Cast iron cylinders bored to 2.7 ?

[Mukilteo911]

Does anyone know if the cast Iron or the Biral cylinders can be milled to the 2.7 size and retain their reliability ?

[scottc]

I have talked to EBS (Engine Builder's Supply) specifically about this possibility. They do not rebore cast iron cylinders to 90mm and recommend the max overbore size as 86-87mm. They say that warpage is a problem with larger sizes. It would be a cheap solution though wouldn't it?

Scott

[Mukilteo911]

Would be nice. BUt I wonder if they are thinking of it as a race engine or a daily driver, that may change things.

[jluetjen]

I think that the iron cylinders are clearly a case of "If it would have worked, Porsche would have done it" -- but instead they needed to go to plated or silicon aluminum. While certainly race engines have shorter lives then the street cars, keep in mind that HP = heat. A 2.7 race engine is putting out something on the order of 250-300 HP which is a pretty good amount of heat. That heat will cause stresses on the significantly reduced walls of the cylinders.

I would expect a race 2.7 with iron cylinders to wear as fast in a season as a street 2.7 with iron cylinders again does in a few years. This is because the more dramatic heat cycles as well as the extra stresses imposed by the higher rev's. I would SWAG that iron 2.7 cylinders would start to have some serious blow-by and ring sealing issues within 1 or 2 race weekends, and by this I mean amataur sprint race (~50 mile race) weekends.