Engine Dilemma
Turbo Mini Forums

Its getting to a point where my rebuild is coming together now and it wont be long until i'm looking at getting the engine in. here is my build so far

http://turbominis.co.uk/forums/index.php?p...id=312776&fr=25

I’m fairly confident with N/A carb engines, but even though I’ve been a member on this site for a long time the turbo conversion is new to me.


After spending a lot of time and money building the car how I want it, I am wondering if the engine I have put together will give the car the go to match the looks.


The current spec is this:

Low mileage non mg metro bottom end
Block drilled for 11 stud fitment
Standard crank
Main centre strap
SW5 camshaft
Duplex timing gears
High capacity oil pump

Head –

Austin 1300 gt big valve head
Valves reground
35mm inlet (original), 29mm exhaust (a+)
lightly ported and polished.
Cr of around 9.25:1
Cooper S rockers, bushed to aprox 1.4


Gearbox

Straight cut close ratio
S/c drops
4 pin diff (all tran-x)
centre oil pickup
long magnetic sump plug
2.9 final drive

Clutch/flywheel

Minisport ultra light flywheel
Grey diaphragm
Ap fast road/rally clutch plate



If I were to build a quicker engine I would use the gearbox, clutch and flywheel setup, T3 stuff for now, but would mod the block/head, as i feel that this is the weak link.

Was thinking of a 1360 overbore with hypertech pistons, reshell the crank, keep the sw5, and get a decent turbo spec head from one of the people who mod them on here.

I’m at a point in my life where I have a decent wage coming in and no commitments. However getting the current engine in and running, only for it not to do it for me, I wonder if I would regret not going for something quicker.

I was hoping for around 110 bhp from the current engine, but was thinking around 160 from a potential new one. One of the main reasons I have kept with the budget engine was in case I couldn’t get a turbo engine to run (+ with megajolt as well).

Sorry this post is a bit long. Just wondering what people think I should do.

if i upgrade to a quicker engine at a later date there would be the setup costs etc again

The only point I could make is re. the Hypatech pistons.

The 73mm ones (1360) or 73.5mm (1380) are certainly the better design ones with oil drain holes rather than slots (which are used on the smaller sizes) but they need a fair bit machining out of the dish to get the CR down.

I've machined mine to 14cc and I think Joe (mini13) has done the same but mine have not run under any boost yet (and I'm not sure about Joe's) so they may be a bit of an unknown.

Schrödinger's cat - so which one am I ???

they have held up well in both my brothers and my na engines. though i apreciate that forced induction is a different ball game. off the top of my head the cc is 6-7 cc? could i just get a load of metal machined from the head?

just did a quick calculation, 29cc head chambers would drop the cr to around 8.5:1

im guessing that this is pretty much as big as the chambers can be worked to?

ideally this is what cr id be looking at on such an engine? thanks

Fom memory, yes, they were about 7cc.

I wanted a lower CR (8.1) without taking the maximum out of the head and also had a fairly low deck volume so chose to machine the pistons and only have the head taken out to 28cc.

Schrödinger's cat - so which one am I ???

I think you'll be lucky to crack 90bhp, let alone 110, with that spec. Not enough cam or compression.

WWW.TURBO-MINI.COM

thanks for the input

the proposed engine would be run with a standard metro turbo setup plus an rs intercooler, was planning max boost at around 9 - 10 psi.

was hoping to crack 100bhp at least.

i apreciate that the pistons are not ideal, hence me restricting the boost. also the head gas flow and valves would restrict

i have read on here conflicting information about the suitability of sw5 cams on turbo motors.

with an overbore to 1360, and a good flowing large cc big valved head from the likes of turbo phil, running a cr of around 8.5, what power could be expected? what kind of boost would i safely be able to run? thanks

Edited by welshdan on 20th Feb, 2010.

I think Tom and Phil were refering to your current engine, not the proposed one.....

Well I hope they were or I'm wasting my time :)

Schrödinger's cat - so which one am I ???

lol. i meant the current one will be running a turbo. was at least hoping for the 100 bhp mark. im not going to rush into a desicion what to do. will have a think about it over the next few weeks and price up parts/machining work.

I assume Tom was reffering to 110hp in NA form, as I was.
110 with a Turbo should easily be possible.

WWW.TURBO-MINI.COM

i think thats what tom meant. maybe i wasnt clear enough in my post.

Your useing a non MG bottom end! You sure those mains are upto the job? I am saying this before I go check my manuals but the MG crank journals are some what larger than your non MG crank journals.

Please correct me if I am wrong.

Own the day

I thought all big bore journals were the same with the exception on Cooper S big ends being smaller. Unless I misunderstood your post

On 12th Nov, 2009 Paul S said:

I think Gary OS has taken over my role as the forum smart arse

WWW.TURBO-MINI.COM

are all A+ cranks not the same with the exeption of early turbo variants...

again correct me if im wrong lol

All A+ 1275 cranks are the same journal sizes. Simple.