6 replies to this topic

[Avtovaz]

just wondered, how far apart is a 12g295 head from a standard one? More of can you mod the standard one to be like the 12g295?

 

I know that would be a lot of work, but is it possible? I see the inlet of a 295 is 30mm while the standard i think is 27. the exhaust valves seem to be the same size...

 

 

I think on the standard head you can remove 3mm from it before any skimming problems.

 

Ive got a 12g940 head and that is massive compared to the standard 998 but the exhaust ports arnt that much different, its mainly the inlet i think... Just wondered as i may stickw ith the head i have and port it and put bigger valves in it...

[Dusky]

A ported standard 998 head can be a lot better than a 12g295. 295 has big inlet tracts and small valve seats.

[Avtovaz]

so whats best to do to them? valve sizes and whats the best way to port it?

[Turbo Phil]

It depends on your application. What's the spec of the engine and what will it be used for ?
Bigger ports will flow more air, but at the expense of velocity reducing volumetric efficiency until higher rpm's are reached.

Phil.

[Avtovaz]

road, 998 cc , mg metro cam. I see the 295 has bigger inlet, all seem to have 1" exhaust.

 

Just reading about this now a bit, seems you dont do much to the exhaust ports, keep the speed up, but get as much as you can out of the inlet almost.

[ACDodd]

http://russellengine...cylinder-heads/

Read that,

Ac

[timmy850]

You also need to consider the desired compression ratio of the engine as the 12G295, 998 and 12G940 have wildly different chamber sizes.