I have discovered that I have been running the wrong spark plugs in my engine. I have a 327 with aluminum heads stock cam. The plugs are NGK 5238. The gap recommendation is 35-45. Where is the best spark 35 or 45? I need a schooling on plugs. I drive the truck some, but not enough. I am using 93-octane fuel. I think I have asked about the plug gap before, but I do not want to know the gap I want to know about the performance for stock fuel mileage. I am using a HEI distrubitor.
rayharris
Location:
Moody, Alabama
Is plug life all I should be concerned with? What about performance, like running rich or too lean? Is a larger gap going to affect my spark plug wiring ability to transfer spark?
Location:
Moody, Alabama
Here is what I have found since posting the question.
Approximately 0.040-0.045 inch
The recommended spark plug gap for an HEI distributor is approximately 0.040-0.045 inch, which is higher than the factory-recommended 0.035-inch gap123. This gap typically provides the best possible engine performance1. After 100 miles of driving, check the plugs to ensure that the white porcelain around the electrode of a properly gapped plug has khaki tan coloration. If the plugs look black, close the gap by.005
In testing aftermarket HEI conversions, I’ve found that a spark-plug gap of approximately 0.040-0.045 inch (up from the factory-recommended 0.035-inch) typically provides the best possible engine performance. Remember to also install new HEI plug wires. What spark plug gap should I use when using the ACCEL HEI coil?.045 is a good starting point. Check your plugs after 100 miles of driving. The white porcelain around the electrode of a properly gapped plug should have khaki tan coloration. If the plugs look black, close the gap by.005 to.040. Using point type or HEI, the spark plug gap should be.035" when using AC Delco 44 or 45 spark plugs. However, with a HEI be aware of rapid electrode erosion which will make the gap open to.045" -.050" in 10,000 miles. To avoid rapid electrode erosion, use Autolite AP85 platinum sparkl plugs gapped.035" out of the box.
Approximately 0.040-0.045 inch
The recommended spark plug gap for an HEI distributor is approximately 0.040-0.045 inch, which is higher than the factory-recommended 0.035-inch gap123. This gap typically provides the best possible engine performance1. After 100 miles of driving, check the plugs to ensure that the white porcelain around the electrode of a properly gapped plug has khaki tan coloration. If the plugs look black, close the gap by.005
In testing aftermarket HEI conversions, I’ve found that a spark-plug gap of approximately 0.040-0.045 inch (up from the factory-recommended 0.035-inch) typically provides the best possible engine performance. Remember to also install new HEI plug wires. What spark plug gap should I use when using the ACCEL HEI coil?.045 is a good starting point. Check your plugs after 100 miles of driving. The white porcelain around the electrode of a properly gapped plug should have khaki tan coloration. If the plugs look black, close the gap by.005 to.040. Using point type or HEI, the spark plug gap should be.035" when using AC Delco 44 or 45 spark plugs. However, with a HEI be aware of rapid electrode erosion which will make the gap open to.045" -.050" in 10,000 miles. To avoid rapid electrode erosion, use Autolite AP85 platinum sparkl plugs gapped.035" out of the box.
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