Spigot rebore

[blue72s]

I wanna ask a question about reboring spigots. Obviously reboring warped spigots (of mag case) to make them round again would make its diameter bigger than original size. Wouldn't that be a problem? How critical, tolerance wise, is the spigot?

thanks

[Bobboloo]

As for rebuilding I know it's not uncommon to deck the spigots to get a nice flat suface for the cylinders to sit on but I wasn't aware that spigots were rebored to make them round again. It would seem if they needed that much machining then maybe case replacement would be the best alternative.

I know that people bore spigots for a displacement increase so they can use larger P+C's as in a 2.4 to 2.7 conversion.

[Wayne 962]

Most good shops will run a bore (flycutter) into the holes to make them round again. Typically, this has no effect on performance or reliability...

-Wayne

[john walker's workshop]

it's just a tiny cleanup cut. some 2.7 cylinders, for instance, would require a big plastic hammer to work the cylinder into the case if this was not done. some are equally difficult to get the cylinder out when you're doing the teardown. case-saver installation can also make the bore go out of round.

[Wayne 962]

Right-o, forgot about the case-saver install problem. The over-boring of the hole can sometimes push material out into the cylinder spigot areas.

This is one of the procedures that Walt (Competition Engineering) does on the cases. I'll say it again - when you get a case back from Walt, it's ten times better than new.

-Wayne