I've been given two new tappets for an engine that is going to be rebuilt. I understand that only 'exhaust' ones should be used for that purpose. Is there anything 'visual' that identifies a correct 'exhaust' one, as these didn't come with part number labels(or anything). My gut feeling is just to use one of them for the inlet. Both the original ones from the engine look identical, but the new ones differ in the amount of metal, and the angle of it, on the 'head'. Definitely thinner and shallower on one. There is no reason to believe that the originals were necessarily the correct items so I don't feel I can rely on them for comparison:-)

email (option): cruiserchooserAThotmail.co.uk

On the side valve engines only, the 'foot' of the exhaust tappet is hard chrome plated...

Visually you can tell the difference when you compare the finishes of the tappet surfaces...

The hard chrome plated finish has a more 'silvery/white' appearance than the non plated part...

Also, around the outside edge of the tappet you will sometimes see some roughness or flaking of the plated finish...

OHV engines such as the B31 used the same part for both sides...

The plated finish helps improve the lifespan of the exhaust tappet which can be compromised in the side valve by heat transfer from the valve..

The valve operates at a higher temperature than in OHV engines...

Putting an inlet tappet on the exhaust side may thus shorten its life somewhat but won't affect the running of the engine until, or when, that takes effect....Ian

email (option): ian@wright52.plus.com

Thanks Ian, nice to know these details. I'm sure others find it useful too.

email (option): cruiserchooserAThotmail.co.uk

Hello,

I remember that in the past I studied the subject when I was
Putting an engine from NOS parts.

If you are using NOS tappets, then the exhaust one (If I am not mistaken..)
Is marked with a silver paint dot on the bottom surface. (Contact with cam)

Noam.

email (option): noam10@gmail.com