Procharged vs. roots Alcohol 355" SBC - Chevelle Tech
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  #1  
Old Jul 1st, 08, 2:38 PM
helicoil helicoil is offline
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Default Procharged vs. roots Alcohol 355" SBC

Looking for feedback from those with experience in blown alcohol SBC's. I am looking at using either a F1R or F2 Procharger vs. a 6-71 roots (BDS stage 3 or The Blower Shop - cast rotor large case) on top of a 355" aluminum rod, 10:1 comp, shortblock with AFR 210 Eliminator heads to propel a 3500 lb raceweight Chevelle into the 9.50 or better zone.

My experience with the alcohol roots set-up assures me it will hit the customers goals. He went 10.00 with a 4-71 Dyers @ 9lbs. and an alcohol 850 Holley with a flat tappet Speed Pro cam and cast iron Dart Sportsmans.

My restrictions are the amount of boost he can generate due to the pistons used in this shortblock. They are not boost specific, just an old Arias 2618 forged flat top with the top ring down .200" from the deck. He will probably be restricted to about 12 lbs, maybe 15 lbs tops.

Induction for the 6-71 roots would be a pair of alky 850's or possibly even a bugcatcher. For the Procharged route, he is looking at a C&S purpose built piece.

I have already installed the custom Isky roller which was spec'd for a roots set-up. Specs below:

.276/.286 @.050"
.690/.690
112 lsa
IO 26 BTDC
IC 70 ABDC
EO 75 BBDC
EC 31 ATDC

My reservations with the Procharger (although I have 0 experience with them) is that boost will build much slower than the roots and with his current converter (10" on the tight side) it will not allow the car to leave hard like the roots set-up will. I would tend to think the roots set-up would outperform the procharger at lower boost numbers as mentioned and help accelerate his heavy car quicker resulting in quicker ETs. Also, the cam was chosen based on Roots/blown alcohol set-up....will it work with a Procharger?

If the car had the optimal converters for both applications how would they (Procharger vs. roots) compare to one another at 12 - 15psi? Which would be quicket at the dragstrip?

Customer is wanting to go with a Procharger set-up, but is has a goal at the dragstrip of mid 9's with room to grow with another (bigger inch) shortblock in the future.

Sorry for the length.....
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  #2  
Old Jul 1st, 08, 3:10 PM
forcd ind forcd ind is online now
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Default Re: Procharged vs. roots Alcohol 355" SBC

the big problem with a cent supercharger is moving the fuel-just an alc. carb alone needs to move a huge amount, and add in boost ref it, now a whole lot more fuel
theres a guy on
www.turbomustangs.com
running alch.
a tight 10" converter sure seems way off for the cam specs, but dont know the rear end specs
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Old Jul 1st, 08, 3:14 PM
Eric68 Eric68 is offline
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Default Re: Procharged vs. roots Alcohol 355" SBC

Have not messed with a blown alky motor personally, but can tell you are right on the money regarding a big centrifugal blower being a little slow to build boost. A friend with an F1R (gasoline) on a 383 is going 9.9's at 136-138 MPH with only a low 1.5 sixty due to a too tight converter. I built the engine and helped him with the blower tuneup, but the converter is obviously too tight. We could fix that, but he seems to like going the 10.0 'ish ETs he is at and without the risk of spinning.

Bottom line, I like the centrifugal better than the roots, but the converter needs to be right to build boost quickly off the line and leave hard.
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Old Jul 1st, 08, 11:54 PM
eric13617 eric13617 is offline
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Default Re: Procharged vs. roots Alcohol 355" SBC

There's a guy here who went 5.40's @138 eigth mile,in a Mustang,Sat.night in the EZ Street class.Michael Newcome,I think is his name. That's 8.50's in a quarter.He's running a 383 with a F-2 on race gas,with fuel injection.
Brad Shultis,went 5.10 @149 with a 500" fuel injected, wedge and a F-3 on Alcohol,in a 70 Road Runner.Only his 7th pass with the ProCharger.
Several others running mid to low 5's with small blocks and either a ProCharger or 88mm turbo.
I haven't seen a Roots Blower on a door car since Jim Howe Jr.s' Camaro last year.At 3200+ lbs.,and 500",he went 4.98 @146.
And all these cars run 10" tires.
Since I can't vouch for every car and don't know your situation,I will say that you can't go wrong with either if the combination is correct.

I do know however that a roots blower moves air,like puff,puff,puff,puff and so on;
A centrifical blower,screw blower and turbos move air like,pufffffffffffffffffffffffffffffffFFFFFFFFFFFF FFFFFFFF.
For this reason,the latter are not as hard on the lower end of the engine.


If you want to PM,me;I'll give ya a buddys num.who runs Blown Small Blocks,and has for 20 years.
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Old Jul 2nd, 08, 10:19 AM
helicoil helicoil is offline
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Default Re: Procharged vs. roots Alcohol 355" SBC

Quote:
Originally Posted by eric13617 View Post
There's a guy here who went 5.40's @138 eigth mile,in a Mustang,Sat.night in the EZ Street class.Michael Newcome,I think is his name. That's 8.50's in a quarter.He's running a 383 with a F-2 on race gas,with fuel injection.
Brad Shultis,went 5.10 @149 with a 500" fuel injected, wedge and a F-3 on Alcohol,in a 70 Road Runner.Only his 7th pass with the ProCharger.
Several others running mid to low 5's with small blocks and either a ProCharger or 88mm turbo.
I haven't seen a Roots Blower on a door car since Jim Howe Jr.s' Camaro last year.At 3200+ lbs.,and 500",he went 4.98 @146.
And all these cars run 10" tires.
Since I can't vouch for every car and don't know your situation,I will say that you can't go wrong with either if the combination is correct.

I do know however that a roots blower moves air,like puff,puff,puff,puff and so on;
A centrifical blower,screw blower and turbos move air like,pufffffffffffffffffffffffffffffffFFFFFFFFFFFF FFFFFFFF.
For this reason,the latter are not as hard on the lower end of the engine.


If you want to PM,me;I'll give ya a buddys num.who runs Blown Small Blocks,and has for 20 years.
Thanks for the info. Didn't realize the potential in with the Prochargers. this guy is probably going to do an F1R with an alky carb. His compression is 10:1 and changing it is not an option right now.

I am pretty comfortable with the blown alky roots engines, I ran a 400" Rocket SBC with Pro Action 14* heads back in 2000-2001 in the 10.5 class and ran 4.90's in the 1/8th at 35lbs in 3250lb car. This 355" has started out as a budget build and is now progressing. He may run this short for a year or two and then build a bigger inch mouse, so there is a little planning for the future going on.

After searching on some other sites, I have found that these smaller cube engines can make enough power to go mid to low eights at 3000lbs with the centrifugals. This customer will be happy with 9.50's for now. I think I can get there.

Have any carb builder recommendations? C&S is in town here, but I'm not opposed to someone who is not. SteveMorrison, etc Any experiences?
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