Blower pulley question...

I have a 671 BDS on a small block Chevy 350. I'm wondering what would be better to replace the harmonic balancer with, BDS's crank hub or ATI's fluid dampener? What's everyone else running? Apparently I don't have BDS pulleys, so it's making this process a little harder. Ultimately, I want to run all 6 blower pulley bolts into the dampener or crank hub. The Harmonic balancer didn't work out too well. 6 bolts holding the blower pulley to the two groove fan pulley and 3 bolts holding that on to the harmonic balancer. Not too good.







Suggestions???
Thanks,
Monkey

 

I'd ditch the balancer and go with a degreed hub. And two keyways. Lippy

 

just giving info i know. im sure experts will chime in. a fluid damper is a no.dont remember why but remember that much. on my big block im running an 871 with a crank hub. experts will have their own opinion.. the blower belt absorbs the harmonics so a crank hub works fine. a good billet balancer works fine as well. a second keyway is a plus in a smallblock crank but in my opinion not needed for most street applications running moderate boost. especially if you dont want to dissasemble a running engine.i had a stock iron balancer break in the keyway, but the crank was ok.( smallblock 350 )replaced it with a hub good to go. car has been sold a few years ago so i have no idea now. also runn the belt real loose cool. it will tighten with heat and stress the bearings. also when switching to a hub you might have to fool with the pulley spacing, the hub is thinner than the balancer.

 

Crank hub, duel keys and 6 bolts is the way to go. JC

 

ATI makes a hub that is larger on the seal area (BB Chevy) and that will eliminate flexing of the hub and cracking along the keyway.

 

School me on dual keys.

Sent from my DROID device using the TJJ mobile app

 

steel hub....

Dual keyways are two keys on opposite sides of the crank. The added one is usually 1/4" wide. This way you have a lot more meat holding the hub to the crank, which is an issue on a small block because the crank snout is so short.

Of course you have to pull the crank out to get it machined

 

You can have a 3/16" keyway cut 180 degrees from the factory keyway. Better yet, you can also have a SBC crank that is made with the BBC 1.6" nose diameter and with dual keyways.

 

oh yeah....small block would be better with a 3/16" keyway, big blocks are bigger hence they use 1/4" for the second one

 

Jeg's has a balancer with the stock three bolt pulley pattern and the six bolt blower pulley pattern.

 

You don't need a damper with a blower...the belt seems to do the job of damping torsional vibrations in the crankshaft.

But you could run one if you want, make sure it has the proper pilot hole size so the blower pulley will be centered.

 

ditto...

 

Back in the 90's I got a Fluidamper from Jim Oddy. He cut the extra keyway and drilled/tapped the 6 bolts for the blower pulley. Worked great and never a worry about it.

 

If you can't do the double keyway deal, get a good balancer bolt ARP with an integral washer head. Torgue it to spec and go. Check and recheck that belt tension. Should be fine. Use quality pulley bolts also.

 

I think this guy runs a blower on the street. I'd listen to him.

 

Might try talking to BDS as well. Most of these companies now have very good customer service lines

 

Yes, i called BDS and they said run their dampener. Or they said call ATI and that they offer balancers with 6 bolt for blower pulleys. So i called and they said there are 2 different bolt patterns. I need to call BDS back and ask what pattern. There is a 2.810 Chrysler pattern and a 3.200 Chevy pattern. BDS didn't know what they had. So now I'm thinking either just go with the dampener from BDS or checking out this balancer from jegs. Do i need a degree wheel if i go with the dampener from BDS?

Sent from my DROID device using the TJJ mobile app

 

I'll throw my 2 cents worth in. I have ran BDS blower set ups on the street and race. The small crank hub from BDS has a stick on timing tape with it. I like to spray clear over it . It helps it stay on with the RPM'S. You have your correct number of holes for the pulleys and every thing lines up.
I would recommend the double key ways.
I haven' ran a dampener with any of the set ups.
You can drive several things off of the front hub also.
On the street I ran this set up for several years and put 70 to 90,000 miles on it. I wore out one set of pulleys.

Go online to BDS, RCD Engineering, or Good Vibrations [ the hot rod place] they have lots of stuff for blowers.

Good luck,
Hooley

 

say you didnt want to disassemble your motor,could you drill and pin it some way ? also im looking for a isky sbc hub anybody?

 

I've run a BDS crank hub on my SBC 6-71 over 15 years. It's a street only car with one key. It's been totally reliable. As others have said, you don't need a dampner on a blower drive.

 

I really don't want to pull the motor apart. So i guess i would have to go with a single key crank hub? Is that my only option?

Sent from my DROID device using the TJJ mobile app

 

If you do not want to take it apart, your going to be running one key. So buy a single key crank hub, install it with a good bolt such as Lippy suggested, mount the pulley with grade 8 bolts and DO NOT overtighten the blower belt. If you don't run a lot of boost and don't over tighten the belt, you'll most likely be OK.

 

I run the belt with the BDS recommended tension...push the belt in 3/4" from "straight" when the motor is cold. When it gets hot, that slack drops to about 1/4". As long as there is some slack when it's hot, it should be ok. No slack means it's putting a lot of load on stuff like the snout, front main, blower drive snout, etc.

The BDS stuff I have is 2.76" bolt circle, 2" pilot, as I recall. I knew it a couple weeks ago when I was ordering parts.

 

That's exactly how i had it. 3/4 tension. And i just checked it.

Sent from my DROID device using the TJJ mobile app