Piston Weights Difference?

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stephenpolhill
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Piston Weights Difference?

Post by stephenpolhill »

Hi There.
We are hoping to replace just the one knackered piston from my 1098 engine. A friend has given us one that is the same only after having weighed it, is is 6g lighter than the others. The original 4 pistons are at most 1g apart in weight but the 'second hand' one 6g. Could anyone tell me is this difference is fine and we can use it, should we make the others lighter or any other option?
The second hand piston has a 3 on, and all but one of my original pistons have a 2 on it. Maybe this changes things? If so, please explain? :lol:
Thanks
Steve


Just J-j-j-jiggle it a bit.
'Fiona' - a 1965 original 'C' 2dr in Almond Green
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bmcecosse
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Re: Piston Weights Difference?

Post by bmcecosse »

If you are sure it's a 1098 piston, and same bore size as the others - and same 'dish' as the others - then yes -I would take weight off the others to make them all the same! But then - I always did that with my engines anyway! The '3' won't matter! You're ging to be running it in a pretty well messed up bore anyway.
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stephenpolhill
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Re: Piston Weights Difference?

Post by stephenpolhill »

And is there a recommended way we should take the weight off the other pistons?


Just J-j-j-jiggle it a bit.
'Fiona' - a 1965 original 'C' 2dr in Almond Green
http://www.facebook.com/album.php?aid=1 ... bc64c7805b
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bmcecosse
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Re: Piston Weights Difference?

Post by bmcecosse »

I used to take it off the skirts. But - I also used to machine most of the skirt away anyway - to lighten the pistons as much as possible! I would check the new piston very carefully - does it have the exact same 'dish' as your own ? And the same compression height - ie distance from gudgeon pin to top of piston. If all seems ok - and you don't intend to 'rev' the engine highly - just use as is. But - since you have taken the trouble to weigh them all - it would be nice/satisfying to get them all to the same weight!
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PSL184
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Re: Piston Weights Difference?

Post by PSL184 »

6 gms won't make a jot of a difference in a standard engine =- don't worry about it !!
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bmcecosse
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Re: Piston Weights Difference?

Post by bmcecosse »

It is well out of spec - as you can see - the remaining 3 are within 1 gm. It would be nice to get them right - now you know they are different! And - it won't take more than a few minutes - just file off the skirt.
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linearaudio

Re: Piston Weights Difference?

Post by linearaudio »

About 1 1/2 teaspoons full of alloy dust for a rough idea! File at an angle round the inside of the skirt to get a nice even chamfer all round.
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