My 318 w/850 Thermoquad never idles well in gear, and stumbles off the line
It can stand a good bit more initial timing, but you will probably need to end up limiting total mechanical timing somehow. My stone stock 351M in my 75 F250 for example is at 20* initial and 35 total.
This ^^^^
Unplug and cap or crimp closed the vacuum line to the distributor. Set the initial up a bit more try 15* first. Reset idle speed. Limit advance to 35* max and then reinstall the vacuum line for a max advance of 52*. The vacuum advance canister should have a Allen key to limit the total mechanical advance. I keep for getting the size, but, *I think* it a 5/32. Someone correct me here if need be! You also may like the Chrome box or a FBO box better than the orange box.
The reason people are saying the carb is to big for your 318 is because the teen can only pump 460 CFM @ 5000 RPM, thru it if there were no restrictions at all. In reality it only gets about 400 CFM thru it @ 5000 RPM. The only way to get more CFM is to use a turbo charger or a blower. Using a carb that's twice as big as needed seams kind of a waste.
(Not busting your balls, just some sarcasm for fun)
Yes, and this is why a 600 performs better than a 500 carb. Some fellas here even use a 750 Holley. Crazy huh? There must be some madness to the method? What black magic could it be? :banghead:
(LOL on this with me)
As A/J said, since the secondary side has a spring loaded velocity valve above the mechanical secondary butterflies, the door opens as much as needed. The carb calculators will give you a conservitive cfm size for the engine size and HP. This cfm rating is good for a city/around the town driver that will see limited Hwy. useage and that is fine. Like a 500 on a stock 318. It is even better in a heavier car.
For what I would consider a better driving experience, a 600 square bore carb should be used. Even though a 500 would work great. On the TQ, or other spread bore carbs, look for the smaller primary for a better throttle response. That is the first key on a spread bore carb no matter the maker.
8v, what car is this in? What;
Rear ratio
Tire size
Transmission
And are there any upgraded parts?