I'm running a two-groove modified 250 cid harmonic balancer on my 235. It was purchased from Buffalo Enterprises (Steve) and required the use of a Felpro quick sleeve on the seal surface as well as balancing. I was a bit skeptical of the suggestion of getting it balanced but after seeing the material removed to get it down to .3 of a gram I understood what was meant.
The balancer is drawn on by using a small block Chevy balancer bolt available at most parts suppliers. I don't recall the exact drill sizes but would caution you to only go about 5/8" deep. My crank drilled very easily with a hand held power drill. I used a longer fine threaded stud to draw the balancer down.
BTW....the balancer and balancing was right at $240.00. No bargain but worth every penny to run a/c, p/s, and an alternator.
Dave
