I have bought forged rods and pistons and will use them with a stock crank. Is there any advantage to balance internal or is it even possible. If going with external balancing should both damper and flywheel be imbalanced?
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The advantage to an internally balanced engine is that you can change components at will without having to rebalance the entire assembly.
The flywheel and the dampener need to also be zero balanced. You can buy new zero balanced dampeners for the 351c already done.
I do not think that is so of the flywheel.
I think that the crank will take a few Euro's worth of Mallory Metal to balance. Weight needs to be added to the throws counterweights.
Nice pussie, I mean avitar.
The flywheel and the dampener need to also be zero balanced. You can buy new zero balanced dampeners for the 351c already done.
I do not think that is so of the flywheel.
I think that the crank will take a few Euro's worth of Mallory Metal to balance. Weight needs to be added to the throws counterweights.
Nice pussie, I mean avitar.
Does he need to shot peen the crank first to give it more strength?
A 90° crank V-8 needs a bob weight at each end to balance out the motion of
the reciprocating masses (pistons, pins, rings, and small end weight of the
rods). Internal/external balancing is a matter of where the two bob weight
masses are located or distributed. A V-8 has an unbalanced couple that
rotates the same direction and frequency as the crankshaft. If you hang a
V8 engine from a chain and run it with no balance weights on the crank, it
will wobble. A point on the front of the engine will travel in a circle,
as will a point on the rear of the engine but the middle won't move. Like
holding a broom handle in the middle and moving one end in a circle. The
other end moves the same but is opposite. To balance this, offset weights
are needed at the front and rear of the crankshaft. The farther away from
the center of the engine and from the center of the crankshaft these weights
are, the smaller they need to be. If this weight is inside the block, it
is considered to be internally balanced, if these weights are on the flywheel
and front pulley, it is externally balanced. External weights apply their
force through the first and last main bearing. Moving the weights inside
means more force is needed, but it distributed over more main bearings.
In addition to these weights, other weights are placed on the crank to
minimize main bearing loads.
Sometimes you will see it claimed that internal balancing is best but
that's not strictly true. Splitting the "bob weight" portion of the
counter-weights between internal and external, both front and rear will
generally give the lowest crank bending stress. The "bob" weight is best
centered about the #1 and #5 bearings. Note that all of this applies only
to V-8's with 90° cranks. My engine builder claims it's pretty common
to see internally balanced SBC engines showing distress on the number 1
bearing. He prefers some weight on the balancer. Ford used two balance
factors on the Windsors, 28.2 oz-in and 50 oz-in. They used only 28.2
oz-in on the Clevelands (and small variiatons around that for certain
variants like the Boss 351). 50 oz-in is too much and can lead to crank
problems. 28.2 oz-in is fine for most applications though very high RPM
may require less.
Many race engine builders will zero balance so changing flywheels and
harmonic dampeners doesn't require re-balancing. To internally balance,
the iron or steel of the crank is drilled out and replaced with denser
Mallory metal (a tungsten alloy). The metal is expensive and a lot may
be required so it's not uncommon for the cost of internally balanceing
a crank to exceed the cost of the crank itself.
> I have bought forged rods and pistons and will use them with a stock
> crank. Is there any advantage to balance internal or is it even possible.
It's possible. There may be an advantage if you turn very high RPM or
replace balancers and flywheels frequently. Otherwise, the standard
28.2 oz-in balnce factor is suitable for most purposes.
> If going with external balancing should both damper and flywheel be
> imbalanced?
Yes. You'll find the stock 351C balance and flywheel have small balance
weights.
> You can buy new zero balanced dampeners for the 351c already done.
> I do not think that is so of the flywheel.
You can buy new flywheels with zero balancing for the Cleveland.
Ford even made them, though they installed them on the 300 inline
truck six. Knowing that little bit of trivia allowed me to purchase
a very nice neutrally balanced aluminum flywheel for cheap. It had
been sitting on the shelf for a long time because no one wanted an
aluminum flywheel for a 300 truck six. However it is the same tooth
count and bolts right onto a 351C and it's quite easy to add a balance
weight during balancing.
> Does he need to shot peen the crank first to give it more strength?
No. Shot peening doesn't give more strength, it's meant to prevent
fatigue cracks from propagating.
Dan Jones
the reciprocating masses (pistons, pins, rings, and small end weight of the
rods). Internal/external balancing is a matter of where the two bob weight
masses are located or distributed. A V-8 has an unbalanced couple that
rotates the same direction and frequency as the crankshaft. If you hang a
V8 engine from a chain and run it with no balance weights on the crank, it
will wobble. A point on the front of the engine will travel in a circle,
as will a point on the rear of the engine but the middle won't move. Like
holding a broom handle in the middle and moving one end in a circle. The
other end moves the same but is opposite. To balance this, offset weights
are needed at the front and rear of the crankshaft. The farther away from
the center of the engine and from the center of the crankshaft these weights
are, the smaller they need to be. If this weight is inside the block, it
is considered to be internally balanced, if these weights are on the flywheel
and front pulley, it is externally balanced. External weights apply their
force through the first and last main bearing. Moving the weights inside
means more force is needed, but it distributed over more main bearings.
In addition to these weights, other weights are placed on the crank to
minimize main bearing loads.
Sometimes you will see it claimed that internal balancing is best but
that's not strictly true. Splitting the "bob weight" portion of the
counter-weights between internal and external, both front and rear will
generally give the lowest crank bending stress. The "bob" weight is best
centered about the #1 and #5 bearings. Note that all of this applies only
to V-8's with 90° cranks. My engine builder claims it's pretty common
to see internally balanced SBC engines showing distress on the number 1
bearing. He prefers some weight on the balancer. Ford used two balance
factors on the Windsors, 28.2 oz-in and 50 oz-in. They used only 28.2
oz-in on the Clevelands (and small variiatons around that for certain
variants like the Boss 351). 50 oz-in is too much and can lead to crank
problems. 28.2 oz-in is fine for most applications though very high RPM
may require less.
Many race engine builders will zero balance so changing flywheels and
harmonic dampeners doesn't require re-balancing. To internally balance,
the iron or steel of the crank is drilled out and replaced with denser
Mallory metal (a tungsten alloy). The metal is expensive and a lot may
be required so it's not uncommon for the cost of internally balanceing
a crank to exceed the cost of the crank itself.
> I have bought forged rods and pistons and will use them with a stock
> crank. Is there any advantage to balance internal or is it even possible.
It's possible. There may be an advantage if you turn very high RPM or
replace balancers and flywheels frequently. Otherwise, the standard
28.2 oz-in balnce factor is suitable for most purposes.
> If going with external balancing should both damper and flywheel be
> imbalanced?
Yes. You'll find the stock 351C balance and flywheel have small balance
weights.
> You can buy new zero balanced dampeners for the 351c already done.
> I do not think that is so of the flywheel.
You can buy new flywheels with zero balancing for the Cleveland.
Ford even made them, though they installed them on the 300 inline
truck six. Knowing that little bit of trivia allowed me to purchase
a very nice neutrally balanced aluminum flywheel for cheap. It had
been sitting on the shelf for a long time because no one wanted an
aluminum flywheel for a 300 truck six. However it is the same tooth
count and bolts right onto a 351C and it's quite easy to add a balance
weight during balancing.
> Does he need to shot peen the crank first to give it more strength?
No. Shot peening doesn't give more strength, it's meant to prevent
fatigue cracks from propagating.
Dan Jones
When the Cleveland was run is NHRA Pro Stock class, way back, the recommended treatment for the stock crankshaft was to nitride it.
I personally have never used the process and it requires someone with a crankpress. The process "warps" the crank and it needs to be pressed back and straightened.
If you could get that all done for free then do it. It would would probable be better to go with an aftermarket steel crankshaft.
The racing rules required a stock crank and block back then. That is why the effort and money was put into it.
The Boss and the CJ crankshafts are not known to be failure prone. The blocks will fail under NASCAR type of abuse eventually.
It's all kind of academic these days anyway and some people can break anything regardless.
I personally have never used the process and it requires someone with a crankpress. The process "warps" the crank and it needs to be pressed back and straightened.
If you could get that all done for free then do it. It would would probable be better to go with an aftermarket steel crankshaft.
The racing rules required a stock crank and block back then. That is why the effort and money was put into it.
The Boss and the CJ crankshafts are not known to be failure prone. The blocks will fail under NASCAR type of abuse eventually.
It's all kind of academic these days anyway and some people can break anything regardless.