Board index Flathead Power-Technical Questions, Answers, and Suggestions Big Twin Flatties Oil pumps

Oil pumps

Post Tue May 20, 2008 6:13 pm

Posts: 377
Location: madison wisconsin usa

looks like you got the hang of it!

nice work btw!


Post Thu May 22, 2008 8:26 am

Posts: 1676
Location: Interlaken, NY USA

Woody, et al.,
I just found this tech sheet in all the junk I have around here, and it's kind of interesting. Somewhere here on the webboard awhile back someone posted the opinion that they always felt that the Sportster "carried too much oil in the crankcases". It appears that H-D racing agreed. It appears the intent of the tech sheet is to get oil out of the motor more efficiently, and by rerouting the head returns, put less oil in the crank chamber. There is also mention made of a "1/16" oil restricter pump, Part no 25234-53R". I presume this restricts oil flow to the Crank? Anyone know more about this?
It would seem that harley racing's efforts were in opposition with what I've been trying to do in my Big Twin Side valves. HOWEVER, they were racing and measured longevity in 201 mile lengths. :lol: And I've got an engine design that originally received 1/12th the oil a sporty does!! So, I'm going to see what my oil mileage runs before I get too worried about these revelations. I'm out to get more than 10K from a top end job on one of these motors.

Post Fri Sep 05, 2008 10:36 am

Posts: 112

Post Sat Sep 06, 2008 6:00 pm

Posts: 1676
Location: Interlaken, NY USA

X-WLCH, glad to hear there are others playing with more oil in these motors. Is yours going on a Big Twin as well? I'd like to hear what others are getting for results when using high capacity oil pumps. I've got two Big Twins running them now, and I'm quite happy with results so far. Oil consumption seems to be 700-1000 miles per quart.
If you're running some sort of piston oiling, I'd like to hear how that's doing also,

Post Mon Sep 08, 2008 7:17 pm

Posts: 543
Location: Wa, USA
Thanks, X. I am using a seal on the shaft. I have gotten sidetracked on this project, but will probably get back to it this fall.

Post Fri Sep 12, 2008 3:07 pm

Posts: 219
Location: Georgia
Here is a thought about boosting supply oil pump capacity. What would be the problem with cutting another slot in the existing rotor and adding 2 more vanes? The extra slot would be 90deg. from the existing one. The center of the rotor could have a roll pin installed for the springs to seat against. The spring could be cut and shortened about the amount of the diameter of the roll pin. There would be no modification to the engine case or any change to the outside appearance of the engine whatsoever. This should about double the output of the stock pump. That should be plenty enough to run piston sprayers. If what has been discussed here is true the return pump has enough capacity already.
What do you think?

Post Fri Sep 12, 2008 6:45 pm

Posts: 1676
Location: Interlaken, NY USA

I think that's been done, you might do a search here to see if you can find the topic. Paul Friebus does something to the stock supply pump to achieve more flow. And it must work! As a point of reference, the stock pumps rate of flow is 1 quart per 12 minutes. The sporty pump is 1 quart per minute, the stock return pump is about 2 quarts per minute. My point being that Paul has a successful solution, Jim Casey of the webboard has one as well using the stock pump. Your idea may be a good one as well, I'd say give it a try and let us know how it works out.
The bottom line is these motors need more cooling, and the oil is a likely candidate to do that job.

Post Sat Sep 13, 2008 5:02 am

Posts: 219
Location: Georgia
I do not have the extra old parts laying around, nor the set up to test anything like that. Just ideas. I also had an idea for a cooling passage in the cylinder. It would use return oil flowing through it to cool the exhaust port area. It would also need someone with a supply of old parts (not usable ones) to test. I brought it us some time ago but most thought it would not work either. They were probably right.

Post Sat Sep 13, 2008 8:07 am

I don't think the delivery rate of return oil is enough to do anything useful for cooling a cylinder. It's also partially aerated, and doesn't pick up heat as well as a liquid. I don't see any convenient places to channel the oil without adding some extra piece to the cylinder.

Post Sat Sep 13, 2008 3:28 pm

Posts: 801
Location: Planet Earth
I haven't been on for a while but thought I would chime in on this one.

I don't think a second slot, reservoir, 90 degrees opposite the existing one would have any great advantage. It might increase the volume slightly but not much. After the vanes pass the first reservoir, the space between the rotor and the rotor bore is full of oil, there isn't much room if any for more oil. However, a second reservoir once filled would increase the volume of oil in the rotor bore slightly and if it did not cause and problems, some of that oil might be sent into the motor. There may also be a problem with trying to keep the second reservoir full. I doubt that it would double the volume of oil to the motor.

Another problem, there is less than .100 wall thickness between the rotor bore and the pressure regulating passage at that location. If there were any restriction or resistance caused by the oil in the second reservoir, it might cause the vanes to be pushed back into the rotor.

If you were to get a second reservoir in any location in the rotor bore, not sure if you would be able to feed it externally which would be better. It might work or possibly the vanes may try to push the oil they have picked up from the first reservoir into the second one and into the second feed line.

Four vanes should push more oil. Just remember, you can only get as much oil into the motor as the components will allow. The rest is just going to go into the bypass circuit and and back to the oil tank.

I hope to be back up and running on all 8 cylinders in a couple of months, only running on 4 ½ right now, and might do a re-release of the book then.


Post Sun Sep 14, 2008 7:45 am

Posts: 219
Location: Georgia
Almost everyone here thinks the old side valves need more oil and I am not sure how much more is actually needed than the stock pump delivers. The only thing else I can see needing to be oiled is piston sprayers. I am not sure how much more oil is needed to supply them. Extra vanes just seemed like a simple way to get it. The Sporster pump seems like a viable solution but also a lot of trouble.
Ever take apart an automotive power steering pump? The rotor is actually about the same size. They have many vanes and no springs. If a power steering line bursts it will shoot fluid 10 feet and lots of it.

Post Tue Sep 16, 2008 2:45 pm

Posts: 1676
Location: Interlaken, NY USA

Been thinking about your question about how much more oil is needed. (As many of you know, it always gets dangerous when I finally start thinking!!)
Here's what we know:
Jim, me, and many others have burnt up BTSV's with the stock oil system. (My first time was in '74, 3k miles from home :( )

The symptom is burnt piston/scoring of cylinder on valve side

My adaptation of the sporty pump with lots of oil shot at the bottom side of the piston looks to be working out so far. Only 1500 miles on first test engine, 500 on the second. Neither show the hot spot on piston as yet.

Also, Paul Friebus races BTSV's, FAST, and he doesn't burn up engines either, at least he says he doesn't. ( and I believe him)
HE also modifies the stock oil system and is spraying the underside of the pistons with oil. This I was told second hand however, not by Paul.
He makes changes to the supply pump, but I don't know what they are. It just looks stock on the outside, is all I know.
He also changes the shape of the combustion chamber, which I suspect is also an important part of his success, power wise and engine longevity wise.
My guess is that the shape of the stock heads and block create a hot spot directly over the piston at the edge closest to the valves. It seems to be where most of the combustion, or the hottest part of the burn, occurs. This I deduct from the coloration of deposits on piston, block and head.
So, I think Paul changes the shape of the combustion chamber and gets more power and changes or eliminates the hot spot at a vulnerable area. With whatever changes he makes to the oil system, which I'm sure must include increased flow from the supply pump, he keeps the engine cool enough to do the things he does!
As for me, as I'm not changing the shape of the combustion chamber, I have to compensate with lots of oil aimed at the bottom of the piston, to keep the piston cool enough to not destruct.
So, back to the original question, how much oil does the BTSV need?
Answer; It's going to depend on how you've built your engine.
I may be going for overkill with the sporty pump, when less would do the job.
Perhaps what Jim's come up with is going to get the job done also.
I'd certainly like to hear from Paul his thoughts on all this, but suspect as he gets people to pay for what he does, he's not at liberty to freely discuss the matter.
One note on the sporty pump conversion. All the oil from the pump goes into the flywheel cavity. Either from the full flow 3 hole crankpin, or via the piston squirters. As configured on my motors, there is no bypass. The passage is blocked off. This is how the pump was designed to function on the Sportster as well.
I certainly would like to hear others point of view on all this, as most of this is speculation, not observation.
By the way, I don't know that any of this applies to the 45, just don't have the experience to speak about it.

Post Wed Sep 17, 2008 11:13 am

Last edited by panic on Thu Sep 18, 2008 9:17 am, edited 1 time in total.

Post Wed Sep 17, 2008 12:05 pm

Posts: 1676
Location: Interlaken, NY USA

Jeff, Boy, you made me think for a minute. I double checked and that's the pressure feed from the supply pump to all lubed parts coming out of the pump. The valve is actually the anti siphon valve and has a relatively light spring pressure. You did have me going for a minute wondering if I'd missed something really obvious :(

Post Thu Sep 18, 2008 9:19 am

Yup - sorry, you're right, it's just a check valve. That's what happens when you try to memorize everything instead of looking it up!
Very interesting design theory though - gear size determines output, which allows no excess pressure to compensate for bushing wear etc.

Post Thu Sep 18, 2008 11:03 am

Posts: 1676
Location: Interlaken, NY USA

Somewhere I've got a picture of a racing pump that has a pressure relief valve built into it. A friend picked it up at a swap meet. I'll keep looking to see if I can find that pic. It is interesting how they did it.

Post Thu Sep 18, 2008 11:41 am

Posts: 2688
Location: Los Angeles, CA
Here is a way to cut down on the heat and polution of the oil. :D ... ducts_id=8

Post Sat Sep 20, 2008 1:16 am

Posts: 93
Location: Norway
With your sportypump, what is lubricating the cam chest?

Post Sat Sep 20, 2008 3:19 pm

Posts: 1676
Location: Interlaken, NY USA

Sidewinder, the cam chest is lubricated by the oil returning from the flywheel chamber. It returns through the breather tower as a mixture of oil and air and thoroughly lubes everything inside the chest. In fact, there is much more oil present than with the stock pump. An indication of this is the amount of oil present at the tappet guides. I originally used the late style tappet covers, but I could not get them to hold all the oil getting up to the tappets. It was a leaky mess. I changed to the earlier screw type covers and have no problem with that now.
If you think about it, the cam chest in the Sporty is lubricated in the same way.
I have also installed shovel style valve guide seals by modifying the guides to accept them. The first time out with the sporty pump, the guides and rings were worn, and I went through lots of oil... 1 qt/ 300 miles. The seals may have been overkill, and new guides might have been all that was required, but I wasn't taking chances. Current oil consumption is about 1 qt/1000mi.
I think I've just about gotten this modification ready for prime time. You have to be aware of some things that have to be done differently, such as the tappet covers. That might bother those concerned with originality. Likewise the external oil line to piston squirters. You also have to be very particular with assembly procedures. I've had both of my motors leak at the crank case center joint, which required dissassembly, thorough cleaning, and sealant application to resolve. Likewise, you must be very careful assembling the oil pump to the motor, making sure all joints are flat to eliminate leaks.
There is lots more oil present than with the stock system, and care must be taken..
I will point out that there is no extra oil at the breather, which indicates that the system can handle the extra oil and not spew it out the breather.
At this point I'm just waiting to see if there's a long term payoff in engine longevity.

Post Sun Sep 21, 2008 7:57 am

Posts: 1676
Location: Interlaken, NY USA

Found some pictures of the Race pump with built in pressure relief valve. Thought I'd post them for enlightenment purposes...
You can see the plunger inside the vertical drilling to the right of the gear chamber. It has a connecting passage that goes back to the left and connects to the return oil passage on the entry side of the pump gears.
Below is the cap to the plunger/spring ass'y, located where the supply nipple usually goes.


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