You don't need to block off the heat riser chamber under the carb. You can add a heat kit to the Fenton's, that's what those plugged holes that are visible on the Fenton's are for. Langdon sells a kit and so do other vendors. The kit will include a plate, tubing and fittings to plumb exhaust gasses into the chamber and seeing you live in Indiana, you're probably going to need the heat kit.
