21 replies to this topic

[rally515]

Hi folks,

 

 Just wipped the head off of an engine i have for inspection pre re-furb and im un-able to find details of the piston numbers and also the head stampings are to one side as apposed to the centre area under the rocker

 

Just wondering if anyone could shed some light on what i,ve got and what its for ?...

 

Piston numbers: "FRONT M2007 A51"

Head Casting: 12G202

 

Thanks in advance,

Cliff

[lrostoke]

according to Calvers casting list 12g202 is off 997 cooper and Austin 1100

 

although could have been retro fitted

[rally515]

according to Calvers casting list 12g202 is off 997 cooper and Austin 1100

 

although could have been retro fitted

 

Theres no 10th and 11th studs on the block or head so can't be a cooper can it ? i thought coopers were all 11 stud :/

[Cooperman]

The Cooper 'S' had the 11-stud, well 10 studs & 1 bolt actually.

The 997 & 998 Cooper was a 9-stud engine with a 12G206 or 12G295 head. It is also possible that the 12G202 head was fitted. I don't have a definitive list of heads to blocks for 997/998 Cooper models. The 1100 engine also had the 202 head, I think, but I could be wrong.

[rally515]

The Cooper 'S' had the 11-stud, well 10 studs & 1 bolt actually.

The 997 & 998 Cooper was a 9-stud engine with a 12G206 or 12G295 head. It is also possible that the 12G202 head was fitted. I don't have a definitive list of heads to blocks for 997/998 Cooper models. The 1100 engine also had the 202 head, I think, but I could be wrong.

 

Ahh intresting, guess you learn something new everyday everytime coopermn comments

 

I'l upload some photos if it may help, definatly small bore i think due to tappet chests

[Cooperman]

The 202 head is a good head for a 998. It's not as good as a 295, but if gas-flowed with the valves de-shrouded it can perform equally as well as a slightly modified 295. Bigger valves can be fitted. The only problem can be that if fitted to a 998 with dished pistons or flat top ones which sit too far down the bores, after re-shaping the combustion chambers it is easy to break into a water-way when skimming the head surface to get the correct compression ratio. That's something I remember from the 60's. At my age I don't remember much, but I do remember that!

[rally515]

I did turn the engine over and thought the pistons were going further down than normal but i guess you cant tell by eye can you ?

The previous owner said his old man thought it was bored out to 1300 or similar a while back but im not sure if its been touched atall

 

Theres no tag on the back of the block or anything id call cooper so im guess its a 1000cc or 998ccblock with a fancy head on ?

What is bugging me is the piston numbers, i usualy can find then from an internet search but im getting nothing from this o thought id ask you guy and guru's

 

Anyways here are some shoddy late photos haha:

 

Sorry again about the quality :/

[Cooperman]

That is probably a 1098 engine, judging by the engine number tag. I notice the pistons are dished too.

Measure the stroke and bore diameter to ascertain the cubic capacity. It was possible to take the 1098 out to around 1200 cc, but of course, it still won't rev like a 998 or a big-bore engine. For a bored out small-bore engine the best option is a 998 bored to +0.080" which gives 1060 cc and still has the ability to rev to up to 7000 rpm if properly balanced and lightened.

[lrostoke]

its a 1098...engine number starts 10H

 

don't oversize pistons usually have + whatever thou oversize stamped on.

Edited by lrostoke, 28 August 2013 - 08:47 PM.

[rally515]

Ahh right so the previous owner wasnt far off then haha

Cheers again

 

 

its a 1098...engine number starts 10H

 

don't oversize pistons usually have + whatever thou oversize stamped on.

 

I know aftermarket pistons do (laser etched ?) but arnt these somesort of stock piston ?

 

Another thing is the "A" 's, theres the letter A stamped all over the engine including the block mating surface which i find odd

[Cooperman]

When over-bored to give a big capacity increase I seem to remember that Hillman Imp pistons were used.

Could they be from an Imp I wonder.

 

Edited to add that when I last worked on an Imp engine I seem to remember the pistons were flat tops.

Edited by Cooperman, 28 August 2013 - 09:03 PM.

[rally515]

When over-bored to give a big capacity increase I seem to remember that Hillman Imp pistons were used.

Could they be from an Imp I wonder.

 

What ? haha this is intresting, didn't think you'd be able to mix and match like that for some reason or another, i'l have a ganders around the web now

[Cooperman]

I think with Imp pistons the block has to be offset bored in the same way that taking a 1275 out to 1380 requires offset boring. It may be necessary to machine the block deck down a bit so that the pistons come right to the top of the bores.

A 1200 engine would give a lot of torque, but the rev limit would still be about 6000 rpm, maybe 6300 if all lightened and balanced and with a centre main cap.

It would be interesting to build such an engine with, say, a 266 cam and 10.2:1 C.R., etc.

[rally515]

Just been reading up and the imp pistons seem to be machined out in anyway but a dish so that rules that out, although for future reference imp pistons can be used in the A-series with Offset boring like cooperman's just stated and using Minor conrods in many cases it seems with one guy replacing the gudgeon pic and circlip with a teflon bush.

 

Wish i could afford to build a performance engine cooperman

[Cooperman]

Can you post a link to the Imp piston stuff as I would like to read up on it. It's a long time since I heard about Imp stuff.

 

I think the guy must have fitted Teflon plugs to replace the circlips, as you can't really have Teflon gudgeon pins  .

 

You could call F.W. Thornton of Shrewsbury as they might be able to identify the pistons you have.

 

There might be the basis for a really good engine there, especially if the bores are good and just new rings are needed. Might just need a good hone. The head will be easy to improve by some gas-flowing, valve de-shrouding and larger inlet valves. Add a good 2nd hand MG Metro cam and it'll be a nice engine.