Carburator question

[Mr.Fixit]

Originally posted by Cobra #42
Sorry to disagree with your comment about not using a dyno with fuel /air & EGT measurement mr. fixit, but I wonder how one can read a plug at every rpm range from idle to redline ??

Guys have been making more HP than you ever will, prior to EGT probes or multi-gas analysers. Idle is easy, you can put a vacuum gauge on it, or just go for highest idle speed by trimming out the idle mixture screws, then re-adjust idle speed at the throttle blades. After that, run it hard for 1/4 mile, push clutch in and kill motor, coast back to the pits then pull plugs and inspect. Once you get the plugs looking good, you will have to most likely adjust the squirter/pump cams, and make fine adjustements to the transition circuits. Adjust for as little gas as you can in all the perameters, without turning your plugs ash white or having any stumbles in any rpm or condition, these things run too rich most of the time reguardless. The problem with dyno tuning a carb is the dyno puts a different load on the engine than the car will, you are fine tuning it for a condition unlike it's home in the car. The dyno tune will be close, but you probubly just paid somebody a few hundred dollars at least to do that tune to it, so you won't want to change his work. There's more to fuel curve tuning than looking at sparkplugs or reading the monitor attached to the smog machine, you must use your ears, eyes, nose, and "seat of the pants" to determine under what conditions you need more or less gas. The instinct is to go more gas, but you should try for less gas until it stumbles, then richen it up until the flat spot goes away. But by all means, if you really want to, run EGT probes in you car's headers, you will get an important measure of what's happening in the combustion chambers, and buy them from Exhaust Gas Technologies in anaheim CA.