A little background first... A car club member very recently died after a lingering illness and I'm helping his widow clear up some of the unresolved issues with his just-finished-before-he-died truck and selling some excess parts for her. He originally had a 6-71 blown 383" SBC built and installed in it, but after a 100 yard 'test drive' he decided that wasn't for him. He had the motor pulled and changed to a single carb, but whoever did the change left the blower drive hub on. Now this has no harmonic dampening capability, being a bare-bones hub with only attachment for the aluminum v-belt pullies and the lower blower drive pulley; I'm ***uming that the full blower drive (belt/blower) acted as the damper. I'm also ***uming that it may have been left in place to maintain the existing motor balance. There's no vibration issues I can see or feel (I have driven the truck) but I have a lingering concern that the lack of a conventional damper may pose some longer-term issues with crankshaft life. The trans is a TH400 if that makes any difference. Should I be concerned? The truck has less than 300 miles on it, not enough time IMO for a problem to surface. And if it needs a damper installed, how would you determine what to get? She's planning on p***ing the truck on to a son, I'd hate to see him have issues down the road with it. Any help appreciated....
I run blower hubs on my blown racing engines but for street driving you really should have the correct harmonic balancer for that engine. Crank hubs for internally balanced engines are "zero balanced" meaning they have no counterweights on them. Crank hubs for externally balanced engines have a counterweight which can easily be seen, even with the hub installed. Drag racing engines are not usually operated at a constant rpm. They accelerate rapidly and decelerate after just a few seconds, so there is little time for a damaging harmonic vibration to set up. Hope this helps.
There are two sizes available as well, 6.75" and 8". If you have the extra bit of clearance run the larger one. It should be obvious on the blower hub if it is a neutral balance one or not. Since it's a 383 it's likely an external balance hub, unless the fells spent the money to get the engine internally balanced. If it hasn't seen a bunch of high RPM time the crank is probably OK.
These replies confirm what I was thinking... So, if there's no counterweight on the hub I just need to buy a generic SBC damper? If there is a counterweight, will there be an available damper for it? My understanding is the 400-sourced stroker crank usually had external balance, should that be the right one? I'm not a Chevy guy so I need to ask. I'm ***uming the motor was balanced, I also ***ume this won't upset it enough to matter as long as I get the 'right' damper. I was going to go look at the truck today to verify that is what's there, but got rear-ended last night coming back from hosting a cruise-in so I've been spending the day on the phone to insurance, body shops, etc... Luckily I decided to take my DD '13 Mustang to the cruise-in instead of my avatar... Those plastic bumpers come right off...
Steve the last SBC without a balancer was a 283 a 327 has .525 journal overlap a 383 is .400 run a balancer.
Damper boys, "harmonic damper"..! Even the original poster called the same item both a damper AND a balancer..!?? Kinda difficult to...harmonic "balance" anything..! If the engine was done correctly, the crank was balanced as should be done for a 383. Been there. Therefore, you do not...have a "balancer" hanging off the the front of the crank, but you DO...have a damper. Details mean something. Getting the details wrong could be dangerous. Mike
If the dampener has a counter weight attached for balance,,,does it then become a balancer? Like when an engine is externally balanced? But,,,if not,,,is it still a balancer ,,but with neutral balance? Or is a neutral balanced balancer,,just a damper then? Just curious? Tommy
The balancer is the person who balanced the rotating ***embly. The name is given to the person who engages in the process of balancing. No engine mounted objects, on a HAMB friendly vehicle do this.
@Crazy Steve - Hope you're ok after the mishap. Stuff like that makes me paranoid to even take my car out. ATI dampener on my blower engine.
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