Crankshaft pulley

[mobylette]

I am rebuilding an engine and found the crankshaft pulley to be badly worn where it runs inside the timing case oil seal. I found this nice cast pulley on E bay. Stated Part No: 12A1380 & suitable for a mini 850, it fits perfectly, but is some what larger than the original, 135mm outside diameter against 118mm. This will spin the water pump & dynamo a bit faster. Do you think this will cause problems? Picture attached. Thanks.[frame][/frame]

[lambrettalad]

if it does it will at higher revs,dynamo will think the engine is going faster than it is and the water pump will make the engine run cooler(if they can think??? )I would be a little concerned with the quality of the remade water pump bearings, and a slipping fanbelt is a possibility,but if you dont thrash the engine,should be ok all the rest being equal .tho some on here may know better ,

[katy]

At higher revs the water pump may just cavitate from turning too fast.
Why not just put a speedy-sleeve on the original pulley?

[bmcecosse]

I've NEVER come across a larger pulley - are you sure? Don't measure the OD - measure the size across the fan belt driving groove. But in the event - it won't matter a hoot. Later Minis etc used a large diameter water pump pulley to reduce the fan and water pump speed....but this larger crank pulley is a real mystery. Can you point me to the ebay sale - even though it's now finished...... ?

[mobylette]

Definitely larger, and the seller has plenty more. They are new old stock, see this link: http://www.ebay.co.uk/itm/NEW-AUSTIN-MI ... 8892173%26

[bmcecosse]

The centre hole looks too large........have you tried it on the crank??

[mobylette]

I have found some info on this pulley (part no 12A1380) from a Somerford mini parts catalogue as follows:

Crankshaft Pulley
The 848cc engine was never fitted with a vibration damper type pulley. The 997cc unit did receive one,
or in fact two different ones. The original design was a separate pulley with a damper screwed to it;
eventually a one-piece damper pulley was offered as a replacement but in fact both set ups remained
available as spares alongside each other for many years. If you want the original pulley, it is still
available today from Somerford Mini.
Note that the bolt retaining the pulley to the crankshaft is specific to the type of pulley being fitted.
Later ’85H’ 848cc engines from 1980 approximately onwards received a pulley with a strobe timing plate
attached as par t of the A Plus modification programme.
848cc Crankshaft Pulley
26 2A940 PULLEY, crankshaft 1 1959-70, dynamo fitted models .
12A1380 PULLEY, crankshaft 1 1959-70, alternator fitted models

[mobylette]

As I said, it fits perfectly.

[bmcecosse]

Well done ! I've learned something new today - and a good buy at that price because the old pressed steel pulleys are now beginning to fall apart - this 'solid' one should last for ever.

[mobylette]

Thought you might like to see the pulley fitted. I have used the standard fan belt, and the tension adjuster plate is using about half it's travel . Looks OK to me. I'll let you know what happens once it's on the road[frame][/frame]

[bmcecosse]

The later Minis used a larger diameter water pump pulley - so you could fit that to slow the pump (and fan) back to normal speed.

[rayofleamington]

Or fit a decent cam & bigger valves and run everything at higher speed... (sorry Roy, it's been Roy bating day so couldn't resist a cam reference)

[bmcecosse]

Yes of course - but it becomes a very different engine then....... I'm all for that approach. And by the way - my experience with the toothed belts (in industry and on Minis/Minors) tells me to AVOID them.....

[mobylette]

I agree re the toothed belt, but I acquired it gratis, and have a spare "proper" one in the boot. I will see how long it lasts.
Can't afford fancy cams and big valves sadly. I find the best way to go fast is not to slow down.

[M25VAN]

Is the notch on the pulley in the correct place for timing purposes?

[mobylette]

Yep

[bmcecosse]

Why does the notch matter? 'Timing' is a waste of time !!

[M25VAN]

Why does the notch matter? 'Timing' is a waste of time !!

I walked straight into that one.

[bmcecosse]

[MarkyB]

'Timing' is a waste of time !!

You don't actually mean this, just the method of achieving it.