Boring from 98 mm to 100 mm

[Boxer 6]

I'm curious (and I apologize in advance if this question is silly). How much can the existing 3.2 liter cylinders be bored out while maintaining a safe wall thickness? If the cylinders can be bored out to 100 mm's or 102 mm's, that would seem like a cost effective alternative to buying new P&C's. (I understand that new pistons would have to be purchased). Thanks in advance!

[Jeff Alton]

98 seems to be the standard.......

Cheers

[jbell959]

I think 98mm is about the limit. At 100mm it would be extremely thin at the bottom. Check with Henry @ Supertec. He can probably get you new 100mm cylinders for about the same price as a set of 3.2 cylinders and the cost to bore and re-plate.

[cnavarro]

With the cylinders for the 930, you're limited to 98mm with a 103 case spigot register, approximately 4" 101.6 on the 105mm register, and 102mm on a 106.50 or 107mm register. There really isn't any more meat around the studs to do anything more- the cylinders end off sealing off against the case like a vw 94mm cylinder at the 107mm register (~.140" ledge).

[Jeff Alton]

Charles, how big can we go with a 3.2 based motor using your cylinders and pistons?

Cheers

[cnavarro]

Jeff, I've done 102s in the past, but I don't stock those- I make them as needed, since it's a specialty part.

[Boxer 6]

Don't the spigots get really thin at that point (102 mm)?

[cnavarro]

You end up with not a whole lot of meat around the studs when you open the case spigots up to 106.5 or 107mm from the 103mm. But nothing any different than what we get away with on other applications without sacrificing reliability. It all depends on the combination.