My signiture includes what's in my engine for reference on this topic. After driving the car for a while on some occasions, the motor just gets kind of weak. It'll hardly squeel the tires and seems weak on the bottom end. I don't know why this would happen, it seems very odd. Any suggestions? Also, would i gain some low end by making the air door on my secondaries stay closed longer?
Are there any other Dart enthusiasts here with street performance in mind from a 318?
Well, so far with my never-rebuilt, 116 K mile,low compression 318 w/ only minor goodies and 2.76 gears with 28" tall tires, i've been able to pull off a 15.3 @ 88 mph. Sounds good to me!

 

I take it your intake is a dual plane, does it act this way regardless of temperatures or just during the summer? It could be fixed by adjusting the secondary door tension if that's the problem. Your gearing sure doesn't help, but neither does the low compression and the mileage.

 

It really only does it in the summer, which can get very hot here in Phoenix. The intake is a dual plane.
I remember today while at school that when it was hot before the winter, I fixed the problem by completely un-hooking the linkage to the accelerator pump, so that it wouldn't squirt any gas down the throats of the carb. While the throttle response isn't as quick this way, once the engine spools up, it takes off much better. In the winter, i hook the linkage back up and it works great. It's been getting warmer lately, into the 80s, so i'll try unhooking the linkage again and see if that helps. I really only need like half the amount of gas in the accelerator pump stroke as i get with it on the lowest setting.