Spectre

Hi, as the subject implies, im looking for a roots blower..
In which vehicles did it come in ? and as I understand,
there is the 4-71, 6-71, and 8-71.

I think the 4 or 6 would be nice, since im running near 10,1 cr.

(ps. im running vortecs.. u modifie the base 4 that ?)

thx

jon_volk

i wouldnt advise running a roots blower on anything w/ 10:1 compression unless your cam has ALOT of overlap w/ very little boost or run on race gas. if youve got a 10:1 motor id just spray the thing.

Spectre

well, the engine has 9.6 cr.. i was thinking rraising it a bit..
but if its not compatible .. it could be changed..

i could get thicker head gaskets..

But im set on buying a roots type.. doesnt matter if i dont use it
in this build up.. im swapping engines.. i could put the roots
on an other build up.

AFBCamaro

The *-71 Blower units are great units. You might want to look at mini blowers if you dont plan on cutting your hood or buy more than one carburator(cost escalates quickly).

I put a 6-71 on my 305 with about 12psi of boost. I just recently took it off and have a forged piston 350 waiting. Thet 305 was killer though. I didnt know a 305 could do such things.

Anyways if you have any specific questions dont hesitate to ask. I'm playing extensively with these blowers now!

bEtUr4dRustang

well here's a question then.

You think i could get a 6-71 to fit under the hood if it was mounted the same way Saturn 5 mounted his two M90s (over the valve cover)?

Also, there are tons of 6-71s on ebay that are straight off their industrial purpose and rebuilt and sell for roughly 300 dollars. What does it take to get one of these up and running for street use? And where do i get the parts like the whole front assembly with the snout for the pulley and the various pulleys?

Thanks,
Jay

AFBCamaro

The units are incredibly BIG. You can put them anywhere in the hood of the car and you will have to cut the hood, and a 4 inch cowl wont hide it either.

I would price the front drive snout (270 used), coupler(80 used), cover(180 used), pulleys(60 each), belt(100 new), intake (250 used) lower pulley separately and two carburators, crank hub (75) and if you still dont find the cost outrageous then you should buy the blower unit. They are the cheapest part, trust me.

This is well worth it, exept for the fact that you wont be able to hide what u did. Most people wont really want to race you anymore and the few that do only want to see the thing in action. It whines beutifully at WOT.

Those blowers for 300 dollars rebuilt have to be reclearanced for gas use. Now if you are looking for the cheap route as long as they are rebuilt you can put them in as is, but an already bad efficiency rating will go down. Plus if the rebuilder was crappy it could damage it at high speeds.

There are so many "hidden costs" in this is crazy. But i did it and would gladly spend it again.

Spectre

I dont really care if it comes out of the hood.. the 6-71
obviously will ...

here im montreal quebec.. I can get units for cheap..
Just wanted to know from what vehicles the come from..

i can get the 4-71 for 600$ last time I checked..
im sure theres hidden costs since its a custom install..

but at the end.. it pays off ..

bEtUr4dRustang

These blowers weren't ever on "vehicles"

They ran in industrial machinary on the exhaust side of a 2 stroke motor. I think Caterpillar and other such companies used these. They aren't from cars at all.

BTW, its just my personal opinion but having a hole cut into the hood of a third gen automatically brings back the hill-billy conotations that are finally starting to go away with respect to these cars.

Though maybe a picture of yours might change my mind AFB.

Cronic3rd

They were in GM big trucks (like 3/4 ton) for a while (70's). But they didn't blow a thing they were used as exhaust pumps.

Spectre

cool, thanks man

Cronic3rd

More spefically they were used on the detroit desiel engines.

AFBCamaro

none of these blower blew(positively) on anything. They did come in some trucks. They were used as scavenger pumps, they were used to scavange air into the motors since the bores were so big they needed the extra help.

Kingtal0n

Damon wrote a Tech article on roots blowers and there is a ton of info on this site already written. do a search for roots blower and blower and supercharger and you can find it.

unless you have a 400+Cubic inch motor or are running the thing above 6500 RPMS there is no need for a 6-71 blower. the smaller more efficient blowers, 174, 142, 250, from holley and weiand can put out more boost, cooler boost, and have less tendancy to heat it up or beat it up than the bigger 6-71's. most motors under 400Cubes cant take a 6-71 at anything more than 4% underdrive, which is completelly inefficient at low rpms.

I've had a 144 and a 142 on my 350, and now im building a 383 with a 142... for cost efficient and cheap un intercooled boost there is no easier way.. .

but if you want 650 RWHP out of a 355 you cant do it streetably with one of these blowers. once you pass the 450RWHP range you need to step up to an intercooled centrifugal running between 14-17PSI, and some EFI with boost referenced everything. there are a few people running D-1SC's on this board, putting down 650-850 RWHP on pump gas, and getting 25-28 MPG highway. thats what im working on, 355, stealthram, solid roller, D-1SC @ 15 PSI, commander 950, pump gas and some street tires.

614Streets

For the street a 4-71 is the ticket. I finished building my 355 back in june or so, still ironically sits in garage.

Here is my 4-71 355 , oringed by fowlers, the works, but just a lowly flat tappet hyd street cam, motor is all street and set up to spray something cool all over her as lil ***.

614Streets

They were used in gmc buses as well. Also to note there are many types of the 71 series not just sizes. Some have smaller displacement such as the small bore 6-71 versus the big bore 6-71. The v series which no performance manifold is available for(Dyers did make a few). Stay away from the v series and buy a unit from kuhl, hampton, bds, or dyers. Some 6 cylinderdetroit diesels run a 6-71 and a turbocharger

614Streets

Also to not the 71 series used to be commonly run off the crankshaft with what is known as a potvin drive. Also take note two brothers ran a potvin drove 6-71 feeding into a belt drive 4-71 on a dragster way back and it shattered records , and note no tires were available at the time to allow it to gain traction. This technique has never been tried since and I have a feeling once it is tried you will see the roots really shine and take doorslammers into the 5's.

Cronic3rd

So.... Why don't you try it?

614Streets

MrDude_1

im jsut going to take a stab at it and guess that he doesnt have the MASSIVE AMOUNT OF MONEY that it takes to make a car run that fast.

Cronic3rd

LOL

D M N

what does it mean when you say "used it in the exhaust??"

Cronic3rd

They were used as suction pumps to pull spent exhaust gasses from the cylanders and help pull fresh air in. They didn't ever blow into the engines they sucked.

Abaddon_fallen1

Just slap a 12-71 on it and go aginst NHRA railcars. They're using the same thing, but you might have to get a big block first.

D M N

so they suked instead of blow?? is that better??

MrDude_1

they are just air pushers... they move air from one side to the other. they can be used in anything that moves air... even AC systems.


i wouldnt say its better for power, however, for that application, im sure it helped.

83 Crossfire TA

iTrader: (2)

As I've mentioned before, they're used in industrial vacuums

Cronic3rd

useing them in that manner on our small displacement gasoline engines would kill emissions and create only a marginal HP gain due to the fact that our engines scavange their cylinders pretty well with out any help. On humongous diesel engines it is a diffrent story.

Timz2882

iTrader: (1)

actually the top fuel and funny cars use a 14/71 supercharger.

83 Crossfire TA

iTrader: (2)

It’s not a question of size or diesel… it’s a question of it being a 2 stroke without time for a proper blowdown so you can control it’s breathing better by forcing the blowdown.

Cronic3rd

that is completely true - I forgot that they were 2 stroke motors.

Kingtal0n

wait a minute... diesels are 2 stroke motors?

1989RS

detroit diesels are two stroke

83 Crossfire TA

iTrader: (2)

just like gas engines, there are 2 and 4 stroke diesels...