Normal Oil pressure fluctuation

[brad@elevated.org]

Don-

When I first start up, my oil pressure gage reads almost 40 lbs. After about 20 minutes at idle it reads about 18 lbs. I've run the engine about 10 hrs since purchase last fall, so an oil change is logical since I don't know when it was last changed.

My question is, is this a normal fluctuation in pressure from cold to normal temperature? Everthing else seems fine.

One other question-if the the dipstick shows the level to be in the full range, should there be oil around the lower distributor gear? How does that get oiled?

Thanks--

Brad Shinn
Cal 34

[Don Moyer]

Brad,

The best time to evaluate your oil pressure is when the engine is fully warmed up and at your favorite cruising power setting. The oil pressure should then stabilize between 35 and 40 psi. When you retard the throttle to idle, the pressure will usually stay at 20 psi or above, although Universal allowed a minimum pressure at idle of 10 psi.

Your question regarding oil level in the bottom of the accessory drive is a bit more complicated. Any time the engine is running, the accessory drive is receiving oil through a small "splash basin" built into the front of the main accessory drive housing. The oil level reaches a return drain hole in the forward face of the housing, which maintains a level within the accessory drive that just barely reaches over the bottom of the distributor drive gear, and at a level that is difficult to see when looking down into the distributor mounting hole.

During our rebuilding process at MMI, we plug the original drain hole and provide one that is approximately 1/2" higher than the original. (See our tech tip for more details of this modification.)

Best regards,
Don Moyer

[tartan30cirrus]

My oil pressure situation is different...it is opposite what Don states above....warmed up and cruising RPM she is at 20 or below and at idle (albeit cool) she is 35. My issue, I think, is that the oil pressure keeps dropping too low and the engine seems to be shutting down in response. If I let the engine sit turned off for awhile she starts right up and runs well but then I seem to lose RPMs and she shuts down when the oil pressure is well below 10 psi if not lower. What do you all think?

Cheers,
Clint

[Don Moyer]

Clint,

You should definitely turn your oil pressure regulating valve in a turn or so. Your oil pressure should settle in between 35 and 40 psi at your normal cruising RPM with the engine at a normal operating temperature. You can make this rather large adjustment (a turn at a time) with the engine off and cool, and then check for the result the next time you run the engine.

Don

[tartan30cirrus]

From FAQ:

"since we've been dressing all the orifices of the oil pressure regulating valve in the block and using early style regulating valves during our rebuilding operation, we have essentially eliminated the hassle we used to face in getting oil pressure to settle down during test runs."

Do I have the ball or the old style regulating valve? My problem continues (see post in troubleshooting) and my homework brought me to the FAQ site. Also saw this...

"Other symptoms of regulating valve problems include oil pressure decreasing as RPM increases (another manifestation of the ball moving off center) and low oil pressure which doesn't respond normally as the adjusting bolt is turned in. This problem is sometimes caused by a regulating spring that has worn thin by rubbing along the inside of the threaded hole into which the adjusting bolt is installed."

I am wondering what to do. Please help as I am a bit lost.

Cheers,
Clint Chase

[Don Moyer]

Clint,

We definitely want to get your pressure a bit higher, and more consistent.

According to our records, we didn't notice anything unusual during our test run, so we left the spring and ball type of regulating valve in your late model engine (your engine is one of the latest we've ever seen, with a serial number of over 204,000).

I'm going to send you a new regulating valve, made in the style of the early model valves which have a tendency to provide more consistent pressure regulation.

Don Moyer

[Don Moyer]

Clint,

We have an address for Brewer's Marine and for 25 Deblois St. in Portland. Please let us know which address you would you prefer us to use.

Don

[tartan30cirrus]

Don,

Would you recommend just using the dressing tool to do the redressing rather than the 1/8" NPT...sound easier and more effective. What kind of pressure should I use?

Cheers,
Clint

[Don Moyer]

Clint,

That's a good idea. The dressing tool is much more effective than the old Universal procedure. I got the tool to UPS this afternoon, so you may have it tomorrow.

Would you please give me a call when you receive the tool so that I can talk you through some of the finer points in its use.

Thanks,

Don

[tartan30cirrus]

Don,

I think I have the OP regulating properly now. Can I give it a few more runs and a little more monitoring before I send back the redressing tool? Just want to make sure I don't need it again for "touch up".

Cheers,
Clint

[Don Moyer]

Clint,

Sure.

Don