3/5/7 angle valve jobs?

[pingu393]

PeterBurgess said:

Just fixed valve openings followed by rolling road testing, race wins and a few championships, seems to work ok

Thanks

[PeterBurgess]

I wish I could help more but I only developed the flow bench enough to move on to the next stages. It is a good tool when used in conjunction with others, a strong weapon in the armoury none the less.

[stevesingo]

Inline__engine said:

stevesingo said:

For referance, here is the workshop repair manual for the BMW s14 engine valves and seats...





V= In 36.6mm Ex 31.4mm +0.1mm tolerance
B= In 1.2mm Ex 1.4mm +0.1mm tolerance

Interesting that the valves are bigger than the seats..

Steve

some of the issues i am mentioning are briefly raised here

i.e. T is bigger than V by a smidge. but what is the 45 width on the valve ?

I would suggest the vale seating face is slightly larger than the head sealing face. Otherwise the wear pattern may be unhelpful.

[DVandrews]

It’s common practice for the valve seats to be smaller than the valve, it allows for differences in concentricity and provides a service limit so the seats can be recut without going beyond the valve seat diameter.

Dave

[pingu393]

This may seem daft (but every little helps)...

The valve head being bigger than the seat will mean the head is protruding into the combustion chamber by maybe 1cc. This will very slightly reduce the combustion chamber volume, hence increase the compression ratio.


I see it as a fortunate unintended consequence, rather than a reason for doing it.


I suspect that it is more to do with sealing than anything else.

[PeterBurgess]

Good explanation Dave. I notice sometimes the seat in the head can be well over a 1.5 mm smaller than the valve head, especially some ex valves.