Topic: oil pressure too high ?

[zray]

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

[Soaring]

Yeah, that's a little high.  When cold, it should be 40-50 and when hot it should be 30-40.  If you basically have a stock engine, why do you have a high pressure pump on there?  And why are you running 50 wt. oil when you should be running 10-30? 

[zray]

Yeah, that's a little high.  When cold, it should be 40-50 and when hot it should be 30-40.  If you basically have a stock engine, why do you have a high pressure pump on there?  And why are you running 50 wt. oil when you should be running 10-30?

engine sees extreme use, so I went with a high volume pump. Using 15w-50 as it is the only Mobil 1 oil containing all the zinc (zddp) I feel necessary: 1200 ppm.

The only reason I'm reluctant to go to a lighter oil is mainly due to the history of seven year/ 24,000 miles without any problems. But I will do some more investigation before deciding.

Z. Ray

[Soaring]

O.K, well, it's your engine, but those two things are the reason why your pressure is that high.  If you haven't had any problems, just keep doing what you are doing.  Just understand that you will have erosion damage to the bearings due to excessively high oil pressure.  But, if you are hammering that engine that much, you understand the wear and tear  of racing. 

[exxodus]

Just, for the next oil change to put some 15w-40 in. Pressure will down when hot.

- - - -

More the 1st figure is close to "0", the more fluid the oil is (cold) (that help to quickly protects the engine at startup (70% of wear occurs in the first few minutes of operation)).
 
The 2nd figure is high, the more viscous oil is in hot condition.

[Beeroxin]

yea running such a thick oil will make it hard for your motor to get lubed up in the first minutes after starting up and thats the most crucial time otherwise when ur hammering it a thinner oil will do just as well protecting your engine as a thick oil
so believe it or not that thicker oil is doin u more damage then ud like to anticipate
plus a thinner oil will run at lower pressures because it flows easier
think about puttin clay into a pop bottle vs. water
it will take some pressure and time to force the clay into the bottle whers water will flow right in

[zray]

O.K, well, it's your engine, but those two things are the reason why your pressure is that high.  If you haven't had any problems, just keep doing what you are doing.  Just understand that you will have erosion damage to the bearings due to excessively high oil pressure.  But, if you are hammering that engine that much, you understand the wear and tear  of racing.

still waiting for that erosion damage, 25,000 later & no measurable wear.  ( Don't know how you got the idea I was racing. Just "extreme use" on our nice TX hiways & back roads.

All kidding aside, I use the heavier oil to get the 1200 pm of zddp that the 15w-50 Mobil 1 has.

http://www.mobiloil.com/USA-English/MotorOil/Oils/Mobil_1_15W-50_.aspx

Z.

[Beeroxin]

25000 is still early to tell
say u have a motor thats built to go 200000 miles
instead it might only last half that
again
the oil is soo thick that it cant get to the motor soo soon as a thinner oil can when u start up and thats the most critical time u need lube
other than that the extra strain will prolly wear out ur oil pump sooner than later and if that happens n ur not carefull that could result in scored cylinders lost compression even a siezed motor
those #s on your oil bottles were developed for a reason and just as anything else on a car going to one extreme causes excessive wear no matter what way u look at it

[b1dill]

A litte high especially at cold idle. I would try 2 quarts of 5-30 mobile 1 and 3 quarts of 15-40 or 15-50 mobile 1. They will mix and bring oil pressure down some mainly while cold. I put a 302 ford factory remanufactured engine in my 68 and it came with recommended 15-40 shell rotunda for diesel for cam breakin. Also anything that will keep a diesel clean is good so that is what I use.

[Beeroxin]

the reason those fluids are recommended for break in is that regular oils such as full synth race oils wont allow a motor to break in because they do thier job so well protecting the engine
when u use the recommended break-in oils your allowing the motor to go through accelerated wear in order to shorten your break in period and the detergents are there to pick up the debris loosend up from break-in
this is why diesel oil makes a good break-in oil, but i wouldnt use it for the long haul

[BlackShadow]

You can buy  zddp as a oil additive and use a lighter weight oil.10-30 or a 10-40 and your oil pressure will come down.