Motor boog

bam bam · Jan 22, 2017

My brother has a 69 chevelle it has a 396 a d is a 4 speed Muncie
It has 410 gears the lift on the cam is 502 lift a d 220 duration , his problem is on acceleration he gets a bobble rumble from the motor like a boog . Can it be the carb is a vacumm secondery or can it be the timing . Any input will be help full
Thanks dean

hotrodg726 · Jan 22, 2017

could be both. look at timing first.

bam bam · Jan 22, 2017

Any idea what the timming should be on it

hotrodg726 · Jan 22, 2017

a 396 has short stroke for a big block, my personal preference would be initial of about 16-18 degrees and 36 total with vac advance connected to ported vac. Smaller size big blocks like timing down low as long as it doesn't ping or kick back against the starter.

bam bam · Jan 22, 2017

I told him that this was the two things could be wrong the car was a autoa few weeks ago , he had a bunch of stuff apart . My first thought it was because of the carb being vac and not mech . Is that not rule of thumb On the carb and trans

Rick_L · Jan 23, 2017

Nothing wrong with a vacuum secondary. In fact it usually has less tuning problems than a mechanical secondary carb.

Is this "bog" at low speed when opening the throttle? Usually it's fixed with ignition timing as already advised.

If the problem persists once the timing is set as suggested, then you should look at the accelerator pump on the carb. First to see if it's operating as it's supposed to. If that's okay, then a bigger accelerator pump squirter may be needed.

bam bam · Jan 23, 2017

thanks guys if it makes a difference it is a edlebrock carb a msd vacuum advance distributer , i will tell him to time it .
thanks again

Motor boog

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hotrodg726

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Rick_L

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