Oil Pressure

[Barc Cunningham]

Would it be possible for someone who has changed to the flex lines and
has some experience with the pressure drop to go back to the old rigid
lines again and see if the pressure increases back to the original.
Would prove the point! Barc TC1315

billsoquel wrote:

> My oil pressure also dropped 10-15 pounds to 40-42 pounds at normal
> engine temp, when I changed to the stainless steel braided lines. I
> had done nothing else, so it had to be the new oil lines. My MG TC
> guru said 40-42 pounds is fine, Not to worry.
>
> I did purchase a new pressure oil spring, but it is still on the work
> bench. Will get to it and will comment to the group when I do.
>
> Bill Webb
> TC 3338
>
> [Non-text portions of this message have been removed]
>
>

[Non-text portions of this message have been removed]

[BUD SILVERS]

Hello all;



If you have oil being pumped at a fixed rate (fixed size pump at a fixed
RPM) and you increase the size of the line, the pressure will decrease, and
the volume will increase. If you decrease the size of the line the pressure
will increase and the volume will decrease.



Consider your bathroom faucet, when you open it the water flows, the more
you open it, the more water flows, increased volume flowing out and
decreased pressure in the line. When you close the faucet the water stops
flowing, the volume decreases and the pressure in the line increases.



Therefore at any given (fixed) RPM the larger, less restrictive, lines will
show a lower pressure and give a higher volume.



In an automobile engine ideal oil pressure is 40 to 50 pounds at cruise RPM.
More than that steals horsepower to run the pump and in extreme cases can
cause the bearings to become "washed out." Less than that can cause the
engine bearings to contact the crankshaft rather than riding on a coating of
oil, thus causing bearing failure. At idle the engine is under no load so 15
to 25 pounds of oil pressure is sufficient.



Bud Silvers

TC 8192 - Low n slo in the Black Forest of Colorado...





[Non-text portions of this message have been removed]

[Pavone, John (GE, Corporate)]

It has to be the new flexible lines, since nothing else was changed (oil
included) prior to the pressure drop. I've read that the general rule of
thumb for oil pressure is 10 psi per 1000 rpm. I guess the TC is no
different. Since I'll be observing a 4200 rpm redline until next winters
engine teardown, I should be ok.

If Peter Egan can run a 2600 mile trip at an indicated 20 psi, I should
have nothing to worry about!

Thanks!

JP

TC2797

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>..

Would it be possible for someone who has changed to the flex lines and
has some experience with the pressure drop to go back to the old rigid
lines again and see if the pressure increases back to the original.
Would prove the point! Barc TC1315

billsoquel wrote:

> My oil pressure also dropped 10-15 pounds to 40-42 pounds at normal
> engine temp, when I changed to the stainless steel braided lines. I
> had done nothing else, so it had to be the new oil lines. My MG TC
> guru said 40-42 pounds is fine, Not to worry.
>
> I did purchase a new pressure oil spring, but it is still on the work
> bench. Will get to it and will comment to the group when I do.
>
> Bill Webb
> TC 3338
>
> [Non-text portions of this message have been removed]
>
>

[Non-text portions of this message have been removed]






[Non-text portions of this message have been removed]

[Tom & Emily Wilson]

I am looking for suggestions before I dig into this problem. Newly rebuilt
XPAG with 300 miles on it. This morning it took one minute for the oil
pressure gauge to register any pressure at all. Then it slowly rose to
about 35 pounds. After driving a bit it went up to 40 and stayed there.
Same situation occurred with each engine restart, after it was warm. This
hasn't happened before on this engine.
This engine has not had oil pressure above 45 pounds since the rebuild.
We're working on it this coming Thursday - oil change, retune carbs,
etcetera. And hopefully find the cause and fix this problem.
Any suggestions?
Tom Wilson
Zionsville, Indiana USA
TC0272 & 0273


[Non-text portions of this message have been removed]

[BUD SILVERS]

Tom;



You probably already know this, but if you are using the braided stainless
lines in lieu of the stock steel lines this would account for some of the
oil pressure being low. I don't believe it would account for the low
pressure on start up. I have not done it myself yet, but I understand that
there is an oil pressure relief that can be adjusted with shims. Maybe you
should check that.



This last thought might be a dumb idea, but could you have air in the oil
pressure line from the block to the gauge? Could that cause a low reading on
start up? Just a thought.



Good luck.



Bud Silvers

TC 8192 - Low n slo in the Black Forest of Colorado......



From: Tom & Emily Wilson [mailto:twilson@indy.rr.com]
Sent: Tuesday, May 20, 2008 2:34 PM
To: mg-tabc@yahoogroups.com
Subject: [mg-tabc] oil pressure



I am looking for suggestions before I dig into this problem. Newly rebuilt
XPAG with 300 miles on it. This morning it took one minute for the oil
pressure gauge to register any pressure at all. Then it slowly rose to
about 35 pounds. After driving a bit it went up to 40 and stayed there.
Same situation occurred with each engine restart, after it was warm. This
hasn't happened before on this engine.
This engine has not had oil pressure above 45 pounds since the rebuild.
We're working on it this coming Thursday - oil change, retune carbs,
etcetera. And hopefully find the cause and fix this problem.
Any suggestions?
Tom Wilson
Zionsville, Indiana USA
TC0272 & 0273

[Non-text portions of this message have been removed]





[Non-text portions of this message have been removed]

[Tom & Emily Wilson]

Bob - thanks for the notes. Additional info on slow to build low oil
pressure:
Oil level is not low.
Oil is Castrol 20w-50.
Filter is the Grunau spin on unit.
Exterior oil lines are the original steel ones. I have new braided flex
metal hoses I haven't installed yet (from John Seim).
I didn't check bearing clearances or oil pump gear end clearances, as I
didn't build the engine.
Problem hasn't occurred before. Oil pressure came up immediately when engine
was started every time prior to today. Odd that it started after 300 miles.
Tom



_____

From: Bob Grunau
Subject: RE: [mg-tabc] oil pressure


Tom,
Check:
1- bleed the oil pressure line at the guage to let air out?
2-either replace the oil pressure relief valve spring or put a shim under
the spring. I use a 1/4" lock washer with the set removed. Should raise
pressure 10 psi.
3-I assume you have original steel oil lines and my spin-on filter adapter?
Or are you using an original type oil filter? If original, or one with
removeable filter insert, make sure the filter is not restricting the oil
flowing out the side of the original cannister.
4-did you check bearing clearances and oil pump gear end clearances??
Bob





[Non-text portions of this message have been removed]

[Peter Roberts]

Tom,

There was a recent thread regarding low oil pressure after a valve train rebuild. Did you rebuild the valve train? This might be a place to look. The fact that you eventually do get pressure up to 45 lbs and holding is contrary to this.

As for the slow buildup, why not take the valve cover off and (with rags handy) start the engine. You will know immediately if you have a flow problem. Absent a flow problem (and a tidy bit of cleanup), the gauge starts looking guilty. Are you sure the gauge is reliable? Can you swap in an alternate?

What type oil are you using? I made the error of using synthetic after a rebuild. Lousy pressure, lots of smoke Dropped it and refilled with dino and the problem was solved.

_Peter

----- Original Message -----
From: Tom & Emily Wilson
To: mg-tabc@yahoogroups.com
Sent: Tuesday, May 20, 2008 4:33 PM
Subject: [mg-tabc] oil pressure


I am looking for suggestions before I dig into this problem. Newly rebuilt
XPAG with 300 miles on it. This morning it took one minute for the oil
pressure gauge to register any pressure at all. Then it slowly rose to
about 35 pounds. After driving a bit it went up to 40 and stayed there.
Same situation occurred with each engine restart, after it was warm. This
hasn't happened before on this engine.
This engine has not had oil pressure above 45 pounds since the rebuild.
We're working on it this coming Thursday - oil change, retune carbs,
etcetera. And hopefully find the cause and fix this problem.
Any suggestions?
Tom Wilson
Zionsville, Indiana USA
TC0272 & 0273

[Non-text portions of this message have been removed]





[Non-text portions of this message have been removed]

[D & J Edgar]

Tom,

Regarding the slow build up of pressure, I believe there is a very small
port where the oil line connects to the gauge. Sometimes this becomes
partly clogged and it just takes time for the pressure to seep past the
port. Could be the line feeding the gauge has some restrictions too. Pop
off the oil filler cap and see how fast the oil reached the rockers once
engine is started up. If you have access to another gauge try that. You
could hook one up for a test or even with some connectors run them in tandem
to test compare.

As far as 40 lbs of pressure running I think that is fine. Many years ago I
asked the question of if my 30 lbs of pressure was OK after reading many
reports of people running 60. I had run 30 lbs for many years without ill
affects. I was assured that 30 was very adequate and that what you really
should be concerned about is oil flow. It really is better to have plenty
of oil flow at 30 lbs than less flow and 60 lbs. Flow helps cool the
engine, flushes out particles faster and flips around to other components
too. I could boost my pressure with additives and/or heavier weight oil but
have elected not to.

Just my two cents worth,
David Edgar, TC 5108
El Cajon, California

[John]

I had a similar problem on a Y Type and what it was, was the new paint
on the engine had made its was inside and was occasionally blocking
oil ways until it lost all oil pressure and I had to do a internal
investigation.

[Rick Waters]

I have found that the thinner the tube to the oil pressure gauge, the
less responsive is the gauge. The line on the TC is very small ID, and
the gauge behaves in a manner that I would consider normal. I have a
Stewart Warner racing gauge (from the 60s), and when I hooked i up to
the TC, it confirmed that the TC gauge was accurate (at least they gave
very similar readings). The SW gauge was originally on a small block
Chevy V8, and was attached with a larger diameter tube. The gauge was
much more responsive in that situation.

The whole notion of lubrication of rotating bearings is often
misunderstood. The actually prevention of wear is caused by the oil
forming a hydrostatic wedge between the journal and the shell. It is the
same principle which supports a water ski. Obviously, the key to good
lubrication in this circumstance is the maintenance of a large volume of
oil in the journal area. Large diameter, clean oil lines, and good
pressure from the pump assure this, but of the two, the volume is the
more important, in my opinion.

-Rick, TC 7881

Tom & Emily Wilson wrote:

>
> I am looking for suggestions before I dig into this problem. Newly rebuilt
> XPAG with 300 miles on it. This morning it took one minute for the oil
> pressure gauge to register any pressure at all. Then it slowly rose to
> about 35 pounds. After driving a bit it went up to 40 and stayed there.
> Same situation occurred with each engine restart, after it was warm. This
> hasn't happened before on this engine.
> This engine has not had oil pressure above 45 pounds since the rebuild.
> We're working on it this coming Thursday - oil change, retune carbs,
> etcetera. And hopefully find the cause and fix this problem.
> Any suggestions?
> Tom Wilson
> Zionsville, Indiana USA
> TC0272 & 0273
>
> [Non-text portions of this message have been removed]
>
>