jim williams wrote:
>
> In my opinion the reason a lot of the
> British car owners in American have not experienced
> major problems is because few of our cars are used in
> an every day high rpm commute.
Perhaps. Yet I do a 'high rpm commute' every day I can in my TR3
(especially high rpm when the OD isn't working), and I've never had
problems with valve seat recession. My commute each way is typically
15-20 minutes of freeway driving at speeds up to 80 mph, plus 20-30
minutes of stop and go city driving at up to 55 mph. I don't dawdle !
Several studies have validated the concept that lead can go on
protecting the valve seats long after the engine is switched to unleaded
fuel.
Also, since the issue is essentially heat, it makes sense to me that
valve seat recession is affected by many other variables, like fuel
mixture, ignition timing, cam timing, valve seat cooling, etc. IOW each
engine may respond differently.
I finally put in hardened seats a few years ago, since I was rebuilding
the head anyway. The rebuild was due to advanced valve guide wear
caused by some unnamed mechanic putting the rear cam bearing in wrong.
(Not me, I swear !)
This is the course I recommend to everyone : if you are having valve
work done anyway, put in the hardened exhaust seats and valves.
Otherwise,
IF IT AIN'T BROKEN, DON'T FIX IT !
Randall
59 TR3A daily driver
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