lets revisit timing
A good curve for a 10:1 340 usually falls around 10 initial with another 24 mechanical for a total of about 34 at around 3000 rpm without vacuum advance which may add another 16 or so for a cruising total around 50.
how might the engine performance differ with totals of 30 - 36 at wot ( no vac adv.)
..would it be noticeable?
Are you talking at the track or around town.
I'm a streeter so all I can talk about is street performance; so
now it becomes a question of ; what transmission, and what gears.
then, if an auto; what stall?
Depending on the combo (say; automatic trans &3.23s) you might not hit 3400 at WOT until over 30mph in First gear. If you take that to 5500 @50 mph, then the Rs might drop down to 3250 in Second@50mph, and there you are again, struggling up the power curve. By 65mph, in Second, your Rs may be up to 4200.
So; will you notice a performance loss, at WOT, at these rpms?
IMO, only if the tires don't spin, and
only if you put a stopwatch on it
that measures to at least 10ths of a second,lol.
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Watch Uncle Tony's videos; sometimes he hunts for a horsepower number just 3 hp more, and tries different max advance settings two or three times, and still can't find it.
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In my combo, by seat of the pants testing, with alloy heads ( 367 cubes with flat-tops at 11/1Scr), I couldn't tell the difference between 32/34/36 degrees, so I just run 32/34 and call it done. It went 93 in the Eighth on that; surprised thechit out of me.
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But if yur talking Quarter-mile, running 4.30s and 1.8second 60fts and stuff. ........ that's another topic.