12 replies to this topic

[robbotheone]

hi.robbo here asking all you mini gurus.
I have a 1959 mini which I restored in 1996 which I did as a'classic' rally car with all period stuff ( the car was a wreck which we dragged out of a lock up in Brum) . I completed the 1997 Monte Carlo Challenge (in fact we won one stage outright) BUT it might have looked good but it was pretty dreadful really. 3 pumps to get any brakes at all(worn and loose snail cams in the backplates) Engine was flat and didn't pick up -grovelled up every col in second at 20mph.
Right the engine is the original 850 - bottom half is entirely original - had a 12G295 head ( strangely it came with this head on it but it had two head gaskets on ! ) anyway a chap in Redditch did the head up skimmed it60 thou and put some ground down cooper S valves in - he described it as the biggest valves you could have without pocketing the block. I put a new distributer I found at a car boot in and an inch and a quarter carb on. Took it to the rolling road where a chap called Nigel Ruben did his best ( he said the dizzy was out of a landrover!! but he modded it. It revs fantastic and sweet and showed 93mph and about 50 BHP on the rolling road but it always just went flat and hesitated when you change down on a bend just when you want it to have some go. after the event various friends and 'I know about SU's and mini's " types fiddled with it - different dizzy's carbs -needles springs to the point that it runs like a sack of S....t and I have no idea where we are with it. I've now got it out again and intend to get it sorted for the historic rally challenge. As a start. I've ordered a new electronic dizzy sports coil and new leads. - The point of these ramblings (yes I do go on) is advise me on the best options to improve it's performance .I'm not looking for speed outright but a quickish reliable useable unit with 'enough go in it' and torque. Cheers .Just found this site this morning so I thought I'd give it a go -amazing really

[Guess-Works.com]

One of the first things which should be done if you're looking to 'up' the performance of an 850 is get cam bearings fitted into the block ( can't remeber if you need to have the block machined for this ). 850's run the cam on cast iron which is not conducive to performance.

[Ethel]

The cam will be running on a film of oil, like any other bearing but it could be more vulnerable to failure with higher revs. You'd be better off swapping it for a 998 and saving the 850, in both senses.

[Cooperman]

Yes, you do have to machine the block to fit the cam bearings and few machine shops can do this nowadays. I think Rob Walker at Witney, Oxon can do this. Line-boring is not something mahine shops do now, or so it seems.
I've prepared and rallied all Minis from 850 right up to my current full-spec Historic 1310 cc 'S' and it's good to hear that an 850 is still being rallied. I even rallied in a works-prepared 850 back in 1962/63.
To achieve the best from an 850 you need to remember that without the original special crank they really won't rev safely beyond 6000 rpm. Those 850 special cranks are virtually impossible to find now.
The pistons are also a bit of a limiting factor, but again it could be difficult to find any which don't have the split-skirt of the standard ones. The 997 Cooper at +0.020" was the same bore as the 850, but I don't know if the 'wrist height' of the pistons is the same. If it is you could try to find some flat-top solid skirt 997 @ +0.020" as they are the clamp-pin type as well. Try Thorntons of Shrewsbury for pistons, but expect to pay a lot. I bought a set of original 997 pistons @ +0.060" recently and they were about £230 for the set.
For a cam the Kent 256 is probably fine and will give a reasonable power band bearing in mind that an 850 won't rev like an 'S'. The 295 head is the best, but measure carefully and check that the compression ratio is OK. With split-skirt pistons it would not be wise to go much over 9.5:1. Measure and calculate accurately. The head needs to be well gas-flowed and matched to a 3-branch manifold of the same bore as the 997/998 Cooper, not a huge bore one as fitted to 1275 engines. The exhaust needs to be about 1.5" internal diameter all the way through and the original standard 997/98 Cooper system is good. Go any bigger and you'll lose bhp and torque.
Fit a 1.5" H4 or HS4 carb on a decent alloy inlet manifold, or even twin 1.25" HS2's as fitted to Cooper 997/998. (a HIF-type is not a 'period mod' for Historics).
A duplex timing chain would also be a good thing just for reliability on a rally car.
With regard to brakes, you can fit the twin leading-shoe fronts and as it's for competition I think I would get all new parts. Brake linings need to be competition ones and Questmead of Rochdale can advise on this - speak to Alan there as he knows the answers.
The regs allow for 'period mods' so that's no problem as lots of 850's had those mods in the early 60's.
I don't think electronic ignition is permitted for historics and I still have points-type on my '64 car because of this.
For engine set-up I recommend Peter Baldwin who is near Royston in Herts. He may be a l,ong way, but he is the best.
PM me if you need any more help.
All the best,

Peter

[Ivor Badger]

As pointed out, you must fit cam bearings. I am actually surprised the block has lasted so long. The back bearing wears out and it runs off centre and shears the oil plump drive.

If running as a 59, it should have single leading shoe front brakes. I take it you have modified to twin leading shoe brakes for obvious reasons. Try fitting a Moprod adjuster kit, it allows you to take the adjusters out to free them and set up the friction.

If sticking with the single HS2, fit an E3 needle.

[R1minimagic]

I have an 850 crank, how do i find out what type it is?

[robbotheone]

Yes, you do have to machine the block to fit the cam bearings and few machine shops can do this nowadays. I think Rob Walker at Witney, Oxon can do this. Line-boring is not something mahine shops do now, or so it seems.
I've prepared and rallied all Minis from 850 right up to my current full-spec Historic 1310 cc 'S' and it's good to hear that an 850 is still being rallied. I even rallied in a works-prepared 850 back in 1962/63.
To achieve the best from an 850 you need to remember that without the original special crank they really won't rev safely beyond 6000 rpm. Those 850 special cranks are virtually impossible to find now.
The pistons are also a bit of a limiting factor, but again it could be difficult to find any which don't have the split-skirt of the standard ones. The 997 Cooper at +0.020" was the same bore as the 850, but I don't know if the 'wrist height' of the pistons is the same. If it is you could try to find some flat-top solid skirt 997 @ +0.020" as they are the clamp-pin type as well. Try Thorntons of Shrewsbury for pistons, but expect to pay a lot. I bought a set of original 997 pistons @ +0.060" recently and they were about £230 for the set.
For a cam the Kent 256 is probably fine and will give a reasonable power band bearing in mind that an 850 won't rev like an 'S'. The 295 head is the best, but measure carefully and check that the compression ratio is OK. With split-skirt pistons it would not be wise to go much over 9.5:1. Measure and calculate accurately. The head needs to be well gas-flowed and matched to a 3-branch manifold of the same bore as the 997/998 Cooper, not a huge bore one as fitted to 1275 engines. The exhaust needs to be about 1.5" internal diameter all the way through and the original standard 997/98 Cooper system is good. Go any bigger and you'll lose bhp and torque.
Fit a 1.5" H4 or HS4 carb on a decent alloy inlet manifold, or even twin 1.25" HS2's as fitted to Cooper 997/998. (a HIF-type is not a 'period mod' for Historics).
A duplex timing chain would also be a good thing just for reliability on a rally car.
With regard to brakes, you can fit the twin leading-shoe fronts and as it's for competition I think I would get all new parts. Brake linings need to be competition ones and Questmead of Rochdale can advise on this - speak to Alan there as he knows the answers.
The regs allow for 'period mods' so that's no problem as lots of 850's had those mods in the early 60's.
I don't think electronic ignition is permitted for historics and I still have points-type on my '64 car because of this.
For engine set-up I recommend Peter Baldwin who is near Royston in Herts. He may be a l,ong way, but he is the best.
PM me if you need any more help.
All the best,

Peter

[robbotheone]

Yes, you do have to machine the block to fit the cam bearings and few machine shops can do this nowadays. I think Rob Walker at Witney, Oxon can do this. Line-boring is not something mahine shops do now, or so it seems.
I've prepared and rallied all Minis from 850 right up to my current full-spec Historic 1310 cc 'S' and it's good to hear that an 850 is still being rallied. I even rallied in a works-prepared 850 back in 1962/63.
To achieve the best from an 850 you need to remember that without the original special crank they really won't rev safely beyond 6000 rpm. Those 850 special cranks are virtually impossible to find now.
The pistons are also a bit of a limiting factor, but again it could be difficult to find any which don't have the split-skirt of the standard ones. The 997 Cooper at +0.020" was the same bore as the 850, but I don't know if the 'wrist height' of the pistons is the same. If it is you could try to find some flat-top solid skirt 997 @ +0.020" as they are the clamp-pin type as well. Try Thorntons of Shrewsbury for pistons, but expect to pay a lot. I bought a set of original 997 pistons @ +0.060" recently and they were about £230 for the set.
For a cam the Kent 256 is probably fine and will give a reasonable power band bearing in mind that an 850 won't rev like an 'S'. The 295 head is the best, but measure carefully and check that the compression ratio is OK. With split-skirt pistons it would not be wise to go much over 9.5:1. Measure and calculate accurately. The head needs to be well gas-flowed and matched to a 3-branch manifold of the same bore as the 997/998 Cooper, not a huge bore one as fitted to 1275 engines. The exhaust needs to be about 1.5" internal diameter all the way through and the original standard 997/98 Cooper system is good. Go any bigger and you'll lose bhp and torque.
Fit a 1.5" H4 or HS4 carb on a decent alloy inlet manifold, or even twin 1.25" HS2's as fitted to Cooper 997/998. (a HIF-type is not a 'period mod' for Historics).
A duplex timing chain would also be a good thing just for reliability on a rally car.
With regard to brakes, you can fit the twin leading-shoe fronts and as it's for competition I think I would get all new parts. Brake linings need to be competition ones and Questmead of Rochdale can advise on this - speak to Alan there as he knows the answers.
The regs allow for 'period mods' so that's no problem as lots of 850's had those mods in the early 60's.
I don't think electronic ignition is permitted for historics and I still have points-type on my '64 car because of this.
For engine set-up I recommend Peter Baldwin who is near Royston in Herts. He may be a l,ong way, but he is the best.
PM me if you need any more help.
All the best,

Peter

[robbotheone]

well thank you all for such pointed information. I forgot to say that I had fitted a duplex timimg chainset and twin lead shoe new old stock.LCB/RC40 and I cut off the inlet manifold to use just that section with a bit of re shaping and flowing (seemed like a good idea at the time) a bit of a dlema -on one hand I'm thinking stick with the old 850 but then common sense tells me get a 998 or even a 1275 if it's allowed especially as a friend locally has offered me a 1275 unit with some fancy head on (something to do with the number of studs !)

[HARBER07]

I have an 850 crank, how do i find out what type it is?

X2

[bmcecosse]

Genuine Cooper S engine has 10 studs + 1 bolt - if that's what you mean ? Obviously larger engine = more power, and lots more to go wrong! Depends on your budget really. But sounds like you had fun with the 850 - so why not stick with it ? It may be easier to use say a 1098 block (which comes with cam bearings) - and sleeve it down to take the largest overbore 848 pistons you are allowed in the class ?

[Cooperman]

Historic regulations allow you to use a non-Cooper 'S' 1275 A-series block as a more available alternative to a genuine 'S' block, but not an A+ which is visually different.
You'll also need the 10" Cooper 'S' brakes, hubs, calipers and drive shafts, or it will be very dangerous, plus 'S' rear drums and the correct wheels all round.
You can modify an A-series non-'S' block to take the 10-studs & 1-bolt head arrangement and you'll need twin 1.5" SU's, H4's or HS4's, not the HIF variety as they are not period carbs for a Mk 1 car. It will then be, in motorsport terms a Cooper 'S' and will need to comply with the 'S' specifications and allowable mods.
I have a full Historic 'S' build sheet if you want one. Just PM me.
If you were to go to 998, you would need to build it as a twin carb cooper, as there were never any single carb 998's built in Historic period, i.e. pre 1968. You could, however, fit the bigger 'S' brakes as they are a 'period mod' on a 998 Cooper.
It depends on what events you want to compete in.

[Cooperman]

Historic regulations allow you to use a non-Cooper 'S' 1275 A-series block as a more available alternative to a genuine 'S' block, but not an A+ which is visually different.
You'll also need the 10" Cooper 'S' brakes, hubs, calipers and drive shafts, or it will be very dangerous, plus 'S' rear drums and the correct wheels all round.
You can modify an A-series non-'S' block to take the 10-studs & 1-bolt head arrangement and you'll need twin 1.5" SU's, H4's or HS4's, not the HIF variety as they are not period carbs for a Mk 1 car. It will then be, in motorsport terms a Cooper 'S' and will need to comply with the 'S' specifications and allowable mods.
I have a full Historic 'S' build sheet if you want one. Just PM me.
If you were to go to 998, you would need to build it as a twin carb cooper, as there were never any single carb 998's built in Historic period, i.e. pre 1968. You could, however, fit the bigger 'S' brakes as they are a 'period mod' on a 998 Cooper.
It depends on what events you want to compete in.