Spark plug gap

[RobertKB]

I am in the middle of doing a tune-up on the '48 Dodge. This car has a motor from the mid '50's in it. I am just wondering what I should be using when gapping the plugs. My manual for my '38 Chrysler says .025 as does my manual on industrial engines. My manual for my '53 Plymouth says .035 so I am confused. Should I go midway and set them at .030? Just wondering what the rest of you do? Any advice gratefully accepted.

[Plymouthy Adams]

I would follow the specification of the motor in place...

[oldmopar]

I think as a general rule the resistors are .035 non resistors are the .025

[Normspeed]

My book agrees with says what oldmopar says. I tried the .035 on non resistor plugs by mistake once and got harder starting. Robert, what brand and number plugs are they? In my 53 218 I use Autolite 306 gapped around .028.

[slategrove]

I was tuning-up my car about a week ago and wondered the same thing, manual told me .025 and the parts store told me .035 for the brand of plugs I purchased. Asked about it at the parts store, and they told me with the new plugs I should follow the recommendations of the parts store, specific to the engine the plugs were going into. Gapped them at .035 and it's been doing really well!

[Plymouthy Adams]

the gap on the plug is set for the voltage output of your coil's abiltity to JUMP the gap for proper ignition..unless you have upgraded the coil to a higher voltage..you should follow the specification of that ignition system..

[RobertKB]

I have gone with the .035 as it is a '55 motor in my '48 Dodge. Now I think about it I'm sure that is what I gapped the plugs at in my '53 Plymouth a couple of years ago. The plug brand I am using is NGK which are Japanese. I have these in my '53 as well as my '63 Ford Fairlane with the 260 CID in it. I have had nothing but good luck with them. Thanks for all the help and advice!