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Discussion Starter #1
Well I was on here few months ago and asking what HP you think a 23 degree 406sbc would put out with small diameter 6-71 on methanol would put out. Now I killed crank so doing some upgrading. How much more power you thinking I will get going from 8:1 to 10.5:1 compression and from 406 to 421? It had AFR 220's on it but have a set of 230 Dart Pro 1's ported by Ron's Porting, you think I should do head swap? The Darts definately flow more but on blown app I am not sure what to do. Either way heads will be getting new, correct blower springs.


I guess what HP you think will put out on 421 with static 10.5:1 with Dart Pro 1's that are ported wickedly awesome. Cams specs are as followed:
  • .270/.280 @ .050
  • .660/.648
  • 112 lobe separtion
Has bug catcher on methanol. About 14.5 psi boost.

Thanks in advance.
 

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I had a small 671 on a near stock BBC 454.Sorry to tell you at 12% over made 7# of boost and very little power.I installed a full size 671 and made 14# of boost and good power......Sorry....Oldhead
 

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Well I was on here few months ago and asking what HP you think a 23 degree 406sbc would put out with small diameter 6-71 on methanol would put out. Now I killed crank so doing some upgrading. How much more power you thinking I will get going from 8:1 to 10.5:1 compression and from 406 to 421? It had AFR 220's on it but have a set of 230 Dart Pro 1's ported by Ron's Porting, you think I should do head swap? The Darts definately flow more but on blown app I am not sure what to do. Either way heads will be getting new, correct blower springs.


I guess what HP you think will put out on 421 with static 10.5:1 with Dart Pro 1's that are ported wickedly awesome. Cams specs are as followed:
  • .270/.280 @ .050
  • .660/.648
  • 112 lobe separtion
Has bug catcher on methanol. About 14.5 psi boost.

Thanks in advance.
More compression with the alky will make a ton more power at the hit.

Bigger is better with a blower. If it don't make the power you want, knock a tooth off the top.

Cam don't look quite right. Needs more exhaust lift, and should be a 114 center line, IMO.

With the right tune, should make about 1200, I'd expect, if the blower is stripped and setup for alky, not gas.

Cubic inches don't mean as much in a blower app. I'd save the cylinder walls if they aren't hurt from the last build.
 

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Discussion Starter #5
Ok first off it's full drag race application. I am spinning way hard at 33% (60 bottom, 45 top). Only reason I am spinning so hard is because small 6-71. The cam is not ordered yet but that is the recommendation from Bullet cams. Think i will call Steve Morris and get camshaft from him or his recommendations. As far as cylinder walls the bore will be the same, was new block with one hit at track, so they like new. Only thing I am doing is upping stroke to 3.875" not OEM 3.75". Eventually I plan on getting big diameter 6-71 but as of now this has to work. I have dumped lots of money in this over past few months.
 

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Actually 33% isnt spining it that hard....thats what your ratio is with 60 bottom and 45 top. I spoke with Little field at length about about this since we run a 6-71 on a blown 392 hemi and I was told we could go as far as 45% over before we lost the efficience of the blower. Now realize this is coming from a man whom I just asked if I should buy another blower and he explained not yet that I still had room to grow.

Also a good question regarding.........what type of blower is the small 6-71?
 

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Discussion Starter #8
To be honest with you I am not sure what company actually built, not BDS, Littlefield, Blower shop etc. It is stripped and all setup for alcohol I know that for sure. BDS helped me find out was small diameter. This is good info because believe me if I can spin harder I will to run the # lol.
 

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Discussion Starter #10
I was wondering the same thing. The only thing I can think of is the V6-71s... Don't they use different rotors? If not, I have no f'n clue what he's talking about.
The case thickness. The cross bar on top opening from top to bottom. If 1/2" thick you have large diameter and if 3/4" you have small diameter blower. This is what BDS told me. Boost at 13.67% over (original OD amount) would be like 14-15 psi with large bore case but with small its only like 8.8 psi.
 

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The only thing I can find regarding a difference in rotor diameters relates to the *-V92 and *-V53 series blowers, which isn't a *-71 series blower. Is this what you're talking about?

From what I can find, *-71 blower rotor sizes are 5.778" in diameter. A 6-71 rotor should specifically be 14.975" long. If you have something different, it's a non-standard case/rotor.

This is the first time I've heard of a small/large rotor diameter since I got into supercharging back in 1992. Not saying it's not possible, just saying I've never heard of it.
 

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Discussion Starter #17
Only on 6-71s that I know of. I didn't know of until was trying to figure out my approximate boost before I started for pulley reason. They asked and I was like huh? Lol.
 

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The case thickness. The cross bar on top opening from top to bottom. If 1/2" thick you have large diameter and if 3/4" you have small diameter blower. This is what BDS told me. Boost at 13.67% over (original OD amount) would be like 14-15 psi with large bore case but with small its only like 8.8 psi.
My 6-71 setup produces 16-17# @ 3% overdrive, on a 383" motor, with hat nozzles only. This is with a tight, alcohol blower.
 
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