MTFCA Forum

Yesterday I scored a set of counter weights at a price too good to pass up. So this is the first time I've actually given any thought to using them in a engine. I would be interested in the opinions of you guys who may have used them in the past. So tell me what you think, pros, cons, successes, failures, whatever. Thanks in advance. Bob

I have run a set of Dunn counter weights very successfully for almost 45 years and MANY thousands of miles on my 27 roadster. I probably spent a week fitting them so they would not distort the crank when the bolts were torqued. And then I had the crank dynamically balanced. I have heard of numerous problems but I suspect that they didn’t spend the time to get the installation right.

Hi Robert,
Talk to Hank ( Henry) Lee I seen a pic of some on that really nice boattailed speedster of his.
Craig.

The Dunn weights are not all the same weight. Per Les’s recommendation, you can’t just bolt them on. You have to take your time and properly install them, then have the crank balanced. That is the top line things do do. The devil is in the details, much more to it.

Les Schubert wrote: ↑

Tue Jun 28, 2022 5:09 pm

I have run a set of Dunn counter weights very successfully for almost 45 years and MANY thousands of miles on my 27 roadster. I probably spent a week fitting them so they would not distort the crank when the bolts were torqued. And then I had the crank dynamically balanced. I have heard of numerous problems but I suspect that they didn’t spend the time to get the installation right.

Correct installation IS key.
I had good service from a set also. Dunn weights are made to fit the early diamond throw cranks. I machined a set to fit the late crank.
I was told by an old hill climb friend to be sure to get them perfectly physically centered around the crank.
Balance the unit, of course.

Gentlemen, thanks for your input. I still don't know if I'd ever want to use them but I guess I'll keep 'em around for the time being. The purpose of the weights seems to be to allow the engine to smoothly rev up faster. I don't know if I'd even want to do that. Something to think about. Bob

Bob not trying to dissuade you but I didn’t want you to think you could just bolt them up and go. I’ll ditto the recommendation to contact Hank Lee on how he does it. He’s an excellent teacher & a true craftsman on this type stuff.

A properly counterweighted crankshaft will allow a T engine to run much smoother and run at somewhat higher RPM without damage. More power will be available to move the car, and the driveline and the entire car will benefit from the marked reduction in vibration. Personally, I'd be inclined to install one of the new counterbalanced crankshafts, rather than invest in a century-old original crank with unknown hours.