mk1-forum.net

Anyway, the new Westlake head has 37.5mm inlet valves. Does this work with a common 1293ccm engine or will it need a short stroke motor

Alloy has a higher HTC (heat transfer coefficient than iron)...considerably higher. What this means is for a given surface area and temperature difference (between chamber and water jacket) more transfer takes place and more heat is lost to the water jacket rather than the combustion expansion process.

This is quite clear in theory, however, there are a few more factors to muddy the water.

1. Does this ability to sink heat lower the peak temperatures slightly to allow a higher compression ratio to be used. (empirical data required).

2. Has anyone compared and EXACT alloy head with an EXACT iron head? When you start mucking around with wall thicknesses and surface areas, you alter the basic comparison of performance vs specific heat capacity of a given material. The test becomes less valid.

However, it may hold true, but with the extra power, you now have extra weight to drag around.

I wonder how alloy heads (with a high coefficient of expansion to boot) fare when ceramic coated. My thoughts are this is unlikely to work, due to the oxidation layer, as well as the expansion range. I wonder how a thick layer of anodised oxide would interrupt the thermal waste element........

Your basic heat exchanger equations are:-

Q=UA (LMTD). Q= Heat transferred, U= sum of heat transfer coefficients (out of a book) A=Area for exchange to take place LMTD= Log mean temperature difference.

then:-

Q=MCpdT M=Mass of stuff to be heated Cp=specific heat capacity of "stuff" (out of a book) dT=temperature difference.

From those you can pretty much do anything and understand a lot more about heat.

Hi,

searching in old regulations I found this in the Annex J from 1972 concerning Group 2.

- Cylinder head of a different shape and/or material, provided that the position
and number of camshafts, and the number of valves per cylinder, remain
unchanged. By position is meant either in the block or in the head.

My Interpretation is that this will allow the AKM 7 port heads from Mini Sport as well for an annex K G2 car. They have quite a different behaviour but it is much more easy to fit Weber carburettors. Any opinion?

"Free" is a relative term....
You will still have to document that the cyl.head was used (leagally) *in period* and in a international race open to the same class as you want to race in.... I.e. if you want this approved for Gr. 2 it will have to have been used - legally - in period and in a international Group 2 race.

I doubt you'll find that....

Hi,

this 7 port was produced in Denmark by Georg Mikkelsen of AKM racing. It's a well known and documented history. Some 15 years ago even Nick Swift tried it with his Britax Mini. The question seems rather to be that how the power will increase.

Hi,

to continue this topic just from our own experience. Older Westlake’s may have the better flow, but worse cooling. The new ones do not exist. Some guys, as myself, have paid for, but did not receive a working one. The older Arden have some problems with the alloy. It might be necessary to reinforce the threads and modify the valve guides. Otherwise it could happen, that these guides drop down when the engine becomes a bit colder and will cause massive trouble. The new ones seems to be quite good.

Astro wrote: The older Arden have some problems with the alloy. It might be necessary to reinforce the threads and modify the valve guides. Otherwise it could happen, that these guides drop down when the engine becomes a bit colder and will cause massive trouble. The new ones seems to be quite good.

the guides in the new '2012' ardens are stepped, so its impossible for them to drop and cause and issues

plenty have been sold, with no issues

Btw, what is about this special non roller rocker assembly for Arden heads?

Astro wrote:Btw, what is about this special non roller rocker assembly for Arden heads?

they are a set of rockers with the correct posts to suit the arden head

but nowhere on the Spares HP.

Astro wrote:but nowhere on the Spares HP.

they are a special order part at the moment, we havent got round to creating a stock control point for them yet

should have known earlier. This years engine is running - knocking on Wood.

Is your bonnet closing OK over the carbs??

yes it does, but not the standard lockplate and we have still a problem with the power. It just lasts until 7.1 rpm. Last climb was Beaujolais and indice class was nevertheless second overall. Next week in Vuillafans we will try other trumpets. Perhaps I had an idea - perhaps not - we will see.

Will the engine get enough air this close to the bonnet??

Hi,

if you watch the pictures from the latest works mini, you see that they have changed from injection to weber dcoe’s. You will also see that the bonnet was never completely closed. OK, we tried. Opening the bonnet for about 8mm was the best result. More was less power and we always corrected the mixture by reading lambda. Nevertheless there seems a problem with the flow. The maximum power is at 7.1 whereas Swift says, it should be at 7.4. I am now building a completely different type of trumpets. Next weekend we will see if something is changing and what is changing. If it will be a dead end we will try something like Day Bos just offered, but for the Arden and perhaps not with butterflies but with a sliding device. Let’s see.

that's better

Hi
Have you run the car without the mesh in front of the trumpets?
Usually mesh is a very restrictive media in that type of application, the air tends to hit the face of the squares and move in an outwards direction with not so much pushing through as you would need. You may find without it you might get the result you are after.
Just a thought.

Thanks

Ian

Not yet. We do competition with it and there is always a lot of dirt on the track. Might it be better when each hole has its own mash? That was my alternative.

Hi Astro,
Looking at your photo, not sure how that would go as you really have ( 2 ) Trumpet type orifices.
Years ago I made up a larger mesh cage ( bigger Squares ) across the front and cable tied filter media over it. Any of the oil type foam filter companies ( K & N, Uni Filter, Finer Filter etc.) sell them in large panels that you can cut to shape.
I would use the backing panel you have with that shape and make the more open mesh and filter to suit. Just cut it larger and bend the mesh like a cave to cover that shape, make it as deep as possible so you can still shut the bonnet and cover with the media.
I think from memory the mesh had about 13mm sections?
It looked alot like the Pipercross filters you see for twin webers today, except not as extravegant or expensive.

Thanks

Ian