Balancer slides in on install
A lot of discussion. I can add as a retired machinist and having built many Mopar’s of my own :
All dampers started with larger bore stepped to a smaller interference fit to finish off.
I never had to measure the bore but I can tell you even a same size bore is difficult to install. I would doubt there is a .001 (larger) press fit. More like .0005. That half 1000th makes a big difference. And I don’t think the entire shaft would be the same as I mentioned before that at first the damper starts easier.
Good point. If a damper is designed for a .0005-.0010 press fit and you have say .0015 that is between a 50-100% increase in press fit. That’s HUGE.
I remember when NHRA made the rule on aftermarket dampers. Moroso (and some others) came out with aluminum hubs. Those were crank and block killers. But others like the Fischer (which I think became Innovators West or at least that is the technology they used) and Fluidamper came out and they had CLEAR instructions to hone the damper to fit if it didn’t have the correct press fit.
If that wasn’t done and it was tight, the constant forces on the hub of the damper would cause a fracture to start in the key way. Once the fracture progressed the hub would lose its press fit and off they’d go.
At the 1988 or 1989 Seattle Nationals we watched a FD come off a Comp engine and it wasn’t pretty. Killed the engine and tore up the car. Someone could have gotten hurt. Bad.
The other side of that was about that time the Chinese cranks were starting to hit the market and crank snout tolerances were all over the place.
Some guys with brand new cranks and dampers ended up with a slip fit. Rather than addressing the issue, some guys were using red loctite.
The end result was a crank failure. The damper was basically just there for the ride and wasn’t doing anything. Next thing you know…zing…crap is flying everywhere.
I saw two specific cranks that failed from that. Both still had the crank snouts in them, held on by the bolt.
How many cranks and engines over the years have been junked and destroyed because damper fit was incorrect?
