Morris Minor Owners Club

Hi Guys,

Whilst rebuilding my 1098 engine, I've stupidly managed to drop one of the piston assemblies. Would this be enought to distort the piston, as it now doesn't seem to fit in the bore?

Does anyone know where it's possible to source a single piston? I don't really want to have to spend £120+ on a new set.

I'm really miffed about this as well as embarassed as I'm an engineer by trade

Regards

John

At a guess I'd have to say they should be tough enough not to distort.

Have you raised a burr on an edge? Carefully file off if you have. That'd be enough to stop it going in!

Never tried to source just one, sorry.

Oh dear - post up some pictures - any obvious damage ? Have you run a vernier over it to compare size with the others ? I would have expected the main body to retain it's shape/size ok - maybe just the skirt edge that's distorted? I used to machine the skirts off anyway - to reduce piston weight !

Which part doesn't fit?
If the piston has distorted it should be fairly obvious where, when you offer it into the bore.

Have you fitted the others?

I couldn't get the piston into the bore, so it could be that the skirt has distorted slightly. There was a slight dink in the edge of the crown, which I smoothed with a fine file.

I haven't fitted the other pistons yet, it was all a bit of a nightmare today. I will go down to the garage tomorrow, now I've calmed down a little.

Try one of the others first.
Have you cleaned off the ring of carbon that builds up at the top of the bore?

Mostly DON'T PANIC!

"Stercus accidit" as the Romans may have said, but we carry on and find solutions.

hi I purchased one new piston complete with rings in 2008 10m122+20 from Morris Minor Centre Birmingham for £38.34 not inc Vat. Hope you get it sorted its quite a bit just for one piston.

Are you refitting original pistons back into the bores they came out from - or are these new pistons going in old bores - or new pistons in new bores ??

Having said that you have not fitted the other pistons, you have got the correct size pistons?

Hi,

these are +20thou pistons in new rebored bores, again +20thou. I haven't fitted the other pistons as I decided to leave them as opposed to really losing the plot and doing something I could come to regret or not afford

I can hardly believe that dropping a piston on the floor could do enough damage to prevent it from fitting the bore.

Now dropping a carburetor or a distributor .... well, don't ask how I know .

Any of the set of pistons you have should fit into any of the newly bored cylinders. If they are already mounted on the connecting rods, those should be in order but for trial fitting - any piston, any hole. Have the rings been put in the grooves? They will certainly prevent the piston going down the hole until you squeeze them with a ring compressor. If the skirts will not even start then the holes must be the wrong size.

Darrell

If the body of the piston wont fit in the bore don't be tempted to tap it in with anything more than your knuckle.
The piston should be a sliding fit.

EASY sliding fit - it's only the rings that touch the bore.

Did the person that did the boring have the pistons at hand to check the fit in the cylinders?
They usually do, so that they can bore and finish to the right clearance for that particular set of pistons.
According to the BMC manual, the clearance should be: Bottom of skirt - .0005" to .0011", Top of skirt - .0021" to .0037"

The piston had been fitted into the bore, turned the block over on the engine cradle to bolt the end cap on and the slippery litle b****r slid out of the bore before I could stop it.

Hazards of using an engine stand.......and actually, I can't think of ANY advantages! Must be a struggle to get it on/off the stand too! An old desk works fine for me, and no danger of anything falling. Have to say - if it was piston with rings - it shouldn't have been free enough to slide in the bore !

Ditto - shouldn't have been free enough to slip out under its own weight.....even when oiled.

Had you fitted the rings?

The weight of the conrod would pull it out without the rings fitted.