At 03:46 PM 1/16/96 -0600, you wrote:
>Hi, all. I'm the one who asked about dizzy vacuum advance units.
>New question: Backfiring. I don't quite understand it. My exhaust
>makes a raspy, popping sound upon overrun. I had assumed that it was
>unburnt fuel travelling through the pipe and exploding when it
>encountered the outside air. Others have told me that backfiring is due
>to a lean mixture. Which is right? I believe my carbs (dual HIF4s) are
>adjusted properly, though I don't have any of those fancy tools or clear
>spark plugs. I use the method outlined in the Workshop Manual: lean
>best idle plus a quarter-turn rich. But since I'm now sure that my gulp
>valve is operative, I can't think of anything else that might cause
>backfiring (I have solid throttle plates). Any gurus? Denise?
>
>>Todd Mullins
Hi Todd, My '74 B used to backfire before I removed the smog equipment. When
I reinstall the equipment (by the way I have acquired as many new smog
parts as possible) the backfiring returns, but ever so slightly since making
sure that all components in the system are in good working order. I believe
that the backfiring comes from the injection of air into the system.
Craig Wiper
early '74B
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