install 1 new piston?

I just pulled the head on my '76 MGB to find #3 piston with the top edge burned through (hole). It was losing oil and suddenly started smoking - compression was 132-120-25-140. The other piston tops appear ok and the #3 cylinder wall looks ok.

My question - can I replace just that one piston? I'd rather not have to so them all if they're ok (the less mucking I do the better). Do I just buy a stock set of pistons or do I need to measure the cylinder to see if they're overbored or something?

Also can all this be done without disturbing the crankshaft?

Thanks for any advice. tom

I just pulled the head on my '76 MGB to find #3 piston with the top edge burned through (hole). It was losing oil and suddenly started smoking - compression was 132-120-25-140. The other piston tops appear ok and the #3 cylinder wall looks ok.

My question - can I replace just that one piston? I'd rather not have to so them all if they're ok (the less mucking I do the better). Do I just buy a stock set of pistons or do I need to measure the cylinder to see if they're overbored or something?

Also can all this be done without disturbing the crankshaft?

Thanks for any advice. tom


Hi, I would only replace 1 piston IF: The cylinder wall is in good shape and the other cylinders are not showing much wear. You must measure the cylinder to be repaired to check its bore size and to see if the bore is not round. Check your measurements against a good shop manual to be sure the cylinder is within specs. Finally, remember when you repair this clyinder, it will have significantly more compression than the others. As far as i know this can be acomplished with the motor in the car provided you remove the oil pan. I hope this answers some of your questions.

Be careful on ordering pistons. MGB's had several styles through the years. A piston swap will not disturb the camshaft. HAve fun!

Personally I wouldn't replace just one. Probability is they've all been in there the same amount of time. The only way I would only replace one is if they are low milage.

I would have to agree, i would be more inclined to replace all four, if the sump and heads are off you might as well do it all!

If budget is more of an issue that balance & vibration, replacing just one will work.
Just match it to the origonal as best you can.