How Important is Spark Plug Gap???
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Post Fiend
Joined: Oct 2003
Posts: 9,176
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From: Western Central NV
A little over an 1/8th of an inch. Around .125-.150 No plug gap tool big enough. Had to use a ruler.
Craig
Craig
Posting Guru
Joined: Jan 2013
Posts: 1,933
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From: VA
Spark plug gaps can matter for efficiency. Generally the gap getting larger doesn't affect that too much.
I recently played with different gapped spark plugs in my 460. The ones I pulled out were worn to about .066 (they started at .045), I threw in a new set of .045 gapped plugs. Drove it a bit, and I immediately noticed better torque. I got the same 10.3 MPG out of a tank as normal. Then I threw in some .035 gapped plugs (stock for engine). I had a little less torque, but I ran a tank of gas at 8.9 MPG with my normal driving.
So for gap mattering, from what I saw, MPG is worse with a gap too small. The bigger gaps had the same MPG in my case (new 0.45 plugs and the worn .066 plugs). As far as it running okay, I don't think it matters what gap it is, it'll start and run. Heck, I think I could run a wire hanger through some JB Weld and stick it in there and start it up... lol
I recently played with different gapped spark plugs in my 460. The ones I pulled out were worn to about .066 (they started at .045), I threw in a new set of .045 gapped plugs. Drove it a bit, and I immediately noticed better torque. I got the same 10.3 MPG out of a tank as normal. Then I threw in some .035 gapped plugs (stock for engine). I had a little less torque, but I ran a tank of gas at 8.9 MPG with my normal driving.
So for gap mattering, from what I saw, MPG is worse with a gap too small. The bigger gaps had the same MPG in my case (new 0.45 plugs and the worn .066 plugs). As far as it running okay, I don't think it matters what gap it is, it'll start and run. Heck, I think I could run a wire hanger through some JB Weld and stick it in there and start it up... lol
Postmaster
Joined: Oct 2008
Posts: 3,026
Likes: 0
From: Renton, WA
Gap, bigger is better until it's too big 
It really is that simple, go big until you no longer have the juice to spark it. Then shrink the gap or get more juice to the plug. Bigger gap means fewer missfires on leaner mixtures meaning more power and more MPG.
It really is that simple, go big until you no longer have the juice to spark it. Then shrink the gap or get more juice to the plug. Bigger gap means fewer missfires on leaner mixtures meaning more power and more MPG.
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