davepl

I've got a 1969 L36 427/390 and need plugs, but it looks like R43N is no longer made. I don't want a red hot ember hanging out there like an XLS, so am wondering what people are running in them now.

You can still buy sets for about $100 but I'm not a "date coded spark plug" kind of guy, so hate to pay that premium for an ancient plug!

MelWff

Not sure what you mean by red hot ember but the replacement number would be a R43XL, I assume XLS would be an extended tip and they run cleaner at low speeds. If your old plugs look too dark consider R44XL or R44XLS.

davepl

By "red hot embers" I mean the XLS plus are extended reach, fully threaded, whereas the original R43N was not (to my knowledge) extended reach.

davepl

That's a different plug. XL means extra long reach and S means extended tip, so you've got:

- Extra Long Reach
- Extended Tip
- Fully threaded to the end

The N plugs were not fully threaded like that. I think only 9.5mm of the plug was threaded versus 19mm for an XLS. I'm concerned that the extra threads hanging out in the cylinder are going to serve as hot spots for detonation.

Which is all a really long-winded way of saying "Does anyone make an XLS style plug that -isn't- threaded the entire way", I guess.

MelWff

the extra threads are on the top end of the plug so they will not be in the combustion chamber. Scroll down and look at the picture.

davepl

I was wondering about that. There are two specs for plugs that seem relevant: thread reach and thread length.

How do you know the unthreaded portion is actually at the top of the R43N? I've never seen one, so have no idea...

davepl

Here we go.... a picture of an actual R43N. You're right, the unthreaded part is up at the top, not in the combustion chamber. So my concern was unfounded in that regard!

CanadaGrant

My 69 L36 is all stock except for the hyd roller cam. I use the R44XLS gapped at .035 and have found them to be the best with perfect coloring.