With a timing light and by loosening the distributor is how use set the timing, I think around 34-36* degrees at 3000rpms, need to double check thou.
The tri-power was a 3 x 2 barell carb/manifold setup.
lawn mowers
Not in the GTO. You had a choice of 389 Tri-power (19,045) or 389 4 barrel. ( 77,901)
1964 Standard 389 4bbl had 325 horsepower. Optional 389 Tri-power had 348 Horsepower
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
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.
the 4 bbl. version was 335 horse and the tri power version was 360 horse.
Depends on the year and the induction system. In 1964 389 4bbl was rated at 325Hp 389 tripower was 348hp. In 1965 ratings were raised to 335 for the 4bbl and 360 for the tri power. Of course all these were "gross" rating which cannot directly be compared to the sae net ratings listed from 1972 forward.
3 2 barrel carburetors (hence the term "tri-power")
"65 4 barrel and tri-power come into the radiator on the passenger side.