turbo standard A+
Turbo Mini Forums

hi all im new to this forum. Im away to build myself a turbo mini and am finding it quite hard getting hold of a cheap mg turbo engine for rebuild. I plan to bore it out slightly and uprate cam, pistons, head, gearbox, dropgears etc.
Can i get a N/A 1275 A+ engine and once built with turbo pistons etc fit a turbo plenum, manifold, carb etc... or is it best starting out with the complete turbo engine? I have rebuilt a few mini engines in the past (1340, 1380 etc..) but never a turbo so am slightly unsure on a few things.

Im presently driving a Nissan 200sx running about 250bhp at 0.9bar and hope to get similar torque/acceleration from the mini if not more.

thanks for looking

Dan

You can start with any block, they're all pretty much the same.

Firstly welcome buddy to the BEST MINI & TURBO MINI SITE IN THE WORLD!

you may be wise if you can drop on a complete engine & box with all the ancillaries
fuel pump plenum turbo etc...ect... but these are becoming rare now!

As it will save you time & trouble scouring the land for ALL those bits!

the turbo engine differs slightley

(ie) from, better pistons a plain btm bearing on the mains but you can always have machined a tang in there.

The standard main bearings on A N/A Engine are ok for power levels up to say…
135bhp……ish…. If a turbo pump is used

the turbo motor sports a better oil pump than NA engines

in the cylinder head department it sports sodium cooled exhaust valves with a slightly larger stem diameter

( but most of us don’t use these as the 214n stainless valves are more than up to the job)

& in the gearbox department a slightly larger 1st motion shaft nose bearing!

it sports a slightly higher final drive crown wheel & pinion 3.2:1

most chaps on here use a N/A A+ PARTS and you still have a motor just as good!

Some chaps on here have seen power levels in excess of 220BHP!!

Good luck!

thanks for the great reply ben and i have to agree the site looks top notch.
I understand most of what you say apart from the plain bottom bearing bit. is this just where the groove in the shell clips into the block or am i way off. Is it essential to have the plain type for high power engines?
Im planning a full rebuild/rebore on the engine using uprated pistons, cam etc....
Now i just have to decide if i want overbore +20,40, 60 or a full blown 1380 although i hear they can cause problems due to the cylinder walls being too thin. Do many people on hear have 1380 turbos? I plan to run with scoobies etc so want a very fast but reliable motor.

Cheers

Dan

Plain bearing gives more area against the crank,rather than approx a quarter of the width being a groove

1293 is the normal way to go as you have a couple of rebores.
1380 possible but a lot of work needed to get large combustion chambers/piston dish to get c/r down for high boost pressures

Edited by Dangerous on 3rd Nov, 2005.

Metro turbo weekend driver,Mini turbo in the making again!

Hi Dan

You are in the right place there is plenty of information on this site!

Along with what the guys above have said, spend some time reading old posts on the forum, there is a wealth of info out there for you to learn about!
Good luck.

you can get plain bottom mains for either type of main caps

always looking for them bigger bunches of bannanas

hoggy i did not know that?

daniel, the Leyland engineers calculated that if a plain btm bearing was used ther would be 80% more axial load carrying the idea was pinched from ford

the turbo metro on the btm main caps the captivation tang was machined in the center for the plain bearing unlike the N/A engines

but turbo hogster has enlightened me now you can get both tang type with the one at the side! in plane main bearings ( great )

the original turbo oil pump is no longer in production but...... THE pump to use is the turbo powerflow pump from avonbar and nothing less!

if you are planning to run with scoobies ! (thats no good)...............lol

you have got to beat them!!!!
THATS EASY!

regarding the block which size??? well the choice is yours

there are pistons available for all sizes with piston dishes CCs available to place you in the right ball park regarding the C/R available from Mr AVONBAR!

Edited by BENROSS on 4th Nov, 2005.

yes tom radial!

NOW placing the kettle on!...............lol

also not wishing to confuse you here is a peice i found on a website some time back which should educate you fully.





"Turbo" main bearings were designed by Leyland’s engineers to meet a perceived need. It was decided probably by both theoretical calculation and practical test that the turbo Metro engine with its increased bearing loads needed a better bearing, so what they did was remove the oil groove from the bottom bearing shell giving roughly 30% more bearing area. It is claimed that this gives about 80% more load carrying capacity, exactly how 30% more area gives an 80% increase in capacity I’m not sure but this figure is widely claimed in both Minis and other engines and is not disputed. O.K if it is possible to remove this groove one must wonder why it was there in the first place? To explain that you need to know a little of how the engines lubrication system works; Oil is pumped through galleries in the block to the main bearings, it passes through a hole in the bearing into the aforementioned groove, from here it flows sideways across the bearing, some of it leaking out the sides, the rest is forced into holes in the crank, travels through the crank and exits through a hole in the big end journal where it lubricates the big end / conrod bearing before leaking out the sides.
Now the next step is to think about what happens if we remove one of these grooves, remembering that turbo bearings still have a grooved top bearing. As the hole in the crank passes the grooved top bearing oil flows through the crank to the big end, no worries here but as the hole passes across the non- grooved shell there is only a gap of 0.002" for the oil to flow through therefore very little if any oil is fed to the big ends during half of every revolution, whether there is sufficient residual oil is debatable I think there isn’t.
O.K. so why don’t all the turbo Metro engines suffer bearing failure? The reason is the main bearing journals are "through drilled" that is to say that they have two oil holes 180 degrees apart so while one hole is in the non-grooved bearing the other hole lines up with the grooved bearing. Why am I telling you all this ? Not all Mini cranks have "Through Drilled" main journals! Fortunately most of them are but I have seen nitrided cross drilled "S" cranks that are not.
So if you are building an engine or having one built and the subject of "turbo" bearings comes up have a good look at your crank before proceeding. This matter is not something that I thought about until an engine I built had a big end failure, and after talking to a number of other engine builders they had not thought about it either. The cause of my big end failure has not been determined but I am almost certain that "turbo" bearings played no part in it. There aren’t a huge number of engines around using these bearings probably due to the price and the hassle to modify the block to fit them,but I haven’t heard of any failures. In fact I have used successfully myself, but only with through drilled cranks.
I am not suggesting that there is anything wrong with "turbo" bearings at all, just saying look before you leap. You have been warned

Edited by BENROSS on 4th Nov, 2005.

I thought with a mini being so light and running relatively small wheels it would manage to out accelerate an imprezza to about 60 atleast?
I remember a mate having a professional built 1380 a few years back and its sheer torque was immense, it would spin wheels in 4th when it was slightly wet but this was no doubt down to cheap tyres aswell though.
Im driving a partially modified Nissan 200 just now but even that struggles to keep up with them so maybe i am hoping for a bit much.
I just want to show people what a classic british car is all about.

Dan

With a turbo you can spin in fourth on the dry. But, only if it's got "the special mod."

It's called having a badly set-up car. If wheels are spinning, progress is slow. Impresses the jail-bate in McDonalds mind....

well i got plain bottom half of the bearings for my N/A block when i went to turbo power , you just tell the supplier which type of tab you have.

i think the either made turbo's at some point with NA blocks or the other way round.

dave i no were you spend your sat nights now then mate lol.

always looking for them bigger bunches of bannanas