Gramma's Car: the new project!

[VintageMusclecar]

What # are you running now?

[njsteve]

UR45

[VintageMusclecar]

UR55 is the next coldest and the only one available with the wide gap. If you're willing to run an .035" gap plug you can go to a UR6.

[njsteve]

Since the car runs an HEI it probably needs the wide gap for the plugs.

[VintageMusclecar]

The reasoning behind the big gaps "back in the day" was to create a bigger flame kernel to try to light off the ultra-lean mixtures they employed back then to get them past the smog sniffer.

I've never had a problem running .035" gaps with an HEI, that's what I'm running with my 357 small block in the Malibu wagon. I don't think you'll have any issues if you're willing to give it a try.

FWIW.

[njsteve]

Oh, if that's the case, I do have an extra set of the .040 gapped NGK UR4 and UR4GP which is the factory heat range for the '72 455HO engines. But that might be too hot of a heat range I imagine?

[cook_dw]

Congrats on the article.. I've ran NGK's for years and never had any issues.. I even have them in the green car.

[VintageMusclecar]

With NGK plugs, the higher the number the colder the heat range, i.e. 4 = hot, 5 = middle, 6 = cold.

I *believe* ranges 4,5 and 6 are the standard passenger car heat ranges for NGK's, you might have to upgrade to a premium or race plug to go colder.

FWIW, I was running UR5 plugs in my 496 and they were too hot. I've since switched to 6's which I am still currently evaluating.

[JRC99]

Just got my copy of Hemming's! Congrats, man!

[njsteve]

Thank you! I just got my extra copies that I purchased, from Hemmings. My subscription copy hasn't showed up yet!