12g 295 Face off how much?

[Plank]

I have come across a bare 12G295 for fiver!
Its covered in suface rust and has been sat in a shed for as long as can be remembered. Any how, My daily drive has only done 4000 miles since I rebuilt the engine and box (998 City E +40 with mini spares mild road cam)
My car has told me that it needs this head fitting now that its nicely run in! So,
How much should I have taken off the face to bring the compression right for the modern flat top pistons? Plank.

[stuttgartmetal]

Light surface skim 'll do it.
I had 30 thou off one of these once, and had it on a 1300 in a pick up.
After the skim there was hardly any combustion chamber left.
The car absolutely flew, for about a thousand miles, then the HG blew to buggery between 2 and 3.

[Cooperman]

The 12G295 is intended to run on a Cooper 998 engine with raised 'D-Top' pistons. So, a flat-top will give a reduced compression ratio. What you really need to do is to remove the original head and do the measurement and calculation to get it absolutely correct.
Email me for more info as to how to do this.

Peter

[Plank]

Thanks Cooperman, thats what I thought, I was in fact being lazy in that I wondered if their was a std skim.

Steve

[Cooperman]

I just checked with my Grandson, and on his 1061 cc engine (998 at +0.080") with flat-tops and a decked block we skimmed 0.035" to obtain a C.R. of 10.2:1 which is about the C.R. you need. The combustion chambers had been opened up a bit to improve gas flow though.
However, you never know whether the head you have has been skimmed before, so unless you measure the volume you don't know where you are starting from.
With a better flowing head and a higher comp ratio you may well need a bit more distributor advance a t full throttle and higher revs. to get best power. We didn't do this, but just advanced it up a bit on the static timing and that seems to have worked for now.

[Plank]

Thanks again cooper man. I shall start work shortly. Steve

[Cooperman]

Plank said:

Thanks again cooper man. I shall start work shortly. Steve

You're welcome Steve. Hope the job goes well. Once it's done you will have a really good spec 998 motor.

[Plank]

An update.
Having priced up the skimming work and the bits etc.
I have found its the same price to send it to Mr Carver, and as he's only up the road in Malton, thats were its going--and it will be right.