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Sir
From the ( 1966 plus ) "normal" 350 horse powered 440 with an
single exhaust and the single snorkle air cleaner housing, the "HP" version in
Imperials was the exhaust manifolds that permitted the exhaust gasses to exit
the heads in an better manner to the dual exhaust system ( dual exhaust pipes to
dual mufflers and dual tail-pipes ). To all that follow power information
of the V8 engine, this is the biggest "bang for the buck" item that one can do
to add power to any year and any make of "V" designed engine. Sooo,
if you have an Imperial V8 of any year just going from the factories " save a
nickel with production cost " with having an single exhaust, to add an
profit by charging more to add the dual exhaust, you too will have the same
power the clothe top Imperials have. ( ... Before the days of the Road
Runners, GTX's and the such they just had dual exhaust on the exhaust manifold
that all vehicles got ).
An item to keep in mind is to only have the exhaust pipe the same inside
diam of the exhaust manifold to the muffler of the same size. For the
driving that most Imperialist Driver's do, to have an exhaust cross-over pipe
connecting the two sides at the notch between the rear of the engine and
the bell-housing is the best set up. For those who know the Imperial was
an lux prestiege car for upper class owners who liked the style of the Imperials
road abilities, to have an "X" instead of the cross-over will permit a better
power, emission and audio of the basic system.
And in all Chrysler Products of the time, if it had dual exhaust, it had an
dual snorkel intake housing.
With the same 440 cubed 375 horse powered engine ( Imperial Speakie
since lower classed Divisions had the 383 with 335 hp ) which also came an cam
shaft of different spec's ( P4529270 ), and valve spgs that had an higher
pressure rating. This permitted the engine to get its power at an higher
winding ( rpm ). Many Imperial owners who are re-building their 413 or 440
cubed Imperial want to use this cam cam assembly but fail to realize the now
made MoPar cam assembly P4286675 is better suited to the weight and all of the
Imperial.
Before the above mentioned 1968 exhaust manifolds and cam assembly used,
the 1966-67 440 was rated at 365 hp with just the twin snorkels and dual
exhaust. The 1968 intake manifold was redesigned, the AVS carb's were also
changed to the newer style/design of the "spread-bore".
The same rebuilding or just retro working person who has an 1966 -1959
Imperial does not know the GTX, Road Runner rear dumping exhaust
manifold will never work on the drivers side of the engine. In order
to get the same level of performance they must use a pair of the later to be
used 440/400 1972 to 1978 Dodge Truck exhaust manifolds( http://www.1aauto.com/1A/ExhaustManifolds/Dodge/PickupFullSize/1AEEM00081/67558/ ).
I re-wrote what Eric was speaking about so that any "newer" Imperialist
will have a short speed course of the subject.
The 66 Le Baron taking up space here has the "X", true 1969 MoPar
Performance Muffler's and Resonator's to keep away that "GTX" sound behind stock
exhaust manifolds. The other car ( 62 Crown two door ) has the 1978-1972
mentioned exhaust manifolds, the cross-over and the same exhaust from the same
mufflers to the same resonators to the same infamous "MoPar hook" tail
pipes. They are both as quite as an Imperial at the gates of the local
"Country Club" and are able to pull the vintage Air Stream with gusto up the
passes here in Colorado.
If I ever wear out either of the above I will use the same 1972-78 Dodge
440-400 truck manifolds ( remember 1959 to 1966 Imperials ), an exhaust pipe of
the same size from the right to an dual in-let muffler of the same diam on the
one side and an equal size exhaust pipe on the driver's side that will have an
"lazy S" to the left in-let of the muffler to an single out-let tail pipe.
This designed system has been dyno proven with OEM Dodge SRT trucks that are
also performance proven.
I do not like added chrome under the hood, flex cooling fans, and the after
market radio cut into the dash. Or, tubed after market headers and mufflers
that sound much in the same audio levels as an logging truck.
About three years ago I spent a lot of time inspecting an OEM 375 horse
powered 1968 Imperial Crown four door in Denver. Since the Imperial
was at an "All MoPar Car Event", the owners just stayed in the eazy
chairs and let me look all over it.
Some of the other hard to find items on Imperials are the 3.23/3.32:1 ratio
Rear Axle assemblies, Sure-Grip, OEM Power Steering Aux Cooler ( looks the same
but has an different sized mounting bracket than an NY'r ), OEM Transmission Aux
Cooler and the factories spec'd towing hitch. One needs the Factory
Service Manual and that years Parts Catalog or in towing, the Towing
Suppliment Data, to make sure.
Rodger & Gabby
COS
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