suejoe6174 Posted October 29, 2009 Share Posted October 29, 2009 Have to change the plugs on 1957 707 thermodyne fire truck. I was told the spark plugs are champion J 6 C. Does any one no the correct gap setting? Thanks Joe Quote Link to comment https://www.bigmacktrucks.com/topic/11229-spark-plag-gap/ Share on other sites More sharing options...
Rob Posted October 29, 2009 Share Posted October 29, 2009 Have to change the plugs on 1957 707 thermodyne fire truck. I was told the spark plugs are champion J 6 C. Does any one no the correct gap setting?Thanks JoeThirty five thousanths will get you in the ballpark.A J6C is still a very common plug.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/11229-spark-plag-gap/#findComment-42630 Share on other sites More sharing options...
Firemack Posted October 30, 2009 Share Posted October 30, 2009 Sue Joe,The F707 A and B engines call for a spark plug gap of .30, the F707C with 7.5 Compression Ratio calls for gap of .25, the F707C with 8.0 compression ratio calls for .30 Firemack Quote Link to comment https://www.bigmacktrucks.com/topic/11229-spark-plag-gap/#findComment-42638 Share on other sites More sharing options...
Allison Posted October 31, 2009 Share Posted October 31, 2009 I posted this under the mack gas engine thread but ill ask you guys as well. Just ordered rotors, caps, wires and plugs. I gave the specs for the plugs right from the manual and the plugs were two different part numbers.. My trucking company that gets all of my stuff was kinda curious why.. I do remember the manual stating i believe the RS being #18 and the LS being #16.. Not sure what the two numbers reference but they came in under two different part numbers and the supplier actually listed specific placement instructions for the respective plugs??? Quote Link to comment https://www.bigmacktrucks.com/topic/11229-spark-plag-gap/#findComment-42712 Share on other sites More sharing options...
Firemack Posted October 31, 2009 Share Posted October 31, 2009 Allison,The plug placement in the heads is different on either side, so the plug lengths are different so they have the same reach. This is only true on the 707's with plugs on left and right sides, some 707's have them all down the same side, such as the 1960 707c. It takes 12 of the same type of plug for that engine.Firemack Quote Link to comment https://www.bigmacktrucks.com/topic/11229-spark-plag-gap/#findComment-42715 Share on other sites More sharing options...
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