100 harmonic balancer upgrade?

[roscoe]

It had not occurred to me until recently that it may be possible to install a harmonic balancer/ pulley assembly on my BN2. Several people have said they have done this so I am looking for the brand and part number that was used. I am not having any particular issues but consensus seems to indicate that a real balancer might be good for stresses on the crankshaft beyond what the little rubber band that is the stock " balancer" can possibly do. I have no clue if a six cyl. balancer would fit and the Moss catalog says it fits BN 4 through 8 but it is also a little unclear. Any input appreciated and if you've done this, was it worth it?

 

[dougie]

This should be what your looking for. https://www.jegs.com/i/Pro-Race/439/64295/10002/-1

FYI, if you're looking to get the true value from this part, the entire internal rotating system should be balanced. We usually balance the crank with the harmonic balancer, flywheel and clutch assembly put together.

 

[roscoe]

Thanks for the reference. I guess the 6 cyl. balancer does fit the 100 crankshaft. I certainly know the advantage of mass balancing the rotating and reciprocating parts. I've dynamically balanced helicopter rotor systems and airplane propellers for many years.
I'd think that the noticeable change in vibration levels might actually be greater in a system where the heavy parts were not specially balanced when a harmonic balancer is added. It might be harder on the balancer and I'm sure that might have an effect on how long the balancer lasts. I am pretty sure my crank and flywheel were balanced when I farmed out the machine work when I built the engine but I don't know if they were assembled for that. In theory it shouldn't matter unless they were mounted in the bottom end they were going to run in with properly fitted main bearings, then it might have a different balance solution. As much as I like to think of myself as a gearhead the mysteries of the serious automotive machine shop are still unknown to me. Now I just have to decide if I can justify the cost. Thanks again.

 

[Bob_Spidell]

You might want to check out Michael Salter's take on this: http://www.netbug.net/blogmichael/2017/01/03/austin-healey-100-crank-failures/

Excerpt: "Installing a damper of the incorrect type can be worse than not having one at all."