My 528 Megablock motor lost a lot of oil pressure after installing a new rollercam , oil through the pushrod Isky EZ roll lifters and pushrods with very large holes( .050+). Pressure was 40 psi on the gauge in the traps with 10 inch of vacuum, so actual was about 45 psi. I sent the pushrods back and had them restricted to .040. That didn't show a lot of improvement at all. So my guess is the Isky lifters are partly to blame, having a reputation of being a bit undersized from what i hear. I installed a Milodon pump with the five lobe configuration and that brought it up to 50 psi on the gauge, or about 55 to sixty in the traps. The bypass was shimmed till it shows 80 psi cold at startup. The block is bronze bushed, with .062 hole for oil to the lifters. I run Vr1 20w50 oil. Single line pickup system. Still not wildly happy with this deal. Any thoughts?

I can't help but wonder what the lifter to bore (or bushing bore)clearance is, if they felt loose during assembly, and so on.

Zippy, they didn't feel loose, so i assume they were no more than .0015 small, likely. Cold 20w50 probably hid any extra clearance well. If i pull it apart again i will measure the lifters and bushing bores. The pushrod situation has me bummed. Having to buy new intake pushrods in 7/16 versus 1/2 inch due to different lifter offset, sending them all back to restrict them to .040,etc i have over $1,000 into pushrods alone. Like they say, speed costs money, how fast do you want to go? Well, i am about as fast as i can afford

You have 80 cold and 60 in the traps. I don't see an oil pressure problem.

.062 holes in the bushings are huge....... as are the .040 in the pushrods.

.020 is plenty big.

Did you check to see how much leakage is coming out around the lifters at full lift while priming?

Somewhere here in the archives is DVW response and DIAGRAM to his ISKY lifter issue in relation to a failure he had of a bushing... IIRC, at that time, some speculation was that because a portion of oil circuit in the lifter body went below the bore there was momentary bleed-off. To further speak to that...It appears now after replaceing the one? lifter that is has been very reliable for several passes ALTHOUGH THERE STILL IS THE SAME LOSS. I do remember him saying his lifter to bore clearance is pretty large too. I'll see if I can't prod him to read/reply here.

To put it in perspective........ if you run the external lines on the Indy heads to feed a set of needle bearing rockers(like Harland Sharps), and you go from the unrestricted fittings that have the smallest portion of the internal passages at .120” diameter, and put one .060” restrictor in each side, the oil pressure in the motor goes up about 10psi.
Even with the .060” restrictor in place, when I prime a motor with Indy heads and the external lines there is a ton of oil coming to the top end.

Greg has 4 times as many .060” sized feed holes going to the top end as what I normally use.

Mega block, Isky Red Zones, .055" pushrod, .060" bushing hole, .0025"+ lifter bore clearance, 1/8" tall Melling pump, Indy single line cover. The relief spring has enough coils clipped off that it rattles in the pump. Running 5w25 JR1 oil. Even with the clearances this loose, oil pressure is great. I've had it apart after 200 passes for inspection. All good. 40-60psi idle depending on oil temp, 70 psi hot@7000. I did notice the axle feed hole is below the lifter bore bushings at base circle. Doesnt seem to bother it.See attached drawing.
Doug

Manton didn't do retrictions less than .040, so i should have checked around before sending them out. I didn't look at the oil going by the lifters. But by the looks of how much is coming out of the pushrods, it is probably plenty. I never thought that a .062 hole in each lifter bore bushing would be a bad deal, since a stock block is often raced with huge holes to the oil galley. If 55 to 60 psi in the traps at 7500 rpm, i'll run it and data log it to compare readings to the gauge.

The more I think about it there are really only 2 normal possible causes. The pump flow is insufficient. Or its hemoraging at the lifter bore due to uncovered passage or clearance issues. For it to be clearance it would have to be huge, worse than mine. I have to believe your pump out flows mine. Open or cracked galley? Unlikely.
Doug

I think after seeing the issues with my son small block I will now be priming every engine I build before I install the intake manifold. Big and small blocks.

If the hole in the bushings line up with the feed holes in the lifter when the cam is on the base circle, it will pump a ton of oil through the lifters.
Depending on how the oil flows through the lifter, it can be totally unrestricted flow.

Experienced it myself on a 572 I put together.
World aluminum block with the Comp 892 lifters.

Primed the motor, and the instant the drill started to drag down when the oil system got pressurized it shot oil out of the top of the Jesel adjuster screws about 15 feet across the shop.

I saw that and the thought that popped into my head was, “well........ I guess that’s not going to work”.



None of the factory lifters for a BB have provisions for pushrod oiling, or ever expose that large opening.

If you were running something like the Comp solid body 829’s(I’m not advocating those for your situation) that .062” hole wouldn’t be an issue at all.

It make not be an issue now, it just depends on if the hole in the bushing is lined up directly with feed the hole in your lifters or not.

Imo, the “correct” arrangement/relationship for pushrod oiling on a BB Mopar is to have the pushrod feed holes in the lifters be parallel with the axles, and positioned just above the oil band.
Then the only oil that gets into the feed hole is what squeezes between the lifter bore and the lifter body, into that hole.

Ive always done that, I really thought everyone did it. I want to see how everything is getting oiled, and also no matter how clean people try to be with clean oil there always seems to be that first shot/hint of slightly discolored oil and since im not really cranking the motor other then to get it fully primed I use a few paper towls to soak iy up out of the lifter vally.

Thats why im not big on assembly lube other the on the cam.

IMO .062" restrictor in the bushing is HUGE, like twice as big as needed. Not saying it is your issues just saying that's WAY more oil than needed up top.

This may be the only time I have 'issue' with something Dwayne said...I'm not sure the math is correct? 4x2is 8 and thee are 16 .062" orifices? So, wouldn't it be "8 times"? While it more emphasis his point of excessive area, the math was wrong? LOL, then maybe I'm off.

Nope...... you’re right.

Brain fade on my part........ he has 8 times as many .062” feeds as what I usually run.

As much fun as it would be to APPEAR fecious...YOU HAVE TO KNOW I KID! But I feel I know you well enough you are humble and smart enough to put it ALL into perspective.

It’s all good Sean 😎

The 8 times larger area emphasizes my point even more!!

This^^^^^^^^^^

I guess the Hippocratic oath doesn't apply to lifter manufacturers.
You know, the one that say "above all, do no harm".
In this case, it would mean "until you KNOW it can't wreck anything, don't sell it".