In message <950407112333_75089016@aol.com> writes:
> I'll keep this short (and hopefully simple):
>
> 1) Is there no consensus on the unleaded question? Should I use a lead
> substitute for my 75 (not unleaded only)?
Carl,
Year before last, I had to replace burnt valves in the Land Rover and the MGB.
I put lead substitute in the Land Rover (when I remembered). I did not put any
in the MG. They both lasted about as long on unleaded. From my experience, the
lead replacement doesn't seem to really extend the life of the valves and you
may not use it all the time because 1. its expensive, 2. you need to keep a
stock so it will be handy while filling, & 3. you need to remember to use it
(Doesn't work well stitting in the bottle in the boot).
You can probably get 5 or more years out with a head set up for leaded before
you need a head rebuild depending upon your driving & how hot the engine gets.
I have hardened seats in the MG, TR3 & Land Rover. It doesn't cost that much
more and I want to maximize reliability.
Be careful about bronze valev guides. The inside diminsional specs are for steel
guides that expand less than bronze at a given temperature. Bronze guides set
up to steel guide deminsions may try to seize valves on a newly rebuilt head.
This is quite common in MGBs. So if you get bronze guides have the internal
dia. enlarged one or two thousands larger diameter than the manual calls for.
But getting back to the original question... Your car with a head set up for
leaded petrol will run just fine on unleaded. You will just need to get the
head rebuilt a few years earlier than one set up for unleaded, and I don't think
the substitute stuff is worth the thousands of dollars you would spend on it
during the years you use it between head rebuilds. If you drive the car at all,
you could easily spend as much lead substitute as for two or three heads set up
for leaded petrol per year. Over the period between valve jobs, if you used the
substitute religiously it could easily cost you as much as your TR6 is worth.
A set of hardened seats & the machine work is a WHOLE lot cheaper.
The decision is yours.
TeriAnn Wakeman Large format photographers look at the world
twakeman@apple.com upside down and backwards
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