Hello all,
Hopefully someone reading this will be able to give me some insight. I have an 85 GMC K2500 350HO/400 Turbo. Problem I am having is in 1st,2nd,or 3rd gear, and while under full acceleration,tach reaches around 3000 and the engine starts lossing power and popping out the exhaust(some out of the intake).First happened when I made a jump at high speed, when truck landed is when the missing problem started. Does not happen with half throttle or less and accelerating through full RPM range and shift points, even for an extended period. Also while driving around 65mph(2950RPM) if I hit a bump in the road, it starts missing and power loss.Let off throttle and push back into it, works good till another major rut/bump. Problem occured with previous engine, carb, hei distributor. All have been replaced for various other reasons(cracked block,upgrade from edelbrock to holley truck avenger, worn distributor shaft)Have verified wire for ignition is not loose or any voltage drop.tested coil and hei module. Fuel side, have verified lines, tight connections and good flow. I am starting to lean toward the tranny as the culprit. Question is am I going in the right direction or am I totally out of the park.Below is a list of other mods that might help.
350 HO Goodwrench crate
Edelbrock air gap intake
Holley Truck Avenger with 1 1/2" spacer
K&N filter w/ Tornado insert
K&N Xtreme filter top
LUND hood scoops
ACCEL bluepoint distibutor w/ accel super coil
Taylor 8mm wires
E3 Sparkplugs
Hooker headers w/dual flowmaster 40 series Race ready exhaust cutouts
200 amp powermaster alternator w/ dual Optima batteries
High flow water pump
March performance pulley set crank, alt,wtr pump
March Alternator bracket/ Turnbuckle
Be-cool aluminum radiator w/dual 15in. elec fans
Turbo 400 tranny w/ B&M shift kit Royal Purple ATF
NP 208 27 spline
Fr axle stock corp filled with Royal Purple
Rr axle corp 14 w/ Powertrax locker Filled with Royal Purple
16x12 Mickey Thompson Classic II Wheels
Super Swamper(Interco) TSL 36x12.5016R
6 in. supension Fr,spring(superlift) Rr, Spring(Procomp)
Greaseable Shackles and bushings rear spring(offroad design)
2 in. body lift
Raised steering arm
Drop pitman Arm
Skyjacker Doubler shocks FRT, single rear
Warn winch bumper
12,500ib T-Maxx winch w/recovery kit  

If you are reading this feel free to throw an idea or two out there. Even if you think it is dumb, anything is better than nothing. I've had this problem for a couple months and am out of ideas myself, hence why I turned to my fellow wheelers for help.  

bent pushrods  

Hey thanks for actually responding!!! Yes I realize you responded in the other forum as well. The previuos engine was torn completely down trying to find an answer before installing the new engine. Everything checked( with the exception of the hole in the block and head), crank, cam,bearings, valve, springs and pushrods all where good