Post by bodieanddoyle on May 20, 2008 20:00:41 GMT
the theory of putting a 12g940 head (mastro) onto a small bore moggie lump can get a bit tangled. basically the inlet valves overhang the bores slightly. really the block should be pocketed. but some say the valves shouldn't touch on a stock lift cam. a suck it and see job TBH. if you can dig one up, you need a 12g295 head from an earlyish cooper. better off to either separate the exhaust/inlet manifold (cheapest mod). or better still throw the cast iron maifold over the hedge and stick an lcb on followed by a mg metro/minispares inlet and a hs4 carb and mg metro filter box. much better idea than messing with the head. according to winsu you pick up like 10% increase. you will need a new carb needle, I can give you a list of appropriate ones if you need.
12g295 prices can be high. I just sold one for £155 with no rockers or studs in the head! 12g940 can be fitted by sinking the exhaust valves into the head (usually by about 40 thou) and putting a shim under the exhaust valve spring to keep the pre load correct. I've never done this but many rave about it. If you can't afford an off the shelf LCB manifold you can use Leylands own LCB as used on MG metros and some Itals. It is a cast 3 into 2 manifold that uses a 2 into 1 downpipe. The downpipe and system to attach to it is available from East Sussex Minors in Sussex. Seperating the single piece cast manifold is definately worth doing.
If you fit the 940 you have to skim so much off for compression (unless you splash out on flat tops) the valves are pretty much guarenteed to hit block! Its easy to do pockets in situe with one of those magnetic drill things tho! don't ask me how i know!
If you fit the 940 you have to skim so much off for compression (unless you splash out on flat tops) the valves are pretty much guarenteed to hit block! Its easy to do pockets in situe with one of those magnetic drill things tho! don't ask me how I know!
The 12g940 head has a smaller combustion chamber at 21.4cc for all variants than the stock 12g202 head which has a volume of 26.1. It's the 12g295 that has a larger combustion chamber (28.3cc). By fitting the 12g940 head you gain a useful increase in CR.
I have a nice little pile of small bore tuning gear and now a 2" mains sprite block to stick all into
Where the hell did you find that? 2" mains 1098 is the stuff of legends.
I always fancied trying to make a 1250cc from a 1098, apparently possible using imp pistons.
I'd go for separating the manifolds as a first step. If you're determined to swap heads, go for the late Mini 998 one. It'll fit straight on and has better combustion chambers. Get one from a G/H plater and it'll be OK for unleaded as well. In fact, while you're at it get the carb and inlet manifold!