swissie

Back with more questions for you
Which plug do you consider the best choice (is there any?)? I've just installed a Pertronix II unit and will add the Pertronix coil. Do I leave the gaps standard? And maybe the most important question: what is the life expectancy of a plug? How often do you change them?
Thanks
Adrian

muncieman

AC plugs work for me, don't know about the P parts, don't like the prolonged crank of the early units so I use Unilites.

firemist1

I put the Pertronix system in my '67 seven years ago. With the hotter spark, I opened the gaps on the plugs to .040" and it works fine. I also switched to platinum plugs and change them every three years.

magicv8

With a Pertronix coil, you put all the ballast resistor wires under the same screw (no ballast resistor in the circuit), open the gap to at least .038, and SB r45s plugs will last a long time. If you have more than 10:1 compression, use r45 - the extended tip r45s might interfere with domed pistons. r45s works for me, gapped at .038inch.

Without the pertronix coil, the original GM coil will overload if you use resistor wires AND resistor plugs - thats why the AC44 was installed at the factory. IMO also leave the ballast resistor in line and use the .035 gap. I ran that way for a few years. Plugs don't last as long as with the Pertronix coil setup. Nothing really spedial about the Pertronix coil, except it can take the heat. Old original GM coils are too rare to roast.

JoesC5

I have the Pertronix II with their coil and run NGK plugs B-4 (stock number 3210) with .040" gap and my 64 300HP runs great. I also run the NGK B-4 plugs (at .035" gap) in my 56 with a duel point dist.

SWCDuke

The best plug for normal street and highway driving is the old AC 45, which is one heat range hotter than the OE AC 44. These are both non-resistor plugs, which are out of production and the closest AC match is the resistor type AC R45, but you can buy an equivalent non-resistor plug to the AC 45 - NGK B4 or ND W14-U.

Gap them to .035 for either point type ignition or an electronic conversions unless the manufacturer states otherwise in their installation instructions.



Duke

swissie

Thanks for your hints
But I seem to miss some basics here. Obviously there is a distiction between resistor ond non resistor plug. Why and what are the effects of using one or the other?

SWCDuke

Resistor plug use began about 1968 to provide additional EMI attenuation, but they consume a little ignition energy. Another non-resistor plug that crosses from the AC 45 is the Bosche WR9EC.

Duke

swissie

What is the reason/advantage/disadvantage of using a hotter plug?

Crazyhorse

Here's a good article about the various aspects of spark plus for you...

http://www.centuryperformance.com/spark.asp

SWCDuke

The spark plug tip must run hot enough to burn off deposits, but not too hot to act as a preignition source. The harder the engine is run the "colder" the plug must be to keep it from overheating, so normal street and highway driving requires a hotter plug than racing, and the plug type is dictated by driving conditions, NOT peak power output.

The AC 45 or equivalent heat range plug works best for ALL SBs in normal street driving. AC 43 works well for race track hot lapping. Even in normal street and highway driving, a Corvette engine has low demand because they have a lot of power and high power output can only be used for a few seconds at a time, so they need a fairly hot plug for normal driving.

Duke

JAF1

Duke,

Would a AC 45 also be best for a BB in a street driven car?

6T5RUSH

Crazyhorse,

Thanks! Great topic. I'm just scratchin' the surface on this one.

Jim