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Sadly I have just discovered a gudgeon pin has walked out and ruined the bore in my S motor, my trouble is its already at 73.5mm. I reckon my options are;

1 Try to get it linered and then go for a reduced bore size which will probably reduce performance

2 What are the chances of going out to 74mm?

3 Try to put the bottom end into a pre A Plus block, I'm not sure if the crank will be a straight swop?

Now, I'm also wondering why the pin moved in the first place, its gone both ways actually. Press fit rods btw, so should I bin the rods too, have a midget set available here, but then will I not trash the pistons (omegas) getting them off the rods now? Or keep the existing rods and use Teflon buttons?

Hello

Sorry to here you have problems with engine , options are -

1 yes , you can liner the block , I have fitted loads of them

2 yes you can go to 74MM , but would not recommend it with a cooper s block

3 yes , you can fit your bits in to a 1300 block but you will have to thin down thrust washers to suit .

Pistons pins normally come loose because the little end in the con rod has stretched and gone out of shape , we always measure them before re-use now

Yes the omega piston will come off and be good to re-use.

Thanks for the reply!
Do you think I will hit the famous oil gallery going to 74mm or is it just gasket problems? Its no use as it is right now anyway. If i get it linered what is it worth to sell on? I am almost starting over again apart from having a really good cyl head, and that was always meant to be on a 1380.

Gonna get dear again, dry builds and setting up squish etc.

If you have sleaves / liners fitted, you'll probably need to do all bores as pressing the sleave in to the damaged bore will distort the adjacent bores, if it doesn't, then it won't be a tight enough fit.

As 251 ENG has said regarding the rods, most likely the little end is out of spec, though the pin could be undersize. IMO, make all the pins floaters (just hone the little ends) and fit buttons.

If you want to let the S block go I can do you a deal on a freshly machined A-series or A+ block .

pm me

Thanks

Simon