[Fot] How far can a GT6 head be milled?

[Jeff Durant]

Jason,
My reason for asking is I'm prepping 2x GT6+ heads for use on my TR6 racer.
Both heads are 517528 p/n. The stock CR as fitted to a GT+ (mk2) is 9.2:1 I
believe.  I thought an early mk3 was 8.5:1 and less on the later mk3.? As the
combustion space is smaller than any TR6 head, the amount of material to skim
by comparison, would be far less to hit my 13.5:1 target.  Both heads measure
3.255" currently and there appears to be plenty of meat around the previously
mentioned thin spot inboard of #1 exhaust port, but I agree there are casting
variations even with heads having the same p/n.  I need to cc the current
space and calculate the final amount to remove after stripping, cleaning and
crack checking. When milling I'll be inspecting carefully after each pass!
BTW what is the p/n of the 2 liter head you working up?
Regards,
Jeff Durant
Sent from my iPhone

On Jun 30, 2014, at 8:00 AM, Jason Sukey <jsukey at gmail.com> wrote:

> Not to worry, this is the later head (off a Mk III)
> Jason
>
>
> On Mon, Jun 30, 2014 at 10:58 AM, SCOTT JANZEN <sjanzen at me.com> wrote:
>> If it's a mk I head, toss it and find a mk II
>>
>> Sent from my mobile device
>>
>> > On Jun 30, 2014, at 10:38 AM, Jeff Durant <jeff_durant at comcast.net>
wrote:
>> >
>> > Jason,
>> >
>> > GT6 mk1 or plus (mk2) head?
>> > Regards,
>> >
>> > Jeff Durant
>> > #12 TR6
>> >
>> >
>> > Sent from my iPhone
>> >
>> >> On Jun 29, 2014, at 1:07 PM, Jason Sukey <jsukey at gmail.com> wrote:
>> >>
>> >> I'm getting ready to mill the head on my GT6 for a bump in compression.
I
>> >> currently measure 3.255" thickness, my math shows that I want to end up
at
>> >> 3.215" when I'm done.  I can't find much info on how far people are
safely
>> >> milling the GT6 version of this head, only TR6 info.  Does anyone have
>> >> experience on this?  Is there enough meat in the casting to remove this
>> >> much material without hitting water?
>> >>
>> >> Thanks,
>> >>
>> >> Jason Sukey
>> >> _______________________________________________
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