SBC 350 Misfire....or Engines for Dummies (1 Viewer)

[retinadoc]

My 76 '40 has an awful misfire that can best be described as the sound you hear when you put a baseball card in bike spokes. Frequency increases with speed. In inspecting the engine one spark plug has a very visible repeating electric arc coming off of it. Am I safe to assume that this is not good and the likely source of the misfire? Misfire occurs at idle and under load.

Off topic: Thanks to the Mudders who posted about LED swap in the instrument cluster. All indicators now working. Without this board I would have never had a clue that LED's have polarity. I was able to access all the bulbs except the high beam without detaching speedo cable.

Strangely after doing this my wiper problems went, away which was fortunate given yesterday's snow.

 

[B y r o n]

Any arching off the plugs or wires is a source for misfires. Cracked plug, burned, cracked or missing insulation on the wires are the most likely causes. Sounds like it might be time for a new set of each.

 

[RWBeringer4x4]

Occam's Razor - the most obvious cause most often is the cause. I'd start with plugs and wires and see if it resolves the issue.

 

[reddingcruiser]

Here is the oversimplified version. Nothing on a vehicle should be going anywhere except where it belongs. This includes electricity (spark), air, vacuum, coolant, fuel and lubricants. If it's visible or is going somewhere it shouldn't be then generally there is a problem.