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I changed spark plugs last week. After 150 miles I checked them, they we totally white. I increased my main jets from 50 to 53. This is what they looked like after 200 miles with the 53 jets. I increased the jets to 55. How long should I wait to see if they are still white, or hopefully tan? The car is running really well, except for hot water temps when the AC is on and I'm doing 75/80 MPH for 15 minutes 
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For the spark plug heat range, I am looking at the color change at the threads. I consider the spark plug heat range to be about right when the color change occurs at two threads in from the bottom of the plug. If the color change is occurring at three threads in or more, then the plug is running on the hot side. Your plug on the right side of the original picture looked to be wet or not burning completely at the threads which would put it on the cold side. Maybe that’s the result of some excessive idle time before removing the plug? The left side plug looks much better. Don’t confuse oil or wetness on the threads for a heat color change. I am looking at a picture so I could very easily be wrong on this one. Autolite 45’s are colder than the Autolite 46’s and yours do look to be 45’s.
Looking at the last picture you posted and based on the wet appearance of the outer ring, I’m going to say you are rich. If it rubs off easily with a swipe of your finger, rich it is. Before the days of the wide band and A/F sensors, spark plug readings did get us to where we needed to go.
For the timing, I look at the color change in the strap. In the middle of the bend is always a good target for that. The color change being closer to where the strap attaches to the spark plug outer indicates too much timing and closer to the end of the strap or center of the plug is not enough.
Other comments always welcome.
  Lorena, Texas (South of Waco)
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Ted (6/10/2026)
For the spark plug heat range, I am looking at the color change at the threads. I consider the spark plug heat range to be about right when the color change occurs at two threads in from the bottom of the plug. If the color change is occurring at three threads in or more, then the plug is running on the hot side. Your plug on the right side of the original picture looked to be wet or not burning completely at the threads which would put it on the cold side. Maybe that’s the result of some excessive idle time before removing the plug? The left side plug looks much better. Don’t confuse oil or wetness on the threads for a heat color change. I am looking at a picture so I could very easily be wrong on this one. Autolite 45’s are colder than the Autolite 46’s and yours do look to be 45’s.
Looking at the last picture you posted and based on the wet appearance of the outer ring, I’m going to say you are rich. If it rubs off easily with a swipe of your finger, rich it is. Before the days of the wide band and A/F sensors, spark plug readings did get us to where we needed to go.
For the timing, I look at the color change in the strap. In the middle of the bend is always a good target for that. The color change being closer to where the strap attaches to the spark plug outer indicates too much timing and closer to the end of the strap or center of the plug is not enough.
Other comments always welcome. When I removed the plugs there was some oil (leaking from valve covers) on the threads. Could this be part of what you are seeing on the threads? I did want to try a colder plug (# 45) because the previous set was very white
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Are AL #45s still available? I thought I read somewhere a while back that they were discontinued.
6 VOLTS/POS. GRD. NW INDIANA
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DANIEL TINDER (6/23/2026)
Are AL #45s still available? I thought I read somewhere a while back that they were discontinued. Autozone has them in stock. I read Autolite's parent company is bankrupt.
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