4-71 blower on a 3.4L v6 ( need help with drive ratio) - Hot Rod Forum : Hotrodders Bulletin Board
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Old 07-21-2012, 04:27 PM
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4-71 blower on a 3.4L v6 ( need help with drive ratio)

i scored a rebuilt and preped 4-71 on ebay for cheap my plan is to put this on a 3.4L v6 in a 3rdgen camaro

the camaros manifold base lends itself to being adapted to mount the blower very well with a lil machine and welding work

getting the blower on the car is not an issue for me, but im wondering if someone could help me calculate how much boost it would make with different drive ratios ,

thanks dave

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Old 07-21-2012, 05:54 PM
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I'M in love with this idea---here are a few charts you can refer to:

Blower Drive Service: We Deliver Horse Power! - Blower Drive Systems, Blower Kits, Blower Cams, Custom Carb Service

i think a 4-71 can be mounted on the 3.4 with no real problems, BUT how much power can this block withstand AND can the crank nose handle all that additional stress from the belt?

Unfortunately, not every engine can really handle a roots blower.
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Old 07-21-2012, 06:14 PM
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Quote:
Originally Posted by against all odds View Post
I'M in love with this idea---here are a few charts you can refer to:

Blower Drive Service: We Deliver Horse Power! - Blower Drive Systems, Blower Kits, Blower Cams, Custom Carb Service

i think a 4-71 can be mounted on the 3.4 with no real problems, BUT how much power can this block withstand AND can the crank nose handle all that additional stress from the belt?

Unfortunately, not every engine can really handle a roots blower.
we have these engines turbocharged to 400hp no problems.theres a handful that are running around closer to 500hp

there have been a few instances of these blocks cracking in the main webs, and mains walking around 400hp but these engines were used in midget racing and saw sustained 7K+ rpms with high compression on alky

with an engine that isnt at sustained high rpm we havent run into the main cap or main web cracking issues with a properly preped engine i.e main studs and align bored

as far as the stress on the crank snout noone really knows, only one company has ever made a roots blower for the 60*v6 and not many were ever sold.
the blower was similar in size to the eaton m90 and used a serpintine drive system so they didnt have quite the same load as the 4-71 will have

if the stock crank cannot handle it a real forged crank out of a 3500 engine can be used by turning down the rod journals to the proper size. they can also be offset ground to get a total displacement of 3.9L if u wanted to do that

according to the chart i would assume a engine with 207 ci would make around 12.5 psi with a 10% underdrive so i will probably start with a 1-1 drive and could maybe step it upto 15% overdrive

with turbo chargers i am not afraid to hit these engines with 25 pounds of boost, but since this will be a first for me with a roots type blower on one of these engines i dont want to hit it with that much boost to start.

thanks for that link it was very helpful
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Old 07-21-2012, 06:28 PM
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i shoudl add i love the look of the old mechanical injection, but a ssomething im going to drive alot hopefulyl im going to go with efi. my first thought was twin tbi units off the 4.3L or 350 engine.

but then i came across these

lil pricey but deff the look id like to go with.
and if i decide to stick with pump gas instead of e-85 it would be real easy to drill and tap that setup for 2 methanol injection nozzles
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Old 08-07-2012, 12:19 PM
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so here is the intake manifold ( well the lower section i will be using )

the plan is to weld up the injector bosses from the outside , then weld them up in the runners and port/machine the runners back into shape , stock the injector bosses hang down into the runner and actually shrink the runner size down.ill have my fuel injectors mounted above the blower, the plan is going to be to run e-85 so that should have a nice cooling effect and keep the blower nice an efficient

the plan is to build a sort of V shaped plenum i can weld down onto the lower intake that opens up big enough for mw to put a thick aluminum mounting flange onto for the blower to mount too.
This is also going to be needed to make sure the blower clears the valve covers , and i can acess all the intake to head mounting bolts.the nice thing is the intake to head bolts are vertical so worse case is i can use studs in the heads and the intake can be droped on and then use nuts to tighen it down instead of the long factory bolts .

im open to any comments or suggestions u guys may have.

also does anyone know what the typical max rotor speed is for a 4-71 blower
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Old 08-10-2012, 05:42 PM
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anyone?............
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