Whilst sat round the glowing embers of the Barby at Longleat Campsite this year, a discussion ensued about alloy (A7) heads and that the best type was xyz's (because I cannot recall which make it was, bar the fact a new one is about £180) which has a top water inlet that runs the whole length of the cylinder head, hopefully giving better flow in the Thermo-Syphon circuit.

Having recently had all sorts of problems with undersized core plugs fitting oversized holes.... one of the suggestions prior to discovering the size errors, was that engine was running very hot and the water/steam pressure at the back of the block was causing the problem, this is a ordinary 'low' compression head as per 1934 RP saloon - the logical solution being to have a much better top water flow system.

Now, looking up the references for the gauge of spokes, but not found - another thread - I see the 'ORIGINAL' cylinder head fitted to XL3 (Reg No. OK 3537 - Built 1922) did have a full length water way along the top - see the Source Book, page 40, Illustration No. 51. I wonder why that idea was dropped.

Just idle thoughts, and I wish I had had the book with me around those glowing embers, no perhaps not, that's anorak territory.

Sandy.......

Sandy

My thoughts about running the water channels the length of the head are that with thermo-siphon systems air traps stop the action. The danger would be if there was not a good flow (read uphill grade) then a pocket of steam could form and make things a whole lot worse.
In a horizontal piece like the head, the designer would balance the as big a ports as possible with keeping sufficient uphill grade to the ports. This could mean few or no ports at the back of the engine.

If I remember correctly Aluminium has better heat conductivity than cast iron which would be a factor.

Need to think more about this
Pat in the USA

Pat

I had a "supalloy" head once, which I never used, BUT I think it was supposed to use a side water manifold mounted on the top as the top water outlet? This would have given it an uphill grade as you suggest. I have also seen pictures of other cars of our era and they have top water manifolds much like this design.
Reference Sandys thoughts.... I had a friend with a modern competition engine which had cooling probs. He arrived at similar conclusions to Sandy after much researching. There was definetely a temperature gradient between cylinders one and four, which Sandy is hinting at.

Steve

Sandy Think you are refering to the Whatmough Hewitt head which is available as a repro.

Look at "Motorsnippets" -----A7s----Austin7 Myths Dispelled

Many thanks for the replies.... The head I was trying to get was a 'Ricardo', I know Steve Baldwin (Cornwall Club) has one and he says something about "...... since sliced bread", it is alloy of course.

Any further observations welcome, it was only chit chat around the 'camp fire', but sometimes with no time constraints, conversatiomn can amble into all sorts of topics you normally don't have time to discuss.

Sandy (Cornwall Club).

Hi,
As brought out by the conversation water capacity and the ease that the hotter water gets out 'uphill' is an important part of a design. I think we've also got to remember that while it all looks OK standing still in the garage, while in motion there's all different angles that the head is away from horizontal and there's lots of swirling going on. I haven't checked the information but doesn't the engine sit at an angle to horizontal anyway with the front higher than the back. That will help the hotter water find its way to the outlet - until you're going downhill but I supose there's not much load on then?

As suggested some replacement (aluminium) heads have integral water outlets with a slope right from the back to the front. Not having a separate outlet also eliminates another possible leak site. See the Speedex website for pictures of all the variations. The head 'ahead' on this is probably the finned Cambridge, not only has it the sloping water manifold but its deeper in section with a bigger water capacity. All 14 studs have to be the long type.

Speedex and Supaloy made heads with a long removable water branch based on the side branch. These will give the same effect as the integral ones and has the added advantage of being reversable for a bulkhead header tank and crossflow radiator. Jem Marsh of Speedex came up with this design. The LRM and Coldwell had three water outlets in a similar fashion to the later works multistud heads. I've also seen an extra outlet made by leaving the back core plug out of a '37 head with a flange held by the studs either side. I have also seen a second pear shaped outlet fitted at the back of an aluminium head. Being flat the holes can be cut and a thread tapped to give a second outlet facing forwards in the region of number 4 pot.

Ricardo and Whatmough Hewitt heads are being remanufactured by Dave Dye (A7 Components http://www.a7c.co.uk/ sell them) and John barlow respectively. Both have the sloping integral manifold. I haven't a good picture of a Whatmough Hewitt for the website - anybody got one? (or any other heads that aren't on the site please?).

I hope that gives you some ideas?

Dave

Dave,

I have an original Whatmough Hewitt (sp???) head and can photograph it for your site, if you would like me to.

E-mail me off-forum.

Cheers

Ruairidh

The Whatmough Hewitt with long water exhaust is v.heavy with poor combustion chamber shape. Early aluminium Cambridge @ 5lbs 9ozs without long exhaust has slightly better combustion chamber. I have just weighed an original unused long water take-off Ricardo with a ridiculous chamber shape i.e. restricted clearance over the inlets and excessive clearance over the exhausts and I’m surprised to find that it is only 4lbs 8ozs, it’s either very thin or Elektron or Magnesium the last two options seeming most unlikely.
The best late market aluminium cylinder head was the L.R.M. only made in small quantities by Roy Lee in the 60’s.
However, it can be equalled, even bettered by modifying a late production C.I. head……
1. Remove between 1/10 inch and 1/8 inch from the surface.
2. Check/machine clearance above valves.
3. Straighten combustion chamber sides as much as you dare on the inlet sides. Don’t touch exhaust sides.
4. Relieve cylinder bore.
5. Gasket. Anneal an old one. Carefully unpeel it. Throw the Asbestos stuff away, clean and trim one of the thin foils to fit the newly modified head. Anneal again.
6. Make 5 very thin copper discs from shim to just cover the water ways about 1/2” od.. The 2 above the water inlet manifold need 3/16” holes in them. The very front one and the 2 by no. 1 and 2 valve side should have 1/4” holes.
7. Assemble using sealant only around the waterways.
This should give about 9:1 compression ratio and was this the setup I used for many years when racing my Shorrock supercharged saloon in the Eighties