IS THIS NORMAL ?

[meteor]

While checking my spark plug wires for shorts I noticed a few of the plugs seemed to be shorting to the block. Is this normal ? It is not constant, but I think it may be causing my slight miss at idle. What do you think? Thanks, Roger

[Larry Schramm]

The only time that I can remember seeing that is when the spark plug was full of dirt/grease and the spark plug wires were bad and the spark path was from the spark plug wire to the grease/ dirt to the engine block. Should never see from a clean/ good sparkplug to the block.

[DonMicheletti]

About 1-1/2 years ago I bought a "new" set of plug wires from one of the respected vendors. My engine developed an intermittent miss recently. It turned out that the spark was jumping through the insulation to the block.

I mentioned it to the vendor, the response was " we never had this problem - you are probably bending the wires to tight".

Having worked in the wire industry I felt this was BS. The insulation is there to prevent leakage regardless of the wire geometry. I ended up buying good plug wire and making up my own plug wires - problem solved.

You may be having the same problem. I wonder if others have this happen too?

This is on a '38 Special and the shorting to the block was under the plug cover where the wiring is close to the block. No problem with the new wiring.

Don

[trp3141592]

Hi,

Ignition wires wear out and start "talking" to each other. Yeah, they really do. And cheap-ass wires are no good from the start.

Old NOS plugs may be cracked. Clean your plugs and check carefully for cracked ceramics.

Then buy some good quality wires.

--Tom

[meteor]

Thanks everyone, it looks like the plug wires are fine, no arcing there. The wells around the plugs have some oil around them. New plugs and a wipe down will hopefully solve the problem. Meteor

[Guest Straight eight]

Past experience with a 1941 and a 47 have shown if the miss is an occasional "puff-puff" the problem can be one of three.

Too lean idle mixture on carb, too tight adjustment on one tappet, spark plug gap too wide, .023 gap solved the problem on one occasion.

Edited May 23, 2014 by Straight eight (see edit history)

[Larry Schramm]

Thanks everyone, it looks like the plug wires are fine, no arcing there. The wells around the plugs have some oil around them. New plugs and a wipe down will hopefully solve the problem. Meteor

The best time to check the plug wires for arcing is at night with a spray bottle of water. Lightly spray the water on the wires and if you see sparks, problem probably solved.