Possible Flattening O' The Cam?

1

1962300

Senior Member
Have a freshly rebuilt '38-'48 Flathead.
I poured in straight 30wt oil.
Fired the motor and raised the rpm's for 10-15 minutes.
I have 80 miles on it and a rather loud valve noise started in.
Pulled the intake and readjusted all vales.
Fired it up and there is still a loud "Tap, Tap, Tap" sound....same side of block as before.

Could I be suffering from a flat spot on the cam?

All cylinders have compression at 110.

Thanks
 
When you re-adjusted the valves, were any of them way out of wack? This would indicate "something" changed on that part of the valvetrain. If they were only off a couple thou here and there, probably normal run in.

We always re-adjust non-hydraulic followers after some run in.

Kind of hard to do on a flathead without pulling the heads, but checking the lift with a dial indicator will tell the tale. Pull the heads and it's easy to measure right off the valve head.
 
usually the valves loosening up is not caused by a worn cam because the valves are adjusted on the heel of the cam which doesn't get to much wear, the lobes will get a lot of wear if not properly broke in, but of course if the lifters are worn a lot and drop down in the lifter bores the valve clearance will change, but I would suspect the valve sticking, try some marvel mystery oil in the fuel. a worn cam lobe will cause loss of compresson and a rough running engine, if you suspect one or two cylinders being weak pull one spark plug at a time till you find the weak cylinder
 

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