Backfiring on decel

Mattcleaver

Member
Apr 20, 2020
10
0
1
19
Hey guys. Second time here. My friend and I just switched his 1980 malibu drag car to open headers. Ignoring the obvious which is that the carb should be rejetted, I’ve got a few questions. First of all, how many steps in jet sizes should we start at? Also, after doing a 6k pull, the backfires hard on decel. I figured this makes sense since there’s nearly no back pressure to keep unburnt fuel in the cylinder but my buddy is kinda worried and I figured it cant hurt to pick the brains of people with a lot more experience on this stuff. The car has a 383 stroker sbc with 10:1 comp and a roller cam. The thing is scary fast but we don’t wanna cause any damage. Thanks in advance!
 

Vilanus

Daily Driver
Jun 2, 2019
22
1
3
Canada
Wont know for jet size until you hook up a wide band. More important are timing adjustment, this might also be the cure for your exhaust backfires on decel. Vacuum advance could help with that.

Something is definately inefficient if your exhaust fills up with gas
 
Last edited:

Redline396

Amateur Racer
Oct 21, 2008
263
0
16
clifton, nj
with open headers i would not use a wide band with out an extension on the header collector, because you may suck back to much fresh air and throw off your reading. read your plugs ,they will tell you all you need to know. I would go up 4 jets higher and start there. and i would also adjust your timing....try 34 degree of timing.