Reground, crank duff?.

[Rust bucket]

Just started rebuilding my 1098 engine, bought a reground crank and shells from a well known parts specialist, the shells match the size stamped on the crank which are +20 and +10
Casting has been rubbed clean with emery paper so no rubbish under the shells, oiled them well but when I lay the crank in and it's fully home I can't turn the crank, only with two hands on the webs, that's before I even put the bottom bearings on and tighted it all up!..

[IslipMinor]

Do you have a micrometer to measure the journals? If you don't, pop round with the crank and I will measure them with you - I live north of Oxford by about 5 miles. PM sent with contact details.

[Rust bucket]

I have a slide gauge and they are 1.734in measuring top to bottom and side to side.

[IslipMinor]

If that is the true size, it explains the problem you are having. The nominal size is 1.7505" - 1.7510", reducing in 0.010" increments, down to a minimum of 1.7105". If yours is -020, it should be 1.7305 - so at 1.734" it is 0.0035" too big, and will certainly bind completely if the cap is tightened in any way.

Would you like a double check, before you go back to the supplier?

[Rust bucket]

It's could be 1.733 or 1.735 but it is sure not 1.7305, thank you very much for the info.

[ferret76]

I had a similar experience. The new crank rocked noticably before I had even put the main bearing caps on. With them on and the bolt finger tight the whole thing was seized. I thought I was losing my mind, how could this be possible with a newly re-ground crankshaft? Took it to a local engineering firm and they confirmed that the shaft was bent and pretty much un-salvageable. My question was, how did they re-grind it if it was bent? I can't imagine that forces exerted on the package on it's way from the UK to Australia were enough to bend it, unless it came by a sub-orbital scram-jet and was bent on re-entry and touch down somewhere in the Simpson Desert.
At the end of the day, I put the old shaft back on with new bearings all round and it has worked perfectly, but I was bl**dy annoyed to say the least. Getting the shaft all the way from Blighty cost a pretty penny I have to say.

I won't name the supplier as I have had otherwise perfect service from them.

[bmcecosse]

Obviously the journal sizes need to be spot -on, so we await confirmation. But a crank could be bent if it was dropped - or had something heavy on top of it during transit. I have had a Mini crank straightened in the past - they simply banged it in a hand press -and it went into my 998 racing engine and was revved to the heavens without the slightest problem. So don't give up on that bent crank!!

[Rust bucket]

Had the crank checked and it's within tolerance, the shells match and the crank, I was told it's the block! centre bearing casting is slightly off and will need line honing too correct the problem.

Would it last once done or is it likely to move again and bind?.

[IslipMinor]

How did they check the block?

I do not understand how the 'centre bearing casting is slightly off' - do they mean the block or the centre main bearing cap? Does anyone else understand what this would mean?

Did they check the crank runout to make sure that it is not distorted in any way. Again, I can check the runout if you would like a second opinion? (I can't check the block as I don't have a co-ordinate measuring machine!)

[Rust bucket]

The crank was checked on two blocks and a dial guage on the centre by an engineer, i watched him do it, the shells were checked against the crank size that was okay so he put a streight edge on the block and a feeler guage did go down one side of the centre casting on the block showing it was out, he said this was very rare and the only answer was to have it line honed with the caps ajusted too match, i just hope it this will be okay.

[bmcecosse]

Never heard of such a thing... take it with a huge pinch of salt. But DO look carefully at the block casting above the centre main. It's not unknown for blocks to crack here, especially if they have had a roasting..... But I doubt the line boring will be cost-effective - just use another block if the crank runs ok in that?

[Rust bucket]

Yes i've been looking around that area, i can see casting marks and ridges, as for cracks no but then again they could be tiny, the engineer who deals a with tuned mini engines from a local firm said it was a very rare but not unkown for blocks to do this, just had it rebored and honed too .

[les]

How does the crank lay in the block without the caps on, does it spin then?

[Rust bucket]

No, that's when i knew something was wrong because i've been watching engine rebuilds on utube, you need both hands on the webs to turn this and it marks the front shell, anyone got a block for sale?.

[bmcecosse]

Was this engine running ok before you had the crank reground?

[Rust bucket]

Bought the car as a wreck, the engine would not start but when i took the head off the plugs were a nice coffee colour a good sign the engine was good, wrong, on strip down the bores and main bearing were shot, had the block rebored,bought a exchange crank (the first one) found the mains were ground to a wrong size for the shells, returned it and got another one, now this problem, the engine turned over before okay because the main bearing shells and original crank were well worn.

[bmcecosse]

I suppose if it was run with desperately worn bearings - it could have distorted the block. Another possibility is frost damage...were the core plugs in place - or pushed out?

[Rust bucket]

Core plugs are all in place,no sign of leakage, bearings were showing quite a lot of copper and the crank was oval, can't remember by how much.

[IslipMinor]

I would want to use much more than a straight edge before being certain that a block is distorted, as cast iron is a particularly stable material. Did the 'engineer' check the opposite side of the centre main to see if the straight edge 'rocked'? If one side has a gap through distortion, the other will be standing proud in relation to the front and rear main bearing bores, so holding a straight edge against the centre bore should produce a gap at the front and rear bores. Even it it did I would still want some other means of measurement to provide a good level of certainty.

The ultimate test is find another block and if the crank goes in and spins freely when fully fitted and caps torqued, then your existing block is the problem.

[bmcecosse]

I think earlier it was said that the crank was ok in another block. The other check would be another crank in this block...if the regrind-place has one handy. But I agree - this needs much better measurement than a straight edge can provide. And -are you sure you got your own block back after the reboring?? I was going to ask if it is any better fitted wrong way round in the block - but I'm not sure you can do that in a Minor - it is possible (only for a trial, obviously) with a Mini crank..