9 replies to this topic

[george91]

Hi everyone i have 93 rover mini with a 1275 carb engine, its pretty much stock apart from a cat to back exhaust and air filter, its pretty tame for my liking and therefore i want to start tuning but i just don't know where to start! i know i am going to get a lcb manifold and link pipe, but do i go from there? Are modified or 7 port heads worth the investment?

Any advice, opinions, options would be great, i don't have a budget, so long as its not crazy money like over 2k i can work something out. please let me know where you would start and parts etc. I have noticed a lot of people opting for getting the engine bored out to 1380 but this seems quite a drastic measure?

Also as a side note i have nearly 83k on the clock now, but the engine runs quite clean and seems fine to both me and my mechanic, other than feeling quite under powered and flat, and the mixture is a little rich. Cheers in advance, George.

Edited by george91, 10 September 2009 - 03:22 PM.

[chappy]

go for a stage one kit to start,

after that it's time to look into modified heads and uprated cams. that'd give you alot of go.

after that, look at twin carbs for better throttle response,


personally, i'd go for the stage one kit, and maybe an uprated head (or get the original machined) then get it rolling road tuned. changing cams is an engine out jobbie.


1.5 rockers aren't really worth it..

after that, look at just making original better, so duplex timing chain etc. and lightweight parts to put the power down...

If your getting an LCB you don't need the 'link pipe' or 'magic pipe' with the stage one kit for 1275 you'll get an LCB, full exhaust system, uprated needle for the carb and uprated air filter.


EDIT: sorry didn't read that you'd uprated exhaust and filter! (im blind most of the time!)

Edited by chappy, 10 September 2009 - 03:42 PM.

[Cooperman]

The idea of going to 1380 seems a bit 'flavour of the month' at present. However, it's not necessary or, maybe, even desirable to go straight to 1380. There will never be anymore A-series blocks made, so anything which reduces the life of a block may be seen as undesirable. The boring work is expensive, too, if done properly and with offset bores.
You are changing the exhaust system, so the best way to further improve the performance is to get a better cylinder head. Ideally you want a nicely gas-flowed one with 35.6 mm inlet valves and 30.55 mm exhausts. Don't take any notice of this 'Stage 1', 'Stage 2', etc bo****ks, just get a head from a reputable tuner or parts supplier, like Mini Spares and make sure that the compression ratio is in the region of 10:1 or slightly higher. Also get a good alloy inlet manifold, such as a Howley, and fit an HIF44 carb (or an HS6), unless your car already has one. an HIF38 is a bit small if you have a better head and inlet/exhaust system.
Get that lot rolling road set-up and you'll notice the improvement. If and when you take the engine out and strip it, say for new rings or even a re-bore, you could fit an MG Metro cam (arguably the best cam ever produced by BMC/BL/Rover for the Mini) and bore it out to, say, 1330 cc (which gives about 4 bhp extra just for the increased capacity). With 1330 and the MG Metro cam you caould easily gain another 7 or 8 bhp in addition to what the head, carb and manifolds/exhaust have already given.
I hope this helps.

[george91]

go for a stage one kit to start,

after that it's time to look into modified heads and uprated cams. that'd give you alot of go.

after that, look at twin carbs for better throttle response,


personally, i'd go for the stage one kit, and maybe an uprated head (or get the original machined) then get it rolling road tuned. changing cams is an engine out jobbie.


1.5 rockers aren't really worth it..

after that, look at just making original better, so duplex timing chain etc. and lightweight parts to put the power down...

If your getting an LCB you don't need the 'link pipe' or 'magic pipe' with the stage one kit for 1275 you'll get an LCB, full exhaust system, uprated needle for the carb and uprated air filter.


EDIT: sorry didn't read that you'd uprated exhaust and filter! (im blind most of the time!)

Thankyou chappy, the only thing is that i won't use a kit due to the fact you stated that the exaust to cat and filter is already uprated, maybe i'll get an uprated needle for the carb and then look at saving for a new head.

The idea of going to 1380 seems a bit 'flavour of the month' at present. However, it's not necessary or, maybe, even desirable to go straight to 1380. There will never be anymore A-series blocks made, so anything which reduces the life of a block may be seen as undesirable. The boring work is expensive, too, if done properly and with offset bores.
You are changing the exhaust system, so the best way to further improve the performance is to get a better cylinder head. Ideally you want a nicely gas-flowed one with 35.6 mm inlet valves and 30.55 mm exhausts. Don't take any notice of this 'Stage 1', 'Stage 2', etc bo****ks, just get a head from a reputable tuner or parts supplier, like Mini Spares and make sure that the compression ratio is in the region of 10:1 or slightly higher. Also get a good alloy inlet manifold, such as a Howley, and fit an HIF44 carb (or an HS6), unless your car already has one. an HIF38 is a bit small if you have a better head and inlet/exhaust system.
Get that lot rolling road set-up and you'll notice the improvement. If and when you take the engine out and strip it, say for new rings or even a re-bore, you could fit an MG Metro cam (arguably the best cam ever produced by BMC/BL/Rover for the Mini) and bore it out to, say, 1330 cc (which gives about 4 bhp extra just for the increased capacity). With 1330 and the MG Metro cam you caould easily gain another 7 or 8 bhp in addition to what the head, carb and manifolds/exhaust have already given.
I hope this helps.

Thankyou very much Cooperman for your help, i think that i am more than happy sticking with my 1275 for the time being now you have said that, i have always thought it was a very big job for not a major power increase, maybe once the rest of the parts have been bought i can look at bolting them to a bored out engine, but i think i would rather have a 1275 engine and 7 port head, than a 1380 with a 5 port head! Once i have the exhaust mainfold then i guess the head is the next thing on the list, and after look at inlet manifolds and new carbs, and finish it with a rolling road tune. Thanks again for your help, George.

[Cooperman]

Yes, to get the benefit of 1380 you do really have to do everything. The limitation is usually the ability of the head to flow enough for the 1380 to breathe properly. A fully worked 1380, say for hill-climbing, can be awesome in its overall performance, but that is very expensive. I have seen 1380 engines where there was really no improvement over a well-sorted 1275 simply because the head and cam were not suitable for the bigger displacement. Maybe the 1380 is just for something to talk about in the pub.
Just get the bits you described in terms of manifolding and exhaust plus, ideally, a fast road head with the valve sizes i quoted and you'll have a great engine.
At 80k miles it would not be wise to try to get too much power, as that sort of mileage in the last 1/3rd of the engine life anyway. Do more when it needs a full rebuild.
A good 1275 can easily give 90 bhp when rebuilt at, say, +0.020", i.e. 1293 cc.

[bmcecosse]

I suggest you run a compression test on yur engine - at 80k miles - it MUST be showing it's age! Then decide what you really want - cam change is highly desireable, but involves engine out job on the 1275, and if doing that - may as well combine with other work. So short term - better head and larger carb on good alloy inlet manifold is the way to go. Going to the 7 port head is quite drastic - and will involve major investment - and would only be wise on a fully reconditioned and carefully assembled (ie 'blueprinted') engine - of any capacity. Best to just go to the next up bore size - don't get suckered into very expensive fancy 'big bore' conversions !

[Cooperman]

Well, that's two of us saying the same thing.
You know it makes sense!!!

[george91]

Ok well thanks for the info and heads up on that one, now i'm thinking a recon engine or sometihing similar might be a good idea as i'm really making this a long term project and i would like a decent engine to build around. Do you have any idea what would be the best way of going about doing something like this?

[Cooperman]

That looks like the basis of a very good Mini.
You could re-build the engine yourself, but unless you've done cylinder head modification before you might be best buying one off-the-shelf from a good supplier like Mini Spares.
What you need to find is a good machine shop who will machine the parts for you and to your instructions. There must be one in your area.
All the tech support you may need is on here to enable you to build a very nice and powerful road engine.
The first step would be to take the engine out and strip off all the ancilliaries. Then come back for an engine strip-down procedure.
The problem may be that you could get too much information and not all of us on here have the same opinions. That's not to say some are right and some are wrong, just that different people have different ideas which work for them.
Now, I build engines but hate gearboxes. My engines work for me, but what I do may not suit others who do things a little differently. The basics of what we do will be the same, however, but we differ on approach slightly.
I could write you a good spec for a strong road engine, but would rather not post it in full on here as there will be others who say, for example, don't have an MG Metro cam, a Kent 276 is better, or an SW5, or whatever. I may say go for 10.4:1 comp ratio. Others will say that 10:1 is quite enough. Then you'll be confused and that won't help you.
In the end it has to be your own choice.
PM me if you want to on this.

Peter

[george91]

That looks like the basis of a very good Mini.
You could re-build the engine yourself, but unless you've done cylinder head modification before you might be best buying one off-the-shelf from a good supplier like Mini Spares.
What you need to find is a good machine shop who will machine the parts for you and to your instructions. There must be one in your area.
All the tech support you may need is on here to enable you to build a very nice and powerful road engine.
The first step would be to take the engine out and strip off all the ancilliaries. Then come back for an engine strip-down procedure.
The problem may be that you could get too much information and not all of us on here have the same opinions. That's not to say some are right and some are wrong, just that different people have different ideas which work for them.
Now, I build engines but hate gearboxes. My engines work for me, but what I do may not suit others who do things a little differently. The basics of what we do will be the same, however, but we differ on approach slightly.
I could write you a good spec for a strong road engine, but would rather not post it in full on here as there will be others who say, for example, don't have an MG Metro cam, a Kent 276 is better, or an SW5, or whatever. I may say go for 10.4:1 comp ratio. Others will say that 10:1 is quite enough. Then you'll be confused and that won't help you.
In the end it has to be your own choice.
PM me if you want to on this.

Peter

Ok thankyou very much Peter for your help, i'll have to have a think on what i am going to do, firstly i'd better get my current engine checked over, if its ok i may sick with it, but if not i'll get a recon one from someone like mini spares to minimalise my time off the road as this is my daily drive as well. Thanks for you help again and no doubt i'll get back to for more help in the near future. Cheers, George.