has anyone every sand blasted a carb?

I've blasted the exterior of brass and aluminum carburetors and magneto housings too. After blasting, they polish up like new. So far, no problems. I do turn down the air pressure to 100 lbs. on my cabinet for brass and aluminum parts.

Dale

The nice thing about the H carb is that the passages that meter fuel are removable and come in a good carb kit. Take out the main and idle jets and you have a clear view of any place grit or scale could give any problems. I prefer to spray carb cleaner that comes in an aerosol can through all the holes in the two halves to flush out any dust and/or grit left on them. Once it dries off, paint some rust-inhibiting primer on them or your carb will turn iron-oxide red instead of Farmall red. I have seen some H carbs at shows that have been blasted then sprayed with clear laquer. That"s certainly a unique effect.

This air stream is introduced through the idle circuit air passages. The air bubbles through the perforated tube as the fuel is drawn into the engine.

When the throttle plate is opened, the idle circuit is shut off. Since the throttle plate has opened, manifold vacuum is admitted to the venturi and the pressure around the fuel tube falls quickly. This causes the air bubbles in the fuel tube to explode and force the gasoline in the tube into the venturi and the engine. This extra fuel compensates for the engine's need for additional fuel to accelerate. I call this an accelerator pump because that is the function it performs.

It was some pretty slick engineering in the '30's by IH engineers. No moving parts, but it is what makes an H or M respond to load changes like a hay baler stroking. Along with an excellent governer, the carburetor lets the tractor respond to every stroke of a baler.

Carburetors with the air circuit plugged are very difficult to tune. One way to check is to adjust the idle mixture screw. On a lot of tractors the mixture screw seems to have no effect. This is because the screw adjusts idle circuit air, in for rich and out for lean, and if the circuit is plugged, the screw has no or nearly no affect on the engine. There is an arc segment on the engine side of the throttle shaft which serves as the idle circuit valve. It must be installed correctly and all the air passages clean in order for the carburetor to perform as designed.

Although the IH carburetors have no mechanical accelerator pump, they do need the function and it is served by the air bleed into the main fuel stream.

JG

A better approach is a long soak in a strong cleaner. I've had good luck with sodium hydroxide solution (get it at the paint store). Also chlorinated solvents like perchlorethylene are effective. Muriatic acid should work, but you need be watchful for corrosion on machined iron and brass surfaces. Also good idea to rinse the parts in a baking soda solution to neutralize any residual acid before reassembly.

Safety warning: All of the above are NASTY! Use only with good ventilation (ideally outdoors), wear eye protection and keep the stuff off your skin!

That would affect the idle circuit and throttle response because you could lose the accelerator pump.