ZZ4 Spark plug recommendation

[Donald L.]

I have a 62 Corvette with a ZZ4 engine that I will be replacing the spark plugs. The current plugs in there are AC MR43LTS. I would like a replacement with a heat range one step higher. Besides AC Delco is there anyone using a different brand besides AC Delco that runs well for normal city type driving?

[Joe L.]

Re: ZZ4 Spark plug recommendation

I have a 62 Corvette with a ZZ4 engine that I will be replacing the spark plugs. The current plugs in there are AC MR43LTS. I would like a replacement with a heat range one step higher. Besides AC Delco is there anyone using a different brand besides AC Delco that runs well for normal city type driving?

Donald------

First of all, AC MR43LTS is a marine spark plug. I don't know how it found its way into your engine but I suppose it's possible that GM originally used this plug in your engine. In the AC marine plug line, it's the hottest plug in this series. For a standard, copper core automotive plug you could go to an AC R44LTS. This would give you one heat range hotter than what you have.

If it were me, though, I'd use a Champion 9404 or Bosch 9653. These have heat range equivalent to the R44LTS but with an iridium core. Of course, they're more expensive.

[Donald L.]

Re: ZZ4 Spark plug recommendation

Thank you Joe.