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MG MGA - Weight balancing of pistons

Hi
I am about to reassemble the engine which has just been rebored. Originally the bottom end was balanced. I have now got +60 pistons to fit rebore and have weighed each one. The lightest is 483g and the heaviest 486g. Do I need to get them all to the same weight or is 3g difference acceptable.
Thanks Brian
Brian Paddon

what was the weight of the original pistons?
mog

Hi Mog
Just checked one of the original pistons and it weighs 498g
Brian
Brian Paddon

I think you want to add some weight, unless you get the crank balanced again.

I am sure somebody will advise how best to add weight to the pin?
mog

Brian,
I checked on Steve Strange's B-Series "The Book" as I recalled that he covered this subject in it. ( Page 136 )

I believe that if you are going to balance your engine, you are supposed to carefully weigh each piston and record these.(as you have already done)
Then weigh each con rod and its gudgeon pin.

You can then match the heaviest piston to the lightest conrod assembly to see if you can even up the weights of each complete con rod-pin-piston combination by doing this.

If you wish to match the weights even more than this, you can carefully remove metal from the inside the heavy pistons from around the gudgeon pin boss. Using a dremel or similar cutting tool.

This allows you to bring down the weights to match that of the lightest combination.

By doing this you have also reduced the reciprocating mass which helps the engine too.

I think I would ask an engine builder to do this for me so I could avoid ruining a piston ( or knowing my luck, a couple of pistons!)

Colyn

c firth

This thread was discussed on 07/12/2015

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