22 replies to this topic

[Cooperman]

Actually virtually all heads for 1275 engines are 12G940 castings. The only exception is the very early Cooper 'S' heads and there aren't too many of those still around as they used to crack (but I've got a fully gas-flowed one on a shelf in my workshop). The MG Metro head is a basic 12G940 casting, but it has been factory machined for larger valves. Any 12G940 can be modified to take those valves, 35.6 mm inlet and 30.5 mm exhaust.
If an engine is out of the car, before re-fitting it's always a good idea to check everything over and if it's done more than a few miles to re-ring the pistons and hone the bores. Personally I always fit new bearing shells if the crank is good, if not I get the crank re-ground and then fit new bearing shells. I also always fit new cam followers and a new top-quality oil pump and water pump.
The compression ratio is the ratio by which the mixture entering the cylinders is compressed prior to burning when the plug fires. The more you compress it, within the limitations of the engine, the better it will perform (sorry if that's an over-simplification). The ideal for a Mini road engine running standard unleaded is about 10:1 and you set this by measuring certain things and doing a simple calculation which we can tell you about when you get to that part of the build of the engine.
It's not that difficult to do an engine re-build. You do need a decent set of tools, including some special-to-the-Mini tools, but most important is having the confidence to do it yourself, albeit with a lot of help from us 'old buggers' on here; and we are all here to help and advise.
A long unused 1275GT engine is probably worth about £200 if it's complete with gearbox.
I hope this helps.

[Jumpinjacks]

Thanks for that cooperman, all the help is much appreciated.
Would it be possible for you guys to tell if the crank is good from pictures when I strip it? As I won't know what is good and bad, unless very obvious.
What would you value the engine im considering with the spec mentioned and gearbox?

[Cooperman]

You need to find a good machine shop used to doing small classic car engines in your area. Then take the crank to them and they'll inspect and measure it. A re-grind is not expensive and then you'll know it's good. Also take the cam for close inspection of the lobes and the block so that the bores can be measured for excessive wear. You just need someone who knows their way around the Mini engine to advise you. Now, who else on here lives in Cornwall? ('Bungle' seems a nice guy and very knowlegable, perhaps he might help).
That 1275 could be built into a very nice engine if done thoroughly and it would then last for a long time in a road car.
I would value it at c.£200 including the gearbox, maybe £250 tops.

Edited by Cooperman, 15 October 2011 - 04:52 PM.

[Jumpinjacks]

I have just checked and the crank and rods were reground when the rebore was done.
It was all done about 25,000 miles ago.
How much life does a cam and crank have on average?

[mab01uk]

I have just checked and the crank and rods were reground when the rebore was done.
It was all done about 25,000 miles ago.
How much life does a cam and crank have on average?

Crank and cam should be fine at this mileage if it has been looked after with correct oil and filter changes, etc. Average life of a Mini cam/ crank/ engine is probably 80-100,000 but can be much more or much less, as it is very dependent on the way an engine is driven and maintained during its lifetime. Tuned and modified engines do tend to have a shorter life than standard due to increased stresses and harder driving.

Edited by mab01uk, 16 October 2011 - 02:54 PM.

[govig]

I think I have just bought the 1300GT engine jumpinjacks has been on about as his description matches mine exactly. I'm just hoping that it doesn't need another rebore as its already at +60........

[Jumpinjacks]

So you was the bugger who outbid me

[govig]

Aye, but this motor might be a crock of ****. I'll let you know when it's in bits . You might have the last laugh after all......