If I plug up the air breather intake at the heat riser and then at the main intake RPM's increase at idle. Should this not be the opposite?

Holding both openings plugged does not choke out the engine at all. It almost seems to idle smoother albeit faster.

Air cleaner on and all hoses connected, top on tight.

 

Re-torqued carb mounting bolts, one was loose, and seems to have improved but now it's either carb gasket, throttle shaft or top gasket between top two sections of carb. Spray only increases RPM by about 100-125'ish. Marked improvement. Any quick solutions? Or am I tearing this thing down?

Might be time to take out the old core I never sent back and try a rebuild on my own for swap purposes.

 

Have you tried replacing the carb base gasket? How much play is there in the primary throttle shaft?

 

Can't really feel any play in the throttle shaft. I have not replaced the base gasket yet. PO included a rebuild kit from napa woth the truck. It is for an E4ME or some such, while I have an M4MED. By the time I figured this all out was not in the mood to mess with it. Jr wanted to hang out and "play" all night.

 

Be very glad that you have the M4MED! Those E4ME carbs were junk and $$$ to rebuild.

It is often difficult to determine if the primary throttle shaft has play in it with the carb on the engine.