Flowing the head....????

[Locktc7440@aol.com]

This is for all of the engineering types out there as well as engine builders. I was having a dicussion with a friend a few days ago and the term "Flowing the Head" came up. I have heard it before and assume it has something to do with intake and exhaust gasses. What exactly is this procedure and how is it accomplished? Please excuse those of us that are not up to date with such terms and procedures....

[Clive Sherriff]

Flowing the head is a tuning modification to a standard cylinder head, inlet and exhaust system. It is usually done with a reduction of the cylinder head thickness to increade compression and hence (usually!) power output. Generally in the 30s and 40s it was accepted that - broadly - thinning the head alone was stage one tuning, After that flowing the head and maybe bigger carbs was stage 2, then more off the head stage 3 and stage 4 was back to a thicker head, but flowed, and a supercharger to regulate compression pressures. (Those with much money and a friend to take them home would have the supercharger AND the high compression head!) Basically the standard head from most cars is just cast for convienience and the minimul work is done to it to make it work - Valve seats cut - mamifolf faces machined and a bit of a tidy up of rough edges. This means that there are sharpish edges and corners, and rough surfaces on the inlet and exhaust ports and the combustion space that cause disturbance to the incoming fuel / air mix and outgoing exhaust gases, rather than there being a smooth fast flow. To make a well flowed head then the inlet and exhaust ports are matched to the head faces so any overlapping bits are eliminated, the inlet and outlet ports are smoothed off and sharp edges and corners smoothed out as much as possible to gife smooth flow and regular section, the cylinder combustion space is polished and any sharp pionts removed, and in sone cases the shape is altered to promote swirling of the incoming fuel and outgoing exhaust to give greater gas flow rates. The most visable result can be the replacement of the original exhaust manifold with an "Extractor" manifold that takes gases smoothley out of the engine and away without hitting a bunch of right angles in the first 6 inches. This can be taken too far though as some back pressure is required by many engines and tuning the length of the exhaust pipe to provide this through resonance is a genuine Black Art from the depths. Theres a lot more to it but thats the basics. Regards Clive Oxford UK =================================================

----- Original Message ----- From: Locktc7440@aol.com> To: mg-tabc@yahoogroups.com>; wargs@Mac.com> Cc: mg-t@autox.team.net> Sent: Sunday, April 28, 2002 12:17 AM Subject: [mg-tabc] Flowing the head....???? > This is for all of the engineering types out there as well as engine > builders. > I was having a dicussion with a friend a few days ago and the term "Flowing > the Head" came up. I have heard it before and assume it has something to do > with intake and exhaust gasses. What exactly is this procedure and how is it > accomplished? Please excuse those of us that are not up to date with such > terms and procedures.... > > > > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ > >

[Donald Wilkinson]

get David Vizard's book- "How to Build Horsepolwer" (which I was turned onto by Joe Curto). He gets into flow benches in some detail, with photos, etc. In the Buffalo NY (USA) area (a few blocks from my boat shop) we have "Jim's Cylinder Head Service". He has a flow bench, Lemco, etc.etc.etc. He's very good, very reasonable. Don TC7993

>From: Locktc7440@aol.com >To: mg-tabc@yahoogroups.com, wargs@Mac.com >CC: mg-t@autox.team.net >Subject: [mg-tabc] Flowing the head....???? >Date: Sat, 27 Apr 2002 19:17:46 EDT > >This is for all of the engineering types out there as well as engine >builders. >I was having a dicussion with a friend a few days ago and the term >"Flowing >the Head" came up. I have heard it before and assume it has something to do >with intake and exhaust gasses. What exactly is this procedure and how is >it >accomplished? Please excuse those of us that are not up to date with such >terms and procedures.... > > > >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ > >

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[Donald Wilkinson]

To which digitaldon can only add-as in all things involving the scientific method- one must MEASURE the results- i.e. on the flow bench. You can't just hog the suckers out on spec, (as we used to do when we were kids). Often, ports hogged out to the max (occasionally into water) turned out to not flow as well as conservatively cleaned up ones. Don TC7993

>From: "Clive Sherriff" clive.sherriff@ntlworld.com> >To: mg-tabc@yahoogroups.com>,wargs@Mac.com>,Locktc7440@aol.com> >CC: mg-t@autox.team.net> >Subject: Re: [mg-tabc] Flowing the head....???? >Date: Sun, 28 Apr 2002 08:52:52 +0100 > >Flowing the head is a tuning modification to a standard cylinder >head, inlet and exhaust system. It is usually done with a reduction >of the cylinder head thickness to increade compression and hence >(usually!) power output. > >Generally in the 30s and 40s it was accepted that - broadly - >thinning the head alone was stage one tuning, After that >flowing the head and maybe bigger carbs was stage 2, then more >off the head stage 3 and stage 4 was back to a thicker head, but >flowed, and a supercharger to regulate compression pressures. > >(Those with much money and a friend to take them home >would have the supercharger AND the high compression head!) > >Basically the standard head from most cars is just cast for >convienience and the minimul work is done to it to make it work - >Valve seats cut - mamifolf faces machined and a bit of a tidy >up of rough edges. > >This means that there are sharpish edges and corners, and >rough surfaces on the inlet and exhaust ports and the >combustion space that cause disturbance to the incoming >fuel / air mix and outgoing exhaust gases, rather than there >being a smooth fast flow. > >To make a well flowed head then the inlet and exhaust ports are >matched to the head faces so any overlapping bits are eliminated, >the inlet and outlet ports are smoothed off and sharp edges and >corners smoothed out as much as possible to gife smooth flow >and regular section, the cylinder combustion space is polished >and any sharp pionts removed, and in sone cases the shape is >altered to promote swirling of the incoming fuel and outgoing >exhaust to give greater gas flow rates. The most visable result >can be the replacement of the original exhaust manifold with an >"Extractor" manifold that takes gases smoothley out of the engine >and away without hitting a bunch of right angles in the first 6 inches. > >This can be taken too far though as some back pressure is >required by many engines and tuning the length of the exhaust >pipe to provide this through resonance is a genuine Black Art >from the depths. > >Theres a lot more to it but thats the basics. > >Regards > >Clive >Oxford UK > >================================================= >----- Original Message ----- >From: Locktc7440@aol.com> >To: mg-tabc@yahoogroups.com>; wargs@Mac.com> >Cc: mg-t@autox.team.net> >Sent: Sunday, April 28, 2002 12:17 AM >Subject: [mg-tabc] Flowing the head....???? > > > > This is for all of the engineering types out there as well as engine > > builders. > > I was having a dicussion with a friend a few days ago and the term >"Flowing > > the Head" came up. I have heard it before and assume it has something to >do > > with intake and exhaust gasses. What exactly is this procedure and how >is >it > > accomplished? Please excuse those of us that are not up to date with >such > > terms and procedures.... > > > > > > > > Your use of Yahoo! Groups is subject to >http://docs.yahoo.com/info/terms/ > > > > > > > > >Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

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