Re: Engine oil

[jlandry@domain.elided (John A. Landry)]

On Wed, 03 Dec 1997 14:19:11 +0000, zee <zee@domain.elided> wrote:

>Excellent opinion,

Thanks... but I wouldn't go so far as using the word "excellent." <grin>

>Now comes the next question, which you may or may not have already read.
>Why would my oil pressure be 40lbs at 2700 revs cruising and then drop
>to 20lbs at higher revs. I am always watching the oil pressure to
>determine my top speed. It really does look like oil deprevation. Maybe
>the oil is getting stuck up top and takes too long to get back down.
>So..two weeks ago I had to do a valve job on both heads. I was hoping
>that a good hot tank would clear out the oil passages and fix this
>problem, but no, I still have it. Someone suggested the bearings but I
>don't want to believe them. What is your opinion on that one?

Sorry... I rambled on for so long that I forgot the original question,
hehe.

My *guess* based on the what I know about the IH engine, about other
manufacturers engines with the same problem, and the lengthy discussions
about this very subject in past Digests...

Probably oil starvation and / or cavitation?  Several reasons I can think
of... there could exist a combination of problems that lead up to this.
Let's say you have the wrong dipstick for your engine so your oil is low to
start with, plus a leaky oil pump gasket (without having my parts manual in
front of me, I *think* there's a gasket in there) so it sucks air when the
going really gets tough, a partially blocked pickup screen and the IH
engine's normal tendency to hold large amounts of oil in the upper reaches
of the engine during operation.  When I had the intake manifold and lifter
valley pan off my 345, I seem to recall one of the biggest areas where oil
could pool would be in the lifter valley... lots of room in there!

I've personally never seen this phenomenon in my Traveler, but you're not
the first person to complain about it on the Digest.  Seems like it's more
prevalent at higher engine rpms when folks run lower axle ratios.  My
Traveler has 3.54:1 gearing and larger tires, so the engine probably never
revs much higher than 2500 rpm even when doing 70+ mph.

Some suggestions previously discussed on the Digest were to try adding more
oil... maybe a half to one full quart above the full mark on the dipstick.
For fun you may want to check the oil level when the engine is running.
You may want to drop the pan (easy to do) and check the condition of the
oil pump and pickup screen.  Make sure everything is in order and tight.

Have you tried changing the oil viscosity and brand of oil filter?  What
was the effect (if any)?  I'm sure you;ll get other good suggestions from
the Digest members.  It doesn't sound too dangerous to drive until you get
a chance to fix it.

Good luck,

John

------------------------------------------------------------------------
jlandry@domain.elided             |
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