[DeTomaso] Why do Camshafts Fail ?

[JDeRyke at aol.com]

In a message dated 11/24/09 11:37:31 AM, charlesmccall at gmail.com writes:

> So what happens during the 100,000 miles of your cam, if you are lucky? 
> Does it gradually wear down a little each year so that your lift is reduced? 
> Does a 50,000 mile cam have a much different profile from a new cam, 
> assuming somewhat aggressive valve springs? I assume that they eventually just 
> wear away...
> 
I've never seen a high mileage cam where more than one lobe was badly worn. 
Most of the wear is at the highest point of a cam lobe where the spring 
pressure is greatest. So if you look at such an engine while its still 
assembled, one rocker arm will rattle around at any point in the engine rotation; 
that's usually a sign of big trouble in the cam area. I once disassembled a 
high mileage 455 Chev engine that had almost no peak on one cam lobe (the 
'lobe' was round), and on that valve, the hydraulic lifter was completely worn 
through the bottom so there was no oil chamber left, just a hollow tube. The 
owner complained of a 'miss' that a tune-up didn't fix....
FWIW- J Deryke