45 replies to this topic

[Pigeonto]

So, are we to take it that if you just loosen no.3 big end nuts,say 1/2 turn each,it frees off? This could be quite a number of things from a little bit of grit found its way behind the top or lower shell,an unfortunate tho unlikely bad shell which is too thick, through to a bent rod. If you remove the cap on 3, you will soon see how tight that piston is by pushing it up and down the bore without allowing the rings to pop out of the bore especially at the bottom, though you would have noticed this when installing the piston initially. If the shells are tight on the crank there will be a noticeable dark area on the shell where the contact is heavy.

Edited by Pigeonto, 21 November 2012 - 06:13 PM.

[Club man]

Yes spot on, half a turn back the engine is perfect, the piston runs in the bore very nicely

Its only stiff on the first initial turn

Is this somthing that will bed in as i run the engine in do you think ?

Could i have done something wrong with the shells ?

Thank you

Edited by Club man, 21 November 2012 - 06:49 PM.

[Pigeonto]

I think I would take the shells from one of the other 3 and try them in the bad one

[Club man]

Ahhh yes, good idea, that can be my next job then, i was thinking of going with the old ones i removed as to me they don't seem massively worn, i was replacing them as part of the rebuild rather than due to wear, but I suppose its hard to tell the amount of wear by eye

I will post what happens when i swap about

Can you buy the bearings in singles rather than complete sets?

Thanks for help

Edited by Club man, 21 November 2012 - 06:55 PM.

[Pigeonto]

ha ha, sadly no you cant ! That's probably a quicker and better idea rather than disturb the other 3.If you only changed them as a matter of course then to be honest the old ones probably werent worn at all. In my experience the shells are very badly sized and do vary. I've seen .4thou running clearance with new -10thou shells on a reground crank.I didnt use it and made him regrind to -17thou then used -20 shells. Ran really nice and quiet too.But i digress. You must check VERY closely that there is no damage to the rod or cap such as being dropped and causing one of the surfaces to have a high spot.As I said, look at the shells and see if there is any dark contact areas

[Club man]

Thought as much, if i have got a dud one im going to pull the originals out and and see how they look, rather than spend another £50+ for poor ones, its quite a low mileage engine and weve had it since new so know its been looked after

Thanks again

[Carlos W]

Have you done this?

Whilst the rings are off the pistons do a 'dummy build' and re-fit the rods/pistons with the rings off. Now make sure with each rod fitted in turn the engine turns with virtually no more stiffness than with just the crank, as the pistons without rings will not cause any drag.

[Club man]

Have you done this?

Whilst the rings are off the pistons do a 'dummy build' and re-fit the rods/pistons with the rings off. Now make sure with each rod fitted in turn the engine turns with virtually no more stiffness than with just the crank, as the pistons without rings will not cause any drag.

Thankyou, yes its how i built it up after stripping down again and testing each part, following coopermans guide, and its also noticeably better when you loosen the cap off, so its got to be this

Going to mess around swaping bearing about as suggested by pigeonto and see how it is then

Thanks

[Club man]

This is the tight bearing on the right of the photo lots of silver showing compared to the rest

The other bearing on the left is one of the originals does this look to worn to use this set again?

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Edited by Club man, 21 November 2012 - 08:29 PM.

[Pigeonto]

Just build it up and see. Looking isnt really any help.I would be extremely surprised if the new ones were any tighter than the old(excepting the problem one) :-/ choose the best looking ones. If you're really keen, find some one with a digital vernier caliper and they could measure an old shell but I'd just use the best two.Put it together and forget it if its nice and free.Unfortunately this is an area where the factory went for a 'safe' fit and this always meant they were loose not tight because it was a matter of how many they could build in a day so a tight one would just hold things up.Not quite like modern jap builds. They did actually colour code the mains,not the big ends, at one point and got a better fit by matching the main shells(3 different choices of size) to the size of the crank

[Cooperman]

It sounds as though one of the shells is a bit too thick and this has happened before to others. If you have a micrometer check the thickness of the suspect shells compared to the originals.
Alternatively the big end and cap could be very slightly undersize but still within tolerance whilst the bearing shells are a bit thick but still within normal tolerance.
I once had an MPI engine where the centre main bearing housing was very slightly undersize as manufactured by Rover. It went very stiff when the centre cap bolts were torqued to the correct figure. I suspected a bent crank, but using a DTI on the centre journal whilst rotating the crank proved that was not the case. In the end I linished the outside faces of the centre bearing shells until it turned perfectly.
You can get some funny things with this old technology and sometimes have to 'hand-finish' parts to get a proper fit.

Edited by Cooperman, 21 November 2012 - 08:58 PM.

[Club man]

Thank you, good information here from you guys again

Pigeonto - do you mean replace the bad ones on no 3 with two of my good old ones provided they check out and turn ok

Cooperman - Would you recommend me trying that method of sanding the thick shell down a bit or is it something for someone a bit more experienced than myself

Thanks

[Club man]

Anyone used these ones they look alright and only a third of the price of my others which may seem to be maybe not so good

http://www.ebay.co.u...85268133&_uhb=1

Ta

[Cooperman]

Try the original shells and see if it all turns freely with those installed. Then go back to the new ones and try nagain. If they are still stiff then it's an issue with the new shells. Two choices then: either lightly linish the back face of the new shells and keep on re-trying until it turns freely or re-fit the original ones.
If you decide to lightly linish use fine emory cloth (or 800 grit wet & dry paper) and do it evenly all over the back faces.
The only problem is that torquing and un-doing, then re-torquing and re-un-doing lots of times is not good for the big-end bolts & nuts, so once it's OK fit new bolts and nuts to that cap.

[Artful Dodger]

If they are the ones in the box then they should be passable. They have a federal mogul stamping on the box