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Cylinder chamfer
Hi All

Engine building on the special has started and I have all the (standard) valves and springs in the block.

My friend is encouraging me to chamfer the top of the cylinder bores to aid gas flow.  Bearing in mind I’m trying to build a “strong” engine not a race engine do the engine builders out there normally chamfer? If so by how much and to what profile?


Howard, this was aired on the forum not so long ago, as usual a range of opinions.
Mine is that a car will go pretty well without this mod and if reliability is your goal I'd simply leave it alone.
Of course there are others who swear by it...
The mod is described in Bill Williams’ Austin Seven Specials. If you do not have a copy let me know.

If you are on standard valves, the flow restriction is in the valve throat. Chamfering the cylinder edge won’t improve breathing and will reduce compression. Unless you are planning oversize inlets and high revs, I’d leave well alone.
Alan Fairless
Hi Thanks all

I did try a forum search but nothing came up and very little on a Google search.

I do have Williams specials book but was more interested the efficacy of chamfering.  The answers seem to confirm my thoughts and I will leave well alone.


One such thread is here Howard: [Only registered and activated users can see the links Click here to register]

I'd go with Alan,derestrict around the valves and re radiused followers will make the biggest difference.
Hi Ruaridh 

Shows the difficulty with search engines.  I put “chamfer” in the search box with several variations and got nothing.  If I’d put “relief” I’d have found it.

After reading the thread (which digressed somewhat from Jon’s original question) I am leaving well alone.



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