<VV> Tune up questions

[Frank DuVal]

That's what I was wondering about the two Autolite plugs listed.

The 425 is a "normal" tip in description and picture on their website. 
Looks like an AC 44F (first thread missing).

The 275 is a "power" tip in description and picture. Just like the 
extended Champions people didn't like back in the 70s. They thought 
engines suffering holed pistons were more likely to have been running 
the extended tip Champions than normal tip plugs.

Spark plugs should be changed when the electrodes form sharp points. OK, 
before then! ggg   With high energy systems, gaps can double in size and 
the engine still runs.

Frank DuVal


On 1/17/2013 10:32 AM, Ken Pepke wrote:
> Spark plugs do not have a 'shelf life' either in the box or in your engine.  Properly matched to your engine [reach, thread length, and heat range] and driven with limited milage per year, as many of us do, a set of plugs will last for many years.  If you have a Petronix or other high voltage ignition system, you may NEVER have to change them.
>
> AC with their 'Fire Ring' design are best and Autolight are a good choice, Champion or other makes with an extended tip design; not so much.  [The flame front starts in the wrong place in the cylinder and under the most extreme conditions can hole the piston.]  A 'worn' plug can be renewed by filing the center electrode tip flat to make the edge sharp again.  At 2000 miles per year that will be every ten years  … or more.
>
> Ken P
> Wyandotte, MI
> 65 Monza 110hp 4 speed 2 door