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Grady Clay Grady Clay is offline
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Join Date: Dec 2003
Location: Arapahoe County, Colorado, USA
Posts: 9,032
Let me tell you a story.

In the early ‘80s I took my CP 914-6 (46IDA 91x66) to a USRRC drivers school just prior to a SCCA double national at Riverside Raceways. We would come into the hot pits and confer with our instructors, say 20 minutes, and then go back out on track. Well, I now know what happens to a carbureted 911 in that situation. It boiled the fuel out of the float chamber, the float expanded and stuck in the down position, there was a slight intake backfire when started, and it didn’t run perfectly when leaving the hot pit. I recognized it wasn’t running right and proceeded slowly around the track. By the time I came down the back strait into the Carrousel it was running worse. Just as I entered the Carrousel GIANT flames came up out of the engine grill – I mean 10’ flames. It got my attention and I’m still at 50 mph or so intending to enter the hot pit lane. I turn everything off, unbuckle, grab the little 2# extinguisher, and sit on the driver’s door (still at speed) steering the 914-6 toward the corner station at the pit entrance. The workers at first scattered as they feared this flaming car was going to hit them. Fortunately the car stopped abreast of the corner station, I fell off the door and the workers extinguished the blaze. The big flames were because the small carburetor fire burned through the fuel lines and then melted the fan belt. The fan had been directing the flames through the engine until the belt broke.
This all happened about 3 PM on Wednesday. A Riverside Porsche shop owner came up offered us the use of his shop. We repainted the engine compartment, replaced the wires and hoses, and installed our spare engine. We were in bed by 11 PM that night and successfully raced for the next four days. The only damage to the engine was the air filters, 46IDAs, fan, wiring, and fan shroud.

The moral of this story: SS fuel lines wherever possible; Pay attention to this carburetor issue; Have a larger than required fire suppression system; Stop at the next corner station if you even think you have a problem. Be PREPAREd.

The fix I came up with was (is) having a pair of aluminum baffles alongside the carburetors/manafolds, attached to the three fan shroud screws. After each session I take a 5# bag of ice and put ice alongside the intake manifolds. It keeps the manifolds from conducting the heat to the carburetors and consequential problems. The float chambers stay full and the fuel cool. When you go to restart the car, it fires on the first turn (no fuel fowling of the plugs) and runs perfectly.

Gasoline is one of the most dangerous substances we normally ever deal with. It is just short of high explosives and nuclear fuel.

I’ll try and find some photos of Hal Shaw’s fire in his IMSA 934. It will make a believer of anyone about multi-multi-layer fire suits.

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Old 01-28-2004, 11:00 AM
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