Checking the plugs on my flathead. Gap is closed almost completely on 2 cylinders on PS rear and DS front cylinders..... I can see where it is hitting the valve. These are old Evans heads on basically stock cam motor. The heads take the larger thread 129 plug. Do they make a index washer for these? Any other ideas? Thickernhead gasket. These heads came off an old dirt track motor and are probaly planed down? Sent from my SAMSUNG-SM-J320A using The H.A.M.B. mobile app
Would not hurt to pull a head and wad up a small ball of tin foil, or clay and mock up the piston to head clearance to see what your quench is. Just throwing on a thicker head gasket without measuring, may create other issues. I would bet there is some washers that would lift the plug out of the hole, if your quench is good.
Is that plug tapered seat? I've never seen a flathead with a tapered seat plug. If not, just put an extra washer or two under the offending plugs. I had some new plugs in my Canadian heads once that got their gaps closed by the valves. I just switched to a different brand of plugs.
Found some copper index washers for old harley. Gonna try those... Sent from my SAMSUNG-SM-J320A using The H.A.M.B. mobile app
I'm with alchemy. I think you are using the wrong plugs for these heads. Have the plug seats been machined for taper seal plugs? Or just smashed down by using the wrong plugs? Look into some proper plugs made for gasket sealing.
The autolite 216’s along with the Champion H10’s have a 14mm thread. The plugs the OP has are 18mm thread. I’m sure that tapered seat is wrong for his application. Maybe an auto lite 386 or a champion 502 would be better suited being a gasket seat, 18mm thread plug. Cliff Ramsdell
Those are the wrong plugs and the heads have been modified for 18mm plugs at some point. I believe you'll be okay once you get the correct plug in it - as it is a stock motor.
Get some 18 to 14 adapters. You will have a much wider selection of heat ranges besides curing the gap problem.
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