lifter galley crossover tube

yellow rose said

Dammit I forgot to mention one other change I made when I moved all that stuff out of the pan was to use an external bypass. I’m not a fan of dumping oil (or fuel) back into the inlet side of the pump.

So I put an externally adjustable bypass in the main feed line to the distribution can. On the dyno the engine made more power up to 100 PSI. And, I put the excess oil at the front of the pan so that oil has to go past two baffles before it got back to the pickup.


The ability to control oil pressure and where the excess oil goes is a big deal at high RPM. Dumping that oil back into the inlet is a cheap way to do it.

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Phreakish said

Here's one to twist your noodle around. Why even use a bypass? A/C compressors use variable displacement pumps in order to help reduce parasitic loss (MPG concerns) when they don't need max volume. Why not a variable displacement oil pump that can be altered to eliminate excess work done to the oil. Less waste heat into the oil, no excess parasitic loss going into pumping oil that doesn't get used. This way the pump also doesn't need to be sized by oil demand at idle/cruise speed.

It's a simple pump design, just not cheap.

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LOL...the cost is the answer. And for mass surface transportation dumping bypass oil into the inlet isn’t a big deal.

The engineer I had look over the system had me use an external bypass. At the time I was running MFI on alcohol and I was running what was called a “pump loop” because at 8500 RPM a main and high speed bypass would get rid of enough fuel, and making the pump smaller would have killed the engine by going lean in the gear changes. So I added a bypass that dumped back into the pump inlet.

My engineer friend had me stop that as well. It’s the same principle with oil or fuel. Dumping high pressure liquids back into the inlet aerates whatever you are pumping.