View Full Version : Carter TQ jet sizing

06-25-2013, 09:11 PM
Would like to install a Carter TQ carb, from a 360 engine onto my 440 engine. The question is should I increase the size of the jets enough to satisfy the bigger engine yet still maintain throttle response?

06-26-2013, 07:13 AM
Depends on how much performance you are looking for and what cam the 440 has. A lot of the 440's are pulled from rv's, trucks, etc and have cams for low end torque. If that's what you have, you probably wouldn't need to re-jet.
Also, the initial response would not be much affected by changing jet sizes. That mostly comes from the accelerator pump, which is very strong on a tq and can be increased by using the second hole on the linkage, and from the metering rods. There is a thread on this forum that goes into tq's in detail and lists the various jet sizes for all the tq applications. Also, tq's are almost self-adapting. Their rated cfm's don't give the whole picture.

06-26-2013, 11:55 AM
Thanks for the response, Chirorod. My particular 440 is a HP version. Stamped near the valley pan...1974 RR. Anyway what you say is helpful.

06-26-2013, 03:32 PM
Since the tq is so forgiving, you might not have to change anything. Some of the 360's had tq's with the smaller primary bores. No matter what you do for jetting, there won't be as much oomph with the smaller primaries. Unless you are going for max performance, it shouldn't be a big deal. If you can give me the carb #'s, I will look them up. Or you can go to the induction section of this performance forum. Everything is pretty well laid out there.
I should say, also, that increasing jet size won't decrease performance off the line. The tq is harder to over-jet than other carbs. It pulls in what it needs and tends to pull in no more than it needs. Where people sometimes have trouble is with trying to get the secondary air door to open too soon. A delay is engineered in so that fuel flow has a chance to catch up. The spring tension on that is adjustable. And the seconday fuel mix can be adjusted with the air door.