Can my 351 Cleveland run well at high oil pressures?

TL/DR: Can’t understand why my engine is running oil pressure so much higher than expected.

Background - I bought this car in 2019 at 94,000 miles. The story (and mods) is documented at My ‘new’ ‘70 Cougar! Where to begin??. FF to today, I have driven 14,000 miles of near perfect performance! My only issue ihas been that the previous owner’s builder used Crane plastic guide plate bushings (which failed after 10,000 miles). Fortunately caught the ticking before it damaged the lifters, cam or pushrod. Last year the heads were machined for proper steel guide plates and 7/16 rocker studs. Now, the car runs and drives like a champ again - routinely eating up 200+ miles of odometer a few times a month.

The only issue I struggle with is the fine mist of 10W-30 VR-1 that is seen streamed across my FL1A filter, that I change every six months/1500 miles. There’s also a drop at the base of the fuel pump. I assume this is only happening during driving because there’s never more than a drop or two on the garage floor when parked. I can’t find the leak. I’ve spent hours looking and even reset the intake and valve cover gaskets.

This all came to my attention when installing a Shelby-style gauge pod with matched gauges/sending units. I operate both (aftermarket oil psi and Motorcraft SW1311 dummy light) senders threaded it onto a brass adapter, which is then threaded to the port on top of the block. I about flipped when the needle was pegged at 80+ psi! First, I blamed the sender, then the wiring, then the ground, and finally the gauge itself. I wouldn’t expect the brass adapter to contribute to the gauge falsely reading high.

So I sprung for a mechanical gauge and threaded it to the T adapter - in place of the dummy light sender. Much to my surprise, it read 85 psi at start up! As the engine warmed up, it gradually dropped to 67 psi @ 1000 RPMs. I put a multimeter to the aftermarket sender wire, which read 73Ω to ground. That matched to about 67 psi. When I took it to 2000 RPMs, it ran up to 78 psi. At 2500 RPM, the mechanical gauge was at 81 psi!!

So now, I actually believe my engine runs at a ridiculously high oil pressure. Could normal driving RPMs at these high pressures and wind be forcing small amounts of oil to “leak” is causing the dispersion on my oil filter, with no garage floor drips.

So…my original question: What might cause my 351 Cleveland to run at oil pressures from 67 psi (warm/idle) to 81 psi (warm/2500 RPM)? Maybe a stuck by-pass valve? I can see a rebuilder choosing a higher volume oil pump, but most of those are standard pressure, anyway. Can I continue to run it without harming my engine? If not, how far after 14K miles would it become a problem?

its fine

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My Clev runs pretty much the same pressure, no worries at all.
Your motor may have the higher pressure oil pump spring/shimmed or bearing clearances are a bit tighter. You have 14k miles, she’ll be good.

I had a 71 XR7 with a Cleveland that consistently ran between 70 & 80 psi oil pressure- no issues. Strong running engine, no leaks.

Pretty common with the hp/hv pump and stock type bearings. The larger opening in the race bearings sheds pressure and volume quicker, which is what the hv/hp pump is for. But I’ve seen hundreds(?) of Clevelands run over the years with this type pressure on the stock bottom ends. Used to be the combo was a 4v engine with a 2v intake in the 2v dirt track class, and those things would absolutely run off and leave all the brand x and y stuff, and they lasted a full season (usually) without being opened up to refresh.
The leaks are general Cleveland problems. The fuel pump and valve covers tend to at least weep a bit til you figure out the fix. Nowadays that’s usually right stuff instead of a gasket.

Like the others said, it’s completely normal. Factory spec on the 351C and 400 was 50~70psi at 2000rpms. My fresh build runs 75psi at cold startup, 60psi going down the road.

I think I’ve found the culprit for the oil ‘leak’.

To be sure it wasn’t the weep hole on the fuel pump, I zip tied a foam filter around the pump and drove 100 miles: the foam was bone dry, but there was a fresh coat of oil where I’d just cleaned up from last time. :face_with_symbols_over_mouth:

I’d been using a vented breather cap on my driver side valve cover. Today, I ran a non-vented breather with a hose to air filter housing and did another 100: bone dry everywhere!!

With my high crankcase pressure (which I now accept as ‘normal’), a fine mist of oil vapor has been coating everything near it. All this time, it’s been just a simple breather cap!

Of course oil pressure is different than crankcase pressure. I agree with everyone that your oil pressure is fine, but you should not have positive air pressure in the crankcase to spray out a mist of oil. Your PCV valve should maintain a slightly negative crankcase air pressure, and draw air out of the crankcase due to vacuum at the carburetor base. As a result, the breather cap should actually draw air into the crankcase from the air cleaner.

So…maybe the PCV isn’t keeping up because it wasn’t swapped for a higher flow when the PO did the rebuild. He used a moderately aggressive street/strip cam (.565” lift/109° LSA), so maybe having the low vac reduces the PCV efficiency?

Maybe I’ll try a high-flow PCV, like M/E Wagner DC-17and add a catch can.