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Long story short, I have a set of pistons that would not work for my block(ring groove to shallow) I bought another set off the web and the problem is they are 17 grams heavier. The rotator was balanced with the other lighter pistons. Question is can I just mill off the 17 grams? They have plenty of dome, or should I take and have the assy re-bananced? Or is 17grams enough to worry about? BBC 555ci 7500rpm max.
Thanks,
Mike
 

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Rebalance.. Period. I switch pistons on my Windsor and they weren't to far off weight wise but still it needed to be rebalanced
 

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Figure the total % it will change the balance... you may be surprised that it's very little. Especially if the engine was possibly overbalanced to begin with. There's a chance you could just run them. I overbalanced all my stuff to 52%.
 

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17 grams is a HANDFULL OF ALUMINUM CHIPS......


find another wrist pin..

or at the minimum, you may be able to machine chamfer the wrist pin inside diameter and gain half of what you need...but do not chamfer below the inner diameter of the spirolock...
 

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because cutting a pin is just not a good idea. you would have to grind it and its easier to buy a lighter set of pins if you wanna go that route.
 

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Figure the total % it will change the balance... you may be surprised that it's very little. Especially if the engine was possibly overbalanced to begin with. There's a chance you could just run them. I overbalanced all my stuff to 52%.
I recently installed a new set of pistons in my engine..They were slightly heavier than my last ones.. And my engine builder was trying to explain to me about "overbalanced".. As the reason my whole engine didn't need rebalancing..
 

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Are the pistons solid dome?

Are they the right dome volume?

Ive milled the dome completely off a set before and made em.flat tops. They were a solid dome design.

Maybe some weight can be lost there as wheel if you need to adjust your compression.
 

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Are the pistons solid dome?

Are they the right dome volume?

Ive milled the dome completely off a set before and made em.flat tops. They were a solid dome design.

Maybe some weight can be lost there as wheel if you need to adjust your compression.
I just had my domes milled off to lower compression and thats what my machinist had to find out ....if they were solid dome before he could do it.....also had it rebalanced......seems to be working fine.
 

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If you know the balance weights it's simple. Bobweight total needs to be 100% of rotating and __% of reciprocating. I used 52% in my small blocks to smooth things out at higher engine speeds. You may well find that 17g doesn't change the percentage significantly and if it's already overbalanced 2-4% which is common... it may be fine.
 

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I'm not sayin to GRIND your pin. I'm sayin its too hard to cut. and when something is so hard you would have to grind... NOT A GOOD IDEA!!! swap pins don't jack with the pins you are asking for trouble. SWAP THEM
 
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