Carb advice needed....
Thread Starter
Melting Slicks
Joined: Mar 2006
Posts: 2,248
Likes: 67
From: Warrington PA
Finalist 2020 C4 of the Year - Unmodified
Carb advice needed....
spoke to my Corvette buddy John today, and he provided me with a good answer. but would like to post the question here also.....
on the Quadrajet Carbs, what is the difference if any between the SB & BB engines on the 73's and 74's and the difference between the Auto and Manual trans carbs...I would imagine that the BB's would flow more CFM's but what else????? thanks...............Tom
on the Quadrajet Carbs, what is the difference if any between the SB & BB engines on the 73's and 74's and the difference between the Auto and Manual trans carbs...I would imagine that the BB's would flow more CFM's but what else????? thanks...............Tom
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
The Q-jet carb is a 'demand' type carb...meaning that it provides the airflow required by any engine, up to the limit of its capacity. Most Q-jets have 750 cfm capacity, but a specific engine will only require what it needs. The differences between Q-jets for SB/BB, auto/manual are subtle including rods, jet sizes, settings for the various adjustments and some differences in design. Only accurate manuals and experts can provide the specific information that you are requiring. Suffice it to know that, except for some design configurations which may limit useability for a specific application, almost any Q-jet will be capable of supplying flow up to 750 cfm and can usually be re-configured to operate satisfactorily on most engine applications. But, you need expert knowledge to decide how to properly accomplish that.
Melting Slicks
Joined: Mar 2006
Posts: 2,465
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From: Orange Park Fl
The early SB Quadrajets were capable of 750 CFM, the big blocks around 800 CFM. Later models all were capable of the larger flow and for racing only applications, they can all be modified to flow a good bit more.
Manuals did not have the mounting stud for the kick down linkage, but they had provision for it, so it is not a big deal.
Also, each carb was engineered by Rochester for a specific application. But they would work over a wide range, and were tunable with rods, jets and adjustments to be usable for almost any application. In extreme cases (using a Quadrajet off a 6 cylinder for a performance big block or vice-versa), the size of some of the internal orifices in the carb may need to be modified.
God bless, Sensei
Manuals did not have the mounting stud for the kick down linkage, but they had provision for it, so it is not a big deal.
Also, each carb was engineered by Rochester for a specific application. But they would work over a wide range, and were tunable with rods, jets and adjustments to be usable for almost any application. In extreme cases (using a Quadrajet off a 6 cylinder for a performance big block or vice-versa), the size of some of the internal orifices in the carb may need to be modified.
God bless, Sensei
Racer
Joined: Mar 2006
Posts: 366
Likes: 1
From: Houston Texas
The automatic transmission carbs have an extra cable connection on the throttle control. This connects to the transmission downshift control cable. You could run an AT carb on a manual transmission car, but it would be difficult to run an AT car with a manual carb without modification for the downshift cable.
Otherwise, per the previous posts, the AT and MT qjets are basically the same.
Otherwise, per the previous posts, the AT and MT qjets are basically the same.
