The MGA With An Attitude
Carburetor HEAT SHIELD (2) Report -- CB-204A

Carburetor heat shield I finally had a chance to cook the crap out of this heat shield setup for a fair hot weather test. I am generally satisfied with the results, but it is not a cure for all ailments.

July 5th, 2011, was one of the hottest days of the summer so far, and we didn't spend much time in the shade. I hooked up a 4x8 ft U-Haul box trailer (about 6 ft tall), and towed it empty 125 miles to Cedarburg, WI, interstate most of the way. Picked up a heavy 2.7 liter engine for an Austin Healey 100, plus some extra parts. Ran that back to Wheaton, Illinois (125 miles), interstate most of the way. Temperatures were in the low 80's in the morning, mid 90's in the afternoon, and way hotter on on the expressway pavement in full sun with thousands of cars in close formation.

We were doing about 65 on the way up with empty trailer, definitely feeling the wind resistance with a little extra throttle to maintain expressway speed with the tall trailer. The temperature gauge was around 220 most of the time. Coming back with the load in hot afternoon, holding it down to 60 most of the time, temperature gauge was hovering very close to 230 for a couple of hours. We stopped for a few minutes early to check the load tie down. Then a bit more than half way we stopped at an oasis for a couple of cokes, shut it off for about 5 minutes, then restarted it with temperature gauge pointing at 95 psi. The gauge immediately dropped to 220, but the carbs were cooking enough to require half choke. Ran it to the floor down the entrance ramp and up to 60 mph, by which time the carbs had cooled off enough to run with no choke. Otherwise the car did fine with civil carbs and good running for the whole trip, even running an hour in 0-15-30 mph traffic for 20 miles with the loaded trailer near end of the trip.

Result is that the new heat shield is definitely better than the original one. The only time it had any trouble when running was when full hot and standing mostly still in traffic for several minutes. Then it sputtered just a tad on acceleration, but settled down within about 15 seconds of moving again. I think I'll keep it, although it is not a full cure for hot carbs when standing still idling in traffic, or for 10 minutes after hot shut down. Now seriously thinking about the bilge blower option (perhaps somewhat detuned).

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