Pat,

Thanks for the reply.

Not sure if we are thinking of the same needle valves. These are the IDLE jets at the base of the carb. All the idle jets I can remember seeing are solid brass, about an inch long. Very susceptible to being ruined by overtightening, and I don't remember ever seeing any that had a soft viton type tip...(doesn't mean there aren't any, however!)

You mentioned a needle valve body at the top of the carb...are you thinking of the float bowl needle valve?
Seems like I have seen "viton tipped" type needle in float bowl assemblies.

Was thinking...don't some Carters and/or Rochester quadrajets have metering rods the are raised and lowered to richen the mixture? Think metering rodwould be likely have a viton tip, rather than a solid brass tip as they would be inlikely to have some ham hand overtighten them.

Thanks