Pontiac 455 cam recommendation

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pastry_chef
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Re: Pontiac 455 cam recommendation

Post by pastry_chef » Sun Apr 08, 2018 2:28 pm

Some extra info:
OP says with 30 degrees of ignition timing the car will backfire out the exhaust when letting off the gas.
With 36 degrees timing the backfire goes away.
Odd.
Mike R

pmd400
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Re: Pontiac 455 cam recommendation

Post by pmd400 » Sun Apr 08, 2018 5:35 pm

pastry_chef wrote:
Sun Apr 08, 2018 2:28 pm
Some extra info:
OP says with 30 degrees of ignition timing the car will backfire out the exhaust when letting off the gas.
With 36 degrees timing the backfire goes away.
Odd.
That did happen. I had vac advance disconnected. I also had initial set to 6* before tdc to get the total down to 30*. I think it was just a sudden close of the throttle combined with slowing engine speed so it was not getting a lot of advance. If vac advance was connected it wouldn't have happened. Iv had some advice to remove the dual quads and put the iron intake/qjet back on. I'll give that a go this week.

tjs44
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Re: Pontiac 455 cam recommendation

Post by tjs44 » Sun Apr 15, 2018 1:26 pm

FYI,The E dual quad is not the best for your pontiac,the Offy is way better.Also your carbs are too small.I do agree that the 30 degree timing is a issue.Tom

mag2555
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Re: Pontiac 455 cam recommendation

Post by mag2555 » Mon Apr 16, 2018 6:35 am

You may be backfiring at 30 because your not burning all the fuel and that unburned fuel is then lighting off in the Exh system.

HDBD
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Re: Pontiac 455 cam recommendation

Post by HDBD » Fri Apr 20, 2018 8:32 am

Consider oil in the combustion as a possible source of detonation.

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