Hello everyone. Some time ago I ordered 12 AC Delco R45 spark plugs to replace both my car and truck old ones. Today I decided to test them and changed all 6 from my car 216 engine. I gaped them at 0.035 as suggested in this forum. After I started the engine and gradually released the choke I noticed it would stall if I didn't accelerate it some, this wasn't the case before. Then I noticed it was misfiring both when idling and when revving it up. After that I took it for a ride to the store and the misfires decreased a bit after the whole trip but they are still there. My question is what could be causing these new misfires? The old spark plugs were Bosch model "W10F" "w95T6" and I noticed they were different from the R45 ones (extended tip?), and gapped at 0.060 (!). The engine worked fine before with no misfires whatsoever. I'm guessing the engine needs a new tune up maybe because the old plugs were too different from the new ones and the air/fuel mixture needs to be adjusted? or maybe one of them is faulty? Hope you guys can help me. Thanks!
You must have really good coil and condenser for a point type ignition to jump a 0.060 gap but the wider the gap the fatter the spark. The quickest way to trouble shoot would be to screw the old plugs back in and see what happens. Your lucky an old stovebolt engine is so forgiving because on most engines not designed for extended plugs the piston will crash the plug. You probably should check the timing with that much difference in gap.
If your old plugs were gapped at 0.060 I would suspect that you have a Pertronix electronic ignition device. If you do, then that is why the new plugs are not working properly
Thanks for your answers. I'm not really sure if I have one of those Pertronix ignition devices since it's been there since forever (the system was converted to 12v though long long ago), but if that's the case what'd be better for performance? should I search instead for other spark plugs like the ones It had and gap them to 0.060? or It's better to stick to the original ones and make the necessary adjustments? if so, which ones are the mandatory ones?
Pop open your distributor. If it has points, set the gap on plugs to 0.035. It there is a little black box where the points should be, you have a pertronix electronic ignition module and should set the plug gap to 0.060
Just to update the outcome of this issue... It turned out the tool I was using to set the gap was in millimeters, so I was setting it to 0.013 inches. Used the right tool in inches and set it to 0.035 and it worked perfectly. I'm surprised it even worked with that 0.013 gap. Thanks everyone for your help.
As usual , YOU did it better than most shops because YOU CARED and so took the time to figure it out .
