Not really that silly. Especially on a carb vehicle. If the engine backfires while the breather is off you can get a pretty nice fire going. I cooked a pretty good riding mower like that once.... didn't learn my lesson though since I still play with the cars with the breather off.
Steve B.
The idea is that the air filter acts as a flame suppressor in a backfire. Unless of course, you're unlucky like my buddy was with his Nova when the backfire lit the air filter ON FIRE.
Ray
No, but I've run engines countless times with the air cleaner assembly removed for some sort of diagnostic testing. Yes, if there's a backfire you can get a bang and fireball out of the carburetor. Its much less likely on EFI engines, especially multiport EFI because the fuel isn't introduced until right at the intake valve. With a carb or TBI, the whole intake plenum is full of a combustible mixture and you can get a pretty big fireball. Which is why you don't stick your face right over the carb or TBI intake. But its really not a very substantial hazard if you're careful, The backfire is there and gone in a millisecond. Its like a firecracker and is very unlikely to ignite anything- the biggest hazard would be to a person's eyes if they were looking down the intake (a dumb thing to do). Plus, as I said its VERY unlikely to happen at all with MPEFI systems. I guess the Haynes manual has to put the warning in there because the world is filled with idiots that would stick their noses right in the intake of a running engine....
Well, I *have* seen a backfire catch a fiberglass underhood pad on fire, but that's easily dealt with by hitting it with an old shop towel...
nate
It have sprayed fuel on the pad- fiberglass doesn't burn so good ;)
Well, this is on vehicles that likely have pads saturated with all sorts of underhood fluids... if they were in good condition, I wouldn't be working on them and they wouldn't be backfiring :)
nate
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