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Long Live The King
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Thanks

I figured something along those lines.
 

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When you can't get any more vac, is when it will stop gaining . And mostly this would be for a carb engine because ring seal is what makes a carburetor function. My experience, is that over 23 inches you really see the fuel curve respond, and the whole dyno sheet just gets really smooth looking(relatively speaking). 23 to 26 inches. Maybe only a few hp increase but a definite average increase, and a better fuel curve. And this would probably vary in terms of significance due to the design of various aspects of the engine. In a high rpm engine, north of 9000 is where this shines. I've never seen anyone make over 26 inches maybe it's possible. For instance, in a large cid engine, like 700+ inches approaching 9000 rpm.... you couldn't possible take advantage of enough vacuum... you just couldn't get there. In other words, I want all of it.
 

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Chris, during a discussion with him about 17 or 18 years ago at Maple Grove regarding the amount of HP required to operate a dry sump pump, Bill Jenkins also mentioned the affect on the fuel curve. This was about the same time when newly available technology was able to increase his Pro Stock engine from 21-22 up to 23-24. Dick Maskin also confirmed the same observation with me a few weeks later. I'm not an engine builder, but if these two guys says its so, I'm inclined to believe it.
 

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Discussion Starter #24
Okay good stuff, I will never see 9000 rpm ever, but I am EFI So interesting comment on carbs. After all the input on this incredible discussion I am happy with what I have now and I am not leaving unattainable hp behind.
thanks
 

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When you can't get any more vac, is when it will stop gaining . And mostly this would be for a carb engine because ring seal is what makes a carburetor function. My experience, is that over 23 inches you really see the fuel curve respond, and the whole dyno sheet just gets really smooth looking(relatively speaking). 23 to 26 inches. Maybe only a few hp increase but a definite average increase, and a better fuel curve. And this would probably vary in terms of significance due to the design of various aspects of the engine. In a high rpm engine, north of 9000 is where this shines. I've never seen anyone make over 26 inches maybe it's possible. For instance, in a large cid engine, like 700+ inches approaching 9000 rpm.... you couldn't possible take advantage of enough vacuum... you just couldn't get there. In other words, I want all of it.
George Brice has commented that if you see anything near or @ 80% barometric pressure, you have a VERY well sealed up engine.
 

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I've been on the dyno where I'm in the 20 inch range with the dry sump pump, or vac pump and the fuel curve looks 'pretty good'... you can see after some tuning on it that it's nearly satisfactory.... many would go off the dyno and say it was a solid fuel curve. Then you hook up a remote electric pump to the engine to gain vac on a run.... vac hits 24 inches or something and your eyes just kind of pop .... like oh yeah. You realize quickly that ring control at high rpm gets difficult... and you just don' know it until that extra vac exposes it and the fuel curve just gets super flat right to the top of the run and the BSFC just shines to the last line.

But.... maybe that exposes some short comings and it isn't really a mandate. Maybe the ring tolerance isn't that great. Or your bores aren't what they could be. Some of these things you don't know and you don't know you don't know kind of thing. Although, i've had 2 cfm blow bye which is pretty good and still show gains with big vac.....
 

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Okay good stuff, I will never see 9000 rpm ever, but I am EFI So interesting comment on carbs. After all the input on this incredible discussion I am happy with what I have now and I am not leaving unattainable hp behind.
thanks

Well, maybe we shouldn't say RPM... maybe we should be calling it Piston speed. A 700 inch engine at 8000 compared to a SB at 9000...... which is more piston/ring speed?
 

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Long Live The King
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I've been on the dyno where I'm in the 20 inch range with the dry sump pump, or vac pump and the fuel curve looks 'pretty good'... you can see after some tuning on it that it's nearly satisfactory.... many would go off the dyno and say it was a solid fuel curve. Then you hook up a remote electric pump to the engine to gain vac on a run.... vac hits 24 inches or something and your eyes just kind of pop .... like oh yeah. You realize quickly that ring control at high rpm gets difficult... and you just don' know it until that extra vac exposes it and the fuel curve just gets super flat right to the top of the run and the BSFC just shines to the last line.

But.... maybe that exposes some short comings and it isn't really a mandate. Maybe the ring tolerance isn't that great. Or your bores aren't what they could be. Some of these things you don't know and you don't know you don't know kind of thing. Although, i've had 2 cfm blow bye which is pretty good and still show gains with big vac.....
individual cly readings, or just bank to bank A/F ?
 

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I've been on the dyno where I'm in the 20 inch range with the dry sump pump, or vac pump and the fuel curve looks 'pretty good'... you can see after some tuning on it that it's nearly satisfactory.... many would go off the dyno and say it was a solid fuel curve. Then you hook up a remote electric pump to the engine to gain vac on a run.... vac hits 24 inches or something and your eyes just kind of pop .... like oh yeah. You realize quickly that ring control at high rpm gets difficult... and you just don' know it until that extra vac exposes it and the fuel curve just gets super flat right to the top of the run and the BSFC just shines to the last line.

But.... maybe that exposes some short comings and it isn't really a mandate. Maybe the ring tolerance isn't that great. Or your bores aren't what they could be. Some of these things you don't know and you don't know you don't know kind of thing. Although, i've had 2 cfm blow bye which is pretty good and still show gains with big vac.....
I used to run the electric pump on the dyno, as it made power, and made things happier. However i feel it really covered up some things, and took it off for the dyno. My fuel curve on the dyno, and the tuneup in the car were so different i never chased that shit on the dyno. When i took the electric pump off, and just used the oil pump, and worked on vac and blowby from just that, my ring seal got better, and the car got faster. BTW, i had stuff that had 22+ " up here in a 23.9 baro...lol so it was 25-26 at sea level when it was really happy. We ran the vac pump in the car as it helped it recover when he let the clutch out faster. IDK if my depac lied or not, but my really good shit had less than 1 scfm blowby when it was happy. And im with you, for the 500, i wanted it all. not from speading the pump up necessarily, but from working and working on it to seal it up. .020 thick, .090 radial top ring with .0003 vert clearance, testing hones. Light checking every ring that went in etc

Unrelated, but answering a question earlier. I was told by someone there is no difference on the gauge with vac, which i know to be not true. So i opened a cap on the valve cover, and the enging literally had no vac. Made a pull. Lost a shitton of power.......lol. Put the cap on, picked up my power, and oil pressure was roughly 10 psi lower on the gauge that it was open. the gauge absolutly sees the depression in the engine

Great discussion BTW
 

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dumb question in amongst all this knowledge.....but I'll ask anyway......sealing an engine? Is it just crank, valve covers and intake?
 

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dumb question in amongst all this knowledge.....but I'll ask anyway......sealing an engine? Is it just crank, valve covers and intake?
no dumb question other than that one you dont ask right before you fuck something up...lol. Thats what i tell my guys here

no, i mean ring seal as possibly the most important. All the other things you mention may add to the total vac the thing pulls, but typically im referring to ring seal, which is top 4 most important things in an NA carb engine. Also is in EFI, but slightly different reasoning. Ive tried god only knows how many different honing techniques in hopes of .2" more vac....lol. I sometimes judged the effectivness of the hone by the jetting. IF its a known engine "500") and you have to change jets either way, the ring seal changed. I miss that, I truly do.
 

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dumb question in amongst all this knowledge.....but I'll ask anyway......sealing an engine? Is it just crank, valve covers and intake?
Those, in addition to the pan, timing cover, china wall and distributor. Don't ignore the intake bolts. Any place there is a gasket. You can use 6-7 psi to check for leaks which is usually an adequate method but just the opposite of sealing for vacuum because although unlikely, it is possible to have a leak under negative pressure and not positive. You will be able to hear the large leaks and find the rest with soapy water, or a smoke machine. Keep in mind that checking the engine in a static condition does not reflect what the rear main seal is doing at max RPM.
A blow-bye meter on the dyno will reveal the condition of the ring seal.
Excessive oil in the vacuum pump is an indication of leaks, abnormal blow-bye or just a poor location (without a proper baffle) to draw vacuum from. A vacuum relief valve especially with a low setting located on the valve cover will also create a path of air to siphon windage form the engine.
It can be a time consuming exercise but hey, if your are currently stuck at home due to the virus BS and are looking for something to do it is definitely worthwhile and could reward you with a few HP and a happier engine.
 

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I have many vacuum test results. We ran the first electric pump on the Team Winston Pro Stock motorcycle.
In 1998 we had to add ballast as we had the girl riding. So I put extra batteries and three vacuum pumps on my engines.
On the dyno, we revved it a little past peak power to learn where the peak was. But on the track we used all five gears all the way up to the limiter before the stripe. Just in the last 10 years the 500 guys do that. When there were no limiter rules in 500 PS, 12000 was common, it was hard to dyno those engines past 12000, as it was to run my 4 cylinder to 14000 on dyno, Teeth clenching pain :(.
What most folks assume, is that vacuum only helps in the range they test in. BUT< listen to me, 1000 rpm past peak power, the advantage is double compared to before peak. And if you are married to dyno results, you will never see the advantage of a bigger, more powerful and more capable vacuum pump.
If you have 23" at peak power rpm, go see how much vacuum you have at 800 or 1000 rpm past peak HP rpm.
Also, your big 600, 700 cubic inch engine is a giant storage tank, of pressure or lack of pressure. Trust me it has both.
When you spin the electric vacuum pump up to max vacuum reading based on ambient barometer reading, at idle.....as soon as you get up into the rpm range where the ring comes off the ring land, tdc and the piston stops and the inertia keeps the ring going....at some rpm that happens 150 times a second, also, when the peak cylinder psi falls off, after torque peak, there is less and less to seal the ring.
Think about 800 rpm past power peak rpm and you are still accelerating towards the stripe, the ring seal is about done. SO, the more vacuum you have stored up in the 700 cubic inch tank, the longer, and further the rings will stay connected to the ring land.
It is easy to think you see a smooth vacuum trace on data recorder, it is not, it is a small average reading of the gain or loss of the storage tank.

okay, I got to go to work and learn more about ring seal....later :)
 

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Does anyone use a piston skirt coating like the one from Line2Line to keep the piston from rocking like they use to use buttons in the pistons skirts on old fuel engines? And hard anodizing on the top ring land to take up clearance and or to make it harder for the ring to micro weld or wear the groove?
 

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dumb question in amongst all this knowledge.....but I'll ask anyway......sealing an engine? Is it just crank, valve covers and intake?
Here's an article that might answer your question.


And yellow bullet thread.

 

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Thanks Nick
I agree with your comment. Pretty much was my thoughts also. Nitrous fellas run a way bigger ring then I do for they massive cylinder pressure. Granted I am 17:1 against a 5.130 bore. But I have small rings for less friction, and may not benefit vacuum. Biggest daily pump also. I usaully run 18.3-19.5 at the stripe 1/8 mile. 5-20 oil.So probably really not worth chasing it too hard except valve cover seal. The rest is pretty tight.
thanks. Again.
How much stroke? Deck height?
 

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When running a wet sump external oil pump using a vacuum pump how much is the pressure gauge affected if your pulling 10” of vacuum?

Secondly does the suction affect the output gpm the oil pump puts out?
This was an argument I had been having with a friend.
makinchips,

Sorry for the late reply as I haven't been on here much lately. To answer your first question, there is no one correct answer. Yes, the pressure will in fact drop but how much is unknown. If one engine has more bearing clearance than another the pressure loss will be different. So basically each engines pressure will drop but the exact amount will vary.

Now to answer your second question. Yes, the engine will actually flow more gpm with vacuum than without. I know the argument is how can it flow more when there is now less pressure. I can see why people think and feel that way. So me telling you this is not of opinion it's based on data. When creating vacuum in an engine it's trying to find a leak anywhere it can. Well, the oil flowing into the engine is seen as a leak in the system. So the vacuum is now pulling on the oil that is entering the engine which in turn you loose oil pressure. Engineering wise we refer to all of this as Deltas but I'm trying to keep the explanations more simple. You loose oil pressure because you now have increased the oil flow. Once the oil pump increases RPM the pressure comes back and the flow at RPM doesn't very near as much as it does at idle. Also remember, the opposite is also happening on the scavenge side. That's why a wet sump system shouldn't pull as much vacuum as a dry sump system. I hope that helped settle your argument with your friend...

Nick
 
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