Heater Boxes

The biggest problem I have had with this conversion is the integrity of the clamp between the heater box and the J-tube. If you retain the stock muffler you will probably be okay, but if you go to a header the vibration causes the asbestos ring to wear very rapidly and you end up with an exhaust leak(not to mention all the problems with a lack of carb pre-heat, but that's a topic for another day...).

The solution with the header system is to weld flanges onto the end of the header and the J-tube, and then you can bolt the system together. You will need a slightly oversized exhaust gasket at the J-tube to header junction, I usually modify the fiber based gaskets, or sometimes you can find the larger ones on the shelf at a veedub shop.

The cables for the heater control can be left disconnected and hanging, and you will want to remove the tubes from the heater box to the body of the car and seal off the ends of the tube(duct tape and coat hanger wire?). The other issue is proper sealing of the engine compartment, you need to cover the holes in the rear breast tin to prevent hot air from migrating back into the engine compartment. You also need to cap off the outlets from the fan shroud. I used some sheet metal for ductwork from the hardware store and a short screw/nut combo to sandwich two pieces of sheet metal over each hole in the breast tin, and I bought some pipe plugs to fill the outlets on the fan shroud.

Chris

I have heard that you can cook your heads !

The heat of the exhaust radiates and warms your heads up (not good ! ) ! with the heat exchangers installed the fresh air keeps them cooler, even if you dont use the air for heating your car.

I suppose you could use exhaust wrap to stop this effect.

Rich

Rh> Hey all, how big of deal is it to eliminate the heater boxes on a '74

Thanks guys! I think I'll put them back on. It gets cold in SW MO so I'll need them anyway.

Randy