'49 8n (front mount dist.) put back together after fixing a slipping sleeve; runs great all RPMs for about 5 minutes until it gets to 180-190 deg. or so, then starts occasionally missing (also pretty much at all RPMs). Cool it off & it's fine again. May be a little blue smoke coincident with the misses, but not much. Also seem to get a little exhaust 'cough' occasionally.Based on earlier posts I strongly suspected electrical at first, but the wiring/plugs/etc. are mostly all new & have had two coils on it. I also used a sparkplug tester to watch on every plug (rubber hose listen was better) for missing spark coincident with engine misses at low RPMs; don't think I ever missed a spark. Also jumpered around the ignition switch (as per Dell I think). Other misc. info...110-115 psi all cyls on compression test. Good oil pressure, no leaks anywhere I can see. 12v electrical. Air filter cleaned out not too long ago, did a carb cleaner soak on carb recently. What about timing or a valve problem? this thing was rebuilt about 10 yrs. ago & I'm not sure everything was aligned timing wise when it was put back together (I haven't had the timing gear cover off to see); anyway it seems to run best when I'm 'stopped out' at the top on the timing adjustment. When I had the head off I checked the valves; I relapped them & they looked good, & I think I gapped them right. Any ideas? Thanx in advance.
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