Spark plugs and gap
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Spark plugs and gap
I have run Autolite 25's gapped at .50 for years in my '95 5.8 XLT. I see that 24's at .42-.46 are recommended. I do run an MSD coil as well. Great power and decent mileage considering.
I notice that the 25's are about an 1/8" deeper and but one step hotter versus the AL 24's.
Any opines as to this application? I've never had an issue, but I am also not an internal engine guy. Seeking information on what running with this set-up means to the truck.
Much THX.
I notice that the 25's are about an 1/8" deeper and but one step hotter versus the AL 24's.
Any opines as to this application? I've never had an issue, but I am also not an internal engine guy. Seeking information on what running with this set-up means to the truck.
Much THX.
Lead Driver
Joined: Feb 2002
Posts: 7,952
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From: Greater Austin, Texas
25 is a hotter plug than a 24. This means it burns hotter to keep the plug clean, but this does not mean hotter is always better. Too hot burns the plug up and can damage the piston in extreme cases, although 1 step hotter is not going to cause this. You should examine your plugs to see if there is any blistering on the negative electrode or any material loss.
The wider gap is helpful to ignite lean mixtures as long as your coil can keep up. Too wide a gap would cause misfire under load (when the mixture goes rich).
If you are not experiencing these issues, then I would say just keep doing what you are doing. You are not radically far way from stock specs on heat range or gap.
The wider gap is helpful to ignite lean mixtures as long as your coil can keep up. Too wide a gap would cause misfire under load (when the mixture goes rich).
If you are not experiencing these issues, then I would say just keep doing what you are doing. You are not radically far way from stock specs on heat range or gap.
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Freshman User
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25 is a hotter plug than a 24. This means it burns hotter to keep the plug clean, but this does not mean hotter is always better. Too hot burns the plug up and can damage the piston in extreme cases, although 1 step hotter is not going to cause this. You should examine your plugs to see if there is any blistering on the negative electrode or any material loss.
The wider gap is helpful to ignite lean mixtures as long as your coil can keep up. Too wide a gap would cause misfire under load (when the mixture goes rich).
If you are not experiencing these issues, then I would say just keep doing what you are doing. You are not radically far way from stock specs on heat range or gap.
The wider gap is helpful to ignite lean mixtures as long as your coil can keep up. Too wide a gap would cause misfire under load (when the mixture goes rich).
If you are not experiencing these issues, then I would say just keep doing what you are doing. You are not radically far way from stock specs on heat range or gap.
What do you think about the added 1/8" into piston which is also a difference between the 24/25?
Cargo Master
Joined: Nov 2013
Posts: 2,168
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From: South Central,MO
Some good readin' about spark plugs. Click on all the tabs, especially the technical training manual.
Tech Specs - Spark Plug Cross Reference, Torque Specifications, VIN Codes
Tech Specs - Spark Plug Cross Reference, Torque Specifications, VIN Codes
Senior User
Joined: Mar 2015
Posts: 450
Likes: 3
From: Merchantville, NJ 08109
I have run Autolite 25's gapped at .50 for years in my '95 5.8 XLT. I see that 24's at .42-.46 are recommended. I do run an MSD coil as well. Great power and decent mileage considering.
I notice that the 25's are about an 1/8" deeper and but one step hotter versus the AL 24's.
Any opines as to this application? I've never had an issue, but I am also not an internal engine guy. Seeking information on what running with this set-up means to the truck.
Much THX.
I notice that the 25's are about an 1/8" deeper and but one step hotter versus the AL 24's.
Any opines as to this application? I've never had an issue, but I am also not an internal engine guy. Seeking information on what running with this set-up means to the truck.
Much THX.
Scott
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What do you think about the added 1/8" into piston which is also a difference between the 24/25?
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