>As I begin long overdue reconstructive surgery on my GT
>I'm contemplating improving performance when I get to the
>drive train. My engine is from a `72, the head has the ports
>for the air injection blocked off with bolts. In my store of parts
>I have a head from a 3 main engine. If I contemplate a head
>rebuild and porting/polishing, which head would be the best
>bet and why?
>
The '72 head ... it has larger intake valves (from '72 to '74 the
heads were fitted with 1.6250" intake valves) and most of the
'gas flow' work required on the early head has already been
done (the 'Westlake promontory' between the valves has
been reduced.)
Note that, due to the air injector ports, the '72 head is not as
durable as the earlier head ... however, a head that has been
cast for the air injectors but not machined for them is the strongest.
>I was also told years ago by an old coworker who raced his
>B that shaving up to .030 off was a good place to start (providing
>of course the rings are in good shape). Anyone care to comment?
>
The standard capacity of the combustion chamber in the head is
43cc. and the removal of approximately .009 from the head
reduces the chamber by 1cc. If the stock 8.0:1 low compression
pistons have been replaced with 8.8:1 pistons then , if my math is
correct <g>, .030 off the cylinder head would result in a 9.325:1
compression ratio (.040 would result in 9.5:1) ... having a head
planed is not that expense so remove small amounts at a time
... it easy to take more off but damn near impossible to put it
back on <bg>. Given the current state of gasoline, you may want
to consider increasing power by overboring in lieu of an increase
the compression ratio.
Don't forget to countersink the head stud holes so that the top
thread is below the surface of the block ... this insures that the
head gasket will seat properly.
>I'm also considering a street cam and electronic ignition.
>I used to have a set of 1-3/4" SU's saved for this project but I
>lost them (don't ask....)
>
... fast road cam ... HS6s ... you have increased intake so you
will need an extractor type header to provide a corresponding
increase in exhaust.
YMMV ... usual disclaimers.
Larry Unger
ungerl@reston.unisysgsg.com
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