12G940 -> 948

Post by **Onne** » Fri Oct 13, 2006 6:46 pm

I happen to have this 12G940 head.
Will this fit to my 948, as a straight swap?

Or should I stick to a skimmed 12G202?

Onne

Post by **Onne** » Fri Oct 13, 2006 9:56 pm

Apparently I have got a big valve 12G940.

Valves are roughly 29mm and 35mm

Post by **Peetee** » Fri Oct 13, 2006 10:57 pm

Advertise it well and you could sell that on ebay and get enough for a 12G295 head. This would give a useful power boost without the hassle of machining the block.
A 948 with 12G295 and 1.5 carb/manifold set up is a very, very nice combination.

Post by **Onne** » Sat Oct 14, 2006 7:31 am

Will ask for a 295, I am sure my friend as those too

Post by **bmcecosse** » Sat Oct 14, 2006 5:20 pm

The 940 you have is ex MG Metro (or Van den Plas version) - the inlet is a wee bit big for a 948 but it will work. You don't need to machine the block - just have the exhaust valves sunk into the head by .040 " (1 mm !!) - and all will be well. It's a great head - far sperior to the 295. Good 295s sell for about £70 these days - your 940 is worth about £30 - it's not 'unleaded'(neither is the 295 unles it has been modified with seats). Use the 940 with a 1275 head gasket - and you must either use the 1275 rocker gear - or spend some time re-aligning the rockers from your 948 engine so they sit directly over the exhaust valves. It doesn't need any skimming - the CR will be fine. If you go the 295 route and get one for a fair price - it does need skimming - .060" (1.5mm) - which can be costly.

Post by **Onne** » Mon Oct 16, 2006 2:03 pm

Just to conclude:
I have now got a 948 block (+0.030 pistons)
1098 standard cam
12G940 head

only need the 803 air filter housing to make my inline A-series series complete

Onne

Post by **d_harris** » Mon Oct 16, 2006 5:46 pm

I didn't think the big valved head was suitable............

Post by **Onne** » Mon Oct 16, 2006 5:54 pm

It seems to fit... all the holes match up, even the four big ones!

Post by **bmcecosse** » Mon Oct 16, 2006 7:15 pm

But with that cam - you MUST sink the exhaust valves by 40 thou.

Post by **Onne** » Mon Oct 16, 2006 7:34 pm

Will do the sinking. Is it better to pocket or to sink?

Post by **chrisd87** » Mon Oct 16, 2006 8:34 pm

only need the 803 air filter housing

Are you planning to use the oil bath filter unmodified? I'm sure they don't flow awfully well, so perhaps it would be best to use a later filter or a K&N? Otherwise the improvements in the head breathing may be cancelled out by the inefficient filter.

This sounds like an interesting project. What sort of hp are you hoping to get?

Post by **Onne** » Mon Oct 16, 2006 8:42 pm

I don't know yet...
But I think I have a 1098 to go in too... maybe that will get the 940 head

Onne

Post by **Packedup** » Mon Oct 16, 2006 8:44 pm

Onne wrote: I have now got a 948 block (+0.030 pistons)

Is that the one from me?

Or is that the most recent one you referred to killing?

Just curious

Post by **Onne** » Mon Oct 16, 2006 8:48 pm

Its yours all right
Very nice engine, had a lot of work done on it too. Feels really nice and tight. No play anywhere

The engine that is dying is from "%%"$^^&"%&* oops I am not allowed to say that

Post by **bmcecosse** » Mon Oct 16, 2006 8:53 pm

1098 with 940 head and HIF38 on MG inlet should be good for ~ 65 bhp.

Post by **Onne** » Mon Oct 16, 2006 8:59 pm

Cool, which exhaust system would you use then?