Spark Plug Gap Question
Thread Starter
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
Spark Plug Gap Question
I'm installing NGK 7173 spark plugs. They are a heat range 8 plug. My current plugs are reading as white, so I'm going to the cooler plug. The NGKs are gapped at .030 out of the box. My older plugs were gapped at .045. So the question is the correct gap for the 7173s?
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
Most of the time it's wise to start at the stock gap (.035) and work your way up until the motor starts loosing power , then back off to the previous gap where it ran best ..You will probably end up somewhere around were you had them gaped before (.045)..It all has to do with your compression and your ignition system... #8 is a pretty cold plug, what is your compression ratio.??.. Im at 10.25 to 1 and running an NGK 7373 (FR5) with a heat range of (5) ...The way most people read plugs is to do a run, shut the motor off immediatly, then read the plug..Letting the engine run to long fouls up the reading....WW
Last edited by WW7; Jan 25, 2014 at 08:34 PM.
Thread Starter
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
Most of the time it's wise to start at the stock gap (.035) and work your way up until the motor starts loosing power , then back off to the previous gap where it ran best ..You will probably end up somewhere around were you had them gaped before (.045)..It all has to do with your compression and your ignition system... #8 is a pretty cold plug, what is your compression ratio.??.. Im at 10.25 to 1 and running an NGK 7373 (FR5) with a heat range of (5) ....WW
