Back Firing

[jtower1969]

I'm no expert....but I would vote for lean. Colder temps have more oxegen in the air...you need to put more fuel in the carb to equal this out. I have a baseline for my car and adjust air bleeds up or down 1 1/4 turn before changing jets.

[Xplantdad]

I thought all smog set ups backfired to a point...which is one of the reasons that people took them off...

[napa68]

Judging by the hood, it's a cross ram. My vote, Too fat!
Excess fuel gets in the exhaust, A.I.R. does its job, wham...backfire! M.O.O. and $0.02
Tim

[wagonman]

[ QUOTE ]
Judging by the hood, it's a cross ram. My vote, Too fat!
Excess fuel gets in the exhaust, A.I.R. does its job, wham...backfire! M.O.O. and $0.02
Tim

[/ QUOTE ]

SOME WORDS OF WISDOM HERE!from the previous post.

Your car is backfiring from where?

Intake? or Exhaust?You didnt specify,but i know by experience that your talking about backfiring out your exhaust.When your throttle plate is closed under your extreme high vac conditions as you described.Your engine is backfiring from either experiencing a very rich air/fuel condition or an exhaust leak,bad diverter valve.During this period of deceleration,are you experiencing plumes of black smoke from your tailpipes?(RICH)

Generaly speaking:

"Backfire" is popping through the carb.....usually due to a lean condition caused by improper air/fuel ratio and or timing.


"Afterburn" or backfiring through the exhaust is caused by an excessively rick air/fuel ratio and or timing.

[sg1747]

it back fires from the exhaust it has a 1971 smog set on it.

[Salvatore]

John, You are a drag racer. Process of elimination. Take the belt off and see what happens. Smog systems do make noise and act up. Check all exhaust connections for leaks. Take a plug reading and see where you are at. Check the dwell and timing. Maybe a carb rebuild or valve adjustment. My car has chambered exhaust and mine pops and raps too. Take it to 6,500 rpm's if it goes there smoothly there is NO major damage. May need just a good tune-up or a nice ride in the country!

[Mr.Nickey Nova]

John,
Did you just install the smog system?? If you did then i would say a bad diverter valve too.Friend of mine had the same problem when he installed a rebuilt smog system on his 70 Z/28.