Piston Clearance

[Ozmadman]

I have just bought a 0.040" O/S Barrel and Piston(minus the rings) from a seller on ebay as a spare for my model 8. Both are not in bad nick(there is a barely discernible lip the top and that might just be a bit of carbon). Can anyone tell me (before I purchase some rings for it)how much clearance I should expect between the barrel and piston when it is in the bore without any rings on. The piston, which is marked +.040", can be moved side to side a reasonable amount??

thanks

Paul

[Rob Harknett]

All the answers should be found in your Manual, Don't forget the piston is oval when measuring, so designed, so when hot it becomes round.

[Ozmadman]

All the answers should be found in your Manual, Don't forget the piston is oval when measuring, so designed, so when hot it becomes round.

Thanks Rob.. I don't have all the fancy measuring gear can I do it with a feeler gauge ??(if so where?) The manual states (one of the sizes as standard) 2.834 with a piston skirt Dia of 2.8276 so that to me is a clearance of 0.0064" what does it mean piston skirt top and is the crown of a piston a slightly smaller diameter than the rest of it then??
Many thanks
paul

[iansoady]

Generally clearance is taken in a fore and aft direction at skirt level. As you say, the piston is slightly relieved in the top section where the rings go. And as Rob says, they're oval.

[Rob Harknett]

Piston position in the bore when measuring is given.
You did state about a lip at the top of the piston. This should be removed when fitting the new piston or rings.
In the new fittings catch it and top ring breaks. I have used the back of a knife blade to scrape off the lip.

[Ozmadman]

Piston position in the bore when measuring is given.

I have the genuine workshop manual but the only measurements I can find are in the front where all the measurements are. That's where I got the piston and bore sizes from as above. I am at work at the mo but will have another look in the manual when I get in later tonight

Thanks
Paul
Ps the lip I mentioned that is probably carbon is at the top of the bore, not on the piston???

[Rob Harknett]

I was referring to a lip on the bore that needs to be removed when fitting new parts in it.

[Ozmadman]

Thanks

[Rob Harknett]

I think you will have to go past the data page, into " engine overhaul " I am sure its in the manual " measuring the piston for wear " etc. Try also Hepolite sales cat. for more info and dimensions.

[corbal]

I also need a set of +40 rings for my 8 rebuild. If you find some please could you add to this string where purchased and cost.

Thanks Alan