[Dragncar]

Originally Posted by John Langer

In a drag race application, you want to pull as much vacuum as possible. This not only helps with reduction of crankcase windage but also stabilizes the rings sealing the cylinder. I have seen as high as 22" on a 5-stage sump pontiac with a vacuum pump. I'm working on engineering a system that will pull around 22-23" with out the vacuum pump. The vacuum pump draws around a 3hp reduction.

Marcella told me about his sbc that pulls a super high number without a vacuum pump. So you high end guys can get it done.
Good luck on your new project.

[R 70 Judge]

I have a -12 fitting on my passenger side valve cover. Moroso fab shop built them. Very nice pieces.

[Elarson]

Originally Posted by Dave Polichena

I run an external pump, on the dyno when we got to 15 inches there was a drop in Oil Pressure, reducing back to 12 it came back up. Don't know the why, so 12 it is for me. I'm running 9qts in my Moroso pan.

You were getting oil pump cavitation at that vacuum. The oil will turn to fizz if it gets too much vacuum at the entrance to the oil pump gears. It's a combination of the amount of vacuum in the sump and the amount of vacuum that the pump exerts to pull the oil from the sump into the gears. You can run higher crankcase vacuum (without cavitation) if you have a really free flowing pump inlet and are running low viscosity oil.

Eric

[Dragncar]

Originally Posted by Elarson

You were getting oil pump cavitation at that vacuum. The oil will turn to fizz if it gets too much vacuum at the entrance to the oil pump gears. It's a combination of the amount of vacuum in the sump and the amount of vacuum that the pump exerts to pull the oil from the sump into the gears. You can run higher crankcase vacuum (without cavitation) if you have a really free flowing pump inlet and are running low viscosity oil.

Eric

That was a big reason why I enlarged the inlet-low pressure side of my oil pump.
Ended up with my version of a Luhn pump ( with Luhns help)
It was a lot of work, kinda fun but with all the time I had into it these days I would just buy a pump from Luhn. At the time they were to busy to get me one in my time frame.
Essentially it works the same as Luhn,s pump. Still have not figured out what their "thrust plate with integral LPI pressurized oiling circuit" is though ?

[Dragncar]

The numbers work out to something like, pulling 10" you are losing about a THIRD" of the pressure needed to push oil into your pumps inlet.
So, making that low pressure side as big as you can is not a bad idea.

[Dave Polichena]

Originally Posted by Elarson

You were getting oil pump cavitation at that vacuum. The oil will turn to fizz if it gets too much vacuum at the entrance to the oil pump gears. It's a combination of the amount of vacuum in the sump and the amount of vacuum that the pump exerts to pull the oil from the sump into the gears. You can run higher crankcase vacuum (without cavitation) if you have a really free flowing pump inlet and are running low viscosity oil.

Eric

Thanks for that explanation. Pump location on my plate and pan sump does not allow a straight shot, oil goes through a swivel at the pump. I may have to do some modification where my pump is mounted for better flow.

[Pontiaco]

at what horse power level should a vacumm pump should be considered or needed?

[ta man]

Originally Posted by Pontiaco

at what horse power level should a vacumm pump should be considered or needed?

Once you see your dipstick shooting out of the tube. I don't think its about hp more about rpms.

[Elarson]

Originally Posted by Pontiaco

at what horse power level should a vacumm pump should be considered or needed?

It's hard to give a definitive answer. For example, a power adder engine with looser piston-to-wall, wider ring gaps and higher cylinder pressure will have more blowby and need one "sooner".

Eric

[Pontiaco]

So my motor it's a 496 stroker piston gap was set at .28 top .26 second if I remember correctly. Solid roller heads by Kauffman high ports , I ask for a 700hp+ combo street engine, lobe it's at 111 sep.
I also have a 200hp kit of NOS