PDA

View Full Version : Speaking of oil pressure.......



sbca96
06-24-2006, 09:09 PM
1963 Avanti R1 - 104,000 miles. Dont know history of the engine, if
its been rebuilt or ??? Was supposedly "restored" in the 80's.

Question, the oil pressure at 70 mph starts out at 60 psi when the
engine is cold, as the engine warms up, the pressure decreases, which
is normal. Whats not normal is how MUCH it decreases. At 70 mph with
the engine at 150 degrees by the temp gauge, the oil pressure is about
35psi, or just under 40 psi indicated. I remember years ago reading
about a relief valve on the front of the engine, could this be the
culprit? If so, how do I go about increasing my oil pressure, and do
I even care to increase it?

Thanks!

Tom

N8N
06-24-2006, 09:42 PM
the relief valve *should* be set around 50-60 PSI. You could try to shim it with some flat washers and see if your oil pressure improves. I kind of doubt it will, however, but it's worth a try. IF it does, just buy a new spring for it and remove the washers. Whatever you do do not try to increase your oil pressure by soldering shut the little hole in the OPRV - that is the oil feed for the timing gears when the OPRV is closed (when it's opened, ALL the bypass oil goes into the timing cover and back to the pan.)

nate

--
55 Commander Starlight
62 Daytona hardtop
http://home.comcast.net/~njnagel

ROADRACELARK
06-24-2006, 09:42 PM
Tom,
The Avanti or Stude shop manuals give detailed service instructions on the valve you are refering to. It states in those instructions not to "stretch" or alter the spring tension in that valve. IIRC messin' with that spring will affect oil supply to the timing gears at low RPMs ( you don't want that:(. Clean the pressure relief valve as it says in the book. You might try a different weight of oil. Some like the Shell Rotella 15W40, they say it increases the oil pressure some, but then so does STP:). It's worth a shot;)
Dan

sbca96
06-25-2006, 12:07 AM
Thanks for the input guys ... what IS "good" oil pressure on these
engines? I remember that it wasnt as high as GM, I seem to remember
it wanting 10 psi per 1000 RPM? I have been "out" of the game for a
while, and been working on GM cars for the last 10 years.

What could cause it to drop THAT much after warmed up? I am using
10w-40 if memory serves, I might try 20w-50, but thats going to give
me some insane oil pressure when cold!!

Tom

Mike Van Veghten
06-25-2006, 12:34 AM
My 259 powered Lark 2dr. wagon does pretty much the same thing.
I attribute it to an engine that is just wearing out....enlarging clearences....

When I bought the wagon about 7 years ago...the pressure was at an averege of about 5psi higher....after full warmup. The cold pressure is...as far as the mechanical gage says about the same as 7 years ago. But after full warmup OR....a long steep grade (over the Grape Vine going to the races in Bakersfield), the pressure drops to about 30ish pounds (3000 to 35000rpm). It used to drop the 40ish pounds!
I tried the Valvoline oil stabilizer (simillar to STP ?) and the pressure cold is 2 or 3 pounds higher....but hot or under a load....it's back to what it was 5 years ago...doesnt drop below 40 at 3000rpm or higher. Hot idle is better too.

And yes....I removed the valve, verified the hole was open, the piston moves freely and inserted a .060" washer....no change.

I understand it's not a fix for a well on it's way to becoming a worn out engine....I guess it's like taking high blood pressure pills...only backwards!!

Mike

PackardV8
06-25-2006, 12:38 AM
A little bit low at 70 mph, but not unusual for a high mileage Stude V8. A rebuilt engine I tore down recently had new pistons, rings, valves and bearings, but the lifter bores, cam journals and rocker arm bores still had 150k of wear on them. The oil pressure was similar to what you describe.

thnx, jv.

PackardV8

sbca96
06-25-2006, 03:41 AM
Strange ... I know that the oil thins when hot, but clearances tighten
up when hot also. It also doesnt take very long for the oil pressure
to jump back up. If you notice the picture post that I just made, I
was hanging out for about 2 hours at the burger place, when I fired
the engine up, it was back at 60 psi. On the drive home (55 miles)
it leveled off at about 30 psi around halfway home. Its also weird
how the difference between idle and 70 mph isnt much, but it doesnt
drop to "dangerous" levels like you would think. Down to about 30 psi.

Strange

Tom

Mike
06-25-2006, 06:45 AM
The adaptor that the oil filter screws onto has two disc valves. One, (light spring), is supposed to bypasses the filter when there is a six pound difference between filter in and out. The other is a relief valve that is supposed to dump oil from the pump directly back to the pan through about a half inch hole, above about sixty pounds pressure.
The adaptor on my R2 was warped and leaking; maybe as a result of the mounting bolts bottoming out in the block - original bolts, wrong combination of washers. After I replaced it with an NOS adaptor and bolts carefully cut to length, I checked the disc valves in the old adaptor; to see if I could blow through them. I could whistle tunes through them!
I never saw an oil pressure problem. Apparently, the pump is able to move enough oil for good pressure in spite of the leak, in a "fresh" engine. I suspect the relief valve at the front of the block didn't open at speeds as low as intended; and the timing gears were oiled mostly through the small bleed hole, though.
In a worn engine, I doubt the pump could maintain good pressure at low engine speeds, with a leaking relief valve in the oil filter adaptor. The valves in mine were in place and looked ok; but some folks have found them missing or broken. It's a good idea to remove the adaptor and check it out.
I wonder if either of the valves in the adaptor are really needed; and would consider plugging them if I couldn't find a good adaptor. Most filters have a built in bypass valve, (check mfg data). Older Stude V8's, with a bypass filter, used just the pressure control valve at the front of the block. With reasonable revs when the engine is cold, and a "racing" filter, like KN's, I don't think it would make a mess on the floor.
Mike M.

DEEPNHOCK
06-25-2006, 08:19 AM
Be careful doing that (shimming).
Zipped phenolic timing gear teeth, and sheared oil pump drive (distributor) roll pin are a definite possibility.
Ask me how I know....and yes, you can blow up an oil filter if you try hard enough[:0]
Jeff[8D]


quote:Originally posted by N8N

the relief valve *should* be set around 50-60 PSI. You could try to shim it with some flat washers and see if your oil pressure improves. I kind of doubt it will, however, but it's worth a try. IF it does, just buy a new spring for it and remove the washers. Whatever you do do not try to increase your oil pressure by soldering shut the little hole in the OPRV - that is the oil feed for the timing gears when the OPRV is closed (when it's opened, ALL the bypass oil goes into the timing cover and back to the pan.)

nate

--
55 Commander Starlight
62 Daytona hardtop
http://home.comcast.net/~njnagel

wagone
06-26-2006, 01:33 PM
IMHO I'd stay away from 10W-40 like it was the PLAGUE! I've used 20W-50 in my rebuilt Avanti engine and it didn't cause insane pressure when cold. That over hauled engine runs 65-70 pounds pressure when cold and never below 50-55 pounds when hot (even with 10W-30). Long term usage I intend to use Rotella 15W-40 as many people with more knowledge than I seem to swear by it. Oh, my engine idles at 20-25 pounds with 10W-30. Great oil pressure, but I do wish the oil mileage would improve.

wagone and the R2 Avanti

N8N
06-26-2006, 03:50 PM
Jeff,

zipped phenolic gear teeth on an Avanti? What does engine oil pressure have to do with the speedometer drive anyway? :P

nate

--
55 Commander Starlight
62 Daytona hardtop
http://home.comcast.net/~njnagel

55Commander
06-26-2006, 04:00 PM
Don't forget the pump itself. The bottom plate that holds the gears
in place can becomed scored and loosen the tollerances, this will
cause a drop in oil pressure.

You can either surface the hobbed side of the plate or flip it over
and regain some pressure that way. It's really easy

If it makes you feel more confident in how bulletproof these motors
are I drove home from Chicago to Dallas on 15psi oil pressure a
couple years ago. By the time I got home it still didn't knock but
the #7 rod bearing was in a couple pieces. Luckily the crank turned
OK and I'm back on the road.

raprice
06-26-2006, 04:15 PM
I remember a few years ago in the "Cooperator" section of Turning Wheels magazine, a similar question was asked. One of the answers was to try using a different oil, such as 20W-50 and see what develops. I had a similar problem in my Lark VI and the 20W-50 seemed to do the trick.
Rog

sbca96
06-26-2006, 07:44 PM
quote:Originally posted by N8N
What does engine oil pressure have to do with the speedometer drive anyway?

Sorry, my tach is dead, so the only way I could relay the RPM is by
listing the speeds.[B)][V]


quote:Originally posted by studeroger
I had a similar problem in my Lark VI and the 20W-50 seemed to do the trick.

I will try 20W-50 on the next oil change.;)

Tom

rockne10
06-26-2006, 08:23 PM
If memory serves me, the "idiot lights" don't come on until you've dropped below 6psi.[V] Don't that want ya ta put a gage in the Lark?

DEEPNHOCK
06-26-2006, 08:46 PM
Hey Bub! Don't split hairs with a bald guy!;)
You know what I meant![B)]
Jeff [8D]


quote:Originally posted by N8N

Jeff,
zipped phenolic gear teeth on an Avanti? What does engine oil pressure have to do with the speedometer drive anyway? :P
nate

Roscomacaw
06-26-2006, 08:46 PM
My Transtar's well-worn V8 has been showing 25 PSI on it's gage forever. This is hot - at speed - 20W-50 Valvoline. YEARS (17?) like this. No failures. And I DON'T baby it. There's way too much angsting about this topic here.;)

Miscreant at large.

1957 Transtar 1/2ton
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe
1957 President 2-dr
1955 President State
1951 Champion Biz cpe
1963 Daytona project FS

N8N
06-26-2006, 10:12 PM
quote:Originally posted by sbca96

[quote]Originally posted by N8N
What does engine oil pressure have to do with the speedometer drive anyway?

Sorry, my tach is dead, so the only way I could relay the RPM is by
listing the speeds.[B)][V]

you missed the reference, I was just pointing out to Jeff (who ought to know better) that an Avanti ought not to have a phenolic cam gear to zip, as all the R-motors were factory equipped with aluminum cam gears. :) He does make a good point though, if shimming the OPRV doesn't raise your hot oil pressure, take the shims back out, because all you're doing in that case is raising the oil pressure when the engine is cold and stressing all the components involved in driving the oil pump with no real benefit to the rest of the engine.

nate

--
55 Commander Starlight
62 Daytona hardtop
http://home.comcast.net/~njnagel