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Quadrajet??
Is that the carb that has small primary's and humungous monstrous secondary's?
...or is that the thermoquad I'm thinking of?

Yeah, q-jet was a "spead bore"

Meaning different sized primaries & secondary�s.


tiny primaries & huge secondary�s.

Other manufacturers offered spread bore configurations back in the day as well but quadrajet was the most famous for it.

"Square bore" configurations are most common in 4 barrel carbs. Meaning the secondary�s are the same size as the primaries.

Holley offered a spread bore 4 barrel, I'm sure you can still buy it. I think it was mostly an efficiency theory, running on the restricted cfm of the tiny primaries as long as you behaved yourself & then when you drop the hammer those big secondary�s open up & it makes a distinct sound... like a hurricane coming through an empty train tunnel.

A lot of the aftermarket intake manifolds tooled in the 60�s-70�s have a carb interface that is of a spread bore shape. Like an edelbrock performer intake for instance, you can stick a square bore holley or carter afb on there just fine but the shape of the interfacing ports were actually designed to complement the spread bores.

Spread bore is definitely not the current �mainstream� in hot rodding or performance engines but it has its niche. As does the idea of multi carb set ups like tri power or six pack, 3 deuces etc.

Basically the same principal with the engine usually running off the center carb under average driving conditions and a progressive throttle linkage opens the �outboard� carbs on further travel of the throttle linkage. For GM & Ford this usually was a mechanical secondaries or mechanical outboard carb operation and for Mopar the �six pack� actually used vacuum to open the outboard carbs.

OK thats what I though.
I had a built 440 Plymouth Roadrunner that had a high rise dual quad tunnel ram intake and I ran dual quadrajets (I think) anyway the sound you described was exactly what it was like when I mashed it......along with the tires screaming for mercy!

I swear if it was a lowrise tunnel ram and I was able to run a hood on it.....it would probably suck that hood into the carbs.

yeah probably, lol!!

Scan some pics of that baby Tom.... I love me some vintage Road Runner.

See if I can find em....they are at my parents.