20 replies to this topic

[Chris11K]

Hi all!

 

Been keeping an eye on the forum for a while now but only joined today.

 

Finally managed to source a 1275 A series engine and remote change gearbox to replace my current 1100 engine.

 

Main reason is driveability of the car. My 1100 is reliable, fun to drive around the hills 3rd-4th gear but when it gets out to the open road the screaming revs

make it quite unpleasant.

 

So main objective of the build is a good, reliable engine that can cruise around 100-110km/h (Welcome to South Australia) and can have a conversation in there without yelling and

don't have a headache at the end of the drive :)

 

The plan is to go for 1330cc (or 1340 is the correct size??), this should be enough without comprising reliability or should I go straight to 1380?

 

1380 I'm aware that we have to offset bore, is it the same for the 1330 option?

 

Also, were it gets really confusing for me is all the options for the parts. So many different brands, shops, etc. I mean it's great that we have so many products available

for our cars but how do we "weed out" the lesser brands? It's an expensive exercise to go by the trial error method with an engine build so any recommendation for the main 

components like pistons, camshaft, seals and gaskets, bearings etc is highly appreciated.

 

Cheers,

 

Chris

[Fast Ivan]

1293 (+20) is the next size up from 1275 so probably best for you

the 21253 piston is pretty good value seeing as you haven't mentioned going for to much performance

I would advise using minispares for engine build parts

[sonscar]

The size of the engine does not alter the revs of it at speed.The diff ratio does this.Depending on what diff is fitted to each engine you could potentially be worse off.Check the ratios before fitting is my advice.Have fun,Steve..

[ACDodd]

As above change the final drive ratio to reduce the engine rpm at speed.

Ac

[nicklouse]

As above work out what the final drive is and then just change the crown wheel and pinion to give you a more suitable final drive ratio.

 

just a quick question. When you say screaming revs how many is that? 

[gazza82]

1293 (+20) is the next size up from 1275 so probably best for you

the 21253 piston is pretty good value seeing as you haven't mentioned going for to much performance

I would advise using minispares for engine build parts

And sign up for TMF+ as that 7.5% discount mounts up quickly!
 

[MrBounce]

I would be aiming for a 3.1 final drive for the gearbox, along with a central oil pick-up pipe in your gearbox (why these weren't fitted from the factory I'll never know). For all-round driveability. I would be looking at camshaft choice - something along the lines of a Swiftune SW5, Mini Spares Evolution 001 or Kent 266 as these give a usable power band and low-down torque without having to rev the nuts off them. They have a decent low idle speed and aren't awful in traffic.

 

The 1st size overbore as stated above is +'020 - there is no real world gain to go any bigger unless engine wear or a race series dictates it. Get the bottom end balanced too. And finally, make sure that you have a cylinder head worthy of a well-built bottom end. It's no good making an excellent engine if you're then going to strangle it with smallish valves. An MG Metro or late Cooper-Spec head is a good starting point as these have the bigger valves. How far you go with porting and polishing depends on the size of your wallet. A good, reliable engine is easy to achieve if you give the thought, attention and budget it needs.

 

Finally, make sure that you speak at length with your engineering shop on what you want to achieve. Make sure that everything is well measured and if you're the one building it, make sure that you research what you're doing before getting started. There's a lot of very knowledgeable people on here happy to help.

 

And the most important thing? Have fun doing it. 

Edited by MrBounce, 30 November 2020 - 05:13 PM.

[Spider]

Welcome to the Forum Chris11K, you're in some of the best Australia has to offer there mate

As the other guys have said re: Final Drive Ratios, but you'll also need to add more sound proofing inside your Mini to get the engine noise down to what you'd like. Also, what have you got on your exhaust system presently ?

Plan ahead with your first re-bore, even if only going to +0.020 now, that if later down the track you think you may go to one of the bigger over-bores, as you'll want to start off-set boring it from that first rebore.

[Chris11K]

Thanks for all the info guys!

 

Yes, I'm also aware of the ratios. I know I will have to pick between the 3.1 and 3.2..... 3.1 seems to be recommended by most.

 

@nicklouse I'd say High 4000-5000 rpm.

 

@mrbounce We are going to a shop that we have used before and he has proved his work so we have this covered :) 

 

@Moke spider Thanks mate! by the way I bought my mini from Sydney and drove it back to Adelaide! Noise cancelling headphones FTW! Stock exhaust but we'll go for an aftermarket option with the new build.

 

Besides Minispares I was also looking at Swiftune and Calver. looks like I can source most of the important bits (pistons, distributors, cam etc) from them. Any feedback?

 

Cheers,

 

Chris

[timmy850]

Minisport in Adelaide sells the Hypatecs which have a good reputation

The cam is a hard choice as there are so many different profiles around. My advice is to make sure both the cam and the followers are correctly ground and hardened for them to last a long time. Clive Cams in Melbourne has some good profiles available, so do others here in Aus

Edited by timmy850, 01 December 2020 - 02:34 AM.

[Chris11K]

Also, forgot to mention that we have a 12G940 head for the build. 

[nicklouse]

Thanks for all the info guys!

 

Yes, I'm also aware of the ratios. I know I will have to pick between the 3.1 and 3.2..... 3.1 seems to be recommended by most.

 

@nicklouse I'd say High 4000-5000 rpm.

 

@mrbounce We are going to a shop that we have used before and he has proved his work so we have this covered :) 

 

@Moke spider Thanks mate! by the way I bought my mini from Sydney and drove it back to Adelaide! Noise cancelling headphones FTW! Stock exhaust but we'll go for an aftermarket option with the new build.

 

Besides Minispares I was also looking at Swiftune and Calver. looks like I can source most of the important bits (pistons, distributors, cam etc) from them. Any feedback?

 

Cheers,

 

Chris

If you call 4-5k screaming then you have the wrong car. That is the normal usage range for the Mini and you should be doing 120-130 KMH at those reeves in 4th gear. 
 

changing to a 3.1 final drive will drop the rpm to about 3.5k at similar road speed.

 

plug your info in http://www.guess-wor...ech/ratioKM.htm

[gazza82]

Also, forgot to mention that we have a 12G940 head for the build. 

There are several different 12G940s .. check out Keith Calver's website for a list https://www.calverst...casting-number/

 

[Turbo Phil]

12G940 means nothing on its own, it’s a generic casting number. Though they can all be modified to give the same results.

Phil.

[Spider]

 

Yes, I'm also aware of the ratios. I know I will have to pick between the 3.1 and 3.2..... 3.1 seems to be recommended by most.

@Moke spider Thanks mate! by the way I bought my mini from Sydney and drove it back to Adelaide! Noise cancelling headphones FTW! Stock exhaust but we'll go for an aftermarket option with the new build.

 

 

With the Hills around Adelaide, if it were me, I wouldn't go taller than 3.44. And it's in them hills where the fun is in that town

 

If you are new to Minis, they are a 'revy' engine, one that happily sits on 4000 RPM all day (and more if you like). I've tired taller ratios and while had their advantages, I didn't like them and personally found the 3.44 is a happy middle ground, especially given there's few places in Australia that you can legally drive over 110 kph (65 mph), unless you frequent the Top End, in which case, a Mini's not the wisest choice, only for the stock that tends to wander on to the road up there.

Not sure if you know Adrian Flynn or any of the other guys in Hot Bricks ? Adrian's been in the Mini scene a very long time and as he's a local in the town, I don't think you'd go too far wrong from his advice.

I've done the Sydney - Adelaide - Sydney run may times, a few in a Mini, I wouldn't do it these days, but in the 80's I came back from Adelaide in under 14 hrs - including breaks - in one of my GTs