>TR Head Modification for "Run On"
>
>I understand that there is a modification that can be done to a TR3-4 (Others
>?) cylinder head.
>
>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.
>
I don't know about the intentional part, but ... here is what I have
heard said: the well-defined edges on the underside of the cylinder
head, in and around the combustion chamber, act as hot spots - they
are right in the thick of things during ignition, and since they are
forming a sort of point, there isn't as much metal behind them to
draw heat away (as on a flat surface, for example). These
edges/points are sometimes hot enough to cause ignition of the
compressed air/fuel mixture, so even when the engine is turned off,
run-on can occur - it's almost as if the plugs were still firing.
Any practiced automotive machine shop ought to be able to round these
edges a bit - one with experience in TRs might know better just where
to start.
Does this make any sense? (hope it does!)
Dan
--
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Dan Buettner - Des Moines, Iowa - mailto:danb@thelittlemacshop.com
1957 TR3, TS15098L, now with an O! Undergoing frame-off restoration
begun 9/99. Currently awaiting warm weather and funds.
1977 Spitfire, FM64159U, with an O. In need of a comprehensive
restoration (again); will probably become a Spit6 or a Spit8.
Visit the Team.Net Triumph list member pages at:
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