Unknown Cylinder Head

[chris_bates]

I currently have a cylinder head fitted to my 1098 engine which does not have any of the usual head codes which I understand are to be found on the top of the head between ports 4 and 5. The only mark I can see on my head is by the thermostat housing which reads "14H6".

I'm a little intrigued as the performance is quite a bit better than standard although I do have an HS4 carb. I didn't check the valve sizes when I last had the engine in bits so I can't remember if it has larger exhaust valves or not but the bottom end was upgraded with big end bolts which are superglued rather than relying on tab washers and there was a strengthening bar over the central main bearing cap.

Any ideas would be appreciated.

Thanks

Chris

[picky]

Are you sure its not "1456"? as David Vizards "Tuning the A series Engine" List a cylinder head with part number 12A 1456.

According to the book that cylinder head was originally fitted to the 948cc morris minor, and has a slightly small inlet valve than the normal 1098cc head (12G 202)

[chris_bates]

No definitely 14H6. Also I have just remembered that I changed the exhaust valves when I had the heaad off and they were std sized for 1098.

Chris

[picky]

No idea then. Put it on ebay as a rare cooper S version

[bmcecosse]

Which is the same size as the 803/848/948/997/998.......and the 1098

[philthehill]

The exhaust valve size is the same (1") for all the small bore (803cc - 1098cc) cylinder heads until you get to the large bore (1275cc) 12G 940/12A 185/AFG 163 heads (1 5/32") so knowing the exhaust size is not a lot of help. Do you know the inlet valve size? That is where the difference lies.
Has the head got locating rings for the inlet manifold? If it has it is either a 12G 206 or 12G 295 cylinder head.
I am intrigued by the lack of I.D. letters/numbers on your head.
I have checked my 12G940 head and the numbers in the same location as yours are 18H7. I am pretty sure that these numbers are casting batch numbers and bear no relationship to the type of head.
I suspect that your big end bolts were Loctited in place with thread lock and not retained with superglue
The extra strap over the centre main bearing is a well used mod for holding it all together.

[bmcecosse]

Phil -the 206 doesn't have grooves for locating rings - it's pretty much the only difference between the 206 and the 295.
Loctite is normal for engine rotating assembly. The strap on the main is not much good on a 1098 - since the crank will break anyway if it is revved...unless perhaps it is a 10CC engine?? Which may well have come with a 206 head!

[philthehill]

bmc
Many thanks for pointing out that the 206 does not have the locating rings for the inlet manifold.
No experience of the 206 only the 12G295.
Info taken from the Vizard book and is reproduced below.
Notes on the side do not differentiate between 206 and 295 as regards the locating rings.[frame][/frame]

[bmcecosse]

Chris - are you SURE the head doesn't have a number? I've just been working on an old 202 head to see if it can be re-used - and it only has a very small 12G202 beside the #4 exhaust valve spring - not like any other head I have seen.

[chris_bates]

Thanks for all the replies. Yes the big ends were loctited couldn't think of the name at the time.

First, there are no locating rings for the manifold and unfortunately without removing the head, I can't measure the inlet valve size.

However, mystery solved Following bmc's comment about very small numbering, I had a really good look at the head again and found 12G202 marked right at the back of the head behind no.8 valve and almost obscured by the gasket. So it's a bog standard head but I confess I've not seen this small numbering before. I note from the Vizard identification that it was used for both the 997 cooper mini and the mk 11 midget and mk 111 sprite, so it's just possible the head has been skimmed to increase the CR which would explain the better than normal performance and the bottom end mod (even if it doesn't contribute much to the end performance!

Thanks again everyone for your help - another gap filled in my learning curve.

Chris

[chris_bates]

I of course mean that it was fitted to the mk1 midget and mk11 Sprite

Chris

[bmcecosse]

That was lucky! I just took it into my head (!) this afternoon to strip the 202 I bought v cheaply from ebay a few weeks ago. It has a few challenges....not least 3 broken studs - which were disclosed on ebay, and probably the reason for it being cheap! One of the valves was quite tight in the guide - probably because the by-pass hose was completely blocked with muck.....

[ian.mcdougall]

so are you saying the bypass hose cools the head better and we should all be putting back our bypass hoses after all these years

[bmcecosse]

Errrr - NO!

[philthehill]

I agree with bmc in that the by-pass hose has no affect on the cooling of the engine but if you do remove the by-pass hose facility you should either drill a couple of holes in the thermostat of fit the thermostat blanking sleeve Pt No: 11G176 see link :- http://www.minispares.com/search/classi ... leeve.aspx
Doing either of the above allows some circulation of water around the engine when initially started and whilst the engine gets warmed up. The blanking sleeve directs water to the rear of the head. The engine should not be run without either the thermostat or blanking sleeve as water is not directed to the rear of the head and you could end up with a hot spot at the back of the head.

[bmcecosse]

Oh dear...what have I started......

[Matt]

Oh dear...what have I started......

I'm saying nothing