[Johnny406]

To better optimize my centrifical supercharger, I am going from a 80 tooth to a 112 tooth drive sprocket on the balancer. My concern here is the size and weight of it. The bigger sprocket weight 5.2 lbs. That will come down some when I machine it to fit the balancer hub. I may also lighten it some more by using a holesaw to remove some excess weight. My big concern here is the weight of this thing, I am worried about shearing the four grade 8 5/16 mounting bolts or shearing the woodruff key on the crank.

A couple of ideas I had is to run a longer balancer bolt with a big washer to the outside of the belt pulley (for the alternator). Another idea I had was to find a stud that will allow me to mount the balancer in the usual spot with a nut and use a second nut to help secure the pulley and sprocket.

[360Rocket]

I would be concerned with losing structural strength of the pulley by removing material with a holesaw.

[fast72lemans]

The crank key will outlast the snout on the balancer by far, I split mine when the belt wadded up in the tensioner. Larry Hansen of Hansen Racing made me a custom balancer hub with the external size of a BB Chevy that was press fit, never had an issue after that. The pulley will be fine the way it is as long as it has a tight fit at the center.

[6D6GOAT]

why not in addition to the 4 5/16th grade 8 bolts, drill and countersink 3 holes with the BBC bolt pattern and use 3 ( i think 3/8th in coarse thread) counter sink allen head bolts like these ( i know they are the wrong size but just so we are on the same page) http://www.summitracing.com/parts/MRG-5321/?rtype=10

as for lightening it up, i dont think i would take a hole saw to it but i would mark off a nice symetrical grid and take a 1/2 drill bit to it and put 20 or so holes in it. there is a lot of meat there....reminds me way back when i built a battlebot and it was a couple pounds over weight, i drilled the crap out of everything to make weight

[Johnny406]

Originally Posted by 6D6GOAT

why not in addition to the 4 5/16th grade 8 bolts, drill and countersink 3 holes with the BBC bolt pattern and use 3 ( i think 3/8th in coarse thread) counter sink allen head bolts like these ( i know they are the wrong size but just so we are on the same page) http://www.summitracing.com/parts/MRG-5321/?rtype=10

as for lightening it up, i dont think i would take a hole saw to it but i would mark off a nice symetrical grid and take a 1/2 drill bit to it and put 20 or so holes in it. there is a lot of meat there....reminds me way back when i built a battlebot and it was a couple pounds over weight, i drilled the crap out of everything to make weight

I was thinking the same thing about also using the BBC pattern. I have a 3/4 holesaw that I was thinking of using, I see I forgot to mention the size in the first post. I think you're right about just using a 1/2" bit, my so-so drill press would prefer it.

This little procedure will take my ratio from 3.33:1 to 4.67:1

[Johnny406]

I took the big pulley to a machinist to drill out the center section. My drillpress just didn't have enough____. Now I'm just waiting for the cam to come in and a bit of warm weather...