8-71 Overdrive %

Good morning,
I am building my first Blown Alky Combo, for some local 10.5/Radial Heads up classes here in NC. The motor is a 489ci KB Hemi, with a set of old KB heads worked over by Ray Barton. The compression is 11:1. It is not the most current setup by no means, but i figured i could get my feet wet with it and upgrade to a newer setup later. The blower i have is a Hampton Super II 8-71, this blower seemed to be fitting since most classes limit Blown BB to a max of a 10-71. We are fixing to hit the dyno with combo in a few weeks and i'm trying to figure the overdrive of the blower. I have a 20% setup currently, but i am unsure of how hard i can spin it and what % does it lose its efficiency. Any info would be greatly appreciated!

Thanks!

 

Hampton talks about the Super II on his Web page. I would trust JR at RBS Superchargers for information.

 

what rotors?

 

Its has the older straight 2 lobe, blower has never been ran. Bought the entire combo off a nostalgia dragster. Guy put it together never done anything with it. Still had the ass'y lube on the push rods when we tore down the motor.

 

Your going to want a hi-helx 8-71 or 10-71 if you want to make good power. Id go to the class maz size blower and go from thier you will make as much power as you will want to pretty much. thier is alot that gose in to. Like cam and heads and blower is the big thing because if its not making boost your not make power or if your making heat your not making power. It come down to how much boost do you want ot make and how much hp

 

I did a 540 BBC with an 8-71 straight rotor Littlefield at 45% on alcohol. It was a tall deck Bowtie with worked Brodix BB2X heads. Compression was 10.5. Lunati cam in the .286/.292 range with 114 cl. and SuperMag IV. I used it primarily in minirod tractor pulling (2050 pounds), but sold it to a RED friend who was in the 190/200 mph range (powerglide with foot brake) if this info helps. JW

 

Thanks for the replies! I know a more modern blower would help greatly and that is definitely in the future. I am not interested in crazy overdrives or trying to focus on big boost numbers i just wanted to try and get a feel of what common ratios have been used efficiently with these type blowers. I am trying to get a couple of different pulley setups for take to the Dyno but i also don't want to get a bunch of stuff i will never use. I already have 26, 31,39, and 41 tooth pullies (14mm).

 

hello im building a very similer combo for my nos funny car very interested in your build an how much power you get ,,I have a bds air lock 8 71 an every on has told me its to small, but I got a smoking deal on it new in box id realy like to start with it .

 

No problem! Should be hitting the Dyno at the end of next month.

 

We run top dragster with a 540 ci and we had an bds 8-71 on it the last few years this year swiched to a 14-71 but we went 6.43 at 208 with hte 8-71 it was a high-helx blower. we spun it at 66%od the manifold temp was only 105*