Pat wrote:
> Between the Intake and Exhaust ports there is a point in the casting of the
> head that heats up to circulate the air/fuel mixture (?). It heats up, which
> is intended, but too much for using unleaded fuel.
>
> I'm told that if we round this pointed tip to a 3/8" dia it does not get as
> hot and will help stop the "Dieseling" of the TR when it "stops".
>
> It is a "Old MG" trick... I'm told.
>
> Any comments group ?
>
> Thanks, Pat
> Victoria BC
Pat, that's exactly what it is - an old MG trick. The combustion chamber in an
MG is 'heart-shaped' on one side and thus has the point at the intersection of
the top two circles (the other side of the combustion chamber is more
conventionally oval shaped). The point is a hot spot and radiusing it can be a
benefit in a high performance MG engine.
The TR-3/4 (or any other TR head for that matter) has no such point and no
resulting hot spot. If however you have the head off, and especially if you
plan
on raising the compression, any hard sharp edge in the combustion chamber should
be smoothed off. We use a nominal .030" radius here, which is achieved with
handwork using a Scotch-Brite abrasive wheel in a die grinder. If you mill your
TR-3/4 head considerably, you will also expose the tops of the liners in a
similar fashion as a result of the change in the shape of the combustion
chamber. Be sure to address these areas as well if your head is milled to that
extent.
Cheers!
Brian Schlorff
Power British
1242 East Ridge Pike
Plymouth Meeting, PA 19462-2754
610-270-0505
610-270-3059 fax
http://www.powerbritish.com/~britcars
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