Identify my cylinder head

[Tommyzoom]

Hi

I've just removed this head from my Mini Cooper 970s, pretty sure it's not the original type as that would have been an aeg163, this is a 12g940. What I would like to know is what it could be from, what state of tune it's had as the valves don't look standard to me (I've added the sizes in the photos) and what it's likely to be worth in order to sell it and buy an original type to put back on. If anyone has an aeg163 and would be intrested in a part exchange please get in touch. Any help is much appreciated.

[mk1]

The chambers on that look HUGE!

I am surprised it was on a 970. As the C/R will probably be well down.

It has nice big valves fitted & looks like it has been modified by a home enthusiast as per David Vizards designs in his book How to modify your Mini & tuning BL's A Series engine or whatever its called.

Those sort of extreme chamber profiles are not as fashionable as they once were.

Hope this helps,

M

[Tommyzoom]

Thanks for the info, weather or not the previous owners ever got it running well is another thing. Maybe fitting a fancy head was all the rage in the 80's regardless of if it actually made a difference! Haha

[Spider]

The chambers on that look HUGE!

I am surprised it was on a 970. As the C/R will probably be well down.

M

I was thinking the same thing, it would most likely suit a 1380 or bigger.

[ianh1968]

28.48mm for the exhaust is smaller than the standard 1300 size,
let alone the 'S' size... (1.15625"=29.36mm & 1.21875"=30.96mm)

The valves really need taking out to measure properly.

It does look like one of the 1970's heads. If the chambers
really are as huge as they look, this may be an ideal head for
a stroker, a 1480, maybe...

Ian

[LarryLebel]

Also you need to measure the volume of the combustion chambers before coming to any conclusions. The face could have been skimmed a lot. The shape doesn't look like a Vizard shape to me and the work looks professional rather than DIY.

[mk1]

Also you need to measure the volume of the combustion chambers before coming to any conclusions.

True, but it is plainly OBVIOUS that those chambers are FAR bigger than 21cc, the depth is very easy to gauge by the photos. OK, You can't give a definitive volume, but it is obvious that its MUCH larger than standard.

If I had paid someone to cut me a head & he came back with that for a 970 S I'd want my money back!

No one with any real grounding in A Series heads are using those radical sloping sided chamber designs any more unless its for a 1460 or something where you need to find every molecule of volume you can.

[LarryLebel]

For comparison here's a12G940 head DIY ground to Vizard's specs.

[Tommyzoom]

Interesting stuff, hopefully I will get chance over the weekend to measure the cc volume. The measurements I did on the valves were just a rough guess so the exhaust could be a little bigger than what I measured. I can't seem to find another one similar to compare it against. Any ideas what it could be worth?

[Tommyzoom]

Ermm yeah. 25cc!

[ianh1968]

For comparison here's a12G940 head DIY ground to Vizard's specs

The photo of the head we are talking about does look like a pictute of one that is in Mr Vizard's "Tuning the 'A' Series Engine" book.

The caption says:

"Here's one of my trick heads of 1973. These were difficult to produce as the combustion chambers
had to be done with a profile-formed grinding wheel. Heads like this did produce good results,
but I am now getting significantly better results from simpler, less critical mods, as a result of
thousands of hour of flow bench and dyno testing"

The book does also provide the detailed and dimensioned drawings for a specification
that Larry's head is based on.

They are possibly both "Vizard" spec heads...

On a 970 'S', the stated CR is 10:1, with a 21.4cc head.
This requires a TOTAL combustion chamber of 26.9cc.

The 1970's head is 3.6cc bigger, at 25cc, therefore giving
a TOTAL combustion chamber of 30.5cc.
(Assuming no other changes...)

30.5cc TOTAL on a 970cc engine gives 9.0:1

My guess would be that the actual valve sizes on the 1970's head
would be:

1&5/32" (1.15625" or 29.36mm)
or
1&7/32" (1.21875" or 30.96mm) for the exhaust

and either:
1&13/32" (1.40625" or 35.7mm)
or
1&7/16" (1.4375 or 36.5mm)
or
1&15/32" (1.46875" or 37.3mm)
or
1&31/64" (1.48438" or 37.7mm) for the inlets.

The above sizes are the traditional tuning sizes as per the "ST" manuals etc.

The valves would almost certainly be "64th" sizes, ie Imperial
and there would have been "no such thing" as a 37mm valve.

I have had this discussion before about tuning shops selling valves as
metric sizes when they are in quite often a nominally smaller imperial size.

MiniSport, in Lancashire sell "37mm" inlet valves:
They are actually 1&7/16" (1.4375" or 36.5mm)...
(I bought some, measured them, and this was how big they were)

Oh, it's only 0.5mm, why are you being so picky? (I hear you ask...)
Well, would you put 73.5mm pistons in a 74mm bore?
When I wrote to MiniSport detailing this logic and returning my items as
"Not as described" they did not provide a formal response...

Ian