MG Metro Turbo cam

[edd_barker]

Hi all,

Can I drop the MG Metro Turbo cam in a 12G940 going on a 1098 block? Project not started yet but scouring eBay for parts.

Cheers

[bmcecosse]

You can - but the Turbo cam is no different to any ordinary Metro engine cam.......the one you want is the MG (NON) Turbo cam! Hard to find these days -beware of being sold a standard cam for silly money. In fact - the 1098 cam works very well with the 940 head - so my advise - just use it! DO look for a crankshaft damper .....

[edd_barker]

OK, so I wanted the MG not-metro-not-turbo cam from a 1275?

That's where I was getting confused. So not much improvement over 1098 cam?

No other radical mods planned if I can find a ported/polished 12G940 for less than the £170 most eBay sellers want.

Point noted about damper! Have read as many threads as possible on this head swap so think I'm fairly up to speed, but no doubt many questions will follow.


Thanks

[bmcecosse]

You don't need a ported head - just a nice standard head is fine on a 1098. There is NO improvement using a standard 1275 cam. Only the MG cam is any better. Or - a 266 as sold by some - but that probably has some xtra lift - that will cause problems with the valves.......

[edd_barker]

Ok now I'm really confused...

My cam is from an MG....Metro Turbo. Is this the wrong kind of MG? I'm afraid I wasn't born till the Metro had become the Rover 100, not too hot on my A-series history!

I thought the 12G940 was vastly improved after porting. This is my first engine build so most knowledge coming from this forum. Ill keep an eye out on eBay.

Thanks! Always good to learn new things.

[IslipMinor]

The cam in Metro Turbo has the same timing and valve lift as a standard 1098 Minor, 1275 Marina, 1275 Midget, 1275 Metro (except MG Metro), 1275 Allegro etc. The only advantage over the standard 1098 cam is that is has the wider 1/2" lobes, which became the standard for all 1275 cams and all OEM Metro cams, including the smaller engines as well.

The cam that Roy is suggesting is the one fitted to the 1275 MG and Vanden Plas Metro (but NOT the MG Metro Turbo), which has slightly more aggressive cam timing, but the same lift as the standard 1098 cam. The tappets are set to 0.015" for both inlet and exhaust, instead of the standard 0.012" - there are suggestions that the standard exhaust should now be 0.015", but where does this come from? Is it the later unleaded head setting? With unleaded fuel now the norm, it is probably no bad thing, as it burns slightly more slowly and can result in higher exhaust valve head temperatures. The additional 0.003" clearance gives more valve head 'seat time', so more cooling through contact with the head.

When fitting the 12G940 head to the 1098 block, there is very little clearance, sometimes negative, between the exhaust valve head and the block deck. This needs to be checked very carefully before finally fitting the head.

All the aftermarket cams from suppliers such as Piper and Kent have significantly more valve lift, even from cams with similar cam timing to the MG Metro cam. The increased valve lift makes it much more tricky to fit the head to a 1098 block, and will involve machining pockets in the block to provide the exhaust valve head clearance.

[bmcecosse]

As above -Richard must have a bit more time to explain it... The 940 is SO GOOD in standard form that it makes a huge difference to a 1098 just as it is........yes - a bit of work on the valve throats (esp the exhausts) will help it even more - but it's certainly not worth spending fancy money for a so called 'ported' head.... When you are ready to do the job - come back and ask how it's done. It's important that whatever head you buy - it HAS NOT been 'skimmed'........... The head should measure 2.750" thick.

[edd_barker]

Richard and Roy,

Many thanks for taking the time to explain that! Much appreciated, I understand now. Will stick with the cam I have.

Is there a particular type/age of 12G940 I should be after? Understand I want small valve, but A+ or not? I'll make sure to check its not been skimmed.

Thanks again,

Edd

[edd_barker]

http://www.ebay.co.uk/itm/12g940-head-/ ... NA:GB:1123

This one for example?

[bmcecosse]

That was a GOOD one - the 1300GT had the larger inlet valves - so it sold for a 'bargain' price considering the larger valves. However you will do better with the normal size valve head. Leave the large valve heads for 1275 engines! Later heads will be 'unleaded' - up to you if you think it is worth paying extra for that.....

[edd_barker]

The beauty of hindsight! I didn't bid. Will keep checking though.

thanks again

[bmcecosse]

This one ideal.... http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... ink:top:en

[brucek]

That was a GOOD one - the 1300GT had the larger inlet valves - so it sold for a 'bargain' price considering the larger valves. However you will do better with the normal size valve head. Leave the large valve heads for 1275 engines! Later heads will be 'unleaded' - up to you if you think it is worth paying extra for that.....

Going back to that 1300GT head Roy, it has the additional holes for the studs by the T/stat and heater tap housings. Can these heads be used on the 1275 Midget block which does not have these studs fitted??

[bmcecosse]

Yes of course -drill and tap the extra holes if you wish - or don't bother. Turned out they aren't needed - the turbo head has NO such provision...

[brucek]

Thanks - will look out for one to have as a spare

[bmcecosse]

But DON'T buy a Turbo head - except for turbo or supercharged application.