7 replies to this topic

[antcole]

Been offered a 1275 unleaded cylinder head and wondered if there is any advantage in fitting it on a standard 998 engine...... or is it a complete no no....?
Any wisdom is welcomed.

[Alex_B]

it has larger valves and better flow rate over a 998 head but you need to either pocket the block or sink the exhaust valves into the head otherwise valves and block faces and then you get a feces - fan interface. 


you also have to work out the compression ratio with the different head and adjust as required :) 

[antcole]

Haha! Faeces fan interface is classic!
Good advice though, sounds like it would be a lot of modification to make it work properly.... might give it a miss.... Thanks for the info mate

[Tommyboy12]

Recessing the valves doesnt require the block to be stripped out the car to be pocketed either.

[lrostoke]

lot of people say its a very good option for a 998 and depending on cam you may not need do anything to the valve seats or block.

 

It is a measure before fitting job though to be sure of valve clearance and compression ratio

[Cooperman]

It depends on what you are trying to achieve by doing this.
There is no point in having a cylinder head which has the capability to flow more fuel/air mixture unless the inlet & exhaust systems are suitable and the cam will provide the lift and valve timing to optimise the power.
Don't consider this unless you can do the measuring and calculations needed and understand the other modifications needed.

[Algordo1100]

Slight thread revival,

But I just found a good pick of a 'pocketed' block. This is a 998 block prepared by MED to accept a 12g940 head (according to the poster on the forum i found it on). Thought I'd share

 

[Cooperman]

Those pockets look quite deep. Wonder how near the top piston rings will come to the base of the pocket. Very near by the look of it.