Before I took the time to show the 5 images above I showed the open power valve. And by contrast it would look like this in the “up” position (away from the power valve: (please see image one below)
Rochester used at least 2 styles of power piston designs and I wasn’t able to unscramble that egg. One had an open shaft and one had a closed shaft and otherwise they seemed identical. The one in this carb has been crudely soldered closed just for illustration purposes and also because when I got it, it looked like somebody had been using it as a toothpick or cleaning something off the bottom of their shoe with it. (please see image two below)
The extra fuel provided by the power system is available to the idle tube and the main metering system. It is metered by what Rochester calls a “Power Restriction,” and in the carb I’ll be using for illustration, this restriction hole was 1mm or .0394” in diameter. Here...you can see it in image three below:
I’m going to overlook the choke system, accelerator pump and throttle body. Those don’t seem to me to be classic problem areas. However if the throttle shaft bore is worn to the point you notice wobble it goes without saying it should be bored and sleeved.
The Problem Areas
The fuel level. You can adjust this up/down with the float and experimentation is easy. A lower level will also lessen the tendency to weep at the seam and my experience has been it is common for these to naturally run rich. However there is a wild card here. The Carter engineers learned the size of the orifice in the seat (needle/seat) was important. Too large of an orifice caused flooding. When the float drops to allow fuel in, the fuel flows through a large orifice faster than the float can compensate for. That is to say there will be a delay involved in a float operated mechanism and the size of the orifice of the seat will be important. An orifice too large will cause flooding. You can see in image four below:
Vacuum loss. This was a problem for 4 of the 5 Rochester B and BC carbs I observed (remember one could not be operated), and I would imagine the same problem exists universally. Every one I had was warped to some degree and in one the warpage was well over 15 thousands. How and why? Only 4 screws to hold them together certainly doesn't help, but maybe those 4 screws have a partner in crime. Please see image five below:
And on to the next post as we’ve used our 5 image limitation...
