Terry, machine shops nowadays use a computer to calculate the compression
ratio. They typically have software that requires inserting all the
pertinent data (bore, stroke, chamber cc, amount piston sticks up or is
recessed in the bore, gasket thickness, etc.) and returns the compression
ratio.
So I'd bet that if you tell your machinist what you are after, he can do the
right stuff to achieve it. Obviously each thing you do affects the
overall ratio, so after doing all the head work and boreing, you will save the
deck or head shaving till the end to achieve what you are after.
Regards,
Joe
Terry Thompson wrote:
>
> The question I was going to ask was what is the final
> result on the height of the stock head, but really the
> answer I need is calculating compression.
>
> I'm currently having a head ported, polished, seats
> stepped etc. And I'm looking to have the shop mill the
> base of the head to increase compression.
>
> Does the machinist need to calculate the capacity of
> the combustion chambers once they've been CC'd to
> figure the ratio and the amount needed to remove from
> the base or is it independant of the combustion
> chamber smoothing?
>
> I'm actually aiming for a 9.7:1 compression ratio
> which R&T did to a '74 1500 by removing .150" from the
> head of a low compression engine. But I'm assuming
> that since there's material being removed from the
> combustion chambers this calculation will be
> increased.
>
> Yes, no, maybe so?
> -Terry
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