Camshaft repair regrinding

[21raceabout]

I have a 1920 era 4 cyl engine with roller lifters.  One of the rollers was apparently stuck and damaged the adjacent camshaft lobe.  I also have a spare camshaft but some of the lobes have significant rust pitting.   Does anyone have (successful) experience having camshaft lobes welded and reground to the original profile?  Are there issues getting repaired lobes to sufficient hardness?  Special heat treat or coatings (parkerizing)needed?  Long term any issues with fatigue/cracking?  

Thanks for any advice/recommendations

[Ivan Saxton]

Clive Stenlake , here in Melbourne, re-ground the camshaft of my Series 4 Mercer camshaft about 1973.   The car had seen everyday use for 40 years, and everything was very worn.  I would need to waste a month to find the figures, but what I checked was the piston travel relative to Top Dead Centre in each cylinder in normal rotation where exhaust valves open and inlets close with standard tappet clearances.  With 6 3/4" stroke of an L head Mercer you can best judge were of the cam lobes where the piston normally moves most rapidly.  I do not think that he had to rebuild or harden the camshaft lobes,  but this may sensibly be done by nitriding.    (John Hancox has had the crankshaft nitride for his Series Six Rochester Trego engine, so he can run International Truck engine copper-lead bearing shells  in the new, unbreakable CNC machined connecting rods that will never break.)    Incidentally, the valve timing drawing which Charles Jackson published for Series six in the three articles he published in Antique Automobile in the 1950s on T head, L head, and six cylinder pushrod OHV cars .  The latter had an astonishingly modern valve timing for the early 1920s;  and it is no surprise how well John Boyle's 1926 Raceabout went while he was alive..  Clive still does camshafts for us here in Melbourne,  and I can give you his phone number and suitable time of day to ask what he would do.   Another thing you need to check is the magneto cam wear.  It can be a trap for people who are not novices.  After my Series Four engine was rebuilt, the engine simultaneously indicated that the spark timing  was BOTH over-advanced, and badly retarded. Advance was very different for the two cylinder pairs, 1 & 4 compared to 2 & 3 !!!   Get other people's advice.   I am pretty sure I had to get new camfollower rollers made, which  I can make myself now.

[21raceabout]

Thanks Ivan - The exhaust roller on #4 cylinder got chewed up  and damaged the cam lobe.  This may have been due in part to excess wear of the cam shaft thrust bearing (center die cast bearings?) which has allowed it to shift aft 0.125-0.150", or by some mis-assembly of the cam shaft  by a previous owner.   This is evidenced as the front timing chain gear seems to be in the right plane with the crank and tensioner, and the front tip of the cam shaft is recessed in the bronze cross shaft gear.  Either way this would have reduced the contact area and in turn increased the contact stresses.  The material from the roller has come off in little chips, some of which have found their way into the pan, so I think I am into a compete rebuild.   I also noticed that #4 EXT valve may have been sticky which would not have helped the situation.  I have ordered a new set of valves and guides from the gentleman who has made some recently for Fred H.  Fred is also in the process of getting new rollers for a client's engine.