Straight vs Tapered bore

[Tkitchen1]

Hello all, I have an O-320 Lycoming that I am going to rebuild. I have 20+ years building drag racing engines. I understand that the factory puts a taper in the top of the cylinder bore to compensate for thermal expansion. I also know of a cylinder re builder that provides straight bore cylinders for lycomings. Does anyone have any information about the pros and cons of each?

[rocketbob]

I have had cylinders done by Chuck Ney, and they are doing fine. I have another engine I recently did an overhaul on, a 300hp 540, that will be flying soon and all of the cylinders are straight-bore steel, also done by Chuck. The Lycoming overhaul table of limits lists bore clearances for cylinders with straight bores. I don't believe for one second that taper is intentional, its there since the head is a .015 shrink fit and the manufacturers don't want to do a secondary machining operation. I believe the 0-235's however have a straight bore, perhaps that is one of the reasons why they have a 2400hr TBO.