Morris Minor Owners Club

I have just aquired a 1275 metro unleaded head (from a 1990 car). Will there be any problems using this on a standard 1275 spridget engine (except the water pump/bypass hose and heater)

thanks

Matt

Bolt straight on. Be glad there is no bypass hose - either plug the pump or get a Metro pump. Just drill 2 x x 1/8" holes in the rim of the thermostat to allow water to circulate - but for best heater in winter use an 88 stat with NO holes !

I have just aquired a 1275 metro unleaded head (from a 1990 car).

Does this have larger valves than a Ital head?

No - same size. Only the early unleaded MG Metro head and the rare genuine Cooper S 12g940 (10 studs + 1 bolt fixing) had bigger inlet valves. The even earlier Cooper S head - AEG 163 - had bigger inlets AND bigger exhausts. They had a tendency to crack between the valves (but not as badly as the even earlier AEG 148 Cooper S head !!) and hence the adoption of the slightly modified 940 head on the last run of 1275 Ss. However - since some of these didn't even have the proper EN 40B nitrided crankshaft - they are somewhat despised by the Mini lads !!

Whoops, I made a slight mistake, its a head of a 998 metro , however it is unleaded I am assuming its the same instaling it on a 1098 as mentioned above, but will there be any power benifit/restriction over the standard head? (at the moment it has standard carb, inlet mani, exhaust etc, although I might start playing).

Power LOSS. The 998 head has smaller inlet valves and ports - so you will lose power. Look for a 1275 head - loads of them on ebay !
Just re-read your post - it will be HUGE power LOSS - the 1275 head has much bigger inlets and bigger exhausts than the 998 head. The 998 head however could be used on an 803 or 948 engine - and it makes a good door stop.

You might have misunderstood, I was asking how the 998 head stacked up against a standard 1098 one (for some reason its not in my copy of vizard)

Inlet valves are smaller than the 12g202 - 1098 head - so power loss. If it's a decent head for a 1098 that you seek then Wanderinstar may still have the 12g206 head - with bigger inlets - in the For Sale section.

Wanderinstar may still have the 12g206 head - with bigger inlets - in the For Sale section

Be aware that is is difficult to find the inlet valves for this head (and the 12G295) should they need replacing.

No I am more interested in the unleaded bit of it.... If I attack it in the way vizard suggests eg, deshrouding the valve and streamling the ports will that bring it up to the standard of the 12g202?

Well you would need to fit the bigger inlet valves and do lots of work on the ports etc. Inlets for 12g295 - if they really are hard to find - just use valves for the 1275 engine and have them turned down slightly. But inlet valves last for many many years without problems. The ones in my 295 head have been in steady use for 40 years now that I know of ! Don't worry too much about the unleaded bit - just run it ! I think Rover just used a better exhaust valve - no special seat fitted that I know of. So you could pinch the ex valves from your 998 head and put them in the 206 head.

I want unleaded, thats why I shelled out the £35 for the head. I am not looking at increasing performace ove standard, I just wondered if it had the potential to do so. What I was asking is if I do the vizardy stuff will it be comparable to a bog standard 12g202.

Yes - if you fit the bigger inlet valves ! But the 'unleaded' 998 head has smaller ports too - so it will be lots of work - but at the end it can indeed be made the same. Personally - I wouldn't think it to be worth it ! And 998 A+ heads go for very much less than that ! I sold a complete good running engine with unleaded head for £20 - lucky to even get that - they are ten a penny ! Often offered 'free' on Mini forums. If you REALLY want unleaded - then search for a 1275 unleaded head - about £20 on ebay - that will give you a real performance boost. But you must either sink the exhaust valves into the head (I have just had this done) or make little pockets in the block under the ex valves. Pockets are best - sinking is much easier !

Methinks looking at the original post this is a head to go on a 1275 engine, so the problems with fitting a 12G940 to a 1098/ 998 block don't apply, but the performance issue of putting a small valve 998 head on a 1275 block do

Personally I just wouldn't bother fitting a 998 head to a 1275 block - In fact to date I've just stuck super unleaded in my (Triumph small 4) cars and lived with it. I don't do high miles or sustained high revs though, but on the bright side the valve seat recession happens right where you'd be cutting out for unleaded inserts anyway - So if it is a problem, it saves a tiny amount of machining ;)

There should be plenty of 1275 unleaded heads kicking around though, any 1300 Metro from late 88 would do. Can't remember the suffixes to look for off the top of my head, and Metros are starting to get rare in scrapyards (as I've found out trying to get parts for mine), but you should be able to find one without too many problems.

I am putting the 998 head on a 1098 engine. bmecosse, the inlet valves are the same size, I just took one out of a standard 12g202 and this head and measured them. The ehaust valve on the other habd is 65thou smaller on the metro head....

Ahh, your first post said you had a 1275 head to go on a 1275 Spridget engine, my mistake!

I've got a 998 unleaded Mini head spare that I was thinking of fitting to a 1098 (if I get my hands on one, now NOT looking for a Minor as I have somethnig a touch, well, bigger ), and although the valve sizes are going to mean a slight performance hit, I was more worried about cvombustion chamber size. It's been years since I had a copy of the Vizard bible, and I can't remember what the chamber sizes are across the range. Could be that what you lose in valve you gain in compression, could be the compression is pants, could be too high, I just don't know.

As for smaller ports that could result in better low end grunt (higher torque through higher charge velocity) but will obviously hurt top end breathing. Not that that's likely to be an issue as 1098s aren't revvy beasts, and Minors don't seem to be exactly high geared!

I was going to do some grinding to remove as much valve shrouding as possible and do some work on the ports

Something strange then - the ex valves should be same size (1") , and the 202 inlets should be slightly bigger than the 998 inlets. Maybe someone has been messing with these heads ? Yes the chambers in the 998 head will be smaller too - they can be 'improved' quite easily.

It doesn't matter now, i've sold it.