I learned a few things along the way.
In the first post in this thread it is stated the you can shim the pump to 11mm. Im not saying thats wrong or that what I did was right. Im just stating the facts and what I did and what I learned.
First the facts.
- The stock Oil pump by-pass spring un-compressed is approximately 59mm long.
- While installed in the pump it is compressed/preloaded to 45mm long.
- The Oil pump by-pass spring stacks at just under 33mm but over 32mm
- If you install an 11 mm shim the spring only has less than 2mm to compress and bypass oil.
- this is not enough for the by-pass piston to make it to the by-pass port.
Heres a photo of the spring almost bound
Again I am not attacking or pointing out error just stating a fact.
Knowing this I decided to completely block (ie: remove the spring and install a solid rod). Upon first starting the motor I experienced over 110 psi of oil pressure at startup, setteling to 85+psi at idle and peaking well over 110 psi at less than 2500 rpms, I didnt let the motor warm up under these conditions, I wish I had. Thinking this was my problem I removed the oil pan and replaced it with a shim 9mm in thickness. I started the motor and I experienced almost the exact same thing. Just slightly less peak pressure at a warm idle. Still spiking well above 110 while rising the rpms to less than 2500 rpms. Heres a photo of my setup.
Let me preface this by saying I installed an aftermarket Oil cooler sandwich plate adapter, notice the photo. Not having enough time to install an oil cooler I just plumbed the line right back to itself.
Knowing I did not want to pull the pan again, I removed the Oil Filter Sandwich plate adapter and installed stock turbo oil filter adapter. Knowing the problems with the stock oil cooler return lines I blocked that too. I put a socket head cap screw in the oil line to block any oil from being bypassed and as you could guess I got the same results. Next I removed the Socket head cap screw from the oil line and started it again. The oil pressure was a reasonable 45 psi at cold idle. The bummer is it went to a dismal 11-7psi when the oil was warm. This was all with straight 30 weight break in oil.
After consulting with a friend and his changes and results I have concluded that the greatest gains in increasing overall oil pressure can be made by installing a shim in the spring that supplies oil to the oil cooler.
I have yet to test or prove this theory but, the other motor in question was a fresh motor (Bearings, pistons rings, over bored and balanced) and had no modification to the oil pump bypass spring but had the oil cooler completely blocked. The oil pressure of this motor has not been verified by an aftermarket gauge but has been consistantly high on a factory electrical gauge.
To review 59mm minus 14mm (the amount it is preloaded when installed in the pump) equals 45mm. 45mm minus 11mm (the amount recommended for shimming) equals 34mm the stack height of the factory spring is just less than 33mm. This leaves less than 2 mm for the piston to travel. This senario probably works fine if you dont modify the spring in the Oil cooler bypass, or block off the oil cooler. Remember I installed this motor in a Datsun Z and never had an oil cooler or a place for one.
More to follow video of a pressure test between a new oil squirter nozzle check valve and a 200,000+ mile oil squirter. How they work and open might surprise you.
LOL
