Thread: Baffeling Oil Pressure problem

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I think you're sucking air (ventilating) or cavitating. Even with worn bearings I would not expect to see a pressure drop as rpm increases.

When I was fixing the damage to the bottom end, I slid the cam forward, and checked the exposed cam bearings, they all looked good.
I also pulled the lifters out when I swapped to the restrictors and it all looks pretty clean in there.

If there is any debri around, it's not shown up in the oil.
After each test run I drain the oil, sieve it, and it's pretty clean.

I'm going to swap the pump this weekend and see what happens!

If that doesn't work, then my next favourate idea is that there's a huge amount of windage caused by the rotating assembly that's thrwoing the oil all over the bottom of the motor, and it's not getting back into the sump fast enough.

A few people have recommended a crank scraper, others have said make a breather outlet on the mech fuel pump blanking plate

Since the restrictors seem to make no difference, I'm going to take them out to keep the valve springs cool

I'll get to the bottom of this!

Sure sounds like the oil is going somewhere. Is the valley filling up? Check the drainback holes, some blocks have casting flash restricting them.

Yes - Is it filling the valley?

Well, the engine is set up in the car so the carb is level with a Victor Junior manifold, so that means the block is about 10Deg leaning backwards. So during these garage tests, and racing of course, most of the oil returns at the back.

I ground out the rear two oil return holes as much as I dared, which gives me a hole nearly big enough to get my first finger down on one side, and little finger on the other.

The holes over the cam down the valley are all open, but of course they have the cam spinning right under them.

I thought that the lifters may be dropping too far down (small base circle cam), and the oil hemoraging out the bottom of the lifter bore, but I measured it and I think there's enough clearance oil relief on the lifter and the bottom of the bore. Besides, if it was leaking there, I would have thought that would have leaked at any RPM, and also the restrictors would have made a difference.

If only I could miniaturize myself and walk round inside while it was running!!

New oil pump - same problem.

Warmed the motor up, then raised the RPM. 5k,6kOk - 70lbs.
6250 pressure starts to drop slightly, then holding that RPM for a couple of seconds, the pressure suddenly drops.

Took the restrictors out, since they didn't make any difference, and I like the idea of keeping the valve springs as cool as possible. I took the covers off straight away after the test, and there's enough oil to keep the top end lubed, but not enough to say the oil is being "stored" up there.

I wonder, has anyone had trouble with Milodon 31145 sumps?

What weight oil are you using? Try lighter oil, or a different brand. Grasping at straws, maybe, but some engines don't seem to like some oils.
How much blowby does it have at high rpm? Could the airflow be holding the oil up top?