Re: [AMC-list] AMC factory engine balance

[tom jennings <tomj@xxxxxxx>]

On Fri, Feb 19, 2010 at 15:19, Sandwich Maker <adh@xxxxxxxxxxxxxxxxx> wrote:

>
> guys -- when you do the rods, you -do- check big-end and small-end
> weights separately, right?  big end weight adds unbalance at crank
> speed but small end weight, like the piston, adds unbalance at double
> crank speed b/c it stops and starts twice per revolution.
>

Meh. I know that's good practice generally speaking, but this is a 4000 rpm
motor; the big end is 10 times the weight of the small end, and besides, the
moment arm of the little end just sort of oscillates back and forth a bit,
the piston mass swamps it. I dunno what good aftermarket parts weigh, but
this engine each piston and rod setup is 2.5 lbs each! And I got 'em
worst-case-spread (-g rod +g piston, say) of well under a gram, which is
0.1%.

I didn't deem it worth the effort in this instance. I checked a couple,
found them close enough and just did overall mass.
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