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Chapter 18: A hood for the hood….. a new air hat

11/1/01 Winter is nipping at my heals here in Minnesota, and with that, development on the car will need to be in the workshop with occasional forays onto the streets, which will soon be covered with a thin coating of black ice (auto exhaust which has frozen on the asphalt….).  Did pick up a series of jets and needles for the carb to make it run richer yet.  Found an old article in HOT ROD about AFB carbs which states that for blown applications, they were going as rich as 0.150 inch in some cases, and drilling out the idle bleed jets.  Did decide that for the winter, I need a hood, and after some measuring determined that the air-cleaner will fit under the stock hood, but not the “Air Hat“.  I am not satisfied with the side entry hats which are rather simple construction, and way too expensive for what they do.  I set up a manometer using a loop of tubing and some old brake fluid.  I started to fabricate an air hat out of plastic pipe, and did some tests on the air pressure across the “carb-mouth” end.  I hooked up a leaf blower for some pressure.  It is amazing what happens to air when you point it at a wall……  Anyway, I tried various restrictions and wound up with a sieve arrangement inspired by something I saw in a Dick Datson publication.  The plastic sieve is about 3/8 inch thick.  The holes each have an inlet which is counter-sunk, like a small venturi.  My tests showed much less variation in air pressure across the mouth, though I realize that there is some restriction thru the sieve.  I am hoping that the trade-off will be that the ‘straightened’ air will create less weirdness as it enters the carb, with more predictable results thru-out various pressure situations.  This hat will also fit under the hood, and so far has cost me $2.49 for the 5 inch plastic pipe and a few bucks for some epoxy putty (great stuff!).  Haven’t made the top of the hat yet (have been testing with duct tape), but expect it will be rounded on the inside.  Might use a piece of an old motorcycle headlight for this.  For now, I’ve got a piece of Plexiglas fit over the top which could be carved on the inside to give better dispersion, or maybe I will build up that surface with Lego blocks in some different patterns to see what happens!  I will be adding fittings for the blow-off valve, the fuel pump boost reference and the boost gauge #1 right on the air hat, maybe with some angle cut to the part protruding into the air stream to semi-negate the low pressure of a right angle. (Any thoughts on this appreciated).Rebuilt the defroster and heater blower which are 6 volts, but seem to work great, without overheating at 12 volts.  Needed to modify brackets on blower to still fit under hood despite everything else I added there….
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