(re)building a 1275 head

[minijojo]

i don’t plan to build a racing engine, only increasing the power a bit to get little better acceleration.

i am able to do some work myself but don´t have access to metal processing machines

i got a cylinder head with rocker assembly and valve springs last week and are planing to make it ready for use.
i´m not quite sure what exact type of head it is and what parts should be replaced before installing it.

Sure it´s a 1275 head with water inlet under the thermostat housing and the heater valve slot placed like on the 1275er heads. it has groove for placing manifold locating rings on the inlet ports. The last but one owner removed the stamps on the head to make it more difficult to identify it when used on a block normally not build for. I guess this would be no problem in my case..

I would say the overall condition is good









the first problem is, the last owner cannot find the valve spring caps and the tripple groove valve cotters.

now the questions i have
should i place new valve guides?
should i place new valve seats?
should i place new valves?
what kind of exhaust manifold should be fitted?

the valves and the seats seam to look ok and should be good after a bit of grinding. (i would be able to do this by myself)
As i am not able to replace the valve guides myself is there a way to test if they need replacement?
The valves seem to stay strait in their guides

i have a classic mini alloy manifold with HS4 Carb which should be fitted to that head

would be glad for any advice, tips, parts for sale and offers to complete my project

regards
Joachim

[bmcecosse]

Just wiggle the valves in the guides to decide if the wear is excessive. Looks like standard size Valves (can't really see well enough on my phone) - what size are they? Caps and cotters will be expensive so I hope you didn't pay much for the head.
All I would do is to open up the narrow turn In the exhaust throats it really would be better to look for a big Valve head to work on and get any worthwhile power increase.

[minijojo]

thanks bmc for your comment,
the head diameter of the inlet valve is 33,3mm, the outlet is 29,4mm

[bmcecosse]

Ahh right - so the 'small' inlet valve. I wouldn't do anything till you track down the cotters and caps. Note they MUST be the 3 ring type - nothing else will do. Sorry if this seems obvious - but better safe than sorry. You can of course bore out the inlet throats and fit the larger valves - blending the new larger throats into the ports with mounted points or high speed rotary cutters in a die grinder. This is the sort of finish you should be looking for in the combustion chambers.[frame][/frame]

[philthehill]

http://www.minispares.com/product/Class ... ssic/valve caps.aspx|Back to search

http://www.minispares.com/product/Class ... ssic/valve collet.aspx|Back to search

[bmcecosse]

Oh dear - so ~ £75 + carriage for the caps and collets..... If the head was 'free' then I guess it's maybe just about worth it - although small valve heads complete usually sell for a bit less. Here's a big valve head complete for £80 + carriage - maybe you can negotiate a deal...... http://www.ebay.co.uk/itm/MINI-MG-METRO ... Sw1DtXKk5b

[philthehill]

It may be cheaper overall to replace the triple groove valves with good S/H single groove ones with accompanying single groove top caps and collets.
I managed to pick up a NOS set of inlet valves and NOS exhaust valves for a 1275cc engine of the size you require for under £20 from 'e' bay recently.
Whilst not genuine BMC/BL they were from recognised aftermarket motor factors and would be more than suitable for your proposed use.
Or even new for example:-
http://www.ebay.co.uk/itm/SET-OF-INLET- ... Sw~OdVX0IK

http://www.ebay.co.uk/itm/AUSTIN-ALLEGR ... Swll1Wv7QF

[amgrave]

Are you planning on putting this head on a 1098 engine.

[minijojo]

first, tanks to all for your posts. Now i see it would be better to investigate more then i did before buying something.
But i think its good enough for the first build. Learning by doing....
Got a used set of springs and valve spring caps today. The caps are the expensive part of the missing parts. They where offered as removed from a 1275 12G940 head. Will then decide witch way to go when seeing what kind of valve caps i bought. There are two opinions, tripple groove valve cotters when they fit to valve caps or new single groove valves (thanks for that advice). Found out today that the collets got different angels, so i should be able to identify them.
The valve cotters are both available at acceptable rates.
When i got all parts together i will then try to get a result as shown in bmc´s picture

what i found out from the valve sizes, this could be a early 1275 A+ or a single or multipoint injection head

one more question about the manifold locating rings. Should there be a groove on the manifold side too? could the manifold be fixed without placing that locating ring?

[bmcecosse]

It's not an injection head - and I'm dubious about it being an A+ head. It really looks quite old? With the manifold rings I suggest it's probably ex Spridget (or MG/ Riley/Wolseley 1300) with the rings to locate the manifold for the 'tiny twins' SUs. They MUST be the 3 ring type if you use these valves. If you go for single ring valves be VERY careful to get the correct caps or you could have a very expensive disaster. I'm not sure if the earlier standard 'no ring' valves etc were ever used on 940 heads

[minijojo]

the information about the possibly injection head is from this site

http://www.retrominisltd.co.uk/index.ph ... page&id=17

got the valve spring i bought for about 5€ include shipping today. It´s a total complete set with spring upper and under Valve plates and a set of 1 groove valve cotters.
I know they want fit to the existing valves, but i connected the seller of this ones. This are suitable for this head

http://www.ebay.co.uk/itm/231935329128

Thanks to Phil for that link

I guess i will wait a few days, may be the previous owner finds the 3 groove cotters.....

I will keep you updated how it goes on

[bmcecosse]

It's NOT an injection head - makes no difference anyway - it is an early head as indicated above. Not a problem - but because of it's age - do check very carefully there are no cracks between the seats (or indeed chambers) before spending any more money on this. Frankly - without the caps and cotters i would be sending it back for a refund -and get something you can use instead -without spending extra money. These valves are suspiciously cheap! We still don't know which engine you plan to use the head on ?

[minijojo]

The head was cleaned before i got it; by inspecting it at daylight i did not find any cracks.
The Engine installed in my minor is a

9M-U-H 5xxxxx
9=948ccm
M=Morris
U=central gear change
H=high compression

If i am wrong with fitting the head to this block, please inform me.
i know, i have to use a 1300 head gasket.
got the valve stem oil seals today....

[philthehill]

Fitting the head featured in this thread is not a straight forward fit onto a 948cc or small block 'A' Series engine.
Whilst it can be done it does need a bit of thought to carry it through.

[bmcecosse]

We asked you about the engine ages ago - it's far from ideal for a 948 engine. the valves are far too big - unless you are building a high power engine able to rev high, of course. Is that the plan? Does work very well on a 1098 - but as Phil says - well documented modifications are required.

[minijojo]

i assumed that.......
My first mistake was to trust the seller and the MOT tester that this is a 1098 engine. This is also reported in the car´s documents. After talking to Declan about tappet cover gaskets, he told me, that this covers are not used on a 1098 block. So i noticed the engine number and found that it has decreased to 948. So i have to thing about many plans i had before.
But its always good to here your advices. Learning by making mistakes, did that many times in my life before.....
Got a 1000 head nearly for free, so will try to maintenance that one to have a replace, because i think, the valve stem oil seals are gone, because there is blue steam on every acceleration coming out of the exhaust. Even after a longer drive.
Any other devices welcome

[bmcecosse]

What's the casting number on the '1000' head ?

[oliver90owner]

My first post on the forum, but felt it must be said. A 1275 head on a 948 would almost run on paraffin - the compression ratio will be much reduced, unless some considerable shaving of the head is contemplated! Skimming the head sufficiently may well upset the valve geometry and require rocker shims or shorter pushrods. The low lift cam may well reduce the expected improvements.

This 'smoky head' - valve guides could well be shot as well. But there may be other reasons for the smoke.

It is nearly 40 years since I modded my ford engines for extra power, but I think this poster seems to be heading nowhere with his ideas. Time to step back, close the wallet, and think out a cohesive plan before proceeding any further.

Just my opinion, of course, so please don't take it too much to heart!

RAB

[bmcecosse]

Actually - the 1275 head has much smaller combustion chambers - and so the Comp Ratio would be higher - not Low and certainly no paraffin. No need for any skimming - or spacers or push rod changes.....(where does all that come from?) The rockers would ideally need re-aligning - as they do on a 1098, or use the poor design 1275 rockers. The low lift cam would actually probably allow the head to be fitted without any valve sinking or pocketing (but still check) - and indeed it can be, and has been, done before. BUT the valves are so big that the engine in standard form will not pull well except at high revs. So - if that's what's wanted - the job can be done, with all the usual caveats.

[philthehill]

Just to confirm combustion chamber cc's.
Minor (948cc)............24.5 cc
Minor (1098cc)...........26.1 cc
940 head (1275cc).......21.4 cc
Cooper head (998cc)....28.3 cc