ded2sin

I just recently had a used/modified 460 put into my '77 F-250. At idle, it idles smooth and sounds great, but as soon as I push the gas peddle down, instantly it coughs and doesn't what to go. If I push it super slow, then it will be fine. I don't know the true history behind the engine but could there be some kind of vaccum leak or something? It has a Holley 870cfm carb, ported heads, bigger valves, stage 3 Comp cams, flat top pistons, bored 30 over, headers, Edelbrock performer intake, new electric fuel pump, new cap and rotor, new plugs. Also, my transmission is not shifting when it needs to. It only shifts at high rpm's and it has never done that before. One last thing, the truck has been sitting for the last six years because of a blown engine. Any input that is helpful would be greatly appreciated.

jwko

Sounds like a bad accelerator pump in the carb.

Yellovette

There are a number of things that could cause what you described. A vacuum leak could easily be the cause, particularly if your tranny's shifting effected. You just put in a new engine, did the vacuum line to the tranny get connected? Timing is another thing that could be way out. How much advance did you put in? fuel could be another issue, from accelerator pump to clogged fuel filter. that should give you a few things to think about.

Yellovette (Ed)