Triumph Repair: Engine Cylinder Query, oversize pistons, cylinder boring

Question
Hi Howard I have just purchased a MK3 spitfire FD ensgine to fit in my Spitfire with a view to having the unit fully reconditioned prior to installation. I have noticed that the pistons fitted are 0.30 over size and was wondering if further cylinder boring was required do know if the cylinders would take it? They are not scored though the engine as apperently been stood for time and could at least do with honing. Many thanks Mick

Answer
Hi Mick,
To get a preliminary idea if the cylinders are ok, just feel for a ridge at the top of the bore. All cylinders ware most where the top ring stops. Then the ware continues down the bore a short distance and increases again where the rings stop at the bottom but this ware is usually not as much at the top. An auto machine shop can measure it to see what it will clear up at if it needs to be bored. At that time he can tell you what oversize pistons are available for it.

If there is little to no ridge at the top it may be able to just be honed but you still need to measure the pistons as they can need replacing even if the bores are good.

Howard