S&S oil pump

[HogMike]

Will an oil pump made for the oil cooled m8 motors work on a water cooled model?
2019 limited.
I think the only difference is the oil volume is a little more on the oil cooled models?
Am I missing something with the difference between the two?

TIA

[HogMike]

I think the running pressure also had to be increased on the oil cooled model to circulate the oil through the heads and back to the tank.

S&S has an adjustable pressure relief you can adjust up or down about 5psi per half turn.

Anyone have experience with this?

[PoorUB]

I don't know the answer, but the pump has more volume.

I have to ask, why would you want to use a higher output pump? Without the oil passages in the heads the extra oil would end up in the cam and crankcase. Sounds like a sumping problem to me.

[Nastytls]

I don't know the answer, but the pump has more volume.

I have to ask, why would you want to use a higher output pump? Without the oil passages in the heads the extra oil would end up in the cam and crankcase. Sounds like a sumping problem to me.

Agree'd, that's why I'm updated to the latest HD pump which offers more scavenge. That's what seems to be the actual problem, not a lack of pressure to the top end. Added bonus is that it costs a fraction of the S&S unit.

[HogMike]

I don't know the answer, but the pump has more volume.

I have to ask, why would you want to use a higher output pump? Without the oil passages in the heads the extra oil would end up in the cam and crankcase. Sounds like a sumping problem to me.

It is part of a discussion I have with a friend here trying to understand if the higher volume of the feed rotor and the pressure adjustability of the pump would make the pump work on other models properly.
i.e. 107-131 engines.

[HogMike]

I don't know the answer, but the pump has more volume.

I have to ask, why would you want to use a higher output pump? Without the oil passages in the heads the extra oil would end up in the cam and crankcase. Sounds like a sumping problem to me.

It is part of a discussion I have with a friend here trying to understand if the higher volume of the feed rotor and the pressure adjustability of the pump would make the pump work on other models properly.
i.e. 107-131 engines.
Also, the 3 rotors vs the 2 rotors on other pumps.

[les]

I think the running pressure also had to be increased on the oil cooled model to circulate the oil through the heads and back to the tank.

S&S has an adjustable pressure relief you can adjust up or down about 5psi per half turn.

Anyone have experience with this?

Well, not on an M8 but on my previous twin cam bike I adjusted the oil pressure twice with the S&S pump and plate.  I like the setup on the twin cams because the adjuster is on the plate, which is firm bolted to the casing.  However, on the M8 setup the adjuster is on the pump, which I don't like.  I'd be worried that putting torque on the adjuster cinch nut might shift the oil pump out of alignment.

Nevertheless, it's a great feature with the S&S setup to be able to literally dial in the oil pressure by only removing the cam chest cover.  I found it a useful feature with my twin cam 124".

[PoorUB]

It is part of a discussion I have with a friend here trying to understand if the higher volume of the feed rotor and the pressure adjustability of the pump would make the pump work on other models properly.
i.e. 107-131 engines.

I still think the scavenge side would get overwhelmed. Don't forget that on the oil cooled models the oil that feeds through the heads runs out the back head and into the top of the tranny case, through a port into the oil pan. A water cooled all the extra oil ends up in the lower end and the scavenge pump has to bring it back to the pan. Also, once the oil pressure hits a certain point, the excess gets bypassed back to the cam chest from the relief valve. With a higher volume pump, the bypass would be open most of the time.

There is a balance point between the supply and scavenge sides of the pump. Personally, I don't see it working, for the reasons I stated, plus, if it would work HD would have built only one pump to fit either engine.

What is wrong with the current oil pump, S&S or OEM? Harley b]Big Twins really don't need much oil to operate.

[HogMike]

It is part of a discussion I have with a friend here trying to understand if the higher volume of the feed rotor and the pressure adjustability of the pump would make the pump work on other models properly.
i.e. 107-131 engines.

I still think the scavenge side would get overwhelmed. Don't forget that on the oil cooled models the oil that feeds through the heads runs out the back head and into the top of the tranny case, through a port into the oil pan. A water cooled all the extra oil ends up in the lower end and the scavenge pump has to bring it back to the pan. Also, once the oil pressure hits a certain point, the excess gets bypassed back to the cam chest from the relief valve. With a higher volume pump, the bypass would be open most of the time.

There is a balance point between the supply and scavenge sides of the pump. Personally, I don't see it working, for the reasons I stated, plus, if it would work HD would have built only one pump to fit either engine.

What is wrong with the current oil pump, S&S or OEM? Harley b]Big Twins really don't need much oil to operate.

So, dialing back the supply pressure would have the effect of the bypass opening sooner?

[PoorUB]

So, dialing back the supply pressure would have the effect of the bypass opening sooner?

Yes, and dumping the excess oil into the cam chest and overwhelming the scavenge pump.

I wouldn't try what you are thinking about unless I really needed something to take up some extra time!

[To The Max]

I would not put a oil cooled pump into a water cooled motor it will start sumping in minutes. i have seen what happened to a oil cooled motor that had blocked the oil cooler lines . i would go with the latest HD pump . Max

[HogMike]

So, dialing back the supply pressure would have the effect of the bypass opening sooner?

Yes, and dumping the excess oil into the cam chest and overwhelming the scavenge pump.

I wouldn't try what you are thinking about unless I really needed something to take up some extra time!

That's kinda what I had figured with the size of the feed rotor. "Where does the excess oil go".
I think I got it now.

[Admiral Akbar]

So, dialing back the supply pressure would have the effect of the bypass opening sooner?

Yes, and dumping the excess oil into the cam chest and overwhelming the scavenge pump.

I wouldn't try what you are thinking about unless I really needed something to take up some extra time!

That's kinda what I had figured with the size of the feed rotor. "Where does the excess oil go".
I think I got it now.

Mike, We talked about this.. PoorUB has it wrong. The pressure relief doesn't dump the oil into the cam chest. It dumps the oil back into the feed path. You got the pump. Look where the pressure relief valve hole feeds. Pretty much everything back to the later EVOs dump excess oil back to the oil intake.

Now the axtel / baisley pressure relief valve for TCs does dump excess back into the cam case.. Not sure how that is going.

[PoorUB]

Ok, so I stand corrected on the oil bypass, but still wonder why use the oil cooled pump in the water cooled engine? I don't see any advantage.

[Don D]

Consider the OEM 2020 pump

[HogMike]

Ok, so I stand corrected on the oil bypass, but still wonder why use the oil cooled pump in the water cooled engine? I don't see any advantage.

No advantage. Just wondering IF it would work as I have one.
I'll exchange it and go with the water cooled one.
I have a call in to tech support and I'm pretty sure they'll tell me the same.
Bruce, I'll see you tomorrow if you are going.
It's an interesting discussion with various opinions. 🤔

[HogMike]

Consider the OEM 2020 pump

I'm upgrading the motor and kinda like the 3 rotor design with the S&S.
Just personal preference.

[Don D]

I understand.  Another option,  Dan Thayer modifying your stock pump. It saves cost and is an equal or better product.

[HogMike]

I understand.  Another option,  Dan Thayer modifying your stock pump. It saves cost and is an equal or better product.

I've had good service from S&S since the 70's and most of the other parts are theirs.
Nothing against Dan, again, just personal preference.

Thanks for all the replies and messages guys.