Spark plug cross reference

I am having trouble finding plugs for my 340. Looking for Champion N9Y or equal. It seems N9y’s are no longer available. I get a whole lot of possibilities (even within the same brand) when I try to cross reference them but have no idea what is correct. Any advice on a correct plug will be appreciated.

Looks like they're no longer using the traditional #s.
Autozone.com shows the following (all in copper, though platinum & etc are available) :
Champion 404 & 415
Autolite 65
NGK 6578

Thanks for the info but I wonder what plugs are the guys with 340’s actually using?

NGK GR5

Champion Copper Plus Spark Plug 415 / RN9YC plugs are available from Amazon. Same heat range, but are resistor plugs to cut radio interference. $12.50 for a pack if four.


amazon.com/Champion-Copper-Plus-Spark-RN9YC

RRJD - street 340 I used N9Y or N9YC - racecar 340 used C61YC...

RN9YC are resistor plugs,
N9YC are not, the new Champion number is 300

https://www.championautoparts.com/find-my-part/Part-Number-Results.html?part=N9YC

https://www.rockauto.com/en/moreinfo.php?pk=317920&jsn=267

Thanks everyone. I’m going to look for the Champions

The old numbers are not used in the auto parts now. Except for Autolite and AC. NGK and Champions have part numbers that the counter guy needs to cross to so he can find the plug on the shelf. The minimum wage part timers may not know how to get your RN12YCs that are actually 404s. And the software is based on year, make and model. Asking for a BPR6ES without that information may get the "duh-duh" look.

Some of the old plugs, 55-51 Autolites and some on the non resistor numbers are no more. Race plugs are usually what you need for copper non-resistors..

Factory catalogs or websites will be helpful with numbers and what is still available. Have the part numbers when you go to the store.

Take a look at the Autolite 3911 and the colder 3910 non resistor race plugs
They work well for drag racing up to 7800 RPM, so far

Thanks for the info but I wonder what plugs are the guys with 340’s actually using? [/quote]

Autolite 63 on my 340 runs great

https://www.ebay.com/itm/115659614490 If not I`m pretty sure I have some boxes of old stock 64 autolites and some NOS 3420755 62 p plugs and some mopar N12y plugs.

if your doing a lot of street driving a n9y is pretty cold. i'd suggest an n11y for street use. i like autolite 3924's for street driving but they're a little warm for highway driving.

Great. First oil, then tranny fluid, then gear oil, now spark plugs.

Autolite 63 on my 340 runs great [/quote]

65 is the OE replacement. As the number get smaller, they get colder. We ran 55-51 back in the day. Same plug, nonresistor. Many of these numbers are NA. 63, 64 and 65 are still good.

51 is now 315
53 is now 300
54 is now 302
55 is now 38

You can punch the old numbers in the link below and it will tell you the new number

https://www.championautoparts.com/find-my-part.html