New shells too tight

[melanddoug]

Hi all,

Not having much luck at the moment

While fitting new piston rings to my (late) 1971 1098 Traveller , I thought I "Might as well" fit new big end shells at the same time. It wasn't rattling particularly s o this is a case of may as wel while I'm in there.

I ordered a set of these :
http://morrisminorspares.co.uk/shop/pro ... 9b600b575c

And started fitting them. However they seem too big - well sort of. They look exactly the same as the old shells, and seem to fit into the big end and cap ok - but when I tighten them up, they lock the engine solid.

They're standardsize : the crank hasn't had a regrind. I'mnow tempted to fefit the old shells just to get the poor car back on the road, but this surely isn't too good a plan ?

I can't work out whether I've bouight the wrong shells or am doing something wrong techniqe-wise.

Some further info to save "Q-&-A tennis" :

The number stamped on the old shell is 12A630 STD (AVGA4)
The new ones are stamped COUNTY REGD UK 0417 STD LO

(I assume this is just because the're a different make)

I'm fitting the kind of bent tongune part of the shells into the slot in the big end and cap
Said tongues are fitted opposite each other, as they were when I dismantled the car
I don't think the crank is particularly ovalled - as mentioned it wasn't making any horrid noises, so there wasn't any reason to think the bottom end of the engine was shot. Even if the crank is worn, these new shells should fit (even more easily!)

Is there a technique to getting these to fit ?
I'm tightening one at a time and they're all behaving the same way, and dowsing them in engine oil before tightening. I've kept the correct cap with the correct big end.

Any advice gratefully received ..
thanks!

Doug

[melanddoug]

PS. I'd just like to compliment myself on my magnificent typing skills during that passage. World-class tryping.

[bmcecosse]

I suppose it's 'just' possible the shells are in some way faulty - but highly unlikely. The tabs should go TOGETHER - not sure if that's what your 'opposite' means ..... If they have somehow supplied oversize shells (to suit a reground/undersize crank) then indeed that would cause seizure on a standard crank - but they would surely be marked 10/20/30 etc to show the oversize. You certainly must not continue - but refitting old shells - even if you know exactly which cap/rod they came off - is a poor way to go.

[MarkyB]

How many WPM was it done at then .
Do the pistons slide in the bores OK?
How are you trying to turn the engine over and has it be rebored or just reringed?
If you only do one up is the engine still seized?

[bmcecosse]

Hmm - good point there - is it indeed the pistons that are too tight? If you leave the big ends slightly slack - does it turn over ok?

[katy]

Mike the thickness of the old shells and the new ones to see if there is a difference.

[rv8]

refit caps tabs to tabs, dont oil behind the bearings,fit one at a time.
i was an engine manufacturer with pitcairn engineering and thats the best advice i can give.conrods the right way round?

[chrisryder]

silly question, but does the crank turn freely with no big ends fitted? i had a crank that would turn with loose main caps and lock solid when tightened. turned out i'd got main caps of a different engine (took too many apart in one go!), but you could have the middle main cap the wrong way around possibly.

[melanddoug]

Lots of good food for thought here -

First thing I've gleaned is that I'm seemingly putting the caps on the wrong way round - I thought the tongue parts were "away from" each other when I took it apart. I could be wrong - sounds like I am. So they should go together, against each other - I'll try that first thing tomorrow after a truly gargantuan cup of tea.

Since writng that post, I also tried aligning the caps sideways until the bolts were easily finger-turnable (so when in situ: forwards/backwards along the length of the car) which freed things up a bit, but not enough. Seems like even though the bolts and castings look like they'll automatically align, there's still a bit of freedom for things being slightly out. (Er especially if I've got the caps the wrong way around!) Looks like alignment 'helped' by putting the caps on the right way roound is the answer.

If I loosen the big end caps, the crank spins freeely with the pistons in place - about like I'd expect with new rings (no a rebore). The starter turns it easily.
I've checked the new shell thickness vs. the old ones and they're .001 mm different (old ones smaller), which I'd attributed to the old shells being slightly worn, so I don't think i've got the wrong shells.

"don't oil the back of the shells" : Well I was doing that - so I'll stop that particular habit also.
Conrods are the right way round (checked that a few times just to be dead sure! )

thanks again for all your help. Steep learning curve ...
Probably need another new set of shells. Dang.

Doug

[bmcecosse]

You HAVE been putting the caps on wrong way round....... Just wipe the cap, fit the shell - and fit tabs together. It will be fine.

[chrisryder]

tabs go together? i thought they were opposite... pretty sure that's how mine came apart and went back together...

[mike.perry]

There is a diagram in the workshop manual

[Chris Edgar]

When I did mine recently, each con rod & cap have a number stamped on opposite sides .
Numbers 1 to 4, for each cylinder of course.
But the stampings on opposite sides of the con rods & caps are of different sizes, so it was easy to see which way round that the caps should be re-fitted, larger stampings matching on the same side.

Having said that, on No.4 con rod & cap, the stampings were very indistinct with the result that I fitted the cap the wrong way round at first & couldn't turn the engine after No. 4 was fitted. I the noticed that the cap was very slightly offset as regards to the con rod & re- fitted the correct way around.

This was on a 1275 Marina engine, by the way...I don't know if the same system is used on 1098cc.

Chris

[melanddoug]

You HAVE been putting the caps on wrong way round....... Just wipe the cap, fit the shell - and fit tabs together. It will be fine.

when I swapped them around, it all went together like lego and now spins nicely.. thank you all so much!

Doug

[aupickup]

well done

[MarkyB]

Seconded!

[bmcecosse]

[beero]

Well done. You said about a steep learning curve, well I was wondering, as you are doing the rings as well, did you have the bores honed?

[melanddoug]

Well done. You said about a steep learning curve, well I was wondering, as you are doing the rings as well, did you have the bores honed?

Hi Beero,

No I didn't have the bores honed- I checked them and there was hardly any lip at the top of the ring travel so I concluded they were'nt too worn (the rings I took out were worn quite a lot though - lucky!). Also I'm not sure how much a rebore costs but when the cost gets to a "couple of hundred quid" then I'm all for cutting losses (in time) and buying a reconditioned short engine and saving the aggro. (Ended up with more aggro this way though! oh well, I've learnt loads)

Anyway, after I put the caps on the right way 'round it all went together and 4 hours later I was doing my first 2 miles in the car.It started first time, smoked horribly for the first mile but quite suddenly stopped (as the new rings bed in?) - and now I've just done about 15 miles - zero smoke and it runs SO smoothly and quietly! I guess we'll see how it lasts.

Thanks again all - this is probably the 3rd or 4th time your excellent advice has saved me loads of time.

Doug