Flatten spark plugs

[Mertz]

I tried to start 40 Plymouth after sitting all winter and I got it to hit twice but nothing after that. It ran fine when I last started in the fall. I pulled #1 plug and it has a shiny spot on the top and was touching the electrode so no spark possible. I pulled the rest of the plugs and most had very little to no gap. All were black with carbon. Do I have the wrong spark plugs?  They are Autolite 275.  

[Los_Control]

I think you do.

I'm running Champion J8C and from bottom of electrode to bottom of crush washer is 1/2" ... the threads on your plugs looks closer to 3/4" reach

 

[Mertz]

I did some checking and the 275 might be 1/2” where the 295 is 3/8” which cross references the j8c. What plug is recommended Champion or Autolite?

[Los_Control]

Well I'm using Champion because that is all my local Napa has in stock ... Champion copper plus ... I can order different online ... I'm not a huge fan of the Champion.

Many years ago Champion put out some bad plugs and got a bad reputation.

Guys at Napa claims they do not have any complaints or returns on them ... they work for me.

[John-T-53]

I don't believe that plug MFR will make any difference in these engines as long as it's the correct size. For me, I prefer plugs that are plated so they don't rust (purely an aesthetic thing). Champions, NGK, some Autolites are plated, AC Delco, not. 

 

If your side electrode is touching the center electrode, then it's the incorrect plug and the intake valve is making contact. After replacing the plugs, check your valve lash clearance. 

 

Come of the correct plug MFRs p/n's would be: 

 

AC-Delco R45

Auto Lite 295

Champion 511 / 592 / J11C / RJ12C

NGK 3522

 

Source: Rockauto

 

ACDELCO R45 Specifications
Center Electrode Core Material	Copper
Center Electrode Tip Material	Nickel Alloy
Ground Electrode Core Material	Nickel
Height (IN)	1.12
Hex Size (IN)	13/16
Length (IN)	4.16
Manufacturer Heat Range	5
Pre-Gap Size (IN)	0.04
Pre-Gap Size (mm)	0.89
Reach (IN)	0.37
Reach (mm)	9.4
Resistor Type	Yes
Seat Type	Gasket
Thread Diameter (IN)	0.55
Thread Diameter (mm)	14
Weight (lb)	0.52
Width (IN)	3.59

 

For comparison, the AutoLite 275:

AUTOLITE 275 Specifications
Center Electrode Core Material	Copper
Center Electrode Design	Standard
Center Electrode Tip Material	Nickel
Electrical Terminal Type	Removable Nut
Gap Size	0.025"
Gap Size	0.6mm
Ground Electrode Core Material	Nickel
Ground Electrode Quantity	1
Ground Electrode Tip Design	Tapered
Ground Electrode Tip Material	Nickel
Hex Size	21mm
Hex Size	13/16"
Insulator Material	Ceramic
Reach	0.5"
Reach	13mm
Resistance	1 82
Resistor Type	No
Seat Type	Flat
Thread Diameter	14mm
Tip Configuration	Short Projection

 

Edited May 6 by John-T-53

[Mertz]

So it looks like the 275s are a bit too long. I will go with the 295 or j8c

[Los_Control]

kind of embarrassing ... go to walmart and look for spark plugs for a old Briggs & Stratton lawn mower ... same plugs 😆

[Mertz]

Yes I saw that too.

[Los_Control]

16 hours ago, Mertz said:

Yes I saw that too.

Maybe you do not understand ... I have a manly mans ignition system!

Slant 6 electronic ignition, GM HEI ignition control module, Petronix flame thrower coil, 8mm plug wires ... and lawn mower spark plugs 🥵

 

🤣🤣🤣