Carter RBS high altitude adjusments

[Anonymous]

Hey guys,
I have come to altitude at 5000 feet I know there is less air up here and im looking for a leaner mixture. I have a Carter RBS on a 250 in a '74 Maverick with a C4. I have adjusted the idle mixture screw to get it to idle well. I have bought a new set of autolite 45 spark plugs. I know the old plugs are going to be all fouled up. Before I put the new ones in I would like to know if there is a cheap way or anyway at all to adjust the mixture other than idle? Thanks fellas

 

[Anonymous]

Wally;

Don't worry too much about the mixture, but advance the timing about 2-3 degrees more than where you had it before. Adjusting the idle mix will help out pretty much the same as Ford did it. If, however, you plan to spend a lot of time at over, say, 6000 feet, you can do this trick: run a small diameter (7/32" or 9/32") vacuum hose from the intake vacuum tree into a filtered air source, like the air filter can or a small foam filter. Go to the nearby pet store and get a brass needle valve (for aquarium air pumps) with the matching size fittings and connect it inline with the new hose. Start with it about 50% open: this will be your "metered leak". At about 5000 feet, 50% open is about right. Above 7000 feet, open it all the way. Below 3000 feet, close it. This little trick comes from the old Indian motorcycle carbs of the 1940s, and works quite well with the 170/200 engines...