Is there a good chemical to quiet lifter in my '51 Lincoln flathead

[northeastcarnut]

I'm still trying to solve my problem with a noisy lifter in my '51 Lincoln flathead. Is there a good reliable chemical I can add? The noise appears only after the engine runs and warms. When cold, it's quiet and runs great. I have run lots of Mystery Oil in the crankcase, but no help. I'm now running fresh 40W non detergent oil.