best size 2bbl carb or small 4 bbl for my 318?

clhyer said

leave the 4bbl and disconnect the secondaries

I've always heard this but always wondered why doing this doesn't limit, in a big way, your top speed or why doing so wouldn't cause your engine to run too lean at high speed?
Could someone give me a not to technical explanation?
Thanks,
C

Click to expand...

It will limit your top speed and power a great deal. BUT the engine doesn't run any different A/F mixture at high speeds than low speeds; if the engine is spinning faster (requiring more air), the carb meters more fuel into the venturis accordingly. What you do when you disconnect the secondaries is pretty much turn the carb into a 2-bbl. Really that doesn't make sense to me because the only difference it will make is the secondaries won't open when you floor it, which you shouldn't be doing anyway if you're trying to get good gas mileage! When you drive around town at part throttle the secondaries don't do anything at all on a 4-bbl. carb.

What is your ignition and exhaust setup? If you don't already have them an electronic ignition and free-flowing dual exhaust will help gas mileage. Of course they'll also give you more power, so you'll have to try harder to drive with a light right foot. All power-adding mods done to an engine (aside from a longer-duration cam or big-port heads) will also increase gas mileage because the engine is running more efficiently.