6-71 SuperCharger
 

I just made a deal to use a 6-71 blower for my new truck motor, Just taking some opinions here. I got a stockish bottom end 1976 2 bolt main 010 020 350 with clevite bearings and pacific rings,never fired, just built,it has a .454 / .476 cam, 76cc heads with 1.95/1.60 valves,dual roller timing chain, Hadman headers with a dual 2.25 exhause to the back of the cab.

What i need to get for the blower is a crank pully,a nose pully and a nose,im woundering how much these will cost and what teeth sets i should get? I'm thinking 7-9psi boost,i have a basic 8.0:1 compression,and i have to holly 600 vac sec. carbs here i was gonna run,i know a few of you here are into blowers like randy for example with that sweet coupe,anyway,i need some opinions,i think its has 1/2 holes instaid of 14mm or whatever because its an old blower...

SC :bowtie:

TTT,need this info

First- Thanks! :D
There are some things that are an absolute "must" when running a blower. You have to run a forged crank, forged dished blower pistons, fluid damper, and a cam built specific for running blowers and turbos. You can't use a stock harmonic balancer, this is dangerous. They will fly apart!! For 7-9 psi, you will have to get 12% underdrive pulleys. I'm running straight 1:1 drive for 15 psi with no problem, but if I get even 1 deg. adv too far on my timing, I can blow a head gasket. For the heads, you need a good flowing pair, with some porting done to the exhaust side. The carb (or carbs) have to re-jetted. If you run the engine lean, the pistons will melt and your headers will glow bright red. If you need any part numbers, let me know. I get most of my stuff from Summit racing. Since the blower is used, have all of the clearances checked. Also, run a screened gasket between the carbs and blower, this can save you from a major headache if something falls into the carb.

Hopefully, that wasn't too much info, but I should try to answer the question you asked too. :D Where did the blower come from? Is it an old GMC? Blower Drive Service (BDS) carries pully sets for GMC 71 series blowers. If you want the blower to be "noisey", use a Gilmer stlye belt and pulley set-up. For quite, use a metric setup.

Tahnks randy,

I'm still debating if i should run this or not,i just got the motor redone, and im pretty much out of money now, do you think i can run a low amount of boost with stock pistons,i friend of mine put a 6-71 on a stock 400,dont know if its wise or not,your the "specialist here :D

S-C :bowtie:

As Randy said get a forged crank,good pistons,good rods.

PLease get a timming retard box like a MSD BTMw/6AL.

You may get by with running a steel hub or a fluid damper but by all means get rid of the stock damper.

Im with him on the dont run lean issue it has to be right as does the timming.

BDS does a great service on rebuilds so I would send it to them at least to get it checked and you may want to upgrade the bearing plates while its there if its a old GMC blower.

I have to say to you in my personal opinion if its a B&M blower I would not want it if its one of their megablowers (420) style.
They use teflon strips and they have no place in a blower motor in my opinion.

Go with a weiand,BDS,old GMC,hampton,kuhl etc for the best blowers.

If you need any help feel free to email me at anytime.

Randy and I are not trying to sound like a smart A$$ but take the word of people that have done it before....There is no hafe ass blower cars on the street.

You have to have the good parts in it!!!

Please take your time and do it right the first time and you wont have a problem later.

Im sure randy and I can help you with your buildup.

"Ditto"- A blown stock engine won't last long. If the blower in question is a stock diesel blower, it has to be machined and clearanced. Stock pistons will crack. An SFI approved balancer or fluiddamper is a must. I repeated that because I thought that I could get away with running a stock balancer. When it flew apart, it took the end of the crank with it, and wiped out the entire engine. Fortunately, the balance didn't hit anyone. Blower engines that are built to specs and with the right parts are safe, dependable, and very streetable. I've been running mine for 6 years now with minimal problems. If you decide to do it, it will be well worth the effort, as long as it's done right. I will be more than happy to answer any questions that come up.