On Jan 31, 5:58*pm, Jan Andersson >
wrote:
> On 1/30/2012 1:21 PM, Mr. K wrote:
>
> > I was looking at this; and I wondered ; Why are those dowels so short.
> > It would seem like they should be long enough to "fill" the flywheel and
> > the crank . you know maybe another 3 mm in length. Does anyone make
> > longer ones. and are there Oversize ones ?
> > TIA
>
> Well, you don't want them dowels to be so long that the bolt/washer
> starts riding on the pins instead of clamping down the flywheel.
>
> I believe there are oversize pins and also smaller diameter pins.
>
> A very common trick is to install an additional 4 pins, for a total of 8
> pins. Called 8-pinning. I seem to remember the extra 4 pins are smaller
> diameter so the crank end would not look entirely like swiss cheese.
> They are drilled at a non-symmetrical pattern, so the flywheel, once
> drilled in the same pattern, would then only fit on the crank one way.
> Once balanced, it will stay balanced because it cannot be installed
> "off" position.
>
> 8-pinning is enough for most high performance engines.
>
> One more trick beyond that is wedgemating. That means the mating
> surfaces are reworked to a wedge shape, and the tighter you run the
> bolt, the tighter the wedge shape grabs and holds the flywheel to the
> crank. It was popular on some high $$$$$ builds years ago, not sure if
> it was a fad or still around. 99% of builds will be just fine with
> 8-pinning and it's much cheaper.
>
> Jan

Wedgemating is still pretty commonplace on drag racing engines, in
particular.