Changing pistons on balanced rotating assembly?

Today I found out my Eagle 347 rotating assembly was balanced and shipped to me with the wrong (331) pistons. [img]/forums/images/smiles/icon_frown.gif[/img]
The vendor has offered to change out the pistons, but the correct pistons are 6-8 grams lighter. Do I need to have the rotating assembly re-balanced?

No problem with only 8 grams

You do not need a rebalance if all 8 pistons weigh the same. Get a digital scale good to the .1 of a pound and weigh them all then make them al the same weight as the lightest one. If they are all within one tenth of a pound then you should be fine, I think that's about 4 grams...


FE
P.S> I just balanced my rotating assy for my 66 mustang last weekend at home...
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The wrong pistons were all within 1 gram, I hope the correct replacements will be as well. According to the SRP catalog there's only a 6 gram difference between the 331 and 347 flat tops, so all should be good.
I'll off course have to weigh them, cc them and measure them for bore clearence again. I just wish I found out before assemblng the pistons on the connecting rods and installing 32 spriro-locks [img]/forums/images/smiles/icon_frown.gif[/img]
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At least you only have to take out 16 locks [img]/forums/images/smiles/icon_tup.gif[/img]

The actual weight of the piston don't matter.... as long as they are all the same or within a few grams...
Of course it helps to fit the bore and it also helps to not hit the head...

Where did you get a scale to measure up to 20 ounces and be accurate to one gram I am wondering..... Because I want one!

FE
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Ahh, the joys of the metric system [img]/forums/images/smiles/icon_smile.gif[/img] You can get electronic scales that measure in grams just about anywhere in Europe, it's the SBF rotating assemblies you have to get all the way from th US that cause all the problems [img]/forums/images/smiles/icon_smile.gif[/img]

<font size=-1>[ This Message was edited by: tminus3 on 10/18/06 3:26am ]</font>

I always balance my rods and pistons my self. I did a set of rods for a VW that were balanced, they were way off, as a whole they were ok but when I checked the small ends and big ends....not even close.

here is a pic of my clevor rods I got off e-bay I get them to with in 1/10 of a gram. takes a while.....

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The metric system is NOT even close to being as accurate as our original system! Don't even try to tell me it is.


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Our system is a joke. End of story.