Being the 400 is also a short stroke engine, keeping torque up through a few methods helps the engine perform better. Careful cm selection should be an exercise in small vs. the long stroke 440 even with the same c-ratio. That long stroke cures a lot of evils.
Gear ratio and maybe stall converter dependent, the cam can stay small and perform well. Use a split duration to exit the gasses better and use a small primary carb to keep air and fuel velocity up. "Air/fuel speed velocity" is key for these low comp. engines. Remember that!
On the carb, I have tried a Edelbrock 600 and a Holley 600 1850 model. While the larger primaries of these carbs, over the small primary TQ, performed better, they lacked any punch when the secondaries were opened. Performance was flat.
I choose the larger primary TQ. The bigger primary bores over the small primary TQ was much better, about equal to the other 600 carbs I tried out and retained very good mileage. 17 Hwy. in a 3800+ lbs '79 Dodge Magnum w/3.55's and 245/60/15's.
It was approx. 1+ MPG better than the squarebore carbs.
The other thing I liked about the TQ was the huge secondary side which seriously out performed the square bore carbs. It was plain to see for me which one was a better unit to use on my 400, dead stock with headers.
NOW, what I didn't like about the TQ was it was a pain to tune in since it was a early HP 440 carb. I have a few cores to steal jets and rods from to use. It took the smallest jets and rods to get it to run well. But perfect it was not. Close though.
The parts for these carbs are difficult to find. I normally bend AFB rods 3/4 inch's shorter to use. Then clip the ends off. Jets have there own thread count that differ from Holley jets, main plastic bodies are no longer made. And you can not just simply swap one out with another one unless it is identical to the worn out one/broken/cracked one.
Keep the carb cool and away from the heat with a thick gasket,not the paper thin ones. They'll survive.
OH, also, the accelerator pump cluster's are also a part you source from cores and drill out to meet the spec. What a pain.
The last thing I don't like about a TQ is the choke is in a well. When the manifold heats up, then the choke comes off. Setting it perfect is a pain. This was a source of constant annoyance for me. So I sucked it up and used a electric choke TQ that has smaller primary barrels. The performance is down a bit, but it is 100% drive-able in just a few minutes of warm up in the deepest of snows and coldest of days we have had here in past years in New York.
It would always start up even down into the single digits in winters past. Drove just fine.
I have used this electric choke TQ for the last 8 years without any problems.
Once I had this set up, I LOVED it big time. For the arena it was placed on, I would NEVER go to a square bore carb ever!!!!!!!
