1275 cylinder head

[mu0u207b]

Hi there. I was looking through the minor matters mag the other day and spotted the Birmingham minor centre sales a 1275 cylinder head for about 180 pound plus surcharge. Would fitting this head be a straight swop of my 1098 head of a 1971 minor or would i require additional work to the block to fit the head, and if so what. The cam shaft is standard but i have fitted a HIF SU carb, water heated inlet manifold and electronic ignition. Thanks for your help.

[Matt]

You will probably have to machine pockets for the valves.....

[bmcecosse]

It's been discussed at length - unless the head has had the exhaust valves recessed into the head you WILL need to machine pockets in the block. You also need the 1275 gasket, and to modify the water pump to get good clearance - and you need the 1275 rocker gear (or spend ages modifying the ones on your engine at the moment to line them up properly with the valve stems). But it does make a good performance improvement !! BUt these heads (12g940) are numerous on ebay for only about £ 20 !!

[mu0u207b]

Hi there. I need to change the head anyway so i think the extra effort for the 1275 is worth it. Does David Vizzards book say about how to pocket the block? Is it something that canbe done at home with a drill? How much depth does the pockets need to be. Any instructions and help would be brill. Where can i get the rocker gear from and what price and what modifications need to be done to the water pump to clear things?

[rayofleamington]

Where can i get the rocker gear from and what price

I got my last one from a Mini rally autojumble - Cost a fiver and the rocker shaft wasn't worn so was a bargain. I dread to think what a complete new assembly would cost!

[Cam]

I think my new Ital one was about £30 from MED...

[bmcecosse]

The pockets need to be 1/8" deep (under the ex valves only) - yes I do it with a leccy drill and mounted points - but this will raise a howl of protest from some who insist it can't be done !! The rockers are the same - it's just the alignment to sit directly above the valves that's a little different. So if you have a spare hour or so - you can re-arrange your existing rockers to do the job. The water pump just wants a very small amount filed off the top edge to make sure the head can sit right down onto the block. Note some 1275 heads have no bypass hose - this is a blessing ! However it means you will have to blank off the connection on the old water pump or get a new one with no by-pass hose connection.

[Kevin]

a 1275 cylinder head for about 180 pound plus surcharge

That price will be for an exchange one so dont be surprised in the extra charge is quite a bit.

[mu0u207b]

Hi guys. With the machining of the pockets what size and shape pockets are we talking about, and what drill bit was used to machine the block. Are the bit used for grinding suitable or would i need some thing else. Vizard doesnt seem to go into great lengths at what work is required, is there anyother books or websites that are good on this. Cheers

[bmcecosse]

I use mounted point grinding stones ion the leccy drill. You need to take the head off - scribe round the gasket, take all the head studs out, mark off where the exhaust valves will hit the block, plug up the bores and all the holes with greasy rags - lots of them - and then grind little pockets into the block under the ex valves. Then clean away all the debris - remove all the greasey rags, put the studs back in, fit a 1275 gasket, and fit the new head !!

[Kevin]

Vizard doesnt seem to go into great lengths at what work is required

Because he assumes that anybody undertaking such a mod has the engineering know how to carry it out, its not a job for the novice.

[bmcecosse]

It's not difficult - only takes about 30 mins after the head is off and the studs removed - which should be done anyway to clean the block surface. However - I have to say it is easier to simply have the exhaust valves set down into the head by the 1/8" - this would need a valve seat cutter - which is something I still don't have. But it saves mangling the block - and although there will be a slight power loss due to the deep-set valves - this will be hugely offset by the huge power gain from the fitting of the 12g940 head !!

[michael.bob]

Hi, very interesting read as I am needing to replace the head on my 1098cc engine also in my traveller. Does anyone have photos of this pocketing?
cheers, michael.

[bmcecosse]

I took a spare 940 head into work yesterday and got the toolmaker to cut the exhaust valve seats down into the head by 80 thou. He did this in minutes using a 45 degree 'countersink' mounted in a pillar drill ! The 80 thou will be plenty since I intend using the MG Metro cam which has the same lift as a standard cam (but much better timing). I then tidied up the head at home - grinding away roundabout the recessed seats to ease the gas flow into them (and doing some of the basic tuning work on the throats etc) - and have now ground in the valves - super seats !! Send me your email address and i will drop you a picture or two. The 'countersink' should be easy/inexpensive to buy (I am looking into this now) - and any pillar drill will do - he simply centered on the old seat - allowing the head to float underneath - and then allowed the tool to cut down the required amount. This is MUCH easier than making the pockets - and means the head can just be bolted on. The water pump MAY need a little metal filed off the top edge just to give the head clear air - two minutes with a sharp file - and the 1275 rocker gear is exactly the same as 948/998/1098 rocker gear, EXCEPT the rockers are slightly differently spaced. So, all you have to do is strip it all off and re-assemble using washers and/or some filing of the edges of the rockers (or pillars) until the rockers align properly with the valves in the 940 head. It takes a little while to get it right - but it's not difficult - and quite satisfying when the job is finished ! Just make sure the pillar with the oil hole still lands on the oil feed from the head !

[wanderinstar]

Roy,
When you did this grinding round the valve seats and head, did you do it with an ordinary drill or with a flexible drive shaft. Can you send me some photos please.
Ian.

[michael.bob]

Hi my e-mail adress is float7@hotmail.com
I would love pics please.

[bmcecosse]

I just used my standard leccy drill - a cheap one ! Used it like this for years - the bearings are beginning to go, but I think it only cost £10. I do have a flexi-drive but to be honest it's more trubble than it's worth. Very important to NOT touch the valve seats when doing this grinding. I will try to get some pics later on this week.

[mu0u207b]

Ho there guys. Im still going to go down the pocketing route as that probably best suites me. Ive had a look on ebay and there a mini A+ rocker for a 1275cc, would that be suitable for the 1275 cylinder head? Could i use one of those small grinding tools bits to suitably grind out the pockets, the type used for grinding polishing etc? Also i need a new water pump anyway so what water pump could i get that is blanked off at the bypass and will bit the moggie, or shall i go for standard and blank it off myself?

[bmcecosse]

Water pump for Metro has no bypass connection. I assume you mean Dremel ? Far too small - just a model making toy really ! Leccy drill and mounted points - but really - the sunken exhaust valves are much easier and a lot less messy.
I got some photos last night - will send them tomorrow.
The rocker gear on the A+ engine is a complete cheat ! They just used very wide sintered rockers and allowed them to operate off-centre on the valves ! I re-aligned an older set tonight - took me about an hour I suppose. The older 'pressed steel' rockers are actually much more reliable than the later sintered ones. The first set i stripped had a worn shaft - but the second set was much better. Ideally of course - a new shaft should be used ! The rocker bushes rarely wear - the shaft goes first - just as well because new bushes are a bu99er to fit and then need reaming.

[Packedup]

Metro pump has indeed no bypass. I've fitted an MG Metro* pump to the 1098 pickup engine, blanked off the pipe in the head, and drilled half a dozen 3/8 holes in the stat. Should be fine, but it's a while till the engine sees the road.

* The pump fitted was listed for the MG Metro, but it was most likely a generic Metro/ Allegro pump. It did have a larger impellor with pressed (I think) instead of cast blades. In theory I suppose that will make for a slightly lighter mass and greater pumping, but I doubt there's any real benefit in that area. The main advantages were doing away with the bypass hose, and having a larger impellor as the pickup will be mostly used in heavy small town traffic.