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Crankcase vacuum, HP increase?
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Crankcase vacuum, HP increase?
Any guess what kind of additional horsepower a person might make on a nice tight sealed 470" motor with the right ring pack and cylinder hone upping vacuum from 12" to 16-18 inches vacuum might make? Running Q-16, 8-9000 RPM
Thanks, Bret
Thanks, Bret
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bigjoe1
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Re: Crankcase vacuum, HP increase?
I dont know if this is your question, but Going from 12 to 18 inches does not make any difference in horsepower. Once you have a number ( say 10 inches ) there is very little change when you increase it. I have seen where no vacuum to a correctly designed piston and ring combo with a pump can be over 50 horsepower.
JOE SHERMAN RACING ENGINES
JOE SHERMAN RACING ENGINES
Re: Crankcase vacuum, HP increase?
If you're asking about the effect of a switch to a ring pack and hone job that increased vac. by 6", that's very different than just cranking up the vac. pump speed to achieve the same result! The value of a new ring package cannot be assessed strictly via an observed vacuum increase, but it would certainly be a good sign.
Felix, qui potuit rerum cognscere causas.
Happy is he who can discover the cause of things.
Happy is he who can discover the cause of things.
Re: Crankcase vacuum, HP increase?
We did that test on a 434" sbc recently. It was holding about 9 inches of vacuum and we ran the regulator all the way closed and on the next pull it had over 20" of vacuum and 9-10 more HP.
I've also seen 8-10 HP going from no vacuum to 15" on an engines with no special ring pack.
Randy
I've also seen 8-10 HP going from no vacuum to 15" on an engines with no special ring pack.
Randy
Re: Crankcase vacuum, HP increase?
Thanks for the replies. To clarify the questions the current ring pack is .043 w/vert. gas ports x .043 napier x 3.0 low tension. 4.56 bore.
Thanks
Thanks
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- John Wallace
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Re: Crankcase vacuum, HP increase?
What's the 'normal' range, using PFC1 example?
Around 10" or 12/14?
(or more?)
Also what would the vacuum be if one used a dry sump?
Do they go by the vacuum or just whatever it takes to evacuate the pan/covers?
Sorry for any hijack, PFC1.

Around 10" or 12/14?
(or more?)
Also what would the vacuum be if one used a dry sump?
Do they go by the vacuum or just whatever it takes to evacuate the pan/covers?
Sorry for any hijack, PFC1.
John Wallace
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www.wallaceracing.com
Pontiac Power RULES !
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bigjoe1
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Re: Crankcase vacuum, HP increase?
Any more than 12 to 14 can cause piston pin problems, so I never use more than 12. I saw no HP increase from 5 or 6, up to 12 or 14-- 20 or more can cause some bad pin gauling problems
JOE SHERMAN RACING
JOE SHERMAN RACING
Re: Crankcase vacuum, HP increase?
I have always wondered how crazy loose you could go on ring tension with the vacuum pump. I would think that the horsepower gains are more directly the result of the ring package causing less drag or friction if balanced properly with the pump assisting in the oil control. I am in no position to know the answer to this but I still remember when the gapless rings were introduced in the early 70's and 0 percent leak downs with no vacuum assist lead to oil puffing pigs for a while. Finally someone realized more crankcase vacuum would help cure that problem. It sure has come a long way since then. Phil D.
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piston guy
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Re: Crankcase vacuum, HP increase?
Beyond 12 inches you need different seals or need to turn them around as the vacuum pulls air through the seals on the crank.
Re: Crankcase vacuum, HP increase?
Horsepower gains with respect to vacuum are proportional to displacement. With all things being equal, the larger the displacement, the more power increase you will see. Larger bores have more ring area. There are a lot of pieces to the vacuum pump puzzle that must all be present to get the big picture and realize all the benefits. I doubt the Pro Stock engines would be operating in excess of 22Hg if there was no more power than operating at 10-12". And I doubt the NASCAR engines would be operating at 20Hg for 500 miles at time (without pin issues) if there were no benefit above 10-12".
Star Hg
Star Hg
Re: Crankcase vacuum, HP increase?
Clearly a lot of factors must be optimized by the pros to benefit from suction in the teens and beyond, but up to ~12" seems pretty fail-safe for all.
Felix, qui potuit rerum cognscere causas.
Happy is he who can discover the cause of things.
Happy is he who can discover the cause of things.
Re: Crankcase vacuum, HP increase?
Has any one ever dynoed this one? http://www.candsspecialties.com/store/html/pumppan.html
I run it on a small block and it pulls 10 to 11"
I run it on a small block and it pulls 10 to 11"
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mystic1582
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Re: Crankcase vacuum, HP increase?
I guess one of the things that surprised me the most w/a dry sump sytem was how many "leaks" a motor could have. you build a system w/"X" number of scavange stages yet there are SO many potential leak paths that counteract the ability to pull a vacuum. I spent a lot of time sealing/chasing small leaks like valve cover gaskets/hold down bolts, intake bolts, intake sealing joints, oil pan (one piece gasket)....seems like unless you use good RTV and use it like Opraha eating chocolate (I.E. dip the mating parts in it) you have a hard time sealing with "gaskets" only.
Re: Crankcase vacuum, HP increase?
Don Terrell wrote a book about building Nascar engines and said the same thing, RTV and lots of it.mystic1582 wrote:I guess one of the things that surprised me the most w/a dry sump sytem was how many "leaks" a motor could have. you build a system w/"X" number of scavange stages yet there are SO many potential leak paths that counteract the ability to pull a vacuum. I spent a lot of time sealing/chasing small leaks like valve cover gaskets/hold down bolts, intake bolts, intake sealing joints, oil pan (one piece gasket)....seems like unless you use good RTV and use it like Opraha eating chocolate (I.E. dip the mating parts in it) you have a hard time sealing with "gaskets" only.
Has Anything You've Done Made Your Life Better?
Re: Crankcase vacuum, HP increase?
Having the engine completely sealed to be successful goes without saying. There are two primary forms of leaks: gaskets & seals and blow-bye. If your vac pump flows 20 CFM and the leaks total 20 CFM you will never make negative pressure. The vac pumps capability must exceed the leakage. Any leakage will also promote oil to be scavenged from the crankcase into the vac pump. Thats why any device used to limit vacuum should never be placed within the crankcase area. The regulator or relief valve should preferably be located directly on the vac pump.
Star Hg
Star Hg

