Plug choice - warmed over 340

[orangecrush]

Asked earlier but didn't title it to get response - 1971 Swinger -1968 340 - .030 over - 727 - ported X's - fly cut flat-top pistons - maybe 9.5:1 - 268 cam - headers - Air Gap, etc.,etc. Was considering Autolite AP65's or Champ N12Y's - should I go a little hotter since comp isn't that high ?

 

[pettybludart]

I RUN THE CHAMPS,about 100 runs down the track,also some street driving.Stroked 340(372)450HP.i PUT PLUGS IN MAY 1 and am putting in sTORAGE THIS WEEKEND AND HAVE HAD NO ISSUES.

 

[rebeldart]

With your compression - I'd think starting with one up hotter than stock - or maybe spec later, lower compression 340 ?

 

[dogdart65]

Run the Champs . I use em in all S.B.'s , even low comp 318's . Then after some hard use , read 'em , they will tell you what the engine needs

 

[fishy68]

N12's should be plenty hot even for 9.5 to 1 compression and possibly even too hot. In my opinion It's better to be safe and put in a plug you think might be a little cold so you don't toast the pistions. If it were mine I'd go with N11y first and read them after some driving to see how they look. My 360 is pretty close to your build. X heads ported and polished, a little bigger cam than yours, 9.9 to 1 compression and I have to run N9y's cause even the 11's are too hot.

 

[GTS Registry]

Never had luck with the Champions in my 340. Always fouled. I use Autolite 63,64,65's depending upon conditions. 63's at the track, 65's on the street. I use the M/P electronic conversion with the chrome box.

 

[abodyjoe]

Never had luck with the Champions. Always fouled. I use Autolite 63,64,65's QUOTE]

me too. i hate champion

 

[stroked 340]

Autolite 3923's..is what i run in my 416 stroker and 360..i would'nt put champion plugs in anything...

 

[Petzschler]

have been using champions for over 22 years now.. luv em'.
N9YC is the only plug i use with any compression ratio. the RN12YC i wouldn't even bother using in
lawnmower. i run resistor type plug wires, so i'm not gonna run a resistor plug with it too. OHMs law.
the quality of champion resistor plugs have somewhat lessoned over the years.

 

[fishy68]

I've been using NGK V-powers for a few yrs. now and they seem to work real good and last long.

 

[dgc333]

If you have headers I would use the small hex plugs for a magnum engine. The reach, thread and heat range is the same. The smaller hex makes accessing the plug much easier.

I use autolites so a 3924 is the stock heat range and 3923 is one colder.

 

[fishman]

Autolite all the way, never had any luck with champs. They worked for two to three runs then start breaking down. Autolite 63 or 64 good place to start.

 

[340sFastback]

Autolite here also. I ran champions years ago and the resistance in the plug caused the spark to jump out of the boot and arc to the head. Tried new plugs, wires, everything. Went to Autolites and no problems the last 28 years. The new engine with the Eddie heads has 3924 Autolites in it now.

 

[AdamR]

Autolite 3923's..is what i run in my 416 stroker and 360..i would'nt put champion plugs in anything...

You have Eddy heads dont you ? Those wont work with stock iron heads.

I would stick a set of Autolite 65s in it and call it a day.

 

[dgc333]

Adam, The small hex magnum engine plug has the same thread, reach and heat ranges as the large hex plug from the LA head.

An autolite 3923 or 3924 will work just fine in an iron LA head. They are a definite advantage if you run headers because you can get at them easier.

 

[mullinax95]

Never had luck with the Champions in my 340. Always fouled. I use Autolite 63,64,65's depending upon conditions. 63's at the track, 65's on the street. I use the M/P electronic conversion with the chrome box.

I have never tried the Champs... always heard bad results. I bought my car it had Autolite 66's in it so I have ran those ever since.

 

[340sixpack]

I've been using NGK V-powers for a few yrs. now and they seem to work real good and last long.

2nd that.Hard to foul out and if they do usually come back.GR5s.