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Alex's 1968 'oldman special' HB Viva discussion....


yoeddynz

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have a few bumpers as well alex, dunno about if the chrome is of quality or just cheaply done but they are shiney... but nonetheless ive got one here if no go with vivaspeedgeoff... goddam tailgaters... need to activate the smoke screen out of the exhaust system next time so they back off a bit/ fumes all up in their grill

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have a few bumpers as well alex, dunno about if the chrome is of quality or just cheaply done but they are shiney... but nonetheless ive got one here if no go with vivaspeedgeoff... goddam tailgaters... need to activate the smoke screen out of the exhaust system next time so they back off a bit/ fumes all up in their grill

 

HB bumpers? 

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  • 2 months later...

Wasted spark yeah. Not sure on pairing etc. No acceleration enrichment set. Been reading and could be a lean out back fire. Last time it happened it was after it sat for two weeks. Maybe needed more fuel. Will put up settings tonight. It normally starts easy as although possibly a bit to many revs at first. Maybe should set it to more cycles before ignition and back off prime/crank pulse. But could be not enough fuel and too much air which causes lean out bang at start..?

Btw- never had backfires with 2.0 litre engine. This engine has peppier cams although not sure if more overlap. I think just higher lift.

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I dont think there's any way you could have a backfire out the intake based solely on being too lean or rich, as the spark should only ever be happening when intake valves are shut anyway.

 

I'm thinking either:

-Physical problem such as a jammed valve (unlikely?)

-A combination of wasted spark on cylinders that arent 360 apart, and/or batch firing injectors giving the possibility of unburnt fuel in the 'wasted' spark cylinder while cranking causing a spark back out the intake

-some weird combo of settings causing mega ignition advance.

 

Thinking about it I doubt that it would be possible to have the wasted spark working unless there were properly paired cylinders, or it would give you all sorts of grief from day one.

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