I'm surprised no one has commented on this in 2 weeks. I wouldn't want to be left hanging on a question like that, but maybe by now you got an answer from your mechanic/tech?
I personally would not choose to run a gap larger than factory spec as that is pretty much the equivalent of putting very old spark plugs in. The ones in your car might not even be worn to that gap yet...... In a situation like that where you had no choice I would absolutely re-gap those plugs to the .8mm
The ONLY time I would deviate from factory spec on plug gap would be after engine / performance modifications. Good example, turbo or supercharged applications usually involve shortening the gap to prevent spark extinguish 'blow-out' from forced induction. There are those that say slightly increasing the plug gap on normally aspirated engines can yield small Hp gains and fuel economy but that is suggested for lower compression engines. Don't think we fit into that category here !! Doing so also taxes the ignition system demanding extra power to jump the larger gap and increases the chance for misfire. That's where Jacob's and MSD ignitions shine on our old Classics
To sum it up, when you get misfires the first thing you do is a tune-up spark plug change because old plugs have potentially larger gaps than new ones (among other things). Last thing you want to do is put in plugs with larger gaps than factory specified unless you have a specific helpful reason for doing so
I personally would not choose to run a gap larger than factory spec as that is pretty much the equivalent of putting very old spark plugs in. The ones in your car might not even be worn to that gap yet...... In a situation like that where you had no choice I would absolutely re-gap those plugs to the .8mm
The ONLY time I would deviate from factory spec on plug gap would be after engine / performance modifications. Good example, turbo or supercharged applications usually involve shortening the gap to prevent spark extinguish 'blow-out' from forced induction. There are those that say slightly increasing the plug gap on normally aspirated engines can yield small Hp gains and fuel economy but that is suggested for lower compression engines. Don't think we fit into that category here !! Doing so also taxes the ignition system demanding extra power to jump the larger gap and increases the chance for misfire. That's where Jacob's and MSD ignitions shine on our old Classics
To sum it up, when you get misfires the first thing you do is a tune-up spark plug change because old plugs have potentially larger gaps than new ones (among other things). Last thing you want to do is put in plugs with larger gaps than factory specified unless you have a specific helpful reason for doing so
