> Speaking of which... Is there a rule of thumb as to when you
>need to beef up your internals? I plan to build a turbocharged 360
>and may use nitrous on it as well. At what sort of power output do
>I need to start looking for a forged crank? As I understand it,
>the rods are already forged in the Magnums, but as the pistons are
>hypereuretic(sp?) I figure I'll need some forged pistons at the very
>least.
>
>
> -Jon-
Hyperutectic pistons are very brittle. Forged is the only thing to run
with power adders that increase combustion temperature and pressure like
NOS and forced induction. Strength of stock cranks depend on engine size
and the actual manufacture of the engine. Castings vary so much between
manufacturers, I couldn't give you an exact HP figure that the stock mopar
crank could handle. As for rods, not all rods are the same. Even though
one set may be forged, that doesn't mean their stronger than a prepped set
of cast rods. One set of forged rods could be weaker than another forged
set. All depends on the type of material used and quality of the
forging. If the material is poor or not enough force was used in the
forging process, stress cracks and risers can form causing weak spots, then
bam!! You cry over your loss.
I could type till my finger tips were numb about the dangers and what needs
to be done to a motor to make it run reliably with lots of nitrous and/or
forced induction. It's a lot of stuff that is involved, and it would make
this email a book.
You can always run 10+ psi and/or 100+ HP of nitrous on a stock motor and
hope is stays together. Hope the oil pump can keep the oil volume and
pressure high enough to prevent bearing failures, and hope the torsional
stress on the stock crank doesn't get out of hand and cause stress
fractures which means a broken crank. Hope your stock harmonic balancer,
which was designed for low RPM use, can still provide enough dampening at
high RPMs to prevent harmonic vibrations from destroying the main bearings
or cracking/breaking the crank. Hope the rod bolts and big-end side of the
rods are strong enough to prevent stress cracks and breaking. Depending on
the bolts size and bolt head shape, and if the rods are spot faced or not,
the bolts are usually the first to fail. And hope the stock main bolts
provide enough clamping force to prevent main cap separation, which then
causes bearing failure, then crank failure. Not to mention valvetrain
components. Hope the stock springs are strong enough to prevent valve
float at the higher rpms. Hope your exhaust valves can handle the
increased heat without burning them. Or you can just run the crap out of
it till it fails, then dig into your pocket and buy all over again. All
depends on how wisely you spend your money. As the old saying goes, speed
costs money, how fast can you afford to go?
Mike
__________________________
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