View Full Version : plug gap?

04-09-2008, 03:04 PM
I have a 326 Pontiac motor with headers edelbrock carb and manifold, I added an HEI awhile ago but used the same plugs. My buddy told me to gap them from stock .35 to .40 is this a good idea should I go more, get a "hotter" plug(I'm not sure what that means) and how do I get the dumb girl at checker to figure out what I want? What is a good brand plug?:help:

04-10-2008, 02:09 AM
If by hotter he means higher heat range, not only is this not necessary but the opposite of what you want to do. The higher spark output of the HEI should allow for a colder plug which reduces the tendency to pre-detonation. You want to run the coldest plug tolerable without fouling. A plug with higher heat range will retain heat at the tip longer (hence the tendency to pre-detonate).

I would also open up the gap to .045" for a stock HEI, and .050" if the coil output is higher than stock.

Find out what was used for your cylinderhead (since heads are often swapped), and then find a colder one. Use www.Wallaceracing.com (http://www.Wallaceracing.com) to help you confirm if your heads are original (sorry non-Pontiac guys, this is for Pontiac engines only). Heat range for AC Delcos is colder = lower (caution: this is not always the case for other brands - do not assume).

For example only: R45TS has a higher heat range than R44TS. (the 45 designates the heat range). Again this is only as an example, as I don't know if the heads you are using are tapered seat or straight.

I like to use the brand that came stock on for the cylinderhead. Take your stock spark plug, go to summitracing.com and input a colder plug number. Then click on the fitment information and that will tell you which vehicles it came stock. Then go tell the ditz behind the counter your driving whatever car the summit site told you and she will hopefully grab the right one (you might want to bring more than one vehicle model and year just in case).

04-10-2008, 04:53 AM
Thanks that is exactly what i needed to know, I appreciate the help