[Fot] Compression

[Scott Janzen]

I’ve found the GT6 head has some thin spots and depending on the casting can’t take milling too much more than 11.5 to 1, maybe 12 if you get lucky with the right casting.  As to the lore that circle B heads are the best, I have not found that to be correct in this respect.  Seems like they are all over the map.
The rest has to come from domed pistons, which I have not yet tried, so there’s probably some more HP to be found.  
Before you mill a head, find a shop that can “xray” it for you to tell you how thick the metal is above the cooling passages.  When I had this done, they just marked the thickness directly on the head with a market.  If memory serves, one of the thinnest spots is not quite outside the fire ring on the head gasket near #1.  I had one fail there that got milled 50/thousandths too much.



On Dec 6, 2021, at 1:36 PM, McKearn McKearn via Fot <fot at autox.team.net> wrote:

Now that we have the crank and rods figured out, how about we discuss making compression?
 I know this can be a sore subject and everyone has an opinion as to how much is enough or too much so where do we start?
 I have built a couple TR6 engines that were in the 13:1 range thanks to much head milling and pop up pistons. Will the 2.0 litre engine be the same ?
                                      Thanks.  P.J.
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