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standard 1275 head vs cooper s head
https://www.ausmini.com/forums/viewtopic.php?f=2&t=84591		 Page 1 of 2
Author:  loveb [ Sat Feb 15, 2014 7:13 am ]
Post subject:  standard 1275 head vs cooper s head
question,

nissy has a 1275 in it now... but not from a cooper s.. And I've just got a cooper S head that can run unleaded here. Was told the 's' head is a little more aggressive? any truth in that?

would be a good time to get rockers and cams before i swap it over probably lol
Author:  goodie [ Sat Feb 15, 2014 7:43 am ]
Post subject:  Re: standard 1275 head vs cooper s head
What No's are cast into both heads , you may already have the same thing .

Depending on port & valve mods that may, or may not have been done to this head , it might be a heap of work for nothing . Do you have any details of your engine specs from previous owner ?

From previous posts , it sounds like you already have a nice performing engine as it is .
Author:  drmini in aust [ Sat Feb 15, 2014 8:28 am ]
Post subject:  Re: standard 1275 head vs cooper s head
A 12G940 Mk2S head is same as a Morris 1100S one, with the following changes:
2 extra stud holes drilled- 1 each end,
bigger intake valves 35.6mm,
double valve springs,
possibly a bit of deburring inside?
stamped 12G1805 in 1/8" letters, on top near the thermostat.

Mk1 heads were an AEG163, valves were shorter, exhausts were bigger, valve guides were bronze.
They worked well but tended to crack between the valves. Many have since been replaced with a 12G940 ,which are more crack resistant.
Author:  loveb [ Sat Feb 15, 2014 12:25 pm ]
Post subject:  Re: standard 1275 head vs cooper s head
the engine i've got now runs great really.

I planned on getting this head long ago as it has hardened seats and what not so I can take unleaded. but ive been putting unleadead premium into the one I've got now.

The one I just got has just been rebuilt though. So I suppose in that sense its 'newer' when the rain stops I'll take pics of both and go from there.

So not sure if worth swapping straight over or if I should make this head more aggressive then get a weber lol
Author:  timmy201 [ Sat Feb 15, 2014 1:26 pm ]
Post subject:  Re: standard 1275 head vs cooper s head
You should need the lead replacement Valvesaver fluid, not just the premium to help stop valve recession
Author:  drmini in aust [ Sat Feb 15, 2014 2:33 pm ]
Post subject:  Re: standard 1275 head vs cooper s head
timmy201 wrote:
You should need the lead replacement Valvesaver fluid, not just the premium to help stop valve recession

Valvesaver coats the plugs, ports and valves with brown crud. I have seen plugs shorted out by it.
I find Flashlube is much better. Valves and seats stay clean & smooth, no crud on anything, last time the head came off I just wire brushed the valves and refitted them. No lapping needed.

A 1L bottle does 1,000L of fuel, so fuel cost is only ~1.6c/L extra.

http://www.flashlube.com/en/products/va ... fluid.html
Author:  AWOODY [ Sat Feb 15, 2014 7:03 pm ]
Post subject:  Re: standard 1275 head vs cooper s head
Valvemaster and flash lube etc I don't think work , just put hardened valve seats in , recession can depend on the quality of the metal in the head, why would one end of the head recess 4mm more than the other?
Author:  Tadhg [ Sat Feb 15, 2014 8:11 pm ]
Post subject:  Re: standard 1275 head vs cooper s head
Throw on the AEG163!!! IF it's an AEG163. Yes, stock against stock, they flow better. And if it has hardened inserts in it, it's less likely to crack between the valves than stock, which is one of only two reasons you wouldn't throw it on. One being cracking, the other being that AEG163's aren't common, can be worth a bit, and aren't something you want to damage.

My 1100S block has an AEG163 on it. It has hardened inserts in it. It's been pretty heavily ported. I run it on straight (premium - 98) unleaded. No issues. It's a great head. :)

New rockers and cams, you can do the rockers anytime. Cam, isn't that still an engine out job for a 1275..?
Author:  Mick [ Sat Feb 15, 2014 8:31 pm ]
Post subject:  Re: standard 1275 head vs cooper s head
On the AEG 163 inserts thing, how do they get them in and machine the seats given they are so close to the inlets? Do they interfere with the inlets?
Author:  Tadhg [ Sun Feb 16, 2014 1:58 am ]
Post subject:  Re: standard 1275 head vs cooper s head
I've no idea, I just know my AEG163 has them. I don't do photobucket, I'll email you a couple of photos. When I did my head gasket, I did it at 1018cc's place, so he can verify that the head has inserts.
Author:  Mick [ Sun Feb 16, 2014 8:01 am ]
Post subject:  Re: standard 1275 head vs cooper s head
Thanks, I've got a AEG163 head here without cracks. I took it off as a precaution and because 940s are easy to come across.

I wouldn't mind recommissioning it however.
Author:  loveb [ Sun Feb 16, 2014 10:46 am ]
Post subject:  Re: standard 1275 head vs cooper s head
so its not an S head from factory. But its S specs with bigger valves. Looks to be in good nick to as per mick.

Might put it on in the future. along with 1.5 rockers. lol
Author:  lockwood [ Sun Feb 16, 2014 4:40 pm ]
Post subject:  Re: standard 1275 head vs cooper s head
The head that loveb has, IS a factory Cooper S head. The heads which were marked 1805 were late Mk11 and Mk111 heads.
The AEG 163 were no more prone to cracking between the valves than later heads, it's just that they established a reputation for cracking after a few cracked. The actual percentage of AEG163's cracking was very small
Author:  Mick [ Sun Feb 16, 2014 5:07 pm ]
Post subject:  Re: standard 1275 head vs cooper s head
I checked it out today, it sure is Cooper S in spec (with mk1S inlet valves), but has the 938 stamping behind the thermostat, not 1805.

Its quite a nice head actually...
Author:  drmini in aust [ Sun Feb 16, 2014 7:26 pm ]
Post subject:  Re: standard 1275 head vs cooper s head
Mick wrote:
I checked it out today, it sure is Cooper S in spec (with mk1S inlet valves), but has the 938 stamping behind the thermostat, not 1805.

Its quite a nice head actually...

12G 938 stamping is a Morris 1100S one.
You shouldn't run Mk1 S valves in a Mk2 head, the valve stems are too short. This limits your valve lift. Buy 1.401" Mk2 S valves instead.
I rebuilt a 940 head for my boss 20 years ago that had the Mk1 inlet valves in, the S springs got coilbound with a 544 cam and S rockers on it.
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