Notice that my exhaust tip have darken after out on long cruises. I remember back in day my then 55 exhaust tip showing a light blue gray after trips. Now on the 272- 2bl-3spd OD, same setup as then show black. Which tells me it might be burning rich. Should I look in to this with that in mined? Some had suggested it might be from the modern fuel. I use pump regular fuel. Only thing I believe mileage is not that good, appear to be running good. Rebuilt carb, without a change. Any suggestions are welcome.

My new motor is running black. I asked Ted Eaton about changing the jets but he said its not rich its the fuel we get today. Engine was dyno'd so the carb was set up then.

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

When fuel was leaded the lead would leave the exhaust tips an ash gray/white color. With the absence of lead you get black instead. Nothing to worry about. Note that modern vehicles that have direct injection have black, sooty tips from the get go. This produced a lot of complaints when GDI first came out but it's completely normal.

After messing around quite a bit with tuning a stocker for better range what really stood out to me is how amazing amounts of fuel can be wasted out the tailpipe without any major changes in the way it seems to run. Jet size sets the AFR (air fuel ratio) for steady cruise on level ground in high gear. It takes very little horsepower to maintain, and fuel mixtures can (and should) be leaned out quite a bit. This part of the tune has a dramatic effect on mpg, esp. on a percentage basis. If one doesn't understand how carburetors work and the relationship between the different circuits - idle, transition, power, etc, one may be left with a motor that "runs good" but really, really sucks the juice. When you hear someone say for example, they "jetted up a couple sizes" to get rid of an off idle bog or hesitation, this is exactly why. It does work of course, but now the calibration is way out and it will run pig rich out on the highway. Neither too lean nor too rich is any good for the motor under any given situation.

Now it is true that a lean condition under load, under acceleration, will cause permanent engine damage. But there is no reason to run a rich fuel mixture (or retarded ignition timing) under low load level ground cruising.

As you know there isn't a single magic bullet that will achieve best economy, it's many things taken together that add up to efficient, clean combustion. Keep in mind this is a slightly different strategy than drag racers and performance enthusiasts so the tables and charts and "rules" and the rest of it are a bit skewed towards that end. But generally best performance and economy go hand in hand.

A good hot ignition system is mandatory for reliably firing leaner mixtures, along with a good advance curve and setup distributor w/ vacuum advance that works. If the ignition system is weak, it will not ever tune correctly without running excessively rich fuel mixtures.

The jet size and carb specifications in the manual are only a starting point, not the end point I found in my case. I used a wideband O2 sensor to determine the carburetor state of tune, keep in mind each engine is a bit different and what works for someone else's motor may not work the same for you. Gearing, weight, and exhaust type all play a role. A dual exhaust for example - the standard rule of thumb is that due to better scavenging a richer fuel mixture and jetting up will be necessary. The real answer is "maybe"; not always, there is a synergy involved when tuning. Higher velocity through the carb may in some cases pull more fuel than it might otherwise. So you have to tune your particular engine in your particular configuration in your particular location - elevation above sea level changes many of the proper operating points.

Plugs are more difficult to read today because of modern gasoline formulations. I can say that if a plug looks "perfect" with the modern fuel it is probably running very, very rich, at least in part of the operating range.

Hope your issue is as simple to fix as mine was.
After looking for the cause of my blackened tail pipes, I found that my choke was constantly closed. but the cable length was correct. Turned out that the spiral from around the cable slipped out of the rod in the cab essentially picking up the slack and keeping the choke closed.
I pushed it back in and never used the choke again