AC Delco Spark Plugs

Are replacement spark plugs even necessary?

No, as long as you are not having any problems. But, if you have installed UltraPower and are looking for that last ounce of performance then yes they are worth the cost.

If you are going to try to justify the cost of Taylor wires and/or AC Delco plugs on increased HP/TQ and/or gas mileage then you are going to be very disappointed. The HP/TQ will only show up on a dynamometer as the "Butt Dyno" does not have very accurate gage. As for the mileage increase, if any, it would be in the .1 or .2 mpg under the very best conditions.

Some 8.1L engines come with Denso brand spark plugs installed. But, most come with AC Delco 41-983's gapped at .060. If you install UltraPower you have 2 choices in spark plug upgrade.

1. Regap the stock 41-983's to .045 and reinstall.
2. Install 41-993's gapped at .045.

Notes:

• If you have Denso plugs installed you may want to consider a new set of AC Delco's.
• The 41-932 plug was replaced by the 41-993.
• There is a How To R & R Your Plugs in the Tech Tips section.

What is the difference in plugs?

The 41-993 is a hotter plug and better suited for the 8.1L with UltraPower installed.

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