crankshafts

Post by **paul.kissick** » Tue Apr 18, 2006 10:26 am

Hello everyone. I was chatting to afella about the 1098 engine and tuning it and he says that the engine would tune fine but the crank would break because its not strong enough to handle any more than its standard 48bhp. Is there any truth behind this, if so would would be the best option. Remember i am trying to keep the car as original as possible.

Post by **picky** » Tue Apr 18, 2006 10:53 am

depends how far you push the car, the standard 1098 crank will take more than 48BHP, but you would be advised to fit a crankshaft damper and centre main bearing strap, which give the crank a bit of an easier life. its mainly high revs that will damage it rather than the amount of power it gets... I think! somebody might correct me... But if you wanted an extra 10-15BHP for motorway driving or something then the crank can stay as it is. If you want it to look original then I would get a modified cylinder head, and keep the rest standard then it will look exactly the same

hope this helps,
Tim

Post by **KirstMin** » Tue Apr 18, 2006 12:19 pm

AND think about the brakes AND think about the handling

Our friend BMC says that you'll break the engine if you rev it highly.

Post by **bmcecosse** » Tue Apr 18, 2006 1:12 pm

Unfortunately the crank has a very long stroke - and breaks if revved much over 6000 rpm for any length of time. It CAN go to 7000 for very short bursts - but it would be best to stay below 6000. Crank damper is essential - I wouldn't worry about the centre main strap - that's for high revs and this engine is not going to rev high!. Of course there was a much stronger bersion of the 1098 engine fitted to Spridgets before they went to 1275. This had bigger main bearings and was therefore good for 7000 rpm. These engines are hard to find now! Best way then is to tune the engine for torque - not necessarily high revs. The MG Metro camshaft and a big valve head from a 1275 engine is a way to go. With a decent carb(s) and exhaust that should be good for 70 bhp without exceeding 6000rpm.

Post by **KirstMin** » Tue Apr 18, 2006 4:22 pm

Hey BMC, what about the 1275? Can that be revved higher than the 1098?

Post by **Packedup** » Tue Apr 18, 2006 5:24 pm

I wonder how the 1098 managed to run in MG tune if more than 48hp kills it...

Post by **Cam** » Tue Apr 18, 2006 5:54 pm

KirstMin wrote:Hey BMC, what about the 1275? Can that be revved higher than the 1098?

Yes it can. Mine is good for 8000 RPM but I only take it as far as 7000. Having said that it's balanced, toughened, has a centre strap and race bearings fitted.

It's got a shorter stroke than the 1098 too.

The 1098 won't break if you take it over 48 BHP but it's not an ideal base for a tuned engine. Best get a short stroke one or start with a 1275.

Post by **picky** » Tue Apr 18, 2006 8:36 pm

paul.kissick,
The 1275 units have more bearings holding the crankshaft in place, so it cant bend as much as the 1098 ones.

Post by **paul.kissick** » Tue Apr 18, 2006 8:40 pm

anybody got a 1275 goin spare as there gettin hard to get over here

Post by **aupickup** » Tue Apr 18, 2006 9:12 pm

and harder and harder over here as well

Post by **bmcecosse** » Tue Apr 18, 2006 9:28 pm

More bearings holding the crank ? NO!! All A series are 3 bearing units. Yes - 1275 engines 'can' be revved to 8000 and beyond - only if the engine is thoroughly modified / balanced / toughened. 7000 is a sensible limit - even then - they tend to become very rough at high revs.
And inline 1275 engines are very very rare up here too - there is an engine reconditioner (555bigboy - on ebay) who pays way over the odds - and then sells them at fantastic prices!! Just last week a 1275 in 'running order' sold locally on ebay for almost £200 !

Post by **paul.kissick** » Tue Apr 18, 2006 9:37 pm

so if the car was revved below 6000rpm with all these mods put in it should be reliable. P.s where can i get hold of a crank stabilizer. Thanks paul

Post by **picky** » Tue Apr 18, 2006 9:40 pm

the 1275 doesnt have more bearings holding the crank?? what are people refering to then when they say a five bearing unit?? im interested...

Post by **bigginger** » Tue Apr 18, 2006 9:46 pm

One which has 5 bearings, which the 1275 doesn't

Post by **bmcecosse** » Tue Apr 18, 2006 9:47 pm

Later MGBs were 5 bearings - but not the A series.
For crankdamper - almost any Mini engine - certainly the East/West 1098 engines had them as standard, and all 1275 engines. New ones are available of course - but quite expensive. Yes the 1098 - if in good condition - will be fine if kept below 6000. hence my suggestion re MG Metro camshaft - it was 'designed' by MG/Rover to die at about 6000 - to cut down on warranty claims on the Mg Metro !! But it has great low-down torque - and is often on ebay for £10/15. You also need a different oil pump (short nose for the 1098) to match - but these later pumps are much better anyway.

Post by **picky** » Tue Apr 18, 2006 9:49 pm

I stand corrected... so the 1275 has a tougher better designed crank than the 1098, and larger bearings??

Post by **paul.kissick** » Tue Apr 18, 2006 9:51 pm

cheers bmc and the rest for the info i have found it very useful.

Post by **bmcecosse** » Tue Apr 18, 2006 10:00 pm

Yes - 1275 has larger diameter main bearings - although the later 1098 in the Spridget also had these. The big-ends are also larger diameter - however the Spridget engine did NOT have these ! The crank is designed to take the greater load of the more powerful engine - in later form in the A+ engine it has 'rolled fillet' edges to the bearing surfaces - again to reduce the chance of fatigue cracks starting at the sharp edge.