oil pressure relief pistons

pjh69911 · 08-25-2006, 02:34 PM

Does someone know whether it is ok or preferable to use a newer style presssure relief piston, spring and guide tube even if the oil bypass has not been performed? I was thinking that the lower spring rate might act as a better pressure regulator. I am using the oil cam restrictors and see pretty high pressures on startup. TIA. Paul.

Grady Clay · 08-25-2006, 02:52 PM

Woah haus,

This is a very sensitive subject that hasn’t been well covered.

Each of these pieces form a “system.” It is critical that all the parts work together. I’m not sure I can give you all the pieces but some Pelican Searching may yield results.

It is advantageous to post the pressure vs, rpm at some oil temperature for others to see. The most important is the transition from idle to when the pressure is regulated by the Pressure [regulating] Relief Valve. These are numbers that allow diagnoses if/when there is a problem.

Best,
Grady

pjh69911 · 08-25-2006, 04:52 PM

OK Grady, as I recall,
Cold: at idle 60psi, at 2000rpm 80psi, at 3000rpm 100psi
at 180 degrees: at idle 20 psi, at 3000rpm 60psi
Paul

Zeke · 08-25-2006, 05:18 PM

Quote:

Originally posted by Grady Clay
Woah haus,

Is that the same thing as, "Woah, hoss" ??

Eagledriver · 08-25-2006, 09:24 PM

you cannot use the new piston without doing the bypass. The pistons are different and set up for the location of the bypass port. The old pistons have holes in the skirt and the new pistons don't.

-Andy

pjh69911 · 08-26-2006, 07:01 AM

Andy,
when the bypass is performed, there are no modifications to the safety valve circuit, yet a new style piston is used there. So why couldn't you use a new piston in both places? I understand that you need a new piston if the bypass is performed, or else you will draw air into the pump intake and hence have no oil pressure. With no bypass modification, wouldn't the new piston just depress under pressure and be ok? Cheers. Paul.

EmeraldE · 01-21-2007, 08:13 AM

I'm experiencing a similar high oil pressure problem with my 1973E. It is 75,000 miles, and original case never been apart therefore no oil bypass mod.

It runs 60+ PSI pressure on cold idle, 90-110+ on cold 2,500 RPM. It used to run about 80-90 PSI at 180-190 oil temp and 4-5,000 RPM, but recently is more like 100 PSI at 180/4,000 RPM+.

I changed the oil recently, and while careful may have slightly overfilled it as the oil level gauge is at/near full at 180 oil temp and idle, but it is not pegged.

Could this be an oil presssure relief issue? Doesn't seem like a modest overfill (if at all) would cause the pressure problem?

Thanks

Eagledriver · 01-21-2007, 08:34 AM

An overfil will not cause a pressure problem. You may have a sender issue. Sometimes they start to go bad and give false readings. On my car I've seen 20 PSI with the engine off when the sensor was failing.

Also realize that in the winter you may have higher pressure because the engine is not as warm.

-Andy