Need to replace the plugs in the 460. I think it's out of a lincoln, 73 to 78 (that's the closest we could I.d. it). Anyways, it's got electronic ignition, the box is a parts store replacement for same time period. Wires are 7mm parts store. It had autolite 26's but they're fouled.

 

I use autolite 45's in mine. They seem to do well. You might make sure you're not too fat on carb.

 

Found out autolite 24 is cold, 25 is medium, and 26 is hot. I went with the 26 again and gapped them about .042, so far they are doing very well.

 

Shouldn't ever really need to change heat range from factory spec.

Maybe if you spend all of your time speeding across Nevada and Death Valley in July as part of your daily routine. Then go one step down to a "colder" plug.

But, if stock OEM plugs are fouling then something else is at fault, NOT the plugs.

 

Now that I reread my post, I completely neglected to state that the 460 has headers, breathes a bit better than stock. Now that I've got it running good I think the owner just never repaved the plugs and they eventually fouled.

 

Headers would need a somewhat richer fuel mix compared to stock exhaust, not leaner. Find out what the stock plug is for that engine and use them. If they start fouling then there is something else going on.