Anyone ever dyno test stock GM BB 3 carb set up ?

[amcenthusiast]

Part of this discussion could be on how the two 'secondary carburetors' effectively shorten intake runner length making 'six pack' induction system function as a variable length runner manifold.

[ZEOHSIX]

If it where not for GMs foresight and getting there hands on the new Rochester 750 cfm Q-jet in mid 67,GM lines would have had a hard time in keeping there hp numbers up after 1970 when the emissions / fuel mileage crap kicked in.
GM may have been forced into trying to keep some multi Carb set ups I think!

The Qjet was such a great carb that Ford even used them on the 429CJ motor.....the SCJ got the Holley of course.

[Schurkey]

Part of this discussion could be on how the two 'secondary carburetors' effectively shorten intake runner length making 'six pack' induction system function as a variable length runner manifold.

While true, I suspect it's a matter of going from "too short" runner length to WAY too short runner length.

I never noticed a dip in the torque when the secondaries kicked-in, but then my 3x2 system is vacuum-operated. Chrysler 440+6 carbs installed over the years on various Chevy small-blocks--283, 350, 400. I have always assumed that I was giving-up horsepower compared to a modern manifold and a single-four carb.

Photos from trial-assembly about twenty years ago:

[Krooser]

I worked at two different Chevy shops in '67.... at Humprey Chevrolet in Milwaukee I had the only twin post lift that would take a Vette with side pipes. I did new car set-up at Holz Motors in Hales Corners... drove too many tri carbed big blocks to remember. My butt dyno never felt any loss of tq.

Set up and drove the first Z-28 in Wisconsin and my "test drive" was done on a county road with a '66 360 hp Chevelle right beside me up to 80 mph... would have done better but that darn frame mounted Muncie shifter wouldn't let me power shift.