Valve lift blown alcohol

Peter Karlsson · Post by **Peter Karlsson** » Tue Mar 27, 2007 10:18 am

On a max effort blown alcohol engine can you see any draw backs using a pro stock based valvetrain with over one inch lift?

I know the hemis are lift limited because of the valves angles but how about a canted valve head?

Thanks, Peter

Ed-vancedEngines · Post by **Ed-vancedEngines** » Tue Mar 27, 2007 4:29 pm

Windsor377 · Post by **Windsor377** » Tue Mar 27, 2007 7:32 pm

Are they truely lift limited or are you concerned about the overlap period?

PS. Recently a combination I really like (I vs E lobe) I discovered has a pretty successful "T/A" track record but used opposite of each other. That is, the intake and exhaust lobes are switched. Interesting.

PPS. I've been wondering the exact same question regarding the P/S style "wedge" with maybe a bit more volume on the intake side. Being a Ford "guy" I've wondered if that would be an excellent opportunity for the BT Thor large port.

I'm curious to see if anybody has anything to contribute to your question, besides my own questions.

Ron C. · Post by **Ron C.** » Wed Mar 28, 2007 12:08 am

When you say "maximum effort blown alcohol" I take that to mean something on the order of NHRA Top Alcohol Dragster, Funny Car or Pro Mod.

I'm not prevy to Pro Stock cams but have heard 1.050 lifts are in order. The "maximum effort" competitive blown alcohol valve trains are the best money can buy and operate pretty effectively in the mid to high 10K rpm's. But most cams are in the mid 290's intake and 300's exhaust and lifts are mostly under .900. You have to keep in mind that with 45+ PSI at the intake valve the very degree it peeks open is flowing postive to the cylinder.
Very different worlds for camshafts to operate.

Personally I think you would be after a miserable adventure trying to run a Pro Stock cam in a "maximum effort" blown alcohol engine. But 20 years ago who would have ever guessed you'd be seeing over 1" lifts in anything.

Racings always an adventure in the laws of physics.

Blessings..............Ron Clevenger.

Peter Karlsson · Post by **Peter Karlsson** » Wed Mar 28, 2007 3:16 am

Yes the max effort engine combination I think about is a AJ 481X. The design is based on fifteen years old oldsmobile pro stock. The valvetrain has bbc cam bearings, no lifter bushings, 1/2" push rods, 1.8 and 1.7 rockers, no radical spring pressures and you are not far away about the cam specs.

I'm interested in applying 60mm camshaft, lifter bushings, 5/8" push rods and more rocker ratio with little less cam duration due to the added rocker ratio.

You have to remember that the alcohol dragster/funny car classes are no pro classes and the R&D are limited. I think the blown Pro Mod classes now are leading the development for this type of engines and they all run hemis

I like the 481X concept and would like to add new technology

People keep on saying that much lift don't work in a blown alcohol engine but nobody can explain why...

I can't see the blower adding much to the intake side but I can see the exhaust valve has to open against a higher cylinder pressure than a N/A engine...

Thanks, Peter

Peter Karlsson · Post by **Peter Karlsson** » Wed Mar 28, 2007 3:32 am

Windsor 377

I have no hemi experience but lift much be limited during the overlap period

In my opinion to much exhaust duration and lobe seperation are no good for this type of engines... A single pattern cam are often a good starting point.

Intake port volume are often discussed. My opinion is you need to compensate for the added fuel...

Thanks, Peter

Ron C. · Post by **Ron C.** » Wed Mar 28, 2007 11:43 am

Well, I certainly would not be one that would discourage you from doing your own R&D and chasing your own dreams. If you want to be on top you can't just follow what everyone else is doing. But you also need to apply some basic science principles and not try to use up a lot of energy and resources in reinventing the wheel.

As far as NHRA blown alcohol or injected nitro racing not being a Pro Class on the National event level, it's called Sportsman in name only. The top contenders field seven figure budgets. People like Brad Anderson or Allen Johnson spend a considerable amount of time, money and energy producing some pretty incridible parts. And racers like Manzo, Newberry or Jay Payne don't leave much laying on the table. And then you've got tunners like Norm Grimes, well....he takes it all to the next level.

Good luck on your adventure. Keep us posted on how your ideas are turning out........................blessings..............Ron Clevenger.

Ron E · Post by **Ron E** » Wed Mar 28, 2007 4:06 pm

Before the injected-nitro invasion, non-hemi's got a weight-break in TAD. If it still exists, does it apply?

n2omike · Post by **n2omike** » Wed Mar 28, 2007 7:29 pm

I would think that a person wouldn't want too much overlap in any blown application, so....

I would think 5/8" pushrods, incredibly steep lobes, high rocker ratios, etc.... to get plenty of flow area with less duration would be the ideal setup in a top level blown application.

The main thing 'I' see working against that, is 45psi intake pressures making it harder for the intake valve to seat, and high cylinder pressures making it harder for the exhaust to open... But the above still seems like the 'ideal' to me... and it's just a matter of how far things can be pushed.

(of course, I don't race a top alcohol dragster)

MadBill · Post by **MadBill** » Wed Mar 28, 2007 8:15 pm

n2omike wrote:...The main thing 'I' see working against that, is 45psi intake pressures making it harder for the intake valve to seat...

Hmmm: If the port pressure was higher, wouldn't you want to leave the valve open until the inflow stopped?...

n2omike · Post by **n2omike** » Wed Mar 28, 2007 8:41 pm

MadBill wrote:
n2omike wrote:...The main thing 'I' see working against that, is 45psi intake pressures making it harder for the intake valve to seat...
Hmmm: If the port pressure was higher, wouldn't you want to leave the valve open until the inflow stopped?...

Hmmm.... I see what you are saying. At some point, the piston coming up on the compression stroke would snuff out that 45psi of intake pressure, and flow would stop... and with the flow pressures equalized, the 45 psi intake pressure wouldn't be an issue.

Is this what you are saying? If so, it does sound plausible.

I guess teams delay the intake opening point to try and avoid excessive overlap with a blower...

I would still think, that like any other form of unlimited pushrod racing, huge pushrods, steep ramps, high rocker ratios, etc would provide big gains in these engines...

Thanks for making me think about that pressurized intake scenerio. I guess you just have to experiment to see how far you can delay that intake valve closing point.

Windsor377 · Post by **Windsor377** » Wed Mar 28, 2007 10:07 pm

Peter Karlsson wrote:Windsor 377

I have no hemi experience but lift much be limited during the overlap period

In my opinion to much exhaust duration and lobe seperation are no good for this type of engines... A single pattern cam are often a good starting point.

Intake port volume are often discussed. My opinion is you need to compensate for the added fuel...

Thanks, Peter

All that makes sense for a "TAD" or TAFC" engine. Can you tell me at what lift point your valves will contact?

Peter Karlsson · Post by **Peter Karlsson** » Thu Mar 29, 2007 1:36 am

MadBill: Exaktly my opinion but I can see a difference on the exhaust side just like N2O vs N/A...

Windsor377: I don't have the info from top of my head but I can check.

Ron E: There is no weight break in TA/FC but maybe in TAD?

Ron E · Post by **Ron E** » Fri Mar 30, 2007 9:10 am

My concern would be, if the 481X received a weight-break in the smaller displacement TAD engines, can a more aggressive updated valve-train make up this ground on a larger FC engine?

Post by **Dave Koehler** » Fri Mar 30, 2007 10:32 am

Could the possibility of valve clash at overlap with this much lift be a limiting factor?