14 replies to this topic

[MiniCarJack]

I recently found a 1973 BMC 1300 for sale and fortunately the engine and gearbox seem to be fine and pretty low-mileage. What I'm thinking is that I could buy the landcrab and use the 1275 lump in my Mk1 mini, then scrap/sell off the rest of the car to recoup some of the money I spent to purchase it. However what I'm wondering is how easy it would be to use this engine - I'm unsure whether or not a 1973 1300 would use a verto or pre-verto type clutch, and also if it uses a rod-change or remote-change type gearbox. The remote change would be the ideal option for me because my Mini has already got a hole pre-cut for a remote shift to be installed.

 

I'm also thinking that it will be necessary to change the diff as the ratio will be wrong, and also acquire some drive shafts and a 7.5" disk brake conversion kit to be installed at the same time as the engine for extra stopping ability to match the extra power, but is there anything else I've missed? I'm not 100% clued up on the differences between an Austin/Morris/Wolseley etc 1300 engine and the Mini's 1275 so any expertise on this front would be very helpful for me, as I'm trying to work out whether or not this would be a relatively "easy' project or something which would require modifications and lots of different parts.

[Chrome_GT]

Hi

I did something very similar. See my project thread: http://oldschool.co....s/?hl=chrome_gt

Hopefully it helps!

Cheers

[MiniCarJack]

Hi

I did something very similar. See my project thread: http://oldschool.co....s/?hl=chrome_gt

Hopefully it helps!

Cheers

 

That does help a lot actually, thanks! I never even considered the differences in the engine mounts so it's good to see those pictures and info you posted. I'm hoping I will also be able to re-use my existing radiator since the previous owner upgraded it to a nice new aluminum one not long before I bought the car.

[Cooperman]

All those pre-A+ blocks are interchangeable. However, the gearboxes are not as the engine mountings and gear change systems are different, as is the final drive ratio (FDR). Best thing will be to use the original gearbox with the 1275 engine from the BMA1300 on top.

With the extra power & torque you would be advised to use 7.5" disc brakes with the correct drive shafts, but the existing gearbox output couplings will work OK.

[Chrome_GT]

I never upgraded the brakes.

My thoughts are: 

• You don't apply throttle (the extra power and torque) while you are applying the brakes so why does that make a difference?
• You may have a higher ultimate speed but if you stay within the speed limits then you'd reach those speeds anyway, regardless of whether it was an 850, 1000, 1275
• There may be slightly more intertia to slow down in the crank etc but again, you should be applying clutch.
• The weight of the engine hasn't changed so you haven't changed the mass you need to bring to a stop.  

I know it's standard to upgrade brakes with any engine upgrade, and might even be law, but if you consider those things then it actually isn't necessary in this situation, But it would be nice to have and is recommended even though i didn't do it.

 

 

I think the standard 1300 is actually a 1275cc engine anyway. Mine happened to have already been bored out in the past to oversize pistons so was a 1310 or 1312 based on the piston diameter and some notes from a book 'how to modify your mini'

[MMM1965]

I fitted the engine from a 1965 riley kestrel 1100 in my 1965 mini minor, just removed the original gearbox and fitted the 3 syncro magic wand gearbox to the engine and it fiited straight in with no problems, I think this is probably the easiest way to go about things. I also kept the drum brakes, they work really well as long as you keep them well maintained. I have rebuilt the 850 engine to keep for originality reasons, I found the upgrade really worthwhile as the extra power and torque from the 1100 engine makes a big difference to the driveability of the car so the 1300 engine should be great

[MiniCarJack]

I fitted the engine from a 1965 riley kestrel 1100 in my 1965 mini minor, just removed the original gearbox and fitted the 3 syncro magic wand gearbox to the engine and it fiited straight in with no problems, I think this is probably the easiest way to go about things. I also kept the drum brakes, they work really well as long as you keep them well maintained. I have rebuilt the 850 engine to keep for originality reasons, I found the upgrade really worthwhile as the extra power and torque from the 1100 engine makes a big difference to the driveability of the car so the 1300 engine should be great

 

That's interesting that you were able to do that without any issues, I was doing some reading about using the gearbox from my 850 and apparently it requires some modification to fit properly onto a 1275 engine - maybe this isn't the case after all?

[MMM1965]

Yes now you come to mention it I believe there may be issues with fitting a 1275 engine to a 3 synchro gearbox or even a later type gearbox designed for the small bore engines. I'm pretty certain that all 848, 998 and 1089 pre a plus engines will fit but there could be differences with a 1275, I'm sure the positioning or profile of the primary gears is different or something like that. I'm sure one of the experts on here will know more, but I definitely had no problems fitting the 1098 to the 850 gearbox.

[MiniCarJack]

In that case maybe an early gearbox from a 1275 Cooper/Cooper S would be a good option? I know of someone who has one for sale and he also has a Mk1 Cooper S 1275 engine, but I suspect that'll be a really expensive purchase, so maybe just getting the gearbox (and the clutch from my 850) and fitting it to the BMC 1300's engine would work since the early gearbox should be more compatible with the existing parts of my mini.

Edited by W1NG3D, 29 January 2014 - 11:26 PM.

[Ethel]

Not really my area, but I believe the 1300 and S remote gearboxes are essentially the same, the selector extensions differ a bit (not critically) and, of course, so does the final drive ratio.

 

The point with the brakes is you'll be using them more as you'll arrive at the next corner sooner and faster, it's overheating and fade more than raw  stopping power.

[mk3 Cooper S]

Use the ADO gearchange (which has a rubber sandwich plate) and trim the rear of the floor hole.

 

As for the diff ratio - what size wheels are you planning on running?

[MiniCarJack]

Use the ADO gearchange (which has a rubber sandwich plate) and trim the rear of the floor hole.

 

As for the diff ratio - what size wheels are you planning on running?

I plan on sticking with 10" wheels on the Mini, so I'll probably also end up doing a 7.5" disk conversion.

[mk3 Cooper S]

Check the ratio as I one I bought had a 3.44 diff in it which is fine with 10" wheels

[tiger99]

The gearbox issue with 1275 engines was due to the crank webs or big ends, I forget which, fouling the casing, and a small amount of metal had to be removed from the casing.

 

As for the brakes, it is ESSENTIAL that any significant engine upgrade on any car is accompanied by a brake system upgrade. Please disregard dangerous advice to the contrary, from someone who clearly does not understand the physics involved. The problem is not just with the maximum speed, although that also matters, the energy that needs to be dissipated is proportional to the SQUARE of the speed, but it is more to do with the accelerate to full speed and brake to a stop cycle, as has been correctly suggested. When the acceleration part of the cycle happens quicker, proportionally more of the time is spent in braking, heating the brakes, and less in acceleration, when the brakes can cool, so the average heat input is higher. If the pad and disc tempperature increases, brake fade is likely, as the friction surfaces degrade, but much worse, if the fluid boils, you have instant and complete loss of brakes.

[Chrome_GT]

 The problem is not just with the maximum speed, although that also matters, the energy that needs to be dissipated is proportional to the SQUARE of the speed, but it is more to do with the accelerate to full speed and brake to a stop cycle, as has been correctly suggested. 

That and the brake fade thing - a valid point.  That also comes down to the driver and if their behaviour is going to change now they have the extra power available. Unless he is planning on spending time on a track or racing around suburban streets then in my opinion it isn't essential but is obviously better. I'm not recommending he doesn't upgrade the brakes. I'd always recommend anyone considers a brake upgrade as long as it is done properly. However I'm saying that I didn't, and I haven't found any problem whatsoever with my standard brakes in typical suburban driving conditions. He asked for information about doing an upgrade so I'm giving him info regarding what I've done; even if it is a bit 'half arse' in the opinion of others  Good Luck

Edited by Chrome_GT, 01 February 2014 - 02:43 AM.