which spark plug do you recommend?
Thread Starter
Racer
Joined: Aug 2004
Posts: 442
Likes: 185
From: Zürich Switzerland
2026 Corvette of the Year Finalist - Unmodified
2025 C2 of the Year ('64-'66) Winner - Unmodified
which spark plug do you recommend?
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
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
Instructor
Joined: Jan 2004
Posts: 148
Likes: 3
From: Poulsbo Washington
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.
Le Mans Master
Joined: Nov 2000
Posts: 7,246
Likes: 21
From: Going too fast over the hill. Iowa
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.
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.
Team Owner
Joined: Sep 1999
Posts: 41,732
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From: Springfield MO
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.
Race Director
Joined: May 2000
Posts: 12,712
Likes: 2,271
Originally Posted by 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
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
Gap them to .035 for either point type ignition or an electronic conversions unless the manufacturer states otherwise in their installation instructions.
Duke
Thread Starter
Racer
Joined: Aug 2004
Posts: 442
Likes: 185
From: Zürich Switzerland
2026 Corvette of the Year Finalist - Unmodified
2025 C2 of the Year ('64-'66) Winner - Unmodified
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?
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?
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Verdad Gallardo
Safety Car
Joined: Apr 2001
Posts: 3,574
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From: Middleboro/Boston MA
Here's a good article about the various aspects of spark plus for you...
http://www.centuryperformance.com/spark.asp
http://www.centuryperformance.com/spark.asp
Race Director
Joined: May 2000
Posts: 12,712
Likes: 2,271
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
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
Instructor
Joined: Jun 2004
Posts: 179
Likes: 2
From: Pittsburgh PA
Originally Posted by SWCDuke
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.
Duke
Duke
Would a AC 45 also be best for a BB in a street driven car?
