Factory sparkplug question?

[Warren F.]

This may be a question for Joe Lucia. From several different sources I'm getting conflicting information.

I have a chance on e-bay to get, what I think is the correct plugs for my 1971 LS-6. I think the correct application is AC R44XL. I have found some R 44XLS plugs, what is the S for. Will this be appropriate for my application? This has been a tough find for me, currently using AC R43XL.

[Clem Z.]

"S" means extended tip *NM*

[Joe L.]

Re: Factory sparkplug question?

Warren----

As clem mentions, the "S" suffix denotes "extended tip". I don't think your application ever originally used an extended tip spark plug, although you can use them now, if you wish.

I believe that the R44XL was the spark plug originally used for your application. It's hard to confirm because GM information first released in 1971 and continuing right through to this very day specifies that the plug used for the 1971 LS-6 application was the R44TS. That plug was ABSOLUTELY NEVER used for a 1971 Corvette LS-6. Of course, it's a tapered seat plug not used for aluminum head engines of those days.

The R44XL spark plug is still available from GM or AC-Delco dealers under GM #5612092 or Delco R44XL. Of course, the appearance of these plugs may be a bit different than the originals.

[Clem Z.]

Re: Factory sparkplug question?

R-44TS was for the iron headed BBC in that time frame. like i have posted before for street driven BB corvettes both iron and aluminum heads that use the 3/4" reach plug the R-45XLS works great

[Joe L.]

Re: Factory sparkplug question?

clem-----

Yes, the R44TS was used for the iron head LS-5. However, GM has specified since 1971 that it's also applicable 1971 Corvettes "with SHP 454" or "with 425 hp". Either designation is, of course, the 1971 LS-6.

I think that the confusion "crept into" the parts system becasue 1970 Chevelle with LS-6 (which used cast iron cylinder heads) did use the R44TS. Somehow, that must have got "carried over" to the 1971 Corvette LS-6. It wasn't applicable, though, since the Corvette LS-6 used aluminum heads. The specification error has never been corrected to this very day. GM still specifies the R44TS for both the 1971 LS-5 and the 1971 LS-6. Since there were only 188 1971 Corvettes with LS-6 made, I don't suppose that would constitute a "hue and cry" to get the spec corrected.

[Warren F.]

Re: Factory sparkplug question?

Joe:

Thank you very much. Most of the literature sources do quote the incorrect plug. HOWEVER the GM article in a Corvette News issue for 1971 that describes the new for '71 engine lineup does list the CORRECT application and makes special note of it as well. That was the only factory source I found that lists it correctly!