1992 Spark Plugs - Why Unique?

[Mike B.]

I have a 1992 with the base LT-1 engine. In researching the correct spark plugs, AC 41-904 lists as one-year-only. 1993-on lists AC 41-906. I presume this is simply a heat range difference but regardless my curiosity begs to ask the question. What changed in the engine/ignition system that dictated the change in spark plugs?

Thanks in advance.

[Joe L.]

Re: 1992 Spark Plugs - Why Unique?

Mike-----

I've wondered the same thing since 1993. The amazing thing is that the 41-904 was never later "consolidated" into some other part number. It's still available today and it's ONLY application is 1992 Corvettes with LT-1.

There is no difference that I am aware of in a 1992 LT-1 versus a 1993 LT-1 that would require a different spark plug. Basically, the 1992 and 1993 engines are the same except for a slight difference in the camshaft profile (done to reduce engine "clatter" that made 1992's almost sound like they had solid lifters), the change in the valve covers, and some changes in cooling system plumbing. The latter difference causes the 1992 LT-1 to be unique as to waterpump. I don't see how any of these items would relate to a need for a unique spark plug, though. So, the mystery continues...

[Mike B.]

Re: 1992 Spark Plugs - Why Unique?

Thanks Joe. That's a very interesting and curious mystery indeed.