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I have my engine running, having recently added the following. This is a 1990 FSB with 351w:
Comp Cam
Trick Flow Heads
Edelbrock EFI Intake
BBK Throttle Body
New MSD Dizzy
Also have MSD 6AL, but had that before the top end upgrades.
BBK Shorty Headers

Engine is running great, idles great too. Power seems fine The only issue I have not been able to tune is an occassional backfire through the intake. This only occurs when you hammer the accelerator from a dead stop. It will do it in Park at idle also. It does not do it every time you rev the engine, maybe 3 out of 10 times. The backfire is not loud or massive, but you can hear it if you listen, especially at Park and Idle with the hood up. I had the timing set to 12.5, but backed it down to 10 btc. That did not make any difference. The engine seems to idle OK, and I have not found any vacumn leaks.

The only thing I can think of is that the massive rush of air into the intake is not being met fast enough with a shot of fuel, causing the lean condition and a backfire. During normal driving, you do not see this problem, only when the throttle is hammered, like it might be at the drag strip. I have checked the codes, and there are not any. All emmisions components are in place.

Any thoughts? What is throwing me is that it does not even do it every time you floor the accelerator. I read somewhere that what I am seeing might be caused by something called MAP based acceleration enrichment, which I know nothing about.
 

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Satyr of the Midwest
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17,738 Posts
My MSD box made my truck do the same thing in the months leading up to it completely crapping out. Several other FSBers here have had similar experience with their ignition boxes and coils. I'm willing to be yours is doing the same, or you've got some inductive crossfire occurring.
 
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