4/71 blower info?

Touching base on an old thread. I have found a 4-71 and I'm playing with the thought of it on my 350SBC. My rebuilt engine has a mild cam and lifters. Would a 4-71 work for this or am I just teasing myself. I can get the cam specs later, if it'll help with advise.

 

Compression is the main issue. With minimal boost, about 8.5 max on pump gas with an iron V8.

 

Really? I would have thought I'd need more than that. I have ZERO knowledge about blowers, but the price is crazy good.

 

It's basically a compressor and adds to cylinder pressure under load. So to avoid detonation with limited octane, static compression needs to be lowered accordingly.

 

That makes sense. Oh well. Still nice to dream. Thanks.

 

Was it a complete setup or just the blower itself?

 

Everything but the intake manifold. A plate is being fabricated to mount on a 4bbl intake, but I would have probably gotten a blower intake.

 

Parts can get expensive, 4-71 Chevy intakes are rare but adapters are available to put them on 6-71 intakes. Used blowers can be a gamble unless dirt cheap, look the case, rotors and gears over good and add up what's needed before you commit.

 

It's a fresh rebuild. Still has the tag on it. I know the present owner and he's reliable.

 

Here's some charts and tech to check out in case you grab it.

http://www.blowerdriveservice.com/techcharts.php

 

Thanks.

 

fresh rebuild dirt cheap? what are you waiting for?

 

I have a 471 on my .030 over 327 sbc with 9/1 compression and run on 91 pump gas. Im makind about 7 psi of boost ,The trick is a MSD BTM box. And a good tune, if you don't have forged pistons I wouldn't even try it. The BTM box allows you to adjust the timing under boost by turning a knob, then the best part is you can put race gas in it crank some timing back into it by simply turning the knob and make a bunch more power.

 

I'm running a 471 on a mitchell manifold atop my 49 flattie, dual carbs. 6 pounds boost. Very peppie.

 

Yea, I read about the forged pistons on the BDS link. I don't have 'em, so I'll quit dreaming about it. I may get it for the future at the price I was offered.

 

I have been playing with GMC blowers for many years.I have used a 6-71 on several almost stock chevy engines,327,350 and 400 small blocks. I have never put forged pistons in any of them. I have been driving my 39 chevy for about 35 years with various blown small blocks.I currently an running a 6-71 blown 350,with stock cast pistons.I am also building a T-bucket with a 4-71 blown targetmaster crate engine.The 6-71 is underdriven,the 4-71 is 1 to 1. No I am not drag racing,or abusing them,but they have been completley trouble free.

 

Ah..... now I have to do some more research. Thanks for that.

 

Its true you can get away with it (Cast Pistons) if you dont run them hard and have low enough compression. I started out with cast pistons too, then when I started making some good power they promptly failed. If you keep the timing backed down and can keep it from detonating under a load you will be ok.

 

Back in the day, we used stock 361 and 413 Dodge HD truck motors for blown gas racing. A good low mile take out with 4 ring forged or cast pistons (depending on year model) came with forged crank, big rods, HV oiling, and double row timing components better than Hemi stuff for a pittance of the cost, and only slightly RPM limited. A few $$ more for pistons and there wasn't a better wedge around.
Swap on some #931 (I think) 440 heads, race cam, tunnel ram base with a flat plate for the blower, mag, and boogidy boogidy....... let's go racin'.
This is one with a pair of 600 Holley's we ran on pump gas. The clutch flite made traction an issue with limited tire clearance in a car with springs in stock location. Tom S. in Tn.

 

I wanted to add; Remember that how tightly clearanced the blower is (or plastic stripped air lock rotors added) determine VE as well. The clearance variable is tightness for good VE vs increased power to turn a tight blower + increased heat generated.
Anyone know how much power it takes to drive a blower at 7,000 rpm? Tom S.

 

I just got excited! Should we tell the Chevy guys that Big Block Mopars make a ton of power at a low cost like this?

 

Have at it, but those GM C-70 and 80 motors were like us when a Ford High Riser showed up. Sent us scratchin' our head and ****s at the same time wondering how many rounds we could go until we had to run them. Tom S.

 

I went to see my engine guy today. He said I could do it with what I have, but my right foot would leave me stranded. So, he says if I get it, he'll spec out a blower motor for me. So...... I'm gonna crunch some numbers and come up with a budget. I think I might be getting blown.

So, just how loud is the whine of a street blower? I haven't heard one in a long time.

 

The whine is in the belt. It's the air getting trapped under the teeth. If you don't want the noise you can drill tiny air relief holes in the root of each groove.

The gears don't make noise because they are helical gears.

The rotors roar at WOT.

 

I could live with that.

 

I have a 3"belt on my 6-71,and even with a fully enclosed hood it is not offensively loud,but it makes beautiful music to any gearhead. The 4-71 has a 2" belt and it is really quite quiet.When the belts and pulleys are new they produce a higher pitched whine,as they wear they become less noisy.

 

Once you start driving a car with a blower, you tend to not mind the noise :>

 

Mine has a summer brothers gear drive to boot , and no radio and luv the sound , between blower , gear drive and pipes It screams Hot Rod , luv it
Just traded my Crower setup for a complete 471 setup for my Willys project


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I'm running a Don Hampton 471 on a 283 and it screams Hot Rod!!! It sounds like a jet engine when its cranked up at about 3K,

 

FNG do an intro & Re-read the post: