Possible whiped cam on l05

[screamin86]

Hey guys I'm not around as much as I use to be since I got rid of my 86 but I have a question and hope some can help me. I'm helping a friend work on his 90 k5 blazer l05/700r. Well last September he parked it because it had a loss of power and a bad miss under load. He tore it apart changed the timing gears and chain put longtubes on it and true duals. He also updated the ignition system. I went over to help him time it this weekend and I set it at 8deg initial with the little timing wire unplugged. Starts fast and smooth but has a definite miss on the pass side you can hear from the exhaust. Even revs fairly smooth till upper rpm then it starts popping through the throttle body. Take it for a drive and it has no power at all and will chatter and pop in the upper rpm. I've never experienced a flat cam before but today thinking about it more  wondering if it is the case? If it is and we replace it what would be a good mild upgrade that the tbi computer would be able to handle?

[bd]

Could be a flat cam.  Remove the valve covers and watch the rockers for any that don't seem to be 'a rockin' like they should.  All the valves should appear to be opening about the same amount.  Popping back through the intake will probably be an exhaust lobe. 

There are plenty of good posts on the Forum in favor of the Comp 12-300-4, but unsure of compatibility with TBI, especially if you have to deal with periodic emissions inspections.  On the other hand, the Edelbrock Performer 3702 runs well with TBI and, in fact, was designed to be emissions legal for TBI.  But, it's not a stump puller profile like the Comp grind mentioned.  Search keyword: 12-300-4.

[Displaced_Txn]

get a cam that will work for it and get the ecu flashed or burned will run better and give him more power.
http://www.tbichips.com/truckmods.htm

[Tx_Phil]

If you are backfiring through the carb would this not point to an intake valve being partly open when the cylinder fires? 
I would pull the valve cover and watch those rockers rock. You might find a broken valve spring or maybe a valve that is not closing fully.

[Irish_Alley]

also after you take the cover off wiggle the rockers see if one has more play in it than the others

[winky]

If you are backfiring through the carb would this not point to an intake valve being partly open when the cylinder fires? 
I would pull the valve cover and watch those rockers rock. You might find a broken valve spring or maybe a valve that is not closing fully.

If the exhaust valve isn't opening then it doesn't let the pressure out so when the intake valve opens all that pressure come out instead of allowing fresh air and fuel in. If its bad enough it'll almost sound like a light knock threw the carb. Your problem deffinetly sounds like a timing/ cam issue.  Did he put new valve springs in it? Almost sounds like it might have valves floating?