| > I'm tearing down an engine out of a TR3B parts car and trying  to figure
> what the differences are from a TR3A It has a 4speed synchro
> transmission, and 86mm bore(later part of run). Most importantly, are
> the crank journal and other internal dimensions the same as the 3A,
Yes.  The crank and block should be identical.
> and  is the head slightly different?
Possibly, but I don't believe the change-over was clean.  I've seen early
TR4s with apparently original late TR3A heads.  Teri-Ann has done a nice
write-up with pictures and identifying marks at
http://www.cruzers.com/~twakeman/TR/FAQ_heads.htm
She may have missed one or two 'specials', for example I believe there was a
run of heads that were machined to Kas Kastner's specifications, but you're
not likely to find one of those.
Randall
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