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Crank stroke question?
https://www.ausmini.com/forums/viewtopic.php?f=2&t=83216		 Page 1 of 1
Author:  adnams4ever [ Tue Oct 22, 2013 7:54 pm ]
Post subject:  Crank stroke question?
Hi All,

Which crank has the longer stoke, the 997 Cooper crank or the 1098 crank? Odd question I know but would like to know.

Many thanks.
Author:  simon k [ Tue Oct 22, 2013 8:20 pm ]
Post subject:  Re: Crank stroke question?
997 - 81.28 mm
1098 - 83.72 mm

http://en.wikipedia.org/wiki/BMC_A-Series_engine
Author:  Convertible Mini [ Tue Oct 22, 2013 8:40 pm ]
Post subject:  Re: Crank stroke question?
1098 Cranks have the longest "standard" stroke of all A series engines.
Author:  drmini in aust [ Tue Oct 22, 2013 8:44 pm ]
Post subject:  Re: Crank stroke question?
997 stroke is much the same as a 1275.
I had a 997 motor (back when I was an apprentice) with a 1098 crank in it, we had to machine the tops off the pistons to get them below flush.

A 997 crank had a reputation for being `weak', but I don't see how it was weaker than a 1098- it had all the same dimensions except a slightly shorter stroke. Material (EN16) was identical.
Author:  adnams4ever [ Tue Oct 22, 2013 8:53 pm ]
Post subject:  Re: Crank stroke question?
Many thanks to all who have responded.
Dr Mini, to fit the 1098 crank in your old 997, did you use 1098 rods & did you have to machine or modify the gearbox to clear the crank?
Author:  drmini in aust [ Tue Oct 22, 2013 8:56 pm ]
Post subject:  Re: Crank stroke question?
adnams4ever wrote:
Many thanks to all who have responded.
Dr Mini, to fit the 1098 crank in your old 997, did you use 1098 rods & did you have to machine or modify the gearbox to clear the crank?

I kept the 997 rods (which are same as 850 ones, with split little end & clamp bolt).
I can't remember now if we had to mod the gearbox, it was back in 1964... but it would just about have cleared it I'd say.
These days I would use 998/1098 rods, the floating little end is stronger.
Author:  MrFail [ Tue Oct 22, 2013 9:00 pm ]
Post subject:  Re: Crank stroke question?
drmini in aust wrote:
997 stroke is much the same as a 1275.
I had a 997 motor (back when I was an apprentice) with a 1098 crank in it, we had to machine the tops off the pistons to get them below flush.


so what size did that make it??
What was it like compared to other engines?
Author:  drmini in aust [ Tue Oct 22, 2013 9:55 pm ]
Post subject:  Re: Crank stroke question?
MrFail wrote:
drmini in aust wrote:
997 stroke is much the same as a 1275.
I had a 997 motor (back when I was an apprentice) with a 1098 crank in it, we had to machine the tops off the pistons to get them below flush.


so what size did that make it??
What was it like compared to other engines?

Pistons were 997 Cooper +.030", with a 1098 crank it was 1058cc.
Cam was a Waggott 18/58, it ran a big ported Deluxe head, twin Amal Monobloc 1-3/16" bike carbs (off a Triumph Bonneville?) and a Sonic LCB.
It was pretty quick for what it was, back then in the days of 850s and 997 Coopers.
It went even harder 2 years later when I bored it to 68mm, fitted a new 1098 crank & rods, Imp pistons, a 544 cam, ported 1275 head and twin HS4s... :P
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