this is copied from the July '97 issue of Mopar Muscle;
In general, Magnums are under-carbureted (under-throttle bodied?). That's to
say, Magnums pick up sizable horsepower gains whenever throttle body venturis
are enlarged. Many carb specialy shops enlarge throttle bodies, or sell you
new throttle blades (machining required) if you want to increase the flow of
your OE unit. Going beyond .080 in the throttle bore is touchy because you'll
be close to the end of the OE computers map. Throttle castings start to get a
little thin in the venturi past that point. Even at .080, the body will need
minor filler in the venruti. V6 owners have another option----install a V8
throttle body. OE V6 throttle bodies have 1-5/8 inch blades, while the V8's
are almost 2 inches. A sixer will need to have the manifold's throttle bore
holes enlarged to 2 inches (best done at a machine shop) and you're done. On
a Mag Six, a V8 throttle body change is worth about a quarter of a second and
3 miles per hour!
Yikes!!! Thats a pretty big jump for that mod!!! Ok read on though, Im
reading more on the V8 mods and here it is;
....while your V6/8 Magnum intake manifold is off, the next performance stem
is to shorten the runners as much as possible and cut two inches out of the
plenum divider. This mod will add about 10/12 HP to your engine and raise the
shift points about 300 RPM.......Fortunately, both top-and bottom-end
performance are enhanced. None of these grind/polish/weld V6/8/10
modifications require a high performance computer (controller) because factory
computers require a great deal of latitude to cover everything between lean
high altitudes to rich seaboard environments.
.....concerning the lifters. They're real heavy and overcome the strength
of the lifter bore casting at high RPM. Spinning a Magnum to 5400 RPM is
borderline, 5800RPM too much, and above 6000RPM can be the kiss of death.
What happens is the heavy lifters crack the casting, start to wobble, and the
valve train self-destrucks. When the valve train starts to go bonkers, you'll
notice an upper RPM vibration, almost like the engine is out of balance.
Either limit your shift points, buy a Fluidampr, or pray somebody develops a
lightweight lifter for the Magnum.
Ok, heres the awesome setup Im thinking of, remember, this is all out of the
Mopar Muscle....:
If you really want to go Magnum-performance wild, consider Holley's Pro-
Jextion throttle body (various CFM ratings available) mounted atop onr of MP's
manifolds. This is a four venturi throttle body that's had the sprayers
removed from the upper air horn are and uses the four venturi body as an air
regulation unit. This setup seems to work very well in conjunction with an MP
computer controllin the timing and fuel delivery rate. You can expect a 40
plus horsepower increase over you stock setup. They're available from RC
Performance Engineering. Rc has other Holley based systems for Magnum ownerw
who want to dial the cannon past stun and go straight to kill. Hmmmm does
that make you think of any or all of us on the DML!!!!?
Conclusion
The intake manifold is probably the most underestimated piece of
performance equipment on the engine today. When modified with even simple
changes, it responds unbelievably well. Though some of these alterations can
get quite expensive, a bucks-down performance aficionado can still do quite a
bit on a Saturday afternoon's time span. Though the new millennia will
undoubetedly bring further developments in the intake manifold, onte things
for sure; as long as the internal combustion engine is around, it will always
have need of an intake manifold.
Ok, thats it, thanks for you time guys, now that my fingers and wrist are
killing me!!! I hope that has helped atleast one of us!! I did the intake
mod before the 5.9 instal, and Ill tell ya, I thought it was awesome. Now
that Ive done the TB its totally awesome!! DUDE!!!!!!! oops, sorry! Anyway,
its a lot of work, but it is definately worth it. Good luck all, and you
should really get this edition of Mopar Muscle, the pictures in it are great
for this series of Mods.
Later guys!!
Eric
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