Ex/inlet valves

[joe]

I’m working on my 1928 mag engine and finding all sort of interesting features, for instance, there is a mixture of cylinder valves- see picture, one of which is marked inlet ( they are all Collet type )
Question: is there a difference between inlet and exhaust valves ?
Joe, in Suffolk.

[John Cornforth]

Hi

That's a bit of a mixed bag you have there.

Exhaust valves run hotter, so are sometimes made of superior material though I have no idea if this applies to A7s.

The slots are to aid turning with a big screwdriver when grinding in, and the centre dimple is (I believe) to locate the spring compressor jaw. Aftermarket valves seem to have ditched these features and have plain heads, so you need a rubber sucker for grinding.

[Howard Wright]

Hi Joe

Cherished suppliers only list one valve for both inlet and exhaust unless you are putting in a bigger inlet valve. 

I’ve got a box full of different types of valves for the Seven acquired over time. Some with slots some without.  However I always tend to buy new when building an engine, possibly to save time on cleaning and refacing old valves!

Cheers

Howard

[Ian Williams]

You do come across old Ex grade valves in some A7 blocks, I have found them to be good quality so regrind and reuse them if the stems are not excessively worn. I imagine that all valves now sold by our cherished suppliers are of similar or better quality, I have certainly never found issue with new valves from any source in the A7 world. If I were to be critical at all it would be that the seat face can be a bit wide on some new valves which reduces the effective opening area. If you have a lathe a small performance advantage can be gained by removing that excess material. Looking at the OP's block, I think I would be inclined to replace them all with new.

[Chris KC]

I think historically exhausts were made of superior steel but nowadays they all are. It seems many a year since I last burned a valve.
As Ian says, I personally would prefer a nice row of shiny new ones all of the same type, but if they are running well perhaps no pressing need.

[joe]

What I haven’t mentioned is that this engine was ‘overhauled’ over 45 years ago ( so the garage owner told me, he was a 7 year old when the car came in for repair, the engine stayed, the car disappeared) the grease that held the collets on assembly was still evident, the valve stems and guides show no sign of use, there was no oil in the sump it had escaped through the rust holes in the sump.
Joe