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Triumph TR6 - Cylinder head thickness

Hello Folks: I have purchased a cylinder head, for my
1974 TR6, that measures 3.285 in thickness. Can anyone
give me an estimation what my compression ratio would
be? The rest of the engine is original as it came from
the factory. The bottom of the motor has never been
apart. I have installed an S2 cam, and done mild
porting work to the existing head. Any advice would
be appreciated.
DG Lazarus

Have a look at Richard Good's website - he has a table showing what the compression ratio should be for different thicknesses.

The thickness you mention seems low, though - looks like you would have well over 10:1 with that thickness. I had more than 0.1 inches taken off my '75 head and still had more than 3.4 inch thickness.

Hope that is useful

A Hewitt

Is it off a TR6?

I think Don might be on the right track here - at that thickness it is either a head that someone has cut down a lot, or it is from a 2000cc engine of some sort, by the looks of the chart at this website:

That list isn't complete, at least for US market cars - I think that the 219016 casting was used on the US TR6 for some time, but 219019 was the low compression head used in the later years (that's what is on my '75). The number is on the top at the front (over the #1 cylinder exhaust/intake ports).

I think that there is a thick copper head gasket available which would bring the CR down to a more manageable number but I think it is only for pre-'73 cars for some reason (which eludes me for the time being).


A Hewitt

I'm running, and I use that term imaginary, a GT6 head from TSI

Hello folks! Thank you all for the excellent information. I appreciate your quick response, and
will check these links. The previous owner told me
he cut down the head to achieve 11.5:1 compression.
I will try to verify, and pass along any useful

Thanks all, Dave
DG Lazarus

11.5 , you'd better be racing it.

Yep, thats pretty scary compression to be running pump gas on.
Mitch Smith

Hello again folks: After doing some calculations on
combustion chamber volumes, I estimate thi compression
of this particular head to be 11.9 to one. I think
this head will be put on the shelf for another time.
Thanks again for all the input.

Dave Lazarus
DG Lazarus

Dave- Where did the head come from. Don't give up that easy.
What's the cast #

This thread was discussed between 20/01/2010 and 09/02/2010

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