Bill:
The change in 75 was mainly for the carb water porting. There
was no change in the valve seat hardness or in the valve guide. I am
unsure about material specification on the valve but I do not recall
seeing any change either. This is probably why the heads were only good
for about 40,000 miles before valves holed and exh. seats burnt. At the
time MG was more worried about meeting tightening emmission requirements
and increased costs than longevity.
Now we have the chance to do the job right. Stellite faced
exhaust valves and hardened seats are the way to go. There are still
people arguing about bronze valve guides. If you want them, make sure
they are installed and reamed by someone that knows what they are doing.
If the clearances are too tight the exhaust valves will seize.
Just run the engine as it is until you can budget the work.
Keep the valves adjusted correctly and note if they continually need to
be tightened. This could indicate excessive seat wear which would be
time to start work.
Kelvin.
lots of Bs
Bill Schleusner wrote:
>
> I'm sure this has been discussed at length before, but I've slept since then.
> How do pre-75 B owners cope with unleaded gas. I know the head was changed in
> 1975 to accomodate unlead fuel but what do I do about a 73 engine. Will I
>need
> to change the valves and lifters, etc. or do I just run the engine until it
> needs a new head. Any suggestions welcome.
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