305 Chokes at WOT

[MalibuSSwagon]

So I have an ongoing issue with my truck that no one seems to be able to figure out, or maybe its just me. Its an 86 C10, original 305 with 91k miles.

What happens is that when I gas it suddenly it dies out. Its hard to explain, it just chokes out.I can give it gas gradually and its fine, I tow cars and everything. Vacuum zeros out when this occurs.

What I have done since I got the truck.

Came with a holley DP. I figured it was pumping too much gas into the lil 305 and got a used Edelbrock 1406 and popped that on top. Still same issue, when you floored it it would backfire thru carb. Tuned, runs better, still cuts out.

Pulled the plugs, they looked pretty new, AC Delco R43TS, I cleaned and regapped the plugs and put them back in. Wires look decent, cap and rotos are good and the coil is a fairly new Accel unit. My guess is the guy before me changed all that trying to fix this problem.

Got a timing light, checked the timing. It was way. I have had to play with this many times. Someone suggested setting it at 10* BTDC. Tried that, ran a bit better, lotta pinging. Set to the factory 4*, doesn't run as good. I have it set on 6-7* BTDC now, runs decent. None of the adjustments got rid of the choking. I will also mention, and I think this may be where the problem lies, is that the timing seems to jump around when I set it. yes I do disconnect the advance when adjusting the base timing. Could this mean the timing chain has slack and needs replacement?

Exhaust is tiny, like 1 7/8" dia. I did clear the cat out, its not required here.

Also one of the prevoius owners deleted every bit of emissions equipment on the truck. EGR is blocked, AIR, all that stuff. I think the charcoal canister is still there. Not sure how the previous owner got this thing to pass testing in Mass. There are a bunch of blocked off vac fittings on the IM.

Fuel filter is good, its a clear one and fuel goes thru it just fine. I did replace the fuel pump because I thought it may not be pumping enough fuel. Not the problem, but its cheap insurance to replace the 25 year old pump and I got rid of the stupid ring around the fuel pump rod, no more engine tick! I also replaced the air filter, its an open element.

So thats a brief history. Any ideas? I am at timing chain or blown intake gasket.

[nbpro]

spark control module ?? It can change the timing. Your best bet is to just bypass it. They didnt work right when they were new. The aftermarket ones never work right. Just unplug it from the distributor and splice the green and black wires. at the firewall in the engine compartment Your esc distributor will now function like a normal hei. leave it unplugged after you splice it

[68longhorn]

I would try what he said

[MalibuSSwagon]

Reread the 1406 manual (yes I read it when I first got the carb) and adjusted the pump shot to the lowest hole, now the hesitation is just about gone! Haven't really checked for vac leaks, just kinda looked to make sure there were no obvious ones, there are alot of blocked off ports on the intake.

[nbpro]

well good deal