41 CAD valve lifter

[Alan E. Feltham]

At engine temp above 140F, one valve lifter (pass side at firewall)taps. To alleviate the problem, the following has helped: 6 blade fan, 20-50 oil, new radiator core,flushing, rebuilt waterpump. Short of an engine rebuild (80,000 miles)what can be easily done to minimize the lifter tapping? I have NOT used engine oil cleaning additives.

[Bill Gauch]

Typically, lifter noise is caused by oil starvation. This is typically caused by oil weight that is too high. If you drop the viscosity down to 10W-30 or 10W-40, it should stop the lifter noise. The problem is that, if you drop the weight, you may/will get more blow-by and possibly oil leaks. I would try an oil change with a 10W-30 (10W-40 if you are in the south) and check for drips or additional consumption. If it doesnt help or leaks torrents, switch back and get a loud radio.

[Barry M. Wheeler #2189]

If you can identify which lifter is noisy, you might take the plug out, and with a brass rod, and backing OFF the cam lobe, you might try making sure it is all the way seated by gently tapping on the rod against the valve. This is also a poor mans way of getting stuck valves to move, by using lots of Blaster penetrant down the stem, letting the valve fall, when tapped, and then pulling on the fan blades to bring it back up again with the cam, back off, and repeat ad nauseum till the valve is free.

[Doug Houston]

In order to enjoy the luxury of quiet lifters, you may have to remove them from the lifter gallery. This will be buried on slimy mud if someone hasnt cleaned it out already. You can clean out the lifters, and its a little tedious. There is a coating of varnish built up on them, and also some of that coating gats to the little ball check inside the lifter. It may be that the intermittent clacking is a ball check that isnt working quite right because its got crud in it.

The other thing that you find is that the hydraulic lifters arent really working properly. They stick in one position with the varnish, and have actually become like non-adjustable lifters. You may find that, after cleaning your lifters, they all make a little noise.

Unless you major the engine, you may be wise to just let the one lifter clack occasionally, and not magnify your discomfort by 16.

[alan e feltham]

Thank you all. Some footnotes: 1)when I went to SAE 20-50 oil (from 10-30), it reduced the noise; 2) noise does not become significant until warm-up is reached (higher than 140 deg. F); 3) The 6-blade fan reduced the temp., also reducing the noise;

So, my conclusions are: lowering the coolant or oil temp. helps reduce lifter noise; Not a root cause solution, but it sorta works....but not enough...

[Alan E. Feltham]

Thinking further...maybe the heavier 20-50 oil slows the lifter leak-down rate when hot and serves to quiet things ?

[Bill Gauch]

That is possible, but I wonder if your noise isnt really lifter noise. It is possible, if you are in the south, that 10W-30 was not sufficient when it was hot and you needed the higher weight oil (50 vs. 30). I do wonder, though, if something else is making noise in your engine that sounds like lifter noise. Also, is it possible that your engine is running hotter than you think, thereby causing 30 weight oil to be inaddequate? You managed to cool it down to 140, which sounds extremely low for a full running engine. The thicker oil would be more effective at the higher temps. In any case, my thoughts would be to enjoy the car for the season. Then, when you would put it to bed for winter, plan to pull the engine and do a major tear down and rebuild. I think that is justified after 65 years. Good luck.