29 replies to this topic

[Corey96Williams]

I concur with the others. The biggest problem you have with the mini is its 1950"s technology and you want 2015 performance. You can build a firecracker engine but reliability goes right out the window. Someone mentioned its an SPI, if you convert it to carbs won't you have rego problems?
Why not just get engine done by someone with mini experience, that can put the right combination of parts together to get the best performance AND drivable reliability.

I know I come off this way, but I'm not expecting 300hp. I know the difference will be marginal, but I'd just like the extra 10-20hp. I'd like a complete engine swap, but being an 18 year old, I fall into the young and stupid category for insurance. With a small engine rebore, the insurance won't be an issue.

About the part with a person with Mini experience, that's what I'd like. I was hoping to get  some information about what is best etc etc. I just don't know of anywhere...

[beakerthemuppet2]

The only way to get a 1340 would be to grind a crank down offsetting the big-end journals and changing from 1.75" dia big ends to 1.625" dia, then using the Cooper 'S' con-rods to run the smaller diameter. This would increase the stroke.

A straightforward +0.060" overbore gives 1330 cc.

Not a lot of point in doing either unless it is for historic competition where couple of extra bhp might knock a few tenths of a second off the lap time. Otherwise it's pretty pointless. If an engine needs a rebore & new pistons it is always best to go to the next size up, unless it's already at 1330 cc in which case it needs to be sleeved back to 1275.

 

Doesn’t a +60 thou overbore and a modified head with larger combustion chambers make up a 1340? Or do dished pistons make a difference?

 

I might be completely wrong but that’s where I thought the extra cc’s came from?

[Cooperman]

The capacity of an engine has nothing to do with the size of the combustion chamber. It is a simple calculation of the bore diameter squared x 3.142 divided by 4 and multiplied by the stroke (as determined by the crankshaft throw).

The combustion volume gives the compression ratio which is a comparison between the volume above the piston at Bottom Dead Centre (BDC) and above the piston at Top Dead Centre (TDC)

To get 1340 cc it is necessary to fit a specially offset ground crankshaft & Cooper 'S' rods and there would be no reason for doing this - well, not one that I can think of.

[Spider]

 (no such thing as 1340)

 

Well there could be if the man on the boring bar stuff it up.

 

Might suffer just a tad piston slap though.

[Cooperman]

 

 (no such thing as 1340)

 

Well there could be if the man on the boring bar stuff it up.

 

Might suffer just a tad piston slap though.

 

   . 

[Mrpeanut]

I concur with the others. The biggest problem you have with the mini is its 1950"s technology and you want 2015 performance. You can build a firecracker engine but reliability goes right out the window. Someone mentioned its an SPI, if you convert it to carbs won't you have rego problems?
Why not just get engine done by someone with mini experience, that can put the right combination of parts together to get the best performance AND drivable reliability.

I know I come off this way, but I'm not expecting 300hp. I know the difference will be marginal, but I'd just like the extra 10-20hp. I'd like a complete engine swap, but being an 18 year old, I fall into the young and stupid category for insurance. With a small engine rebore, the insurance won't be an issue.
About the part with a person with Mini experience, that's what I'd like. I was hoping to get  some information about what is best etc etc. I just don't know of anywhere...

I echo the above. A few more cc won't get you anywhere.

I rebored by 78bhp cooper to 1330, upgraded the Cooper free flow manifold to a stage 2 lcb, upgraded the rc40 to the maniflow race system, changed the cam from stock to a minispares evo1.

I gained a whole 5bhp! Granted I gained a lot or torque but overall nothing significant.

I now face having to sleeve back to a 1275 or maxing out my block to 1380 on the next rebuild.

My point? Don't rebore for the sake of it. Do what needs doing and do it well.

[peter-b]

I'm still not quite sure what engine you have but assuming its a 998. In that case its not exactly rare so why not get an old scrap engine and rebuild it ready to fit, doesn't make it cheaper just less time off road. I'm not 100% sure of the actual possibility but maybe bore it, say 40+ and fit 1100 crank? Then a lively grind cam, a good breathing head and twin hs2's. Or if your insurance says no to twins then a hs4. Someone here can correct me or elaborate on it if they like, the A+ motor is just that bit different to the STD A series we had here. That's about the best I can offer in the way of advice.

[gazza82]

Any rebore will probably need to be declared to the insurers so you are best sticking to the minimum you can get away with or face a massive hike in.your premiums. Changing anything from standard needs to be declared. Have an accident and get found out and they will wriggle out of paying ... Plus invalidate your policy. You are then in uninsured driver territory too ...

[Cooperman]

So long as the re-bore is to standard service sizes there is no need to declare it. A standard service re-bore is as listed in the Workshop manual for the car. If you go beyond the service size re-bore then it is classed as a modification.

When you took a BMC car in for a new engine at a dealer you got a 'Gold Seal' reconditioned engine which was re-bored, but the size was never confirmed, just that is had been reconditioned. This was just classed as a normal service repair.

[Corey96Williams]

I'm still not quite sure what engine you have but assuming its a 998.

It's a 1275cc :)

[peter-b]

Crikey, your damn insurance is tough over there. Seems to me you're stuck behind a really big rock with it. Reboring a 1275, even to maximum o/s would do little if you're shackled by having to keep the standard accessories. It would probably end up at about 500 quid a horsepower, not good value in my book. All I can suggest is maybe a head job, for the car that is, and maybe a mild cam. Surely they wouldn't be checking that? What fuel system is it, carb, SPI, MPI?

[Corey96Williams]

Crikey, your damn insurance is tough over there. Seems to me you're stuck behind a really big rock with it. Reboring a 1275, even to maximum o/s would do little if you're shackled by having to keep the standard accessories. It would probably end up at about 500 quid a horsepower, not good value in my book. All I can suggest is maybe a head job, for the car that is, and maybe a mild cam. Surely they wouldn't be checking that? What fuel system is it, carb, SPI, MPI?

SPi :)

[Covert]

Seems to me like you want a rebore not need a rebore

[Corey96Williams]

Seems to me like you want a rebore not need a rebore

Yeah I said on the first page I don't need one, but as I grew up in an era where if you wanted to fast you fitted a turbo, I wanted some more information :)

[peter-b]

Just fit NOS and hide it.

What are you allowed to do in the way of modifications? Can you tell them and its ok, or do your premiums go up too much? We have insurance companies over here that specialise in classic and modified cars, they ask a million questions but if your a reasonable risk it's not to expen$ive. Basicly if its roadworthy they insure it.