Planning a 998 turbo build over the winter
Turbo Mini Forums

Hi guys I know it's all on here but I thought I would run my ideas anyway some advice would be great!!

So to start with I have a n/a 1275 which has just about had it It replaced my metro turbo engine which was fun but never quite right.

I'm going to be the new owner of a Mayfair 998 engine come Saturday, I propose to strip and check it change any parts that need replacing. Use my 1275 box with a cross pin diff and a 12g940 head which I have lying around I'm thinking on a mirage manifold kit to make life easier and a megajolt for reliability and easier tuning.

My questions are would I need to replace the cam and would the head bolt straight on and work or would work need to be done to the block to allow it to??

Thanks jack oh I have some experience with engines I'm hoping to take it on myself!!

12G940 head on a 998 might require pocketing depending on your cam / rocker setup.

12G940 head on a flat top piston 998 (late A+ @ 10,3 CR) need chamber enlarging to bring the CR ratio down.

The head of choice for a turbo 998 is the 12G295 - 998 Cooper : no enlarging, no pocketing.

Second in line is the 12G202 from a 1098 wich need some chamber enlargement but not much.

12G940 head on a 998 is favoured on N/A application for those reasons.

Depending on your power target and budget, the cam can stay.

Obviously a bigger cam makes more power but in a turbo application it has much less importance than the turbo for instance ...

Again, it is all down to budget.

Rusty by nature