NEW 2.5 . when it was" assembled", we "shimmed" the oil pump relief spring (about the thickness of a penny). engine runs Perfect, but it idles at about 40 PSI and when revved will actually PEG Both the dash Gauge And the new Mechanical Gauge, so it is really pushing about 100 when revved ! ( I know, 10 PSI per 1000 RPM) will this blow oil filter gaskets, break oil pump Drive shafts ect ?? thinking maybe I need to remove the shim. LOL
My concern would be focused towards pumping the oilpan dry. Oil moved upwards mechanically with a pump moves faster than oil gravity feeding back down to the oilpan. In the past,with a few engines that I've built,I've had to either use a pump with less volume or go with an oilpan that had more capacity due to pumping the oil to the top of the engine faster than it could drain back to the pan and then I would momentarily lose oil pressure due to the oil pump starving briefly.
Hmmm, Hadn't thought of that. it's a Stock replacement pump, not high volume, but I'll keep a watch on that at higher rpms (well, 4000 at the most) bone stock 1987 2.5 so definitely Not a Race car.
Is this a fresh build? If you're still on the fresh break-in oil, it will read high. The first oil change with the correct oil will see lower numbers. Break-in oil is super thick compared to 5 or 10w30.
It depends on why the oil pressure is high, because of the pump, bearing clearances or a combination of both. Tight clearances increase the risk of bearing damage due to reduced oil flow over them when the load is high but will register the seemingly adequate pressure at the gauge. I doubt you'll blow the filter or seal if it's solely the result of the pump mod as long as it's of good quality and installed properly and as for pumping all the oil up top that's usually the result of a high volume pump with a stock pan and it would show intermittently in the pressure gauge once the oil level in the pan dropped below the pump screen. I'd be more concerned about the mechanical stresses from the timing chain, to the cam and distributor gears and the shaft to the pump as has been pointed out.
To give you an idea of what the load is like, I nearly sprained my wrist priming a V8 with a drill once the oil was picked up and pressurized and on a 3.4L that I plugged the oil bypass passage in and installed spring shims on without checking for coil bind and ended ruining the cam, the engine was slowly dragged down to a stall after the oil filter clogged with metal shavings after I poured flush in the motor to wash the metal down to the pan before tear down.
100 psi shouldn't be the end of the world since 80 was common for the 2.8 new. If you don't know where you are above that I'd be concerned about the potential for a mechanical failure from the stress on the other stock parts.
2.5L Disregard, all that doesn't apply. With a 40 psi idle I doubt you're in any real trouble. I was thinking it was 100 at slightly above idle.
[This message has been edited by Joseph Upson (edited 09-03-2016).]
Is this a fresh build? If you're still on the fresh break-in oil, it will read high. The first oil change with the correct oil will see lower numbers. Break-in oil is super thick compared to 5 or 10w30.
Break-in oil would probably be 30w, with extra ZDDP on an engine going into a street car, and so 5w30 or 10w30, or even 0w30, would all be the same as 30w at operating temperature. The 30w break-in oil would only be thicker at the lower temperatures prior to the engine warming up.
yes, it's 30w break in oil with a can of STP (for the zinc). although I don't know it needs it with the roller cam. was thinking to Wait till it changed to 5-30 synthetic after break in and see what it is then. I see where the stress on the Cam gear might be a concern. It is surprising how much it takes to spin the oil pump ! Thanks
I rebuilt my 2.5 using a Melling high volume oil pump. Every time I rev the engine past 4500 rpms, it blows out the oil pressure sending unit and dumps oil. This has happened at least six times now. I've tried different brands of sending units but to no avail. I have to carry a spare sending unit and oil just in case.
With very high oil pressure I would be concerned with blowing an oil seal.
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Too much oil pressure can also cause valve float. Hydraulic lifters can pump up and lose lash. Its like a mechanical rev limiter on higher rpm engines. High volume/high pressure pumps are ok on v6 and v8 engines due to more places for oil to escape. I will only use stock oil pumps on 4 cylinder engines from now on.
Originally posted by Ventura: Too much oil pressure can also cause valve float. Hydraulic lifters can pump up and lose lash. Its like a mechanical rev limiter on higher rpm engines. High volume/high pressure pumps are ok on v6 and v8 engines due to more places for oil to escape. I will only use stock oil pumps on 4 cylinder engines from now on.
I'm not too sure about the valve float theory as the lifters don't so much pump up as they do fill with a small quantity of oil to bleed off and through while running, not to mention if it were possible, the oil pressure would have to exceed the total opposing pressure produced by the valve spring assembly which is far in excess of 100 lbs because the rocker is offset toward the spring side meaning the resistance produced by the spring would need to be multiplied by the rocker arm ratio producing upwards of 150 lbs or more. Also the amount of plunge travel to the lifter top remaining after lash is set properly isn't enough to allow this to happen. If you over tighten during the rocker adjustment yes but I don't see it happening otherwise.
