The tri-power was a 3 x 2 barell carb/manifold setup.
Info at this site might be helpful. http://www.justanswer.com/questions/2zzo6-timing-a-1966-pontiac-gto-389-with-tri-power-what-is-the-best
1964 Standard 389 4bbl had 325 horsepower. Optional 389 Tri-power had 348 Horsepower
the 4 bbl. version was 335 horse and the tri power version was 360 horse.
lawn mowers
Not in the GTO. You had a choice of 389 Tri-power (19,045) or 389 4 barrel. ( 77,901)
3 2 barrel carburetors (hence the term "tri-power")
is the timing set properly
6.5 liter 389 4bbl puts out 335 hprsepower at the crank. The tri power puts out 360 horsepower at the crank.
look in a chiltons repair manual from the library for your year car.
335 stock and 360 with the tri power set-up.
6
1964 pontiac 389