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12G940 Or 295 +Other Questions

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#1 markking


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Posted 26 March 2020 - 09:58 PM

I currently have a 1275 which goes ok, I’ve been slowly improving and modifying as a running project as time and funds allow.

Next step is an MED cam kit (this one specifically https://www.med-engi...mshaft-kits-946)

My questions are, do I go for the 1.3 or 1.5 rockers to accompany the RS cam
(I’m after a “fast road” spec car, drivable but fun off the line and around the canyons)

Looking to get a head but unfortunately cannot afford any “stage x” from the guys at med or any of the other pros, so a second hand one and some patience is on order.

So the next question is, which is a better starting point the 295 or the 940?

Which valves (sizes and material) will be recommended for my application?

I’m in NZ so I’ve been scouring eBay Uk and both second hand heads are an option for a lot less that the £1400 the big guys want so will be slowly acquiring the associated parts before sending off to a machine shop to work some magic.

Can you guys foresee anything I can avoid/should be doing or ordering to make my life easy?
Any recommendations appreciated.

As always thanks in advance

#2 Cooperman


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Posted 26 March 2020 - 10:15 PM

A 12G295 is an original 998 Cooper head and is not suitable for a 1275 engine.

The 12G940 is the basic casting to use for a 1275, but they come with different valve sizes depending on the model.

For a nice engine the best valve sizes are 35.6mm inlet and 29.5mm exhaust in a head which has had some gas-flowing done.

#3 markking


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Posted 26 March 2020 - 10:44 PM

Cooperman. Amazing info, so that one of my many questions answered definitively.
The 940 be the best starting point! Perfect.

Any opinions on the roller rockers?
Also, there seem to be a few options, which Valve inserts, and caps/collets etc are recommended?

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