Max CID big block OHV oiling question??

W

White Feather

Member
Doing some testing with a friends big block open modified OHV...

Running the sort of RPM I like it appears the splash oiling is at best marginal and I'll have to trim around 2000rpm off the top to make it live, and that makes my camshaft kind of pointless.

I'm in the early stages of 3D modeling and the design phase to build a one off pressure fed oiling system of the dry sump design...

Anyone already done this?

I've built a system like this years ago for a huge CID all billet flat head open using as many components as I could from a 4 cycle dirtbike and machining the rest myself... the improvements to actual oiling were as good as expected, and the performance improvements were far better than expected.

I figure the results for the big inch OHV open will be just as good... if no ones done it yet I guess I'm the Huckleberry. Lol.
 
Billet blocked GX390.

It's currently on my dyno where I was running it not too test the power or tune, but to test some of my self machined components.... so more or less it's simulating laps at the track on the dyno loading and unloading.

Much past 8000rpm and the oiling seems to be lacking in my opinion just from a couple test runs and teardown for inspection.... this engine isn't mine I borrowed it from a friend to use for testing some of my components that I desigm and machine myself... With it not being my engine I'm not trying to push it too a point of failure, but I suspect the cam I have in it would likely twist up to 10k fairly easily if everything else were inline.

My personal engine I will be building after the first of the year.
 
Not sure why you need to twist it that high. The meat of the torque curve on the big block engines is in is in the 3-4000rpm range. Above 7500 you’re just making noise and wearing shjt out.

Is the motor jackshafted?
 
There is an engine builder, I can't recall the name.. But, they've been building small blocks with a sump, not sure if it will fit a big block or not.
 
ECkarter said:
Not sure why you need to twist it that high. The meat of the torque curve on the big block engines is in is in the 3-4000rpm range. Above 7500 you’re just making noise and wearing shjt out.

Is the motor jackshafted?
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Not sure what I'll end up turning it, right now I'm on the dyno testing it too see what it likes that I like.

On the dyno it was still making good power past 8000rpm fwiw...

Most of the cams I've seen in big block open modifieds are actually very mild cams in my opinion... the cam I was intending on using however is not in anyone's opinion mild. Lol.

I'm not using a jackshaft on the dyno... this is a direct drive water brake type dyno that is setup sort of like the hub dynos that bolt onto a full size cars wheel hub, only this one bolts directly to the business end of the crankshaft.
 
White Feather said:
On the dyno it was still making good power past 8000rpm fwiw...
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Right you can still make good horsepower up top but the torque curve usually takes a nose dive beyond 7-8000 rpm. Post your dyno numbers if you can. FYI I’ve seen several sump setups. They’re usually for the top end only, though it should be pretty easy to put a squirter in for piston cooling. Generally there’s enough sent up there by the rod. Good luck with your build.
 
ECkarter said:
Right you can still make good horsepower up top but the torque curve usually takes a nose dive beyond 7-8000 rpm. Post your dyno numbers if you can. FYI I’ve seen several sump setups. They’re usually for the top end only, though it should be pretty easy to put a squirter in for piston cooling. Generally there’s enough sent up there by the rod. Good luck with your build.
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It'll likely be late February or March before I actually have mine complete and on the dyno... I still have to build a lot of stuff, I machine most of my own components myself.

The tracks I run on most of the time taking some bottom end torque out of a larger CID open modified and exchanging it for some rpm up top is usually a good thing.

I've been building open modifieds since around the early/mid 90's.... specifically building my own, I never attempted to sell any open modified engines... I did build and sell a bunch of stock class flatties back in the day though.
 
Rod bearing shell showing heat... a few other minor symptoms.

I'm of the opinion that it's keeping all the oil in suspension by windage so the block doesn't really have much oil in the bottom for the rotating assembly to "splash".

At any rate a true pressure fed oiling system will always be the better option, and a true dry sump system of said doubly so... I'm gonna take a stab at it either way, since I machine everything myself it doesn't cost me anything except time and generally I'm working on this type stuff while on the clock at work machining parts of a size and complexity that sometimes one tool may run several days by itself.
 
White Feather said:
Rod bearing shell showing heat... a few other minor symptoms.

I'm of the opinion that it's keeping all the oil in suspension by windage so the block doesn't really have much oil in the bottom for the rotating assembly to "splash".

At any rate a true pressure fed oiling system will always be the better option, and a true dry sump system of said doubly so... I'm gonna take a stab at it either way, since I machine everything myself it doesn't cost me anything except time and generally I'm working on this type stuff while on the clock at work machining parts of a size and complexity that sometimes one tool may run several days by itself.
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For those of us non-machinists, as well as also not having an actual oil pump at our disposal, do you think adding another .001 oil clearance at the rod journal would give it enough oil? Yes I know the disadvantage would be pounding the bearing a little harder.
 
mike97760 said:
For those of us non-machinists, as well as also not having an actual oil pump at our disposal, do you think adding another .001 oil clearance at the rod journal would give it enough oil? Yes I know the disadvantage would be pounding the bearing a little harder.
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Possibly... but I'm not a fan of creating an additional potential problem to fix or help an existing problem.

The fun of all this for me is the tinkering with the engines..... so I try almost anything I can think of within reason. Lol.

I find I usually have more bad ideas in retrospect than I dig up easter eggs... but...

To me thinking outside the security fence, across the road from where they keep the box I'm supposed to think in can lead to a discovery of a great idea...

There aren't any good or bad idea's until you try it out and have empirical data to prove or disprove the disposition of the idea... it's sort of a schrodinger's cat paradox without the real hard data in my mind's cloudy eye.
 
White Feather,

Get yourself a rear end circulator (used for cooling diffs. on Cup cars.) It is essentially a single stage dry sump pump.
I built a dry sump flatty probably 30 years ago now using a pump like this, ran it belt drive off the jackshaft (same speed as crank,) and used old injector nozzles with deflector tips reamed out to aim the oil in the sump. You will need a larger return than the 1/8"npt oem drain (at least mine did.) I used a large catch can as the oil sump tank. On the original version, the dry sump pump robbed more power than it freed up. With higher HP and higher RPM, you could start to see some advantage, but it was another winter project left in the dark room. One of many over the years. :) At the time, I was looking for HP gains by shedding some parasitic drag and oiling/protection wasn't the problem. Next problem (at the time) was valve springs that would turn over 10Gs. Now we have better springs and that won't be a problem. Making all the rest of the parts live very long at that rpm certainly is though.

I suspect you are correct with the windage. If you could epoxy a window in the sidecover to watch the oil, you'll see most of it suspended just above an idle. Now, with that massive rotating assembly, you can be sure to get a lot of windage in the sump. If it's blowing it against the front and back of the block, then the rod is left in the center of the cyclone so to speak.

Like you, I tried to get a 390 to turn up rpm and live, but found the R&D very expensive. I was using the Dyno P-Open cam, maybe not as aggressive as yours, but certainly capable of turning the desired rpm I was looking for. I ended up abandoning the idea as the weak link in all of these big block Hondas has historically been the con. rod. I recently talked with a mfg'er at PRI about building some rods specifically for me, but that's months in development. Unlike you currently, I am covered up in building stockers, clutches, tires, etc and can't devote the time it takes to develop a 390 revver right now. Good luck in it though.



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Brian Carlson
Carlson Racing Engines
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There are some really nice little hydraulic pumps on ebay, that are made by TRW. They are transmission cooling pumps for VW 10spd automatic transmissions. They flow about 1lpm and will produce about 4bar...they can be ran with an RC motor.
 
A friend of mine just ran a couple of diaphram type fuel pumps pulsed off the crankcase to pull oil from a drain plug and fed squirters to put the oil where he wanted it. It worked.
 
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