Cylinder head choice for 1275cc

Post by **mu0u207b** » Wed Jan 11, 2006 9:28 pm

Im looking at changing my current 1098cc head for an more efficient 1275cc. I was wondering which head was better in terms of performance and how easy it would fit to the 1098 block. I realise that pocket will need to be machined but is there any difference between the 12G295 as fitted on midget and the 12G940 head. Is one more suitable than the other. Also would a machine job be able to machine the pockets into the block and how much that may cost. Thanks

Post by **bmcecosse** » Thu Jan 12, 2006 1:31 pm

The 295 head has slightly bigger inlet valves than the standard 1098 head (which is 202 head) - and the ports and chambers are better shaped too. It has big combustion chambers - so get a decent compression ratio you would need to get the head skimmed 60 thou - but the block needs no modifying. The 12g940 head from 1275 engine has much bigger inlets and slightly bigger exhausts - it is an all round MUCH better head. It also has small combustion chambers and so needs NO skimming. However - the exhaust valves will strike the block (some say they get away with this - I know they hit) and so you can either sink the exhaust valves into the head by 40 thou - which is a 5 minute job in a mchine shop with a 45 degree countersink in a pillar drill - or you can machine little pockets in the block at the point where the exhaust valves will hit. This is how it is done on the MGB engine from the factory ! This can be done by hand with the engine in the car - you obviously need to seal everything up to keep all the crap out of the moving parts. For me - the sunk valves are the way to go, in fact I have just such a head waiting to fit to my 1098, to replace my 295 head which will be coming off. No, it's not for sale! To fit the 1275 head you need to use the 1275 head gasket - and make sure there is clearance off the water pump - it may ned a bit of filing. You also need the 1275 rockers - or re-align the ones from the 1098 engine. To get any benefit from such a head you will need a bigger carb and a decent inlet manifold (MG MEtro is good) and a decent exhaust will help too.