ziff396

So, I thought I would replace my spark plugs in my 455 from champion to ngk. Engine ran fine before, however, I wanted to try the ngk's with a little less gap.
455, 9.7, edelbrock heads, hei, headers, voodoo 60803 etc.
I ran the champion RC-12yc @ .44. So I installed the new ngk's BCPR5ES that cross referenced as the same gapped @ .35.
It run's fine, but it idles like crap and seems rich (lean?) Instead of just a lope, it now like vibrates the whole car.
Just would like some input before re-gapping or putting the old ones back in.
Thanks Again

MDchanic

Why would you run such a small gap with HEI?

- Eric

Redog

I think the biggest problem is those crappy $7 a piece plugs.

I NEVER had any luck with anything other than the correct ACDelco plug in any of my GM cars

J-(Chicago)

If the car shakes, you're probably only running on 7 cylinders.

Pull the wires off the plugs 1 by 1 and see if the engine shudders. If it was firing correctly, it should shudder.

If no difference, that was the one not firing.

.035 gap is good in my opinion. I run .035 with an msd6al box on my car. Also runs a faster et with ngk plugs over the delcos.

ah64pilot

I would run the NGKs at .045" gap. And spark plugs won't make it idle funny, you've got one plug wire incorrectly seated. Most likely, it's the #8 plug wire against the A/C box...if the car has A/C.

ziff396

No AC. I checked all the wires today. No problem. So I pulled each plug, all were firing, and gapped them @ .045. Now she's happy again, and idles the same as before the change. I don't know, but I'll leave well enough alone.

ah64pilot

I'm good for something around here You're welcome, lol!