Heavy backfire when under a load

[Cutlass]

Yeah with a cam and cutout, you might be stuck with some backfiring, but if its REALLY REALLY bad...there's probably something wrong. there are other possiblities for backfire including valvetrain and ignition system issues.

[Lunatikgixxer]

yeah i like it at night when you can see it but mine isnt bad. I think its kinda cool lol

[derekbuckner1]

I think everyone here is talking about two different things. Everyone (mostly) loves the growl and gurgle of a ls motor when you get out of the throttle. On the other hand, if it's a consistent actual backfire, not the steady growl... There is a problem. I'm only saying this because you said you can see it at night. If you are throwing flames through your cutout consistently, get it checked out. Mine is loud on decel with the cutout open, but I am yet to see a flash.

[Lunatikgixxer]

ok.. when im accelerating and shift at 6k rpms it backfires one time, Boom, shoots a flame (i think (what a friend told me)), and i continue on accelerating.. Thats my situation. If it was constant it definitely be bad.

[35th-ANV-SS]

To me, any unburnt fuel escaping through the exhaust port and being burnt off in the exhaust = loss of power.