| Greetings Fred,
I also have, since rebuild in '95, 87 mm sleeves/pistons, stock cam, 
hardened valve seats in my '64 TR4, and have since used unleaded 
"regular" with no pinging or adverse results I can detect.  75-85 mph in 
O/D 4th is also normal for me.  When leaded gasoline was what was sold, 
and I used the TR4 daily (60's, early 70's), I always used "regular" due 
to lack of  funds.  There was no unusual wear on rebuild.  My experience 
would suggest "regular" is ok for a std TR 4 cyl engine in street use.
brgds, Jay
'64 Triumph TR4 since '67
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