Crankshaft Thrust Bearings for an 850
Discussion
I've had an idea that they are the same as those on the 948cc Sprite and maybe MOSS do them as they list 948 Sprite thrusts. If not I'll try Somerfords as you suggest - many thanks.
I'm building so many 'A-Series' engines at the moment that I sometimes get confused as to what bits I need for what engine.
I'm building so many 'A-Series' engines at the moment that I sometimes get confused as to what bits I need for what engine.
I've had an idea that they are the same as those on the 948cc Sprite and maybe MOSS do them as they list 948 Sprite thrusts. If not I'll try Somerfords as you suggest - many thanks.
I'm building so many 'A-Series' engines at the moment that I sometimes get confused as to what bits I need for what engine.
I gather it's hard to get +.030" thrusts for the 1275 engines these days. That makes it difficult if you get a genuine Cooper 'S' EN40B crank that's got too much end float for a pair of +.003" thrusts. I had this recently with a 1275 'S' which had .011" float with standard thrusts. The +.003's would have got this down to .005" float, but that's a bit more than I like on a newly built unit, but in the end I machined down a +.030" to +.006", thus giving .002" float when fitted with +.003" on the thrust (i.e. the clutch) side. I did this so that when the thrusts are renewed, only the clutch side will need changing with the non-standard 'thick' ones being OK to re-use (hopefully).
Interestingly, the problem was caused by the use of the car on a very cold rally. The engine had 20/50 oil and was started, with the clutch pushed down (don't ever do this!), in an outside temp of -15 deg C. The centre main and the thrusts were thus starved of oil which ruined the main bearing shells and damaged the crank on the clutch-side thrust face, which had to be lightly ground. The moral of this is that although a 20/50 oil is best for competition, on winter events in the French Alps, use a 10/40 and never rev or push the clutch down until the oil has warmed up and circulated properly. This can be difficult with a 'hot' cam and high comp ration, but it's important to try.
I'm building so many 'A-Series' engines at the moment that I sometimes get confused as to what bits I need for what engine.
I gather it's hard to get +.030" thrusts for the 1275 engines these days. That makes it difficult if you get a genuine Cooper 'S' EN40B crank that's got too much end float for a pair of +.003" thrusts. I had this recently with a 1275 'S' which had .011" float with standard thrusts. The +.003's would have got this down to .005" float, but that's a bit more than I like on a newly built unit, but in the end I machined down a +.030" to +.006", thus giving .002" float when fitted with +.003" on the thrust (i.e. the clutch) side. I did this so that when the thrusts are renewed, only the clutch side will need changing with the non-standard 'thick' ones being OK to re-use (hopefully).
Interestingly, the problem was caused by the use of the car on a very cold rally. The engine had 20/50 oil and was started, with the clutch pushed down (don't ever do this!), in an outside temp of -15 deg C. The centre main and the thrusts were thus starved of oil which ruined the main bearing shells and damaged the crank on the clutch-side thrust face, which had to be lightly ground. The moral of this is that although a 20/50 oil is best for competition, on winter events in the French Alps, use a 10/40 and never rev or push the clutch down until the oil has warmed up and circulated properly. This can be difficult with a 'hot' cam and high comp ration, but it's important to try.
miniman said:
I'm 5 minutes from Somerford so let me know if you want me to pop up there for you - would be more than happy to do so.
James, that's most kind of you. I just spoke with Chris Spennewyn and he thinks he might have some in his vast stock of 850 bits. I suppose I need a set of standard and a set of +.003" just to be sure of getting the correct end float.
I should know in a couple of days.
I had just the same conversation last night with a local buddy who has a 1996 Sportpack.
With a standard clutch it isn't too bad, but with any sort of heavy duty clutch, and I think that includes the standard Cooper 'S' pre-Verto unit, when you push the clutch pedal down you are putting the full clutch pressure straight onto the crankshaft thrust bearings. Then, if you turn the engine over from cold the full load is then taken whilst the crank is turning, but without any oil flow from the centre main bearing for the first few seconds. I guess this applies to all cars, but the Mini seems particularly vulnerable, probably because the clutch is quite heavy on most performance versions.
I think the idea of de-clutching before starting comes from the days of uni-grade oils when with, say, a straight 40 grade in a Mini sump, the starter had a hard job to turn the lot over on a cold morning. With modern oils, I use a 15/50 or a 20/50, the base viscosity is the lower number and modern bateries and starters should easily cope, even when cold, the alternator keeping the battery fully charged at most times too.
With a standard clutch it isn't too bad, but with any sort of heavy duty clutch, and I think that includes the standard Cooper 'S' pre-Verto unit, when you push the clutch pedal down you are putting the full clutch pressure straight onto the crankshaft thrust bearings. Then, if you turn the engine over from cold the full load is then taken whilst the crank is turning, but without any oil flow from the centre main bearing for the first few seconds. I guess this applies to all cars, but the Mini seems particularly vulnerable, probably because the clutch is quite heavy on most performance versions.
I think the idea of de-clutching before starting comes from the days of uni-grade oils when with, say, a straight 40 grade in a Mini sump, the starter had a hard job to turn the lot over on a cold morning. With modern oils, I use a 15/50 or a 20/50, the base viscosity is the lower number and modern bateries and starters should easily cope, even when cold, the alternator keeping the battery fully charged at most times too.
Cooperman said:
I think the idea of de-clutching before starting comes from the days of uni-grade oils when with, say, a straight 40 grade in a Mini sump, the starter had a hard job to turn the lot over on a cold morning. With modern oils, I use a 15/50 or a 20/50, the base viscosity is the lower number and modern bateries and starters should easily cope, even when cold, the alternator keeping the battery fully charged at most times too.
ah I see. this is where I heard it from years ago
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