Don Terrill’s Speed-Talk

Building a bbf 545 for a friend and he supplied me with a melling m84hv.
Other than adjusting the end play is there anything I should modify on this pump?
Pressure wise it pops off at 55lbs.

I highly doubt you need an HV pump.

I agree but that's not my question

Unless it's a dead stocker. I'd up the pressure to 80 pounds.

Nothing wrong with a HV pump. Who says what high volume really is? It's GPM. That's all. More oil sooner is not a bad thing, unless you have to run down KB racing for the money.

I'm curious if some modifies the hsg so the bypassed oil returns to the oil pan not back into the inlet.

I've built a lot of these using the stock out of the box M84 pump with no modifications. I would not recommend messing with the pressure relief to try to raise the oil pressure because they are already very high.

In the past, I have machined an HV pump's housing and the gears down until they are .100 taller than std volume.

ClassicComp wrote:I'm curious if some modifies the hsg so the bypassed oil returns to the oil pan not back into the inlet.

I have. I do it when I can. It's a bunch of work.

ClassicComp wrote:I'm curious if some modifies the hsg so the bypassed oil returns to the oil pan not back into the inlet.

Yes , I have experimented with doing this a few times.

cjperformance wrote:

ClassicComp wrote:I'm curious if some modifies the hsg so the bypassed oil returns to the oil pan not back into the inlet.

IMG_20170814_39501.jpg

Yes , I have experimented with doing this a few times.

Way less complicated than what I did. I wish I'd have thought of that. I'd have done it to my last engine.

Racerrick wrote:In the past, I have machined an HV pump's housing and the gears down until they are .100 taller than std volume.

Using better rotating parts and clearances a lot of people would consider to be on the tight side, I machine a regular standard volume pump housing and gears down to 1" thick from 1.100" thick using a high pressure spring in the by-pass and it works just fine.

There is absolutely no need for 80 pounds of oil pressure at 2,500 RPM.

All the M84HV pumps I have ever witnessed produce much higher pressure than 55 pounds.

statsystems wrote:

cjperformance wrote:

ClassicComp wrote:I'm curious if some modifies the hsg so the bypassed oil returns to the oil pan not back into the inlet.

IMG_20170814_39501.jpg

Yes , I have experimented with doing this a few times.

Way less complicated than what I did. I wish I'd have thought of that. I'd have done it to my last engine.

Yes thats a really simple way to do it, on the inside of the pump you need to plug the internal bypass hole. The easiest way I found is to make an ally plug to press in there , make a wooden slip fit plug first as you need to grind the end of the plug to clear the relief valve, then copy the wood template to the ally plug and press it in and check that the valve is still free to move. Different brand pumps (the one I posted us a Clevo pump ) are different in this area. The first one I did I simply Devconed the internal relief hole closed! No problem with it either