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.