Spark plug recemondation

-
douglas340

douglas340

Well-Known Member
Joined
Apr 13, 2011
Messages
204
Reaction score
24
Location
Brisbane, QLD
Hi, what spark plugs should I run in this 340?....thanks in advance.
10.5 compression, edelbrock alloy heads, forged pistons. Mopar performance ignition.
 
Stock Champion or equal in heat range.
I like the Champs. I hate the Autolites.
What ever works for you!
 
anything from a rc9yc to a rc12yc champion depending on your engine and fuel .
I would start with a 9yc and go hotter if need be .
 
Aluminum heads need cad plating on plugs, silver not black. I have always got way more mileage out of autolites than champions, I recommend the 3923 autolites, = to N9Y. 3924 = to N12Y
 
Haven't Champions always been the OEM plugs for our MOPARS ? Unless highly modified from stock ( different aftermarket heads, higher compression etc...) I have always gone back to the stock Champion plugs. They always work for me.
 
Whatever the 68-71 340 came with.
 
Let's say the E3 suggestion for plugs and see where this goes? Yes I am stirring up the pot as much as I possibly can. :poke:
 
:D

blowbeer.jpg
 
Aren't all the Champion plugs and I think also Autolite made in China now? I seem to recall reading threads saying that, even though sometimes the box itself may say made in USA. The last time I bought Champion plugs the threads looked like crap.

I bought NGK's since they were made in Japan but since then i've read they've also gone to China and their quality has gone downhill

Honestly not sure what to buy now as far as spark plugs. Subscribed!
 
Start with the Champs. Yes, there OEM.
Write your times and/or mileage down.
Switch to the next brand, compare.
Enjoy!
 
kiss said:
Aren't all the Champion plugs and I think also Autolite made in China now? I seem to recall reading threads saying that, even though sometimes the box itself may say made in USA. The last time I bought Champion plugs the threads looked like crap.

I bought NGK's since they were made in Japan but since then i've read they've also gone to China and their quality has gone downhill

Honestly not sure what to buy now as far as spark plugs. Subscribed!
Click to expand...
I just put a fresh set of Autolite 3924s Copper cores in my j head 10:1 340 and all were gapped at .040 OOTB. Only had to center align one electrode slightly, made in China on the box. It's a shame you can hardly find anything automotive made in USA.
 
I will start something here. NGK plugs are well made and work with my aluminum headed 408. #4091
 
Been using the 3924's for 7 seasons in my Edelbrock heads performing without ANY issues..I wouldn't use Scampions if you gave them to me:D:D
 
jimjimjimmy said:
anything from a rc9yc to a rc12yc champion depending on your engine and fuel .
I would start with a 9yc and go hotter if need be .
Click to expand...
Yea basically. Stock would have been RN9YC. R for resistor, N is - Off the top of my head - the 13/16" wrench hex, 9 is heat range (Champion's). Last C is copper, whatever.
But, you've got aluminum heads so its not really stock. So the wrench hex is whatever fits - you may need to use the C which is smaller hex. JJJ may have posted C for that reason. Edelbrock will know if its not obvious when you look.
As jjj posted, heat range - start coldest and see if you may want hotter to reduce fouling. Advice is usually to run as cold as it likes it.

Which brand ? Pick your poison. :lol. Heat ranges can be cross referenced.
 
Mattax said:
Yea basically. Stock would have been RN9YC. R for resistor, N is - Off the top of my head - the 13/16" wrench hex, 9 is heat range (Champion's). Last C is copper, whatever.
But, you've got aluminum heads so its not really stock. So the wrench hex is whatever fits - you may need to use the C which is smaller hex. JJJ may have posted C for that reason. Edelbrock will know if its not obvious when you look.
As jjj posted, heat range - start coldest and see if you may want hotter to reduce fouling. Advice is usually to run as cold as it likes it.

Which brand ? Pick your poison. :lol. Heat ranges can be cross referenced.
Click to expand...


correct c is 5\8 hex
 
I like the Nippondenso U-groove. Quality looks very good. NGK has a few part numbers made in USA. BRISK USA is made in Czech Rep.
 
Gentlemen,
I the new guy with 40+ yesrs Mopar experience....273 hipo, 318LA, 340, 360, 383, 426 wedge snc hemi and 440-6
Ive always used Champion plugs....in the LA engines all use a 3/4" reach (thread length ) and heat range determined by the cam, compression ratio, spark advance characteristics, final drive ratio, etc.
The original 340 (1968 vintage) had 2 different cams...4 speed engine had a more radical cam ftom the auto engine but both used Champion N-10Y. For street use i liked N-11Y.
In my opinion, stay with Champion but alot of guys like NGK or Autolite.....or....AC's.....of a equal heat range and characteristics.
Btw....alot of NOS plugs are available on the internet (EBay) or even NOS Mopar.....reasonably priced.
In my present ride, 1970 GTX RS33V0A****** 4 speed car, one of 350 cars made...i use Champion UJ-11G plugs fired by a Prestolite dual point distributor. The engine has 11.0:1 compression ratio with Dana 4.10. N96 air grabber
I'm searching for a 1965 Barracuda Formula S.......273/235 hp engine 10.5 compression.....as original as possible.....no 6's with transplanted engines.....
Regards,
Bob Renton
 
You must log in or register to reply here.
-

Back
Top