Torque converter
Loco, I was hoping you would chime in here as you are running a stocker too. This is not the truck it is my new ride. Tire hook is not an issue, car is very soft off the hit. Have played with the carb a bit. Put my bothers 750 HP on it with out much change in 60. I do have a new 750 holley for CM stock. Have heard that sometime a smaller carb will help. The verter is 4500 or so but more then likely that was behind a 800 + hp hemi, which would be much different behind a 400hp 5.9l. Right?
Yes, there will be a big difference in converter "flash" between the engines, even between mild big blocks and small blocks. More torque will flash higher. Slippage is a factor too. But as I mentioned before, there is more to converter science than I know and 2 converterers rated the same can yeild different results.
One reason stockers have good 60' time is that we run more converter, final gear and often more low gear than other racers, sometimes to the point of being overgeared. But with all the rules restricting mods, it's a good way to make up for it as long as the entire package works together.
I've only heard of one or two CM cars running a smaller carb over the years. Not sure if it was for bottom end, to slow it down or because they just had them handy. I believe a 750 is a good size for a 340/360 if you can tune it well. I've only changed jets, pump cams, squirters, throttle blade positions and idle mixture adjustments. No passages, bleeds, etc. But despite playing with them for so long, I'm still tinkering. It seems that getting enough intial volume to squirt without allowing it to squirt longer than needed, and getting both squirters to stop at the same time, is important. Remember that leaving at a higher rpm uses up some of the volume you have available in the primaries. The higher you go, the less gas there is in the pump. But then the primary boosters are starting to flow also! Cam as well as converter changes can affect the carb tune-up so you may have to make more changes. Even a spacer change. Lots going on and each combo can be different.
All 750 carbs aren't the same either. For me, a 4779 DP wants to be run richer than the new Ultra DP carbs. Test, test, test.