Reply to "Stroker engine vibration"

> for a Stroked Cleveland/Windsor You must go with the heavier 50 Oz, Weight!
> Because You are Balancing MORE weight, in Longer Crank 'Throws', Longer Rods,
> Larger Pistons and Other Parts.

I'm coming into this discussion late but this is wrong. First of all, the
balance factor is a product of mass and distance so the units are Oz-In,
not Oz. Second, I would never balance a Cleveland (stroker or not) to
50 oz-in. OEM balance for a 351C was 28.2 Oz-In (Boss 351C's were slightly
different). 50 Oz-In is the balance factor for later 5.0L SBF and is known
to be a problem at higher RPM. With 50 oz-in, the couple across the #1 main
is large; in SCCA A Sedan racing, it's very common for 50 Oz-In 5.0L cranks
to fail at the cheek of the rod throw. 28 Oz-In seems to be fine for most
applications under 7000 RPM, though many race teams will neutral balance so
they can interchange flywheels, pressure plates, dampers, etc. without affecting
balance. The usual choices for a 351C are 28.2 Oz-In and neutral. Neutral is
where all of the balancing is done within the crankshaft, rods, pistons and the
flyhweel and balancer are symmetric (no balance weights). SCAT desings its 351C
stroker cranks to a 28.2 Oz-In. They can typically be balanced to that spec by
drilling the crank throws with no Mallory metal required providing your piston
and rod combination weight is close to SCAT's target bobweight. With a lighter
I-beam rod and piston, the SCAT 351C stroker cranks can be internally balanced
without a lot of Mallory metal. My 403C was internally balanced with $175 worth
of Mallory metal.

> If you do not, they will balance the engine the easiest way for them, and
> that USUALLY means taking weight off of the flywheel and dampener.

Yup. Dave McLain does the machine work on my engines and uses spec flywheels
(neutral and 28.2 oz-in) and does all the balancing within the reciprocating
assembly, leaving the flywheel and balancer alone. That way, if you ever have
a problem where the flywheel or balancer has to be replaced, you can simply
bolt up a new one. You have the option to match balance components but I've
never had to do that, even when switching between flexplates and flywheels.
The guys running internal balancing do this all the time but there's no reason
the 28.2 oz-in assemblies can't be done the same way.

> P. Plates are balanced at the Factory, But they are NOT Balanced to Your
> Assembly!!

Pressure plates should be neutral, within some tolerance.

Dan Jones