Carter Thermoquads ~ 'More General Information'
Just had a look in an old CT magazine. Aug 95. The C & S carb is advertised in it, so that is at least 27 yrs it has been around.
A few reasons I can think of as to why there are not more in use: no better than a std Holley, it costs too much, it costs a lot for little gain.
that's not the original 1969-71 CS carb if advertised that late, they stopped making those in the 1970s. they made AFB/AVS copies and also called those CS throughout the years. the 9800 series was called a CS around 1980-onward. or it was new old stock NOS early CS carbs that were sitting on a shelf somewhere for decades.
the Buick dyno test tells the story, you will always make more HP with a 4bbl using 4 equal size bores, for racing. the Holley DP as designed in the 1960's, was first cobbled up at Smokey Yunick's shop in Daytona Beach, Florida specifically for NASCAR racing. He told the story about how the original prototype they made, was lent to Bunkie Knudsen at GM and later Ford, then never seen again. He asked for it back numerous times but never got it.
The small primaries and tiny secondaries on a spreadbore create a velocity difference that is somewhat detrimental to making maximum HP at high rpm. The primary flow bounces up off the plenum floor creating turbulence. It was designed to use with a factory dual plane intake manifold. Edelbrock made the early Torker 1 open plenum intake with a volu-step in the bottom of the plenum, to counteract that effect. The floor was lowered in the front half of the plenum. To this day that is still a good SS class racing intake for a spreadbore carb, if you can find one.
for daily driving on the street using a cam up to around 230 duration @ .050", a spreadbore will give better part throttle response, mileage. A big Holley i.e. 850 with its big 1.56" primary bores will slow down idle/off idle velocity, the mixture falls out of suspension at idle/off idle, and the plugs will look black and rich. It takes custom air bleeds, bypass air holes in throttle plates, etc. to get a big Holley to work on a stock motor on the street, if at all. If you just bolt it on, the plugs will be black or wet, and the motor runs rich. A 750 is a better choice for a mild motor, the smaller 1.375" bores bring the velocity back at idle. Idle quality is a lot better with a 750. A Holley 850 is a LOT bigger than a Holley 750.
in NHRA Stock and SuperStock, if you can sneak an early CS top/middle section onto the car, and use the oem 72-up numbers baseplate to pass inspection, it would pay dividends with the extra cfm. but if you get caught, you could be DQ'd. This is why the class racers seek out the 1971 Mopar 340 carb. It's got the same basic design as the early CS.
the CS aren't used because the jet/rod kits and rebuild kits are exceedingly expensive, in some cases more than the cost of the carb itself- and carb technology has come a long way since 1970 when the CS was first in use. It's a 53 year old design. the Qjet is a 57 year old design. technology moves onward and forward.