Sneakysportsman

Hey Guys, I need a little help.

I have a backfireing issue with a built small block. Please don't expell me because it is in a truck. I have searched the web over for an answer to my problem.

Here is a rundown of what I have.
357 cu. in.
flat top pistons w/4 valve reliefs
96 vortec heads w/2.02in, 1.6ex 64cc, flat tappete with roller rockers 1.5
Edelbrock Air Gap intake, w/TBI 2" bore
Stock fuel pump
MSD Dist & Coil, 8mm Wires
Crane HI 6 Ignition
Edelbrock 3702 Cam
Duration at 0.006" Lift:Intake: 268°Exhaust: 288°Duration at 0.050" Lift:Intake: 194°Exhaust: 214°Lift at Cam:Intake: 0.265"Exhaust: 0.294"Lift at Valve:Intake: 0.398"Exhaust: 0.442"Timing at 0.050" lift:OpenCloseIntake:10° ATDC24° ABDCExhaust:44° BBDC10° BTDCCenterlines:Lobe Separation - 112°Intake
Full length 1 5/8 headers, 2 1/2 true dual exhaust with 40 series flowmasters.

I have my own programming software for the ECM so any suggestions would help.

slow_90firebird

Mine started backfiring when the cap + rotor went bad?? Started only when wet, then got worse till it was all the time. Had to replace the whole dizzy with a reman to fix it.

camarorsssss

iTrader: (2)

When does the backfire happen, full throttle,3/4 full throttle? does it idle normal? The first thing to usually check is your timing then check your TPS, IAC MAP sensors and any possible vacuum leaks.

zap

I will assume its when you hit the throttle, probably need to increase in the pumpshot area

Sneakysportsman

I failed to mention a few things. When you first crank the engine and it is in open loop, or is running in start up mode, you can bump the throttle and the response is insane. Like 800 to 2800+ rpm in 100 th of a sec. After it warms up and goes into closed loop it will back fire thru the TBI @ 15% throttle opening. I have my own ECM Chip software so I can apply any suggestions.

I am thinking this,
I think the cam pulls too much vaccum and somewhere in the operating program the timing isn't retarding enough to accept the mix. The tuning is new to me so I am in a learning curve on what, where,& how to change things.

zap

Thought I recognize the screen name, Might consider a name change.

I have a secret!!!
http://www.fullsizechevy.com/forums/...400hp-tbi.html