Pontiac was able to run the chamber shape that was first used in the D port heads in 68 right on up to 79 and yet meet emission standards while other car makers where having a hard time doing that!
That in itself says a lot!
Pontiacs leg up so to speak on everyone else is due to in no peticular order 1) big Intake valve to provide fat flow numbers at lifts under .400" due to the big curtain area and the 30 degree seat.
2) 14 degree valve inclination angle that keeps the fuel that does get in from slamming onto the cylinder walls and not getting burnt which lowers fuel mileage, increases emissions and less causing ware!
3) the chamber shape and the high level of low lift swirl it produces.
4) even though the 68 cast number 16 D port heads where still cast with the air injection bosses in the exh ports like the 67 heads, engineering found out by mid production that they where not needed to meet emissions in CAvand where happily deleted from the late year casting 16s!
This is yet another thumbs up to the 68 and up chamber shape.
I have yet to investigate if the changes they made so darn late in the game to the Intake port shape of the 5 series and 6 series heads was done for greater power level, or better emissions, or maybe some of both.
One things for sure this change did not hurt power levels!
The width and shape / arc of the short turn has a effect on the swirl rate as valve lifts rise from .400" on up, this is for certain!
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!
1) 1940s 100% silver 4 cup tea server set.
Two dry rotted 14 x 10 Micky Thompson slicks.
1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.
Education is what your left with once you forget things!
Last edited by steve25; 09-20-2021 at 07:09 AM.
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