlet ports where larger and more, then the one that came off. Cut the filter open and it had some of the assembly grease and such in it but no metal. Primed the motor again, then started it. Had a 10-15 psi increase in oil pressure cold. Was at 80 psi at about 2000rpm. As oil heated up and water temp about 140 and rising had good 45 plus at 2K, and in the 30psi at idle. 1100rpm. Once it warmed up completely pressure down in the 40 range and back down to 25 at idle. Running in the 2200 to 2500 oil pressure is ok, but once I go higher in rpm above 3000rpm and up toward 4K the pressure initially rises but then will start fluttering downward again. Not as low as before, but still down such that I am not at the 10psi per K rpm. I go back to idle for awhile. Then rev back up and it will climb right back up to the 50 even 60psi range, but flutter down again.
Probably could not make the 1/4mile without seeing this loss at the end of the run. Only does this hot and when RPM is above 3K.

Shutdown, drained water and oil after cooling. No oil in water and no water in oil. BUT I only got 3 quarts out of the pan. Plus one in large filter means I had 2 qts at least in the motor above the pan. I was able to work a dip stick under the stock pickup. I could rotate it about 45 degree, but not stand it up vertically. So it is close to pan, but with clearance. Also When I drained oil, I first just drained about 6 oz. No water just a couple of very small metal metallic pieces.

Pulled plugs and covers. Inspected and everything looked good. Rocker plugs in, only some signs of excess leakage around one short shaft at the angled stand (driverside). Otherwise caps dry and no signs the head is flooding with oil.

I think gauge is eliminated unless we think it flutters only when hot oil there. Otherwise it responds appropriately. Cam is Racer Brown H44 with Hyd lifter and stock rocker assembly. No pushrod oiling. No restrictor for head oiling, removed them as recommended.

Plan is to recheck lifter preload while covers off. Swap out the oil pump cover and refill. Then test. If still issue I will add extra qrt of oil. See how that works out.

I guess it is interesting. During an oil change with filter you would add 7 qts, but you probably only get 4 plus 1 for filter out. Meaning your really running with about 9 quarts on a stock motor after first oil change? 2 left in and 7 added?

Having watched several 440 and hemi motor builds and test with only 6 qts in, did not observe this oil pressure type of issue. But I guess my motor upper end could be using more oil that does not get back down to pan fast enough. Especially with windage tray. I did test fill the 70 pan, and if I remember correctly 6 qts was still under the pan baffle level wise.

Flutter is not really rapid, more like pulsing as pressure drops at higher rpm. Starts dropping off, might spike up, then back down, all while trending down at that higher rpm. So I hope this is the loss of suction head to the pump from a too low oil level.

On the bright side I rebuilt the original water pump and mechanical fuel pump and those are function great. More to follow, and thanks for all the insight.

I have had this same type issue , it turned out the be the oil pickup tube, someone shortened the tube by cutting off some threads & it had a ledge step on the very last thread causing it to not seal up good when hot & it would suck air & oil. the hotter & thinner the oil got the worse the pressure flutter was. the tapered threads seal up at the very end of the tube in the block threads

I believe you answered your own question. Only 3 qts came out of the pan. Try adding some additional oil. If the fluttering is gone now you either need to stop the internal leaks, reduce flow to unneeded area, or increase drain back. Or the tried and true method. Add more pan capacity
Doug

On a fresh engine build you will use up oil to fill the passages, fill the lifter valley, some oil in the heads, etc.

Once the motor was warmed up you should have drained the pan to see how much “drainable” oil you had.

If this particular pan calls for 6 quarts you should have drained 6.

Start at ground zero. Drain the pan and add 6 quarts and see if your issue is resolved. Leave the filter in place.

Work from there.

Yes it was oil level. The extra quart resolved the issue. I do think there is excessive leakage internally at the lifter bores. I never saw any aeration in the oil, but maybe you can't see it. My idle pressure hot is low at 20, but solid 35 to 40 at 2K. Continuing to rise to 60 at 4K. Did talk to the engine builder and he has used just 5qts for break in on 440/hemi using the 70 style pan. Those motors have always had high oil pressure, so better internal flow I guess. It is interesting how the windage tray is designed. Oil can only flow out the front and back, until it gets to a much higher level then out the side vents.
Never heard any lifter noise so they must have stayed pressurized with oil. I guess the drop in level really effected the pump head enough to loose flow volume at that higher rpm.