What’s up guys last night, I was driving down the road at about half throttle in shifting to second then all of a sudden my trucks intake manifold backfired and my truck turned off I took off the air intake and quite a lot of smoke came out which I assume was burnt gasoline.. Lately, my truck has been backfiring a lot before shifting into each gear. I know the last time it was cause by the cheap spider injection. I’m assuming it is the spider injection again which I plan to replace but I was curious if you all think the intake backfire could have caused any damage to anything else? any input would be appreciated.. Thanks, Chris.

by the way, this happend in my 1996 4X4 suburban with the L31 5.7L vortec with the CSFI aka spider injection..

 

I can't see how the injectors could cause ignition in the manifold. That has to come from a spark or timing problem. Since it's intermittent you can rule out timing, in other words the distributor isn't way off and the cam hasn't jumped a tooth. (A bad intake valve can cause this but that problem would not come and go - idle would be terrible.)

There are two things you can look for:
1. Cross-firing spark plug wires. Unplug the hood light, idle it at night in complete darkness. Wire #3 and #5 are prone to problems since they are sequential in firing order. Look for little flashes of light and the ticking sound it makes. Solution - replace bad wire(s).
2. The Vortec "Crab Cap" distributor cap has a few electrodes that cross over from right to left. If there is an internal breakdown that you cannot see going on inside the composite material of the cap, crossfiring can occur. In the most severe case I've ever seen the #3 electrode was arcing out to the center common dumping all spark to the #3 plug. Solution - Replace cap.

Keep in mind that for backfiring to occur iginition is taking place at the wrong time, that means there is spark leaking in somewhere.

 

it has 113,xxx miles it isnt stock either.. I have new Edelbrock 170cc aluminum heads,1.6r crane gold rocker arms accel blaster coil,E3 plugs,msd wires,doug thorley mid length TRI-Y's magnaflow cats,magnaflow muffler and two cutouts...

I cant start my suburban without it backfiring and smoking from the throttle body so I cant really check the plug wires I had it towed to pep boys to my mechanic there that knows lots about the L31 he drives a suburban like mine and keeps up with service bulletins, im heading over there in a bit so he could maybe scan the computer and see if he could pin point the problem. I let him know what you said and see if he can check out what you mentioned. Thanks James.B!

 

Okay, now you've given more information.
Crane rockers have to be adjusted. Didn't know you had aftermarket heads. I can now say that your rockers should all be checked, because if they have been cranked down too far the valves will not fully close.
Rockers should be set by going through the firing order and ajusting both intake and exhaust for each cylinder at TDC of the power stroke. Turn down until zero lash, then a half-turn more and tighten the jam nut. Also check your roller contact pattern. The entire contact of the roller across the valvestem must be centered. If it is too far inward or outward the valveguide will get excessive wear.

 

all the mods have been on my burb for over a year and a half could this still cause my problems?

 

Not likely, unless a valve went bad. E-Tec 170's have stainless valves, never heard of one failing.
Black tailpipe smoke can be caused by a failed regulator on the CPI assembly. They tend to expel fuel from the vacuum port internally and that dumps into cylinders 6 and 8 mostly. That would not be intermittent either - it would be happening all the time.