Rockwell Hardness of cam bucket tappets

[red4re]

What should be the Rockwell hardness of shim under cam bucket tappets on an overhead valve engine. I had mine checked and they went from the Rockwell C scale at 40 to 50.

 

[NickE]

How did you check them, how thick were the shims?

HRc is pretty heavy load for normal shim material, you may have bad results, usually shims are best tested with one of the superficail tests, or something similar to A-Scale (100kg-Load).

 

[patprimmer]

Does the cam or the valve stem contact the shim, or is there a hardened insert between the shim and the cam and/or valve stem.

Regards

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[bobqzzi04]

That is too soft. You'll want a minimum of 50, and closer to 55 is better.

 

[Metalguy]

NickE,

Close, but the Rockwell A scale uses a 60 kg max. load.

No big deal, just gotta keep on yer toes around here. <g>


"When the eagles are silent, the parrots begin to jabber."
Winston Churchill

 

[red4re]

There are 24 bucket tappets on this V-6 Lancia Stratos engine. The 4 cams contact the buckets to open the valves. Clearance is achieved with lash caps that fit on the end of the valves. I recently had the bucket faces ground and now will need to have them heat treated. I have been told that the minimum depth of hardness should be .012 or .3mma. I don't know what type of steel the buckets are, would that be a problem for the firm doing the heat treatment. Does anyone know of a source to heat treat the buckets who is familiar with what is required.?

 

[dcasto]

Been through some of this on a toyota 7MGE engine, same arrangement. On the toyota fourms they discuss useing Yamaha shims as they are the same diameter on a seies of engines they make, because Yamaha designs most of toyota's heads.
Finally I found some at $7 each. BUT, through an accident in my shop I bent 4 valves and replaced them. But the shims were wrong. I had read about this so I did it. I just ground about the .005 off the top of the valve. finished.

 

[modesign]

From another posting is this the 4 valve engine that had a camshaft failure from lack of oil? As the origional project used all standard parts where possible have you checked the bucket size against a 2 valve engine. They are available new currently.A new one would give you hardness data.

 

[tbuelna]

Bucket followers on older production engines are likely chilled iron with a nitride (sometimes called tufftride) case. Newer engines use sintered steel (powdered metal).

Unless your grinder was very careful, he likely ground through much of the existing case. And by the way, did he grind the contact surface with the proper crown/profile? If your buckets needed to be re-case hardened, it should have been done prior to finish grinding.

Commercial nitride cases are usually quite thin, maybe .015" before grinding, and maybe .010 to .012" after grinding. The reason being, case depth is a function of time in the furnace. And of course, time is money.

You should not use a Rockwell C test setup to check a nitride case. It's too thin. You should use a superficial hardness test scale, like the Rockwell 15-N.

Finally, if you're going to perform a proper heat treatment, you need to know exactly what type of material you're heat treating or case hardening. If, for example, you're performing a nitride process, some metals do not respond what so ever to nitriding. So it's a waste of time. And if you're trying to carburize a part, you will not have any success unless the alloy has sufficient carbon present in it's surface.

If all else fails, get some new ones made:

http://www.arrowprecision.co.uk/followers_stock.php