Factory racing oil cooler blockoff plate / filter adjustment

[stownsen914]

Hi all,

I'm hoping someone here can help me with this. I have a vintage 911 racecar that has a factory racing oil cooler blockoff plate - an oil filter that sits in place of the oil cooler on the engine, as used on older 911 racing variants. My question is related to a bypass feature that is built into the blockoff plate, I believe to allow adjustment of oil pressure by bleeding off some oil post oil pump back to the inlet to the oil pump. I believe the adjustment for this is the screw in the middle of picture below. My question is which way do I adjust the screw to increase the oil pressure? I know that the mechanic who worked on my car for the PO liked low-ish oil pressure, and the engine is showing 65-70 psi at high RPM currently. This seems low to me, and I'd like to raise it to 75-80 psi. Given we're talking about oil pressure, I'd prefer to understand what I'm doing rather than experiment!

Any input appreciated. Thanks in advance.

Scott

[BURN-BROS]

Hi Scott,

I believe clockwise will make it higher.

That adjustment will only get you there if the case pressure relief spring opens at a higher rate than what you have already.

[KTL]

Interesting setup. I didn't realize that "hand grenade" factory racing filter also has a way to fiddle with the oil path. So the threaded fitting appears to intersect the outlett side of the filter and thereby forces oil down the vertical passage that allows oil to return back to the pump inlet?



I do understand that the shimming of the pressure relief valve is going to allow more pressure to be made before the valve opens and bleeds off the excess back into the inlet side of the pump. This filter console requires the neato RSR t-stat replacement to be installed and what that does is force the oil to ALWAYS be directed to the hot/filter side of the t-stat cavity and blocks off the cold side permanently.



When the filter side of the t-stat cavity is permanently engaged via this t-stat replacement piece, coming out of the filter is short-circuited back to the pump inlet if safety valve kicks in when pressure is too high. So what does this fitting do, regulate how much oil is coming out of the filter (and onward to the crank gallery) vs. being directed back into the pump?

[stownsen914]

Kevin,

I understand that it's as you suggest - to act as a bypass, redirecting oil from the pressure side of the oil pump back into the oil pump inlet, thereby reducing oil pressure in the pressure circuit.

Scott

[stownsen914]

Originally Posted by BURN-BROS

Hi Scott,

I believe clockwise will make it higher.

That adjustment will only get you there if the case pressure relief spring opens at a higher rate than what you have already.

Thanks Aaron. Any idea how many turns on the fitting to get 10 psi increase?

[BURN-BROS]

Originally Posted by stownsen914

Thanks Aaron. Any idea how many turns on the fitting to get 10 psi increase?

You will have to adjust and verify.

If it does not go any higher, you will have to shim the pressure relief valve. (the normal one that in the case.


Apparently, when the 906 case was made, there were no provisions for safety and pressure relief valves. oil pressure was adjusted at the filter console.