Michael :
I think I saw a post saying you were talking about a TR3...
There are actually about a half-dozen different head castings, Kastner's
warning applies primarily to the very early "low port" heads (at least 2
different castings of these). If you have one of these, and want some
performance, my suggestion would be to find a later head and intake
manifold. The TR4A head, curved tube intake manifold, and HS6 carbs
(required to make it all fit between the fenders on a TR3) are supposed to
be good for 5-10 mid-range horsepower all by themselves, even with the lower
CR ...
According to an article written by Ken Gillanders at BFE, the stock
high-port heads measure between 3.325" and 3.330" from the valve cover
surface to the head gasket surface. He says to never remove more than .150"
from these heads.
However, well before you go that far, you will need higher octane gas than
you can buy at the pump. My suggestion would be to only take .080" or .090"
off the head, then use one of the thin .020" head gaskets available from
BFE, Moss, etc. That way, if you find your CR is too high, you can go back
to the .060" stock head gasket. Note that a change in head gasket thickness
has a bigger effect on CR than shaving the head, because the area of the
opening is larger. You should also grind the edges of the combustion
chamber out to match the head gasket, as shown in Kastner's book, as
otherwise the exposed sharp edge will increase the tendency to knock.
I assume you're putting in hardened exhaust seats all around, another
worthwhile modification is to switch to the later exhaust valves with the
smaller stem. There are special "changeover" valve guides available to do
this.
Don't forget to check that the head still clears the water pump housing, and
the intake manifold still clears the edge of the block, after milling the
head.
Randall
Michael Thompson wrote :
>
> Hello all,
> I have burnt an exhaust valve seat and while the head is off
> I would like
> to do a little work on it, primarily shaving it down to increase the
> compression. I have two heads, so I'm not too worried about
> not being able
> to go back to stock.
> I have a good fast road cam installed and 87mm liners and
> pistons. Both
> heads I think are earlier versions. My main question is how
> can I tell how
> far to go with the plainer? Kastner's prep manual warns of
> making the water
> jacket weak on the earlier heads. Where can I measure this?
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