In a message dated 7/23/00 9:33:28 PM Eastern Daylight Time,
fogbro1@bellatlantic.net writes:
<< Can you help me on this one? 1972 MGB with HIF's backfires during
shifting while going up through the gears. Only happens when I let off
the accelerator while shifting up. Otherwise the car runs fine. >>
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I can't be specific, but a backfire can be caused by a faulty exhaust valve.
When it doesn't close, it sets fire to the incoming fuel mixture and
backfires thru the carb. (Not good for the air filter.)
If you are having an occasional exhaust explosion (like my car does
sometimes!) this is usually from an overly rich mixture. Unburned fuel meets
the hot exhaust manifold and BANG! Lean out the carb.
Faulty emissions equipment can sometimes cause both conditions.
The term "backfire" is sometimes used in place of "exhaust explosion."
Allen Hefner
SCCA Philly Region Rally Steward
'77 Midget
'92 Mitsubishi Expo LRV Sport
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