Blower guys i have a question. Im putting together my first blower motor and learning as i go. I am trying to run the 3 v belts like the cragar 4-71. I know when the 3in belt is ran the belt will absorb the harmonic vibrations so a harmonic balancer is not needed. Does the same theory apply with 3 v belts? Motor will be a 331 hemi with 7lbs of boost. Building the motor for 75%street and 25% strip use. Thank you guys
I'm at the same point with my 331 ( '55 ) and I will be using the stock balancer. It appears to be in good shape and it provides the timing marks. I will degree it in to be sure it is accurate.
If you are using the stock cast iron balancer you may split the keyway if the engine backfires, and the crank hub may come off. I have sold many blower set-ups in the past, and I always supplied a machined steel crank hub, never had a problem with them.
I would say the V belts will still dampen like a larger single belt. You don't see V belt drives much on 671's but I know someone here had one at one time on an early Hemi too, and as far as I know it worked fine. A 2" Gilmer belt would also be period correct. I think it was Gary Dyers that told me once that the V belts slipped too much on the larger blowers (671) or when you try to make a lot of boost and thats why you dont see them used very often even back then, but some guys still did use them on 671's. Gary made the 2" Gilmer drive set up for my 471 for me.
I'm running a 2" Gilmer on the 6-71 on my blown 454. Lots of miles on it...lots of drag strip passes. I wonder how much boost you can run, before the V belts slip? although it shouldn't hurt anything, just wont make as much HP as you could with more belts, or a cogged belt.
thank you guys for the replies, dyers makes a nice v belt set up that claim will hold up to 7lbs of boost, I figure that would be enough. a 2in Gilmer belt would be ideal, I just really want to run v belts if possible to keep the cragar blower drive "look". assuming I can run belts. should I go with the safe route and get a sfi approved harmonic balancer or would that be over kill since I would be fine with a crank hub.
I wouldn't use the stock iron balancer, i would either have a new sfi approved balancer or steel crank hub, if I have a v belt drive I figure the belts would slip in a backfire. im just afraid of the v belts not absorbing the harmonic vibrations especially with a blower.
I don't know how well it would dampen vibrations, with the V belts. I've been running toothed belts with steel crank hubs on a couple different blower motors for well over 100k miles, nothing broke yet (although the pulleys have worn out). Seems to me that if V belts could run safely without a damper, then there wouldn't be dampers on most engines? but I don't know, I didn't do very well in Mechanical Vibrations class in engineering school--or maybe we just never had a homework problem, about crankshafts.
Kerry made his own V-belt stuff and has super detailed knowledge. https://www.jalopyjournal.com/forum/threads/my-6-71-v-belt-drive.139394/ -Abone.
Seems to me that if V belts could run safely without a damper, then there wouldn't be dampers on most engines? You bring up a very good point. I know i saw this picture somewhere here before. Guys running a v belt drive on a 6-71. Anyone know who this is?
I had about 80K miles on my blower with a hub only when it did this; BUT, it would have most likely done the same thing with a balancer. This was a stock 60's Pontiac crank that had the radius ground a little sharp once upon a time. Stuck a new crank in her and she has been fine ever since, and that was 2012. Keep us informed and post lots of pics. -Abone. PS. Squirrel is one of the few of us that have clocked more than 100K miles with a roots blower, so pay attention to him.
I just realized that the engine that I put most of those blower miles on, the LS-7 454 that's in my truck now, has been on the road for 30 years. Damn, that's a long time. btw I'm taking it for a drive today, to the robotics meeting. We need plywood to build a crate to ship the robot to the championships in Houston. But that story is off topic
"We need plywood to build a crate to ship the robot to the championships in Houston. But that story is off topic " I think your grandfathered in on the HAMB, give it a try!
The Jalopy Journal
