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1970 911T Fuel Contamination in Weber Jets

Fuel System

Vehicle Information: Model: 1970; Year: 1965; Body Type: Coupe; Engine (type, size, modifications): original 2.2 converted to Webers ; Total Mileage: 106,000;

I have a problem with particles getting past my fuel filter and clogging the jets in my Webers, causing poor running. The cause, I thought, was the old gas tank. The upper third of it exposed more to air formed a fine rusty silt on the inside walls that seemed to get past any filter I tried. I finally gave up and replaced the tank with a brand new one (a year and 5,000 miles ago) and it's better, but I still carry a can of compressed air everywhere to blow out the jets when it happens, which is usually in less than 100 miles. Did in in the PCA corral at Monterey last month (I have been through it so many times I can immediately tell the change in engine pitch). Usually I find a teeny flake of this crud has caught in the #5 or #6 jet orifice. As I said I have tried most types of filters and now run the visible paper type just so I can see what I'm trapping. Just changed it again and the old one had a good collection of the stuff, a very fine dark powder for the most part. The Webers are immaculate so I don't see how I could be getting it downstream from the filter, and I do see it in the filter, although obviously it isn't trapping all of it. So - two questions - 1. What is the best kind of filter I can run in terms of trapping the smallest of particles.2. How can I still be getting this stuff a year later after putting in a new tank? Could there be the same problem with the lines through the chassis? I figure since they are always filled with gas they couldn't oxidize the way the upper part of the old tank did, but it keeps coming from somewhere. Granted I'm in California and we don't have real gas here, but I don't have problems with other cars. I run a blend of Union 76 91.5 (so called hi-test) with some Union 76 110 octane race gas to get a real 93-94 octane. Car gets driven weekly. Thoughts, please, and thanks in advance - John

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