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austinseven
 Post subject: Maximum skim for 12g940
PostPosted: Sun Apr 03, 2011 6:35 pm 
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How much can you safely skim off the 12g940 before you start running into problems?
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drmini in aust
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PostPosted: Sun Apr 03, 2011 6:39 pm 
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unlike any smallbore head, a 12G940 can usually take up to ~4mm off.. provided it's not corroded inside.
[edit] I confirmed this figure with Graham Russell a while ago.

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Last edited by drmini in aust on Sun Apr 03, 2011 7:38 pm, edited 1 time in total.

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austinseven
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PostPosted: Sun Apr 03, 2011 7:31 pm 
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Thanks, that is a lot more than I thought.
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GT mowog
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PostPosted: Sun Apr 03, 2011 7:45 pm 
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Just be careful with the later ones, they have a thinner deck. Check through the small coolant holes near the front of the head.

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gafmo
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PostPosted: Sun Apr 03, 2011 9:51 pm 
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What Measurement should we be looking for...I have a Few
GT mowog wrote:
they have a thinner deck. Check through the small coolant holes near the front of the head.

and are you meaning the temp sender Hole

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simon k
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PostPosted: Sun Apr 03, 2011 10:16 pm 
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gafmo wrote:
and are you meaning the temp sender Hole


I think he'd mean the little holes with the brass plug in the head face...
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GT mowog
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PostPosted: Mon Apr 04, 2011 6:19 am 
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gafmo wrote:
What Measurement should we be looking for...I have a Few
GT mowog wrote:
they have a thinner deck. Check through the small coolant holes near the front of the head.

and are you meaning the temp sender Hole

Simon K wrote:
I think he'd mean the little holes with the brass plug in the head face...


Simon has it here. On the Gasket Face there are 8 small holes on the spark plug side of the head. Check through there. It seemed to be around the time that the MG Metro and MG Turbo was introduced (~83 ish) that this happened. All these heads have the same casting number but I have come across at least 6 or more different versions. I think Phat Kat had a pic up about a year or so ago.

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Last edited by GT mowog on Mon Apr 04, 2011 6:57 pm, edited 1 time in total.

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Phat Kat
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PostPosted: Mon Apr 04, 2011 6:40 pm 
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Yeah I was just reading this... I was asking the doc what he knew about it (because I couldn't be assed diggin out alll the heads). What I found when I measured them (inc a few different post '83 heads) was that at least with the heads I had at hand, there was no serious difference.

I must point out,,, these were not new heads.

These are some of the heads.


Metro MG

Image

Late model injected head

Image

MK II Cooper S head

Image

Sorry, this one is a bit crappy... but its an MG metro turbo head

Image
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.
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.
.

And you know what? :D After digging all the heads out, and taking all the photos.... I just realised, that photographed THE WRONG BLOODY HOLES :oops: :? :lol:
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VulcanBB18
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PostPosted: Mon Apr 04, 2011 7:19 pm 
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Phat Kat wrote:
And you know what? :D After digging all the heads out, and taking all the photos.... I just realised, that photographed THE WRONG BLOODY HOLES :oops: :? :lol:


ROFL!! :lol: :lol:

Sorry it reminds me of a mistake I'd make!

Still whats the go with one of the heads there - the exhausts are *bright* white and the adjoining intake valve looks like it suffered too!

cheers

Jacob

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GT mowog
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PostPosted: Mon Apr 04, 2011 7:32 pm 
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VulcanBB18 wrote:
[ the exhausts are *bright* white
cheers

Jacob


Injection.

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gafmo
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PostPosted: Mon Apr 04, 2011 8:21 pm 
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I always thought it was measuring from the top face where the Rocker Cover was to the face of the Head and for a Guide was the section in the centre on the back of the head as per this pic

Phat Kat wrote:


Image


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drmini in aust
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PostPosted: Mon Apr 04, 2011 9:02 pm 
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All A series heads were 2.750" thick (give or take a few thou) top to bottom, if anyone is wondering.... :wink:

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:
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