High oil presssure on rebuilt 61

[Tim S.]

I've finally gotten my 61 back together - after 15 + year frame off, and am getting a high oil pressure reading (about 60# at fast idle and higher with more revs). Engine has been rebuilt as has guage. No signs of any leaks or burning oil, and there's plenty of power (more than I remember from when I was driving the car). My guess is that the machine shop replaced the oil pump with the high pressure model. (My notes say its a "mellan", but there is no model #). If I can confirm this, I'll probably replace it. In the meantime, am I doing any damage or running any risks by continuing to drive the car?

[Rich G.]

Re: High oil presssure on rebuilt 61

That does not seem to high. When it gets hot it will be lower. I'd be more worried about low oil pressure then high. You have less bearing clearance on the new bearings that's why the pressure is higher.

[Richard R.]

Re: High oil presssure on rebuilt 61

Tim the manafacturer of your pump is Melling. They have the pump bypass spring set at 60+- pounds. The GM pump pressure is normally set at 38 to 42 lbs. I would not worry about the pressure unless it goes above 80 lbs. Hope this helps. Richard

[Tim S.]

Re: High oil presssure on rebuilt 61

Tim,

The pressure reading sound like the pump may rebuilders like to use. If you are having the car judged, you will need to change it. Otherwise, drive it and not worry about it.

Enjoy

[Dennis A.]

Re: High oil presssure on rebuilt 61

Tim...
60 # is no problem and Melling pumps are good. I use 15W40 for break in at 2000 rpm x 20 minutes, plus 500 miles of standard driving. Once you change oil, you will see the pressue drop a little after the engine is warmed-up. (still will be on the 60 side, unless you change the pump.)

[Timothy B.]

Re: High oil presssure on rebuilt 61

Tim,

If the pan is not hard to access I personally would install the correct 45 PSI pump. Do some reading in the archives and you may be able to just replace the relief spring and while your at it check the end clearances of the pump gears to cover, it's very simple to do.

[Tim S.]

Re: High oil presssure on rebuilt 61

Thanks guys. That's reassuring.

[Tom P.]

Re: High oil presssure on rebuilt 61

In 40+yrs of building engines, I've never understood why ANYONE would have ANY grief with a hi-pressure/hi-volume oil pump!
EVERYTHING I build, without exception, always gets a hi-volume pump. The oldest runing, regularly driven, highest mileage engine is the 350 in my 51 Chevy which is literally my daily driver. That engine was built 33yrs ago (basic grocery getter type rebuild) with a hi-volume pump and I'm sure it has over 200K mi on it and still starts and runs good.
The pump in the SB400 in the 56 is a stock pump with the hi-pressure spring added (has the white paint mark). The gauge only goes to 60lbs, and when cold, the gauge is pegged. Once the engine is thoroughly heated up and everything is normalized, the gauge sits at about 55lbs. It's been like this for about 12yrs. No problems.

[Duke W.]

Re: High oil presssure on rebuilt 61

It costs some power and fuel economy and is absolutely unnecessary on a road engine. It's an example of "fixing" something that already works (as engineered by Chevrolet) by "engine builders" who have little, if any, engineering level understanding of what is going on inside the engine or understand that most engines are not rebuilt to "race".

Also, for those who are interested in running their cars throught the NCRS judging process, excess oil pressure for the year/engine option will result in a deduction during ops check in Flight judging and will be an automatic failure of the PV test.

Duke

[Tom P.]

Re: High oil presssure on rebuilt 61

[Mark P.]

Re: High oil presssure on rebuilt 61

If it is a high pressure pump can he just change the spring to make it a lower pressure pump ?

[Stewart A.]

Re: High oil presssure on rebuilt 61

How do you know it has high oil pressure. Have you checked it on a calibrated gauge. You stated the dash gauge has been restored but don't trust the dash. Your local decent w/shop will have a proper calibrated tool. Get a second opinion. Stewy

[Richard R.]

Re: High oil presssure on rebuilt 61

Mark, to answer your question about changing the spring that is the only thing that sets the pressure. It goes into bypass when the desired pressure is reached. I have changed the spring before to acheive lower or higher pressures. Another trick to raise the pressure is to put several 8-32 washers on top of the spring. Hope this helps Richard