Propane Conversion: How to Make LPG Cars

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Now with the carb on the workbench, preferably in a vise, drill a 5/16" hole into where the up-down passageway (throat is narrowest . . . the exact spot is not at all critical, but you don't want to pick a place where you're going to drill through the float bowl or something. Check out a VW carb while it's still on the engine and note that right at the midpoint (up-down) and slightly to the right there's a raised round place with a smaller round depression in the middle . . . a perfect place to drill.

The carburetor is aluminum, so cutting will be easy, with some sticking near the end and lots of flying shavings all along. Don't let the shavings bother you . . . just try to drill straight and don't worry if things begin to seem mighty fragile. As you finish, look down into the carb and go easy to make sure the bit doesn't strike through forcefully enough to damage something inside the carburetor throat.

Now get out that 1/8" NPT tap and a tap handle if you have one (a wrench if you don't). Tap threads into the hole as far as you can, watching down through the carb to be sure you stop the tap just before it strikes anything inside the throat. Then screw the jet into the hole as far as it will go without striking anything (but no further than halfway through the throat). Finish with the jet's bevel pointing down. If you have two carburetors, simply repeat the procedure on the second one.

Apply some pipe-joint sealer, pour gasoline over the carburetor—inside and out—to get all the shavings and grime off and replace the carb. On a VW, put the cylinder clamp back in place after the carb's in and the two 13 mm bolts are secured . . . then have a friend climb into the car and depress the accelerator pedal. This will help you line up the accelerator cable with the cylinder clamp and then you can gently ease the cable end into the clamp as your friend lets up on the pedal. With the pedal all the way up and the lever holding the cylinder clamp as straight up and down as it'll go, tighten the setscrew on the cylinder. Then replace wires, tubes and air cleaner.

For the final step, connect the dangling end of hose B—already attached to the convertor's LP-vapor-out nipple—to the jet and secure it with a small water-hose clamp. For a two-carburetor system, get a simple Y fitting and install it into hose B (bottom toward convertor) and then run lengths of hose B off the two Y arms to each carb.

You're done with the only substantial change you'll make in your car's engine.

Finishing the Installation

Locate the hose or metal tube that runs down from the top of your carburetor to the fuel pump, cut it right in the middle, install the on-off valve where you made the cut and put things together with compression fittings. Don't install the valve anywhere in the fuel system except between the fuel pump and the carb . . . no damage whatsoever can result from the fuel pump working against a stopped line, but much harm can come from the pump sucking on an empty line. If you have a hose-type line, you'll need to attach a small length of copper tubing (1/4" O.D.) to each end of the valve for the hose to fit over.

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