What the F***!!

[Chevrolet Banshee]

I just bought a pickup, its a 1986 GMC High Sierra and wen you stomp on the gas it will die and sometimes shoot flames out of the carb. Its got a 350 in it and a Holley 600 cfm carb

Chevshee

[bobeaser]

I had a nova that done that ,the cam was shot...

[Diesel_Tech]

Definatly a fuel problem. Needs a bigger jet, and possibly a bigger cam on the accelerator pump on the primary side.

I am assuming if you slowly get on the throttle it will accelerate fine, but when you get on it hard it stumbles? You need more fuel up front, your not getting enough at the time you need it. Usually that is a jetting issue, and if that doesnt fix it, you need to mess with the primary accelerator pump by either getting a bigger cam for it, or loosening the bolt (with the spring, underneath the carb on the front right corner looking at the carb) unless it is almost all the way out, that will give you the most throw of the arm for the most overall fuel.

[lt250racer]

Its a timing issue..

[FPMXer]

Let's see a truck from 1986, probably never been rebuilt just had some band-aids put on the motor to cover a shitty engine so the next guy will buy it because it's got some new carb or chrome valve covers. I would say the timing chain is stretched and skipping or has already skipped and it's way retarded. About the only thing you can do is fire it up and let warm. Then loosen the distributor clamp bolt and while reving it move it clockwise or counterclockwise and see if it get's rid of the lag in the throttle.

[Chevrolet Banshee]

Originally Posted by Diesel_Tech

Definatly a fuel problem. Needs a bigger jet, and possibly a bigger cam on the accelerator pump on the primary side.

I am assuming if you slowly get on the throttle it will accelerate fine, but when you get on it hard it stumbles? You need more fuel up front, your not getting enough at the time you need it. Usually that is a jetting issue, and if that doesnt fix it, you need to mess with the primary accelerator pump by either getting a bigger cam for it, or loosening the bolt (with the spring, underneath the carb on the front right corner looking at the carb) unless it is almost all the way out, that will give you the most throw of the arm for the most overall fuel.

You got it right if you do it slow it will rev just fine other than that it dies.

Thanks

[Chevrolet Banshee]

Originally Posted by FPMXer

Let's see a truck from 1986, probably never been rebuilt just had some band-aids put on the motor to cover a shitty engine so the next guy will buy it because it's got some new carb or chrome valve covers. I would say the timing chain is stretched and skipping or has already skipped and it's way retarded. About the only thing you can do is fire it up and let warm. Then loosen the distributor clamp bolt and while reving it move it clockwise or counterclockwise and see if it get's rid of the lag in the throttle.

Lets see... No it had a 305 stock in it then about 5 years ago the guy i got it from bought a 350 for it and replaced everything and rebuilt it, Wen he did it he put a cam in it so I'm thinking all that stuff is fine.

its carb problems for sure.

Chevshee

[2002shee]

It's a timing problem. The fuel is igniting when the intake valves are open causing the flame out of the carb. Double check the firing order too, if a few plug wires are mixed up that will happen. Put a timing light on it and check base timing and total timing.

[2002shee]

Oh yeah, could just be a misfire too. That would be why it's ok reving slow and falls on its face when you step on it. Misfires mostly happen under load. Check the plugs, wires, and distributer cap.

[FPMXer]

Originally Posted by Chevrolet Banshee

Lets see... No it had a 305 stock in it then about 5 years ago the guy i got it from bought a 350 for it and replaced everything and rebuilt it, Wen he did it he put a cam in it so I'm thinking all that stuff is fine.

its carb problems for sure.

Chevshee

Alrighty then. Needed more info off the front. No biggie. Is the cam he put in stock or bigger? If bigger did he match the springs to the cam? If not then bent valves and busted springs will cause your issues. If that is not the case then the carb needs some attention.