Spark plug question

4spdragtop

CONGRATS NORTH AMERICA!
FABO Gold Member
Joined
Aug 28, 2009
Messages
35,639
Reaction score
17,548
Location
Wasting time here
So the FSM calls for Champion N10Y for 273 4bl(commando), 273 2bl is Champion N14Y. Our engine has 2 bl pistons, but 4bl carb/intake, 340 solid cam.
Currently I have new Autolite 66, which cross over to Champion N14Y.
Is there much difference between the 2? Benefits to switching to N10Y?
Handy cross reference site
spark plug cross reference
Thanks
Steve
 

toolmanmike

Moderator
Staff member
FABO Gold Member
Joined
Jan 18, 2006
Messages
71,189
Reaction score
67,313
Location
Office
So the FSM calls for Champion N10Y for 273 4bl(commando), 273 2bl is Champion N14Y. Our engine has 2 bl pistons, but 4bl carb/intake, 340 solid cam.
Currently I have new Autolite 66, which cross over to Champion N14Y.
Is there much difference between the 2? Benefits to switching to N10Y?
Handy cross reference site
spark plug cross reference
Thanks
Steve
Double and triple check the Autolite crossover. I am not a fan of Autolites. I ended up with a converted N9Y which was too cold and chased a rough/rich idle for a couple years. I switched back to N12Y's (middle of the road heat range I thought) and immediately the rough running went away. Those plugs have been in for 10 years with no issues.
 

Rat Bastid

Dunamis Metron
Joined
Nov 23, 2020
Messages
3,036
Reaction score
3,127
Location
22 The Avenue
So the FSM calls for Champion N10Y for 273 4bl(commando), 273 2bl is Champion N14Y. Our engine has 2 bl pistons, but 4bl carb/intake, 340 solid cam.
Currently I have new Autolite 66, which cross over to Champion N14Y.
Is there much difference between the 2? Benefits to switching to N10Y?
Handy cross reference site
spark plug cross reference
Thanks
Steve

Probably not but like TMM said, the crossover is a somewhat close approximation.

FWIW, any of the above Champion plugs can be had with a 5/8 hex and not that clunky 13/16. The plug is the exact same other than the hex. I just hate that big hex.

Always let the plug tell you if your heat range is correct. If the plug has a black shell its much harder to tell heat range.
 

ch1ll

FABO Gold Member
FABO Gold Member
Joined
Jun 12, 2009
Messages
1,775
Reaction score
1,274
Location
Belgium,wi
More compression, the colder the plug. 340 with 10,5:1 compression ratio n9y. Less compression, hotter the plug. 318 with 9:1 compression ratio n14y.
 

AJ/FormS

68 Formua-S fastback clone 367/A833/GVod/3.55s
FABO Gold Member
Joined
Jan 19, 2014
Messages
23,416
Reaction score
10,684
Location
South-Central Manitoba,Canada, 900ftelevation
The heat range, is just that.
The chamber, with the correct AFR, will run cold at part throttle, and get hotter the harder that the engine has to work.
So the plug has to be able to survive for the full range of temperatures that it will be subjected to.
For a 4-bbl engine, that is able to work harder, you gotta install whatever plug it takes to not overheat it, which usually causes pre-ignition, leading to detonation, leading to engine self destruction.
A stationary engine running at 3600 would require it's own heatrange, versus your car, versus a race car.
But too cold leads to the plug fouling and then it misfires.
Hitting the window can be a chore.
I don't think there is any performance to be had in the heatrange of the plugs, unless it corrects for other conditions, such as misfiring, burning up prematurely, or causing detonation.

I have had the best success with Champions.
I agree with Toolman as to 12s in your combo
Coppers seem to run forever; I finally changed the ones in my 367 after over 100,000 miles since 1999. It doesn't start or run any different.
If you are running headers, the 5/8 hex can be a Godsend.
But you will have to pull a few of them, after some miles are accumulated, to see how they are doing.
 
Top