Big Blown/alky motor; will a 632" 14-71 make power without breaking parts?

My 632 nitrous motor is underpowered for Outlaw 10.5 racing. I am debating if a big cubic inch combo with lower boost is a viable option with 12.5:1 compression. Donovan block, 18* big chiefs and a good crank w/dry sump. One of the local tracks mandates 12% OD with a 650" engine size limit. To date no one has gone larger than 540". The obvious answer is to sell the motor and get a KB Olds combo and put a PSI on it, but I would like to keep my piece and see if there is some advantage to a large lower boost (under 29%) motor for 10.5 racing. I am looking to build 2100 hp with moderate torque, and am on the fence between a high helix 14-71 (lots of parts and tune up help) or a screw blower (and start from scratch). All constructive input is appreciated. Just because it hasn't been done before doesn't mean its a bad idea. Thanks

 

The biggest thing to remember about the screw verses the roots is the lack of power required to turn the screw and that means free horsepower. The way the roots blower is going with PSI and Kobelco coming out with new units I would probably just buy the screw and go that route. Now in terms of the overdrive limit is that 12% for the roots or for the screw because if your only turning the screw at 12% over I am not sure how well that would work when most of the alcohol cars would rather turn their blowers at 125%. That might be the deciding factor.

 

The overdrive limit applies only to 14-71, screw blowers are illegal in most classes

The overdrive limit applies only to 14-71, screw blowers are illegal in most classes. The screw blower makes more sense, uses less hp and keeps the charge cooler, but with no baseline tuneup and relatively few events where it will be legal, I am more likely to wind up with a 14-71. To my knowledge Danny Humphreys, Randy Petet and Steve Longley are the only 3 10.5 cars to run the screw blower; petet went turbo and longley put a 14-71 on. I am curious as to why, and don't want to repeat any mistakes.

 

I was were you are at the end of last year. Running a 632 big chief with nitrous and wanting to go faster. I also tried sticking with the 632 and adding a blower. Could not get a suitable piston designed to make it work. So I just swaped out the 4.75 crank for a 4.25 crank. For the blower I went with a F3R centrifical ProCharger driving off the crank. On the dyno with a very soft tune up, not leaning on the blower at all, on C-16 gas and no intercooler, made 1900hp blowing thru a carburetor. With a little water injection, the 2100hp would be an easy reach.
Have you thought about the centrifical route? I run an outlaw deal, so your rules may not allow. Anyway, thought I'd throw that out there for your consideration.

 

I am tuning an ex nitroused SBC buick headed motor with a gear driven D3 on alky for 10.5 (enderle Mech FI). It is taking a lot of time and the fuel curve is way off even after having it flowed by a name shop ($500). I spoke with Mark Micke a while back and he seems to have hit (7.14) and miss days with the 540 procharger on alky. I think Ray sanchez is the only other racer to go fast with the procharger on alky. The jury is out on this one, but after swapping crank rods, pistons and manifold I should just sell it complete and build a little chief SB. We sold an older belt driven F3 over the summer for $3500, it wouldn't fit anywhere with a dry sump. Mark had his about 10" above the hoodline of the car before going reverse rotation gear drive. ( I think he gets a better deal on the units than the rest of us. ) I just get the impression these motors may not respond as well in the eighth mile. I need to rethink the procharger on gas idea though. I wonder what is wrong with a 12:1 flat top piston for a roots unit and is there an advantage to a big motor with lower boost; losing some torque and gaining HP would be an ideal tradeoff. Who set up the carb (what kind of boost #s), we debated an aerosol carb and went to the mech FI; and what static compression are you running? thanks for the input!
http://www.speedworlddragway.com/gallery/2005/wsn/thursday/gary/dsc_2594.htm

 

I think the long stroke and blower would be inviting misery to get a handle on.
CSU engineered the dominator carb. With just some small jetting adjustments they hit it right on. It has the PSI duel float bowls and will flow a ton of fuel. I've not had the boost any higher than 28 PSI at this point. Running 9-1 static. Don't forget that boost pressure is related to restrictiveness. With the same fully ported big chiefs that feed the 632 they now feed 565. It's flowing a ton of air at 28 psi.
Personally, I think the mech Injection would be a hard tune to follow the desired fuel curve. You get a zig-zag curve that at times would probably be hurting parts.
When I started down this blow thru carb route I was not for sure it was going to do what I wanted. I can now say I'm shocked at how well it works and the power it's making.

 

We Run 572 Ci With A Whipple Screw, And Have Had A Lotta Shaking Problems Trying To Put Any Power. We'd Back It Up To 40 Percent Over And Would Be Ok, But We Were Trying To Go 55-60 Over, The Old Car Had No Part Of That! Wedge Motor, Sonnys Head Deal. So Instead Of Taking Power Out We Are Bulding A New Car. Outlaw Pro Mod Car Not A 10.5. I'd Bet A Big Stroke Motor Be Hard To Hook Up On Some 10.5 Ws Anyways, I'd Build A Short Stroke 4.00 Or So And Finesse It With Some Rpms

 

I was considering a Whipple, as their now available reasonably. However, what's the wisdom in buying a part that will no longer cert, and run the risk of a track not allowing you to run one? Case in point: you blow up your Mr. Whipple and injure or kill somebody with the flying debris. Mr. Hotshot lawyer finds that the track allowed somebody to run a part that had a cert. requirement. All sorts of people get hung out to dry....attorney gets rich.

Thoughts?

 

Who says you can't re-cert a Whipple ?

Art Whipple sold them; but they were made by Opcon Autorotor in Sweden. Benny Lybrant of Autorotor has been inspecting and re-certing "Whipple" blowers for European racers for the last couple of years.

 

I wasn't aware of that. Thanks.

However, that sort of proves my point. How many Yanks are going to send a 600 lb. supercharger all the way to Sweden for recertification? I'd wager that if it was that easy (read: inexpensive), then the alky racers here wouldn't all be using the PSI screw deal.

Imagine that: one instance I've seen so far where you guys over there fare better than we do when it comes to racing components!

Thanks again for the tip.

 

Scott,

Point taken about shipping costs; and after checking it appears that Whipples re-certed by Opcon are only accepted by European sanctioning bodies and not NHRA.

It appears that as Art decided he didn't want to "play" with the NHRA anymore and stopped having Whipples produced that they couldn't be re-certed to NHRA satisfaction as the SFI test procedure compares the blower to be re-certed against a sample taken from current production.

This seemed crazy to us in Europe as obviously you don't need current production; just solid numbers recorded from a brand new Whipple to compare against. So re-certed blowers are tested in accordance with SFI but against recorded figures for historical new production, rather than current new production.

Anyway this has allowed European racers who wish to continue using Whipples do so rather than have to dig deep for a new blower. That said all our front running BAD guys are using PSIs.

 

Will thanks for the feedback - it was exactly what I was looking for.

Will thanks for the feedback - it was exactly what I was looking for. IMO the advantage of a whipple / PSI ( I can use the gizmo with no problems) on a hemi is that I can use parts (heads/blocks)that have long been passed over as outdated or wounded but still be very competitive with them in Outlaw 10.5 racing (and do it on a budget). I was pitted two spots down from Danny Humphreys and Nick Williams at Shadyside's $20,000 10.5 race two years ago and was impressed with the motor but realized their biggest challenge was how to manage the power on a marginal track. My smallish nitrous 632 needed some calming to the 60'; theirs was still uncontrollable after 3 qualifiers - 5.0s @ 160mph!! What has developed since this thread was started is that despite my and John Atkinson's prompting the NSCA has decided that the screw blower is too much for them and they will only allow a 14:71. Most tracks in the northeast will use the NSCA rules so it may a tough call since the nearest real outlaw track is 12 hours away. The 14:71 may be the primary option. Another newbie question: how much does the fuel curve change between a 1471 and a screw and are there any hats that will interchange or is it all specific to blower design?? Steve Longley the owner of Brainerd dragway runs both a 1471 and a whipple on his 10.5 hemi Stealth. For those 6-8 races at the end of the year it may be worth having the heavy artillery in the garage, and to my knowledge no one has run a screw in the 10.5 class @ Orlando - yet. Thank you for the insight and recommendations; now I need to get started on a crash course in head and block designs for a hemi. Thanks again, Dan

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