Hi,
I have a similar experience with an 80 MGB so here it goes...
I looked into increaseing the compression ratio from 8:1 to 9:1 in my
B. The easiest way is to get a pre-emmision head which has a smaller
combustion chamber ( similar situation to your older head idea ). On a
B there are only a few small mods required. This may work for you. In
my case I could not find a 73 head that was in good condition.
Something to think about when doing this mod is that older heads were
designed to work with leaded gas and therefore do not have hardened
seats or valves. A seat costs around $10 and $10 to install at a
machine shop and then around $65 for valve job (lap the valves) not
including the price of valves. You can skip this but you might need to
get valve jobs a little more frequently running on no-lead.
Shaving the head...
In my case I took a little off the head to increase compression.
Potential problems are:
If you shave too much off you could run into valve hitting piston
problems
Also, if you shave too much off you can reach a point where you will
not be able to adjust your valves any more. I heard of a case where
someone did this and had to have custom pushrods made. (heard this
from a guy at Crane so "grain of salt"
(You would have to shave a real lot off your head for this to happen
probably some off your block too.
Other solutions...
I ended up shaving my head a little $20. When I found that I also had
to have my cylinders bored 030 over I got new pistons that were pretty
much flat instead of dished like my old ones. Total compression went
from ~ 8:1 ton 8.75:1 . Don't forget to get the head magna-fluxed to
test for cracks before you waist any money.
That's about all I have to say... Any questions regarding, please
reply.
P.S. Find a good machine shop!
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