1275 with a blower
Turbo Mini Forums

Alright chaps,

I've been hiding in the back for quite a while building my mini since last year (all be it a couple months work)
I've always wanted to supercharge a aseries engine ever since owning my first mini when I was 12.
So took a plunge and bought a kit the other day
So got a couple questions to ask and looking for advice.
I bought a 1275 metro engine last year to go in the mini for 300 buck, banged it in the mini and got it running.
I have oil leak to sort from the half moon seal and a puff of smoke on start up (Pretty sure it's the stems) so while I plan to take the engine out to sort these problems I thought it would be prime to give it a refresh and get it ready for the supercharger.
From the looks of the engine number 12ha08aa with a metro turbo head it has a compression ratio of 9.4 and a final drive of 3.1.
I'm planning on starting on low boost then work my way up and running a mega jolt system to control the ignition.
Now for the questions
I gather I would be looking for a lower c.r of 8.3 or something along those lines?
Would I get away with increasing the chamber size of the head or would it be a mix of that and some cc pistons?
Second question is would the final drive be suitable ? I will be change the diff to a xpin to cope with the extra power!

Cheers

The number you quoted above (12ha08aa) is not a turbo engine, and no 1.3 Metro had the 3.1 iirc.
Regardless, all the factory CWPs are strong, and only fail as a secondary failure to something else.

As you need to do the half moon, take your time and give the gearbox a strip and inspect, and you may as well inspect and maybe change the main bearings & big ends as well.
And at this point, piston rings are easy to do, so why not do them as well. You need to remember this engine is at least 29 years old, and already sent one metro to the grave; and you want to add a lot more power to it!

Edited by TurboDave16V on 20th Apr, 2019.

Spending a couple hours checking what the engine number where online, that was the only information i could find! I Started to get the engine ready for removal from the bay and i doubled checking the head numbers. I'm pretty sure now it's not a turbo head just a normal 12g940. (Must of been wishful thinking)
With having a back round In machine maintenance I won't by shy with the mechanical work.
The plan is to strip and check the overall condition of the engine and box and take it from there but by all means I'm not wanting to just bang on a decompression plate and be done with it.
If it's worth doing it's worth doing right.

Edited by Struanbedgar on 20th Apr, 2019.

chances are it'll need a rebore or at least a hone, do you have access to a bore gauge? if you can get away with a hone you can use total seal rings on the std turbo pistons, (if thats what you have)

iIf your a lucky boy you'll have these part no's, whicu are the turbo ones, crank CAM6581 pistons 21254. other wise check below for piston part no's

https://www.minispares.com/catalogues/class...es.aspx?1~2~103

In terms of getting the right compression, its possible to dish out pistons a bit and find 2-3cc's, or you can get the head taken out up to 28cc wotuhot an issue ( std is 21cc). turbo phil on here is a great head guy, and reasonable prices too.

Yeah lucky enough to get my hands on a bore gauge.
Perks of working in a machine shop!
If I am lucky and it's just needs a hone but I don't think I'm lucky enough for it having the turbo pistons.
I have been looking into getting the head work and seen a lot of good reviews of his work.
If what the engine number comes back as (9.4 cr) is correct would getting the head done lower the compression enough or should I really look at getting some cc pistons as Well?
Havnt really come across many in 1275 sizes

well fisrst thing is see how the bores measure up, if theres wear ( and that pretty likly) then you'll be looking at a rebore to +20 so new pistons, and if your getting new pistons, then see what you can get in cc options, often the lager dishes are only in forged versions, so depends on your budget, depends if you can stretch to the 500 quid for a forged set, basically your options are 10cc cast, or 18cc forged.

what ever you do, I would suggest decking the block down to within about 10 thou of the pistons to improive squish, so youd need to factor that into commression calculations, and then you can get the dead chambered to suit. turbo's are a bit more forgiving on CR and most people aim for 8.5:1 allowing upto around 20psi boost with a good intercooler. with the charger youll want to aim lower, more like 8:1 for 10psi.

Signature worthy TM gold right there,

Lol!

Started stripping the motor for inspection today.
Bores look like they could get away with a hone but need to get the bore gauge and check the sizes to double check! The pistons are dished and have the number 20142 g2 h46 stamped on the top but can't seem to get any info on them?

Well finally got some time to fully strip the engine.
On inspection it looks like a good egg to use with no scoring or ovality in the bores and crank looks as good as new.
Question is I came across a set of metro turbo pistons I thought of using for the build but with the removal of the pistons that where in the engine they look exactly the same(3 ring set up) minus the skirt being longer.
What's people thoughts on these pistons?
Could I get away with running these with new rings as can get a hold of a new set.

Cheers

Hard to tell you what pistons they are from that description.

Standard turbo pistons are an excellent piston. Use those if you can.

When both pistons are side by side the piston rings line up, piston hieght is the exact same and the cc are the same ECT the only difference is the skirt.
The number stamped on the piston is 20142 which I was told was just a stock piston.
Plan is to go with the turbo ones but was wanting to see what other thought about the other pistons