[Nitebird]

Just wondering what you guys run for spark plug gap. I have champion RC12YC plugs.

Pontiac 455 10.1 compression
Edelbrock D Port 84 CC
RPM intake
Old Faithful cam
950 HP Holley Carb
HEI distributor
1 7/8 Dougs Headers

[FrankieT/A]

I am using the NGK equivalent and run them at .035.

[jamaca85]

.045 with an hei...

[hurryinhoosier62]

Originally Posted by jamaca85

.045 with an hei...

X 2. HEI ignitions require a wider spark plug gap.

[STEELCITYFIREBIRD]

Soooo how much gap do you run rotor to plug terminals under dizzy cap????

[lust4speed]

Originally Posted by hurryinhoosier62

X 2. HEI ignitions require a wider spark plug gap.

Maybe toss out the "require" and put in "allows". Spark produced with the old points ignition and standard coil had to have sparkplug gap limited to .035" to produce reliable results under all operating conditions. There just wasn't enough juice there to always fire off a wider gap. A longer, hotter spark works much better for igniting the fuel mixture, and this became available with the HEI and capacitive ignition systems. While you can gap your plugs with an HEI system at .035", you are not allowing the system to operate at its fullest efficiency (exceptions being ultra high compression or boost situations). While GM used gaps of .060" or larger some years, most of us have settled on a gap of .045" as a good compromise with HEI and CDI systems.

[FrankieT/A]

Originally Posted by lust4speed

Maybe toss out the "require" and put in "allows". Spark produced with the old points ignition and standard coil had to have sparkplug gap limited to .035" to produce reliable results under all operating conditions. There just wasn't enough juice there to always fire off a wider gap. A longer, hotter spark works much better for igniting the fuel mixture, and this became available with the HEI and capacitive ignition systems. While you can gap your plugs with an HEI system at .035", you are not allowing the system to operate at its fullest efficiency (exceptions being ultra high compression or boost situations). While GM used gaps of .060" or larger some years, most of us have settled on a gap of .045" as a good compromise with HEI and CDI systems.

I agree with what you are saying to a point... GM did increase the gap to .060 and brought it back to .045. So normal spark plug gap for a points ignition is .035, and cars ran fine like that including performance cars. Now HEI comes out and they widen the gap because they can. And, HEI deals with that, agreed. But now you probably double the voltage which gives you a very intense spark comparatively speaking and instead of taking advantage of this intense spark you widen the gap and make it more difficult for the spark to make it across somewhat negating the advantage of the HEI in the first place. . Granted with the bigger gap there is more available spark. But I have doing it this way since 1979 when I put 62 heads on my one year old Trans Am, when I first put the heads I chased a miss for days. Turned out I set the plugs to 78 specs...as soon as I tried reducing the gap the problem was fixed. Since then on other cars I have run up to 10.75:1 on a regular basis run a butt load of NOS though them gapping at .035, my plugs always look great and they have never missed a lick.
This is just my philosophy on the subject and not recommending anybody do what I do, but this has always worked for me...JMHO

[1968GTO421]

Correct me if my thinking is wrong, but it would seem with gaps of .035-.040, there would be a really good spark that is not so large that it erodes the plugs terminals at a ferocious rate.

[Cliff R]

I saw a LOT of HEI's where they burned through the rotor to the top of the distributor shaft back in the days when they tried .060" plug gaps for a while. Not sure if that is why they went back to .045" gaps or not, but I run .035" here with my HEI, NGK V-Power 7 plugs in KRE aluminum "D" port heads. Never had any issues whatsoever and have used the same plugs now for many years.

FWIW I wouldn't run a Champion plug in anything......Cliff

[Formulajones]

I run .035 in everything, including LS coil per ignition systems, MSD CD systems etc...Big power adder cars tend to tighten it up a little more even. I also prefer a copper core plug, nothing fancy.

Smokey Yunick showed decades ago that all widening the gap does is make the system work harder, the coil specifically.

I tend to follow that and have found no gain in drivability or track performance that tells me the wider gap is needed.

[Cliff R]

It's a simple law of physics, the wider the gap the more difficult it is for the spark to find the ground on the other side of it. This raises resistance, and works the rest of the ignition system harder. Every spark created is trying to find the path of least resistance to ground, so if/when you make it more difficult clear out at the plug or end of the line, it will make attempts to jump a gap elsewhere.

I also played around with plug gaps quite a few years ago, and found NOTHING going from .035 to .045" that was measurable at the track. Even went on up to .060" and still no measurable improvement anyplace.

I also absolutely HATE Champion spark plugs. Over the many decades of being in this hobby and in business with these things, we've had more trouble with Champion plugs than any other, and next to ZERO issues with NGK plugs.

The plugs in my engine now have been in service now for the last two engines and every once in a while we hit them with the bead blaster, check the gaps and put them back in service, but that's at most about every 4-5 years or so. I suppose folks who run pig-ars rich gas sucking carburetors have to attend to plugs more often. Mine come out almost white to very light tan, and you'd swear it was WAY too lean if reading them.......FWIW.......Cliff

[Formulajones]

I'm not a fan of Champions either.

I've run NGK's and work great, father has them in his engine right now. I also like Autolites and run those in most of the cars. Great plug, and better than the ACdelcos they sell nowadays.

Used to be an AC fan years back but when they played around with part numbers several years ago, and eliminated some of the plugs that I was using, I made a switch to Autolite and have used those quite a bit since with excellent results.

[FrankieT/A]

I also absolutely HATE Champion spark plugs. Over the many decades of being in this hobby and in business with these things, we've had more trouble with Champion plugs than any other, and next to ZERO issues with NGK plugs. Cliff

I AGREE !!!
And, the irony is I love AC Delco, and the same guy invented both.
AC Delco and NGK for me depending on application.

[arcitech]

I run NGK in everything, period. I had a bad experience with Champion 30 some years ago,(ceramic broke apart as I was replacing them, 15,000 miles and completely worn) and even if they fixed the problem, I still won't buy them. NGK's gap checked out of the box, for the 455, all were .035, same for my Titan, Iridiums at .043. I've used NGK's at stock gaps in: 80 Toyota Pickup, 89 Mazda B2200, 93 Probe GT, 98 Contour v6, 06 Titan, and 66 Tempest (455 w/Edelbrock D-Ports 87cc and Pertronix II), and all my lawn mowers! All of them were replacements for the stock plugs when those became worn. The NGK's lasted more than twice as long as any other plugs with the exception of the Denso's that were in the Titan. IF I was in need of plugs and NGK was not available, Denso would be my second pick. Bosch=nope, AC Delco=no thanks, Champion=Sorry you screwed me once and once only. Some will swear by E3's, but I'm sure they are getting paid to say how great they are, but more surface area to get hot and cause pinging IMHO. If it looks like a gimmick or promises the world, it's crap.

[STEELCITYFIREBIRD]

I run all American V8's between .035" and .040", Set as go-no go with a round gauge and only adjust the ground strap with a tool.

Every circle track motor we ever ran (25 years of racing) was on NGK plugs, and Autolites in my own V8 stuff. I don't run point ignitions in any of my cars and most have CD ignitions.

[Blued and Painted]

I gap all the hi energy stuff at .045 ..

I dont use champion, motorcraft, split fire, e-3, or any other wiz-bang plug.

[FrankieT/A]

Anything over .035 negates the High energy. But that's just my opinion...