Help! 454 bog/die on accel

[rich weyand]

Originally Posted by LynnJr

It occurs at pretty much any acceleration rate other then very slow accel then it does ok

So what you are saying is it will turn to 4500 rpm after it stumbles first or it will never get there?

If it never gets there think ignition

If it eventually gets there think carburetor.

On the ignition you can start the truck and let it idle.Now pull one spark plug wire off of the distributor at a time.The motor should lose rpm sputter or die.If it does nothing you have a bad wire or plug on that cylinder.
Check all 8 individually.

If you suspect it is the carb the quickest test is to swap it out with another carb or borrow one from a friend/buddy just to see if that cures it or atleast improves it.

A weak ignition will produce the symptoms he talks about. At higher vacuum, particularly at low rpms, the charge will be the densest, and the cylinder pressures highest. This is the hardest to ignite. Where a weak spark may work OK at lower rpms, or at lower throttle settings (i.e. higher vacuum), when you punch it, there's not enough spark to ignite the charge.

A higher energy coil (like an Accel 48000 volt) plus better wires (like the Taylor Spiro-Pro) can kick that spark up enough to handle the denser charge.

The issue is the free-flow heads. Better flow means denser charge means higher cylinder pressures means tougher to ignite. Stock engine, stock ignition parts are ok. Better flow, maybe stock ignition not hot enough.