Re: What do I need to do to refine my tune-up?

Posted by BH On 2012/11/5 9:52:57

I would like to add that, if the carb is in good working order, "working the accelerator pump vigorously" does nothing but waste gas and, at the very least, make the engine run rough.

In fact, I shake my head at so-called hot-rodders who wire the choke valve open for better performance and then sit there diddling the gas pedal to try and keep the thing running during warm-up. I can't decide whether they're just too cheap or too stupid to install a manual choke conversion kit. I often wonder how much of that extra gas finds its way past the rings and into the sump, and roll my eyes thinking about what that does for bearing life. Anytime I go look at a car for sale and find the choke wired open, I just walk away.

Yet, I digress...

In ANY vehicle with a gasoline-fueled engine that's aspirated via carburetor, unless the car has been sitting so long that the fuel bowl went dry, all you should have to do for a cold start is depress the gas pedal to the floor once and release before you first turn the key. That delivers a healthy squirt of fuel down the throttle bores and allows the choke to close (under spring tension). Then, you have to give the vehicle a little bit of time to warm-up before you drop it in gear.

If you have to do anything more, then the carb is either improperly adjusted or something in the fuel delivery system needs repaired. (Just because something has been rebuilt doesn't mean it was done right.)

I've adjusted enough carbs in my life to suspect that thermostatic springs may weaken a bit over the decades (though not so much to bother with trying to find replacement parts), and I don't rely solely on the factory index marks. More often, with air cleaner removed so that I can observe the movement, I loosen the choke stat cover screws and rotate it to allow the choke butterfly valve to open completely. Then, I turn the cover in the other direction until the valve is just closed, and tighten the cover screw. The best time to do this is in the spring/fall season, when ambient temps are about midway in their annual range.

Yet, in one rebuilt carb that I was asked to inspect, the choke coil had been installed BACKWARDS!!!