oil pressure too high ?

zray · May 7, 2009 at 7:30 AM

are the following oil pressures too high ?

@ 75 degrees F. with a 180 degree thermostat

cold engine:

pressure @ idle: 82 psi

hot engine:

idle (800 rpm) .... 35 psi

1500 rpm ..............70 psi

2000 rpm ..............72 psi

2500 rpm ..............75 psi

3000 rpm ............. 80 psi

3500 rpm ............. 82 psi

4000 rpm ............ 85 psi

Basically a stock 289 Hi-Po engine w/ vintage Paxton, 10: 1 compression, 0.020 over pistons, a high volume oil pump was installed 24,000 miles ago during a complete engine overhaul.

Aside from the break-in period, I've been using Mobil 1 15w-50 for the entire 7 year/ 24,000 miles.

Z. Ray

Edited by - zrayrichter on 05/07/2009 09:13:25

dunc289_old · May 7, 2009 at 9:01 AM

Your " old " pump may have a stuck relief valve, not allowing the oil to bypass as the pressure builds. Afresh pump would change that. I have a NASCAR pump, unused, if you need one....<img src=images/icon_smile_big.gif border=0 align=middle><img src=images/icon_smile_big.gif border=0 align=middle>

66gtk · May 7, 2009 at 9:06 AM

I have similar pressures on my Tribute. I was recently told that due to the High volume pump and resultant pressure to use LIGHTER weight oil. 0-20 wasn't even out of the question.

zray · May 7, 2009 at 9:13 AM

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>

Your " old " pump may have a stuck relief valve, not allowing the oil to bypass as the pressure builds. Afresh pump would change that. I have a NASCAR pump, unused, if you need one....<img src=images/icon_smile_big.gif border=0 align=middle><img src=images/icon_smile_big.gif border=0 align=middle>

my post is in error. Should have read "oil pump", not "old pump" It was "new" 24,000 miles ago.

I guess the consensus is the pressure is too high.

Z. Ray

Edited by - zrayrichter on 05/07/2009 09:14:59

Edited by - zrayrichter on 05/07/2009 09:16:02

zray · May 7, 2009 at 9:36 AM

<BLOCKQUOTE id=quote>quote:<hr height=1 noshade id=quote>

Your " old " pump may have a stuck relief valve, not allowing the oil to bypass as the pressure builds. Afresh pump would change that. I have a NASCAR pump, unused, if you need one....<img src=images/icon_smile_big.gif border=0 align=middle><img src=images/icon_smile_big.gif border=0 align=middle>

what makes a NASCAR pump different than the high volume pumps ?

Z. Ray

66gtk · May 7, 2009 at 10:03 AM

I'm going to run 0w20 and see what happens. I don't use the car in the winter anyway, but if I did, I'd go with a multiweight oil. Ideally, when warm, you want a 1:100 ratio - 3000 RPM = 30 PSI. For a 5-6K RPM engine, any more than 50-60 PSI in that range is too much. For me, my concern is also at 3000 RPM and idle, when I'm still getting 60-70 PSI.

Here's some good (long) reading on the subject. Don't give up until you get to the good stuff at the end!

http://www.club3g.com/forum/eclipse-…-about-oil.html

RPM_old · May 8, 2009 at 6:32 AM

I've drag raced for years and always liked high oil pressure as I always used 20W50.Your pressure is OK by me as I would rather have it high then low.Usually if oil pressure drops by more then 20lbs after warm up something is wrong in the motor!

zray · May 8, 2009 at 7:55 AM

At high rpm the numbers don't seem that off base:

5000 rpm ............ 85 psi

6000 rpm ............ 85 psi

6500 rpm ............ 85 psi

7000 rpm ............ 85 psi

anyone have first hand experience or know of data that supports the theory of high oil pressure equals washed out / eroded bearings ?

I'm wondering if the numbers will change when summer really hits and the air temperature is over 100 degrees ?

Z. Ray

Zed · May 12, 2009 at 6:45 AM

Hi, I have similar pressures with a 289 in my 64 Futura coupe. I fitted a ford Motorsport high volume pump when I rebuilt the motor many years ago. I have only done 4 to 5000 miles on the engine and it still has high oil pressure,(around 100 psi when cranking and a bit lower once started). I don't think I have a stuck relief valve as the pressure does vary with RPM and it also drops off slightly (85 psi ) once the engine has warmed up.

Zed

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