Q I’m hoping to fit a 1275 12G940 head to my 998 Mini. It’s an A-plus engine from 1985 with flat top pistons, so high compression. I know you usually have to pocket the block to clear the valves, but I also remember reading something about machining the head to sort the problem instead. Is this possible, and who might be able to do this? Rick
A Some say that you can not fit a 1275 (12G940) head to a 998 engine without having to machine cut-outs in the block to clear the exhaust valves - not at all so. By carefully re-cutting the exhaust valve seats deeper into the head, sufficient clearance can be accrued to cope with up to 0.340-inch valve lift. That’s enough to clear for a reasonable fast road spec cam. With the exhaust valve typically around 0.290-inch down from the head face on 1275 head, they need sinking in to give around 0.360-inch. Reducing the valve seat-toface margin on the valve to around 0.050-inch is the first move, then the rest is gained by re-cutting the exhaust seat deeper using a three-angle seat cutter to get the rest. And contrary to what many think, sinking the exhaust valve so much deeper in the head does not reduce flow. Exactly the opposite occurs; the air flow is improved, especially at lowto-mid valve lift. Make sure you use a 1275 head gasket too. Any decent automotive engineering company that reconditions or modifies heads can do this for you.
A 1275 head can successfully be modified to suit a 998 block.