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(This first section of
information came from Roscoe's Impala Page here)
This is a picture of the first 427
produced by Chevrolet

The Z-11 Impala was based on a standard
1963 Impala 2 door hardtop body with the exception of a few weight
saving aluminum body parts. The hood, front fenders, front and rear
bumpers including brackets were all aluminum.
The engine was based on a standard 409
block but it was fitted with a stroked crankshaft. The heads were
unique in that they had large, oval shaped intake ports that were
taller than the hi-po 409 heads. The intake was a two piece design
that was all aluminum. The carburetors were the same units that were
used on the dual-quad 409s. The air cleaner was totally unique to the
W-motor Z-11 Impalas. It was a form of early "cowl-induction." The
"arm" that goes to the fire wall had a rubber boot attached to the
air cleaner housing and the rubber boot fit over an oval shaped duct
that drew air from that cowl area. Other differences to the W-motor
Z-11 engine was the usage of a deep sump oil pan. The pans had a
deeper sump welded to the pan. The pans look homemade but that is how
the factory modified them. Also there was a push rod guide plate used
on the heads and the valve covers had special corners to clear the
guide plate.
On the inside of the car it was standard
Impala trim with no radio and no heater. The stock "dog-leg" shifter
was standard as was the Delco electric tachometer. No sound deadening
was used under the carpet.
The exteriors were very unassuming as
there was no identification as to the 427 engine. Stock 327 emblems
were used and only black wall tires mounted on 15 inch rims with
standard hub caps made up the rolling stock.
As mentioned earlier the bodies were
stock 1963 Impala 2dr. hardtop bodies. The rear end was the stock
unit with 4.11 gears, they had the standard two-piece drive shaft,
the transmission was the Borg-Warner T-10, close ratio four-speed,
the shifter for the T-10 was the stock "dog-leg" or bench seat
shifter, the bell housing was the 409 style all aluminum "553"
casting.
I would like to thank
Rusty Symmes who wrote a book about the Z-11 Impala called Project:
Z-11 [ it was never published ] with the help of many friends, Doug
Hughes, John Mounts, Mike Martin and Steve Gunnels to name a few for
allowing me to include a few pages from his book on my web site. The
rest of this page is all from this book.
The R.P.O. Z-11 Story
The roots of the famous '63 Z-11 actually
began in 1962. Chevrolet, concerned with the poor performance of
their 1962 models on the NASCAR tracks, and to improve performance at
the dragstrip, decided to raise the high RPM horsepower by a redesign
of the 409 cylinder heads and intake manifold. The newly designed
head and intakes were to increase volumetric efficiency and improve
intake cooling. These raised port cylinder heads and two-piece
intakes were released as over-the-counter items before the 1962 NHRA
Nationals Drags at Indianapolis. These special parts carried
blueprint issue dates of May 4, 1962.
Several racers arrived at Indy with these
special parts, and raced in Factory Experimental class. I recognized
these parts on Don Nicholson's (FX, Nalley Chevrolet cars). While
inspecting his cars, I was intrigued by the height of the intake
manifold and carbs, as opposed to the same parts on the '62 409, that
I owned at the time. These parts were reported to have come in a kit.
Most of these cars also had aluminum fenders, inner fenders and
hoods. This was another over-the-counter rush option to improve the
weight distribution on drag cars. The '62 Chevys were heavy compared
to the early Mopars that utilized uni-body construction. Also Pontiac
had already begun to produce 421 CID cars for drag racing, with
aluminum front ends. Chevrolet was not about to take this lying down.
There were also a limited number of
aluminum '62 Impala Super Sports built at the Flint Plant in late
year; some records indicate 18 total. They did not have the new
heads. It seems that all were identified by aluminum unpainted cowl
plates. There were no other known identifications. The cylinder heads
and aluminum parts increased the performance of the '62 cars by 2-5
MPH, when used with a properly prepared chassis and full drag slicks.
Dave Strickler was reported to have turned as fast as 11.53 at 123
MPH in match race form in the '62 Bel Air "Old Reliable".
The early '62 Z-11 style cylinder heads
had pinned studs and were rough. They were marked CFD (Central
Foundry Division) General Motors. The two-piece aluminum intake
manifolds were made at Winters Aluminum Foundry, and have the
traditional Winters snowflake embossed in the casting. The early
aluminum intakes developed a problem with cracking at the bolt bosses
and were subsequently redesigned. Some of these early manifolds had
different odd part #'s and incorrect firing orders cast on them.
1963 R.P.O. Z-11
As the 1963 models were introduced the
Z-11 came into being as an RPO (Regular Production Option) Z-11
engine/chassis option that required zone approval before processing
of the order. As far as I can discern, this was done to make sure the
cars were put in the hands of racers who would campaign the cars, and
further Chevrolets cause at the drag strip.
A note must be made that although the RPO
Z-11 is one of the rarest Chevys, it was not the true mystery motor
that was introduced for NASCAR and withdrawn from service because of
the anti-racing policy of January 1963.
The most important feature of the'63 z-11
engine was a stroked crankshaft bringing the engine up to 427 CID.
This displacement figure was arrived at by both NHRA and NASCAR as
the legal CID limit for stock car racing. The reasoning behind this
decision was that both sanctioning bodies thought the cubic inch race
was getting out of hand, and the brakes needed to be applied by
limiting displacement size. Ford was already rumored to have plans to
field a 483 CID monster motor in 1963, and that was enough to spur
both associations into action. A 7-liter (427.2) was decided as the
most logical engine size to standardize on.
The Z-11 crankshaft, connecting rods, and
pistons differ from the '63 425 HP, 409 CID engine, but the engine
blocks were the same. However, the Z-11 blocks were stamped with a QM
stamp on original engines. It should be noticed that the "M" is a
little deeper impression stamp than the "Q" that was probably
beginning to dull from constant use whereas the "M" was unused and
sharp. The Q stamp did all the 409 engines. The M stamp did 50 or so
engines. The assembly dates appear to around the end of December.
The connecting rods are essentially the
length of the soon-to-come big block Chevy Rod (length 6.134 to
6.136), although they were considered a weak point, the heavy Z-11
pistons were the root cause of many failures.
The camshaft that came in original Z-11
cars came from Eonics Cam Co. in Detroit, and actually had the Eonic
name stamped on the end of the camshaft. This cam timing of the Z-11
became standard issue in 1964 on regular 409 h.p. engines.
The carburetion of the Z-11 car was the
same as the standard 409 425 h.p., and even had a standard choke and
heat rizer setup. Also the Z-11 was equipped with P.V.C. system like
the 409 425 h.p.
The R.P.O. Z-11 had a unique hollow fuel
pump push rod to reduce erratic fuel delivery due to pushrod float.
The fuel pump was a special part number until I believe had special
valving and spring, etc. with no provision for fuel return to the
tank.
Also for the first time on the W block, a
canister type fuel filter was used with a 3/8 line into it. This
canister had an AC designation with only a small white "star" for a
part number.
The Z-11 motor had a new aluminum water
pump assembly which had a tendency to fail due to thermal expansion
and excesive pressure allowing the front bearing to walk and also the
seal to leak. The pump caused more than a few problems on the Z-11
motors.
W's, X's, Y's, & Z's
W - 409 Style Chamber in Block
X - Engine Experimental Engine (small
block)
Y - Engine Experimental Engine (small
block)
W - 1-307 409 Style
W - 2-327 409 Style
W - 3-348 Production
W - 4-409 Production (?)
Mark I - AFX 62 Style Engine 3833117-425
h.p.
Mark Is - 63 RPO Z11A-3837729
Mark II - 63 427 Mystery Motor (Z33)
Never R.P.O.
Mark III - Paper Only Engine
Mark IV - Rat Motor..we all
know
Mark V - Redesigned Rat Motor
Chassis Section
The most obvious and important common
feature was that all Z-11 cars where produced on straight 2 door
hardtop Impala bodies.
The aluminum component consisted of the
fender, hood, splash pan, grill brackets, front & rear bumper and
mounting brackets, and also an aluminum fan shroud. Body did have sound deadener from all that I have seen, and where available with or
without a heater. They were all shipped through standard channels by
truck or by rail to the dealerships from the only plant producing
Z-11s, the Chevy Flint Assembly Plant. All cars had vented backing
plates and metallic brake lining. These vented backing plates came
equipped with bolt-on rain covers, so if the cars were to see any
rain, the brakes would be able to work. These plates are rare and
sometimes are mistaken for brake scoops.
Body identification is located on the
upper firewall. Some Z-11 cars, probably on the later production run
cars, have a Q-11 embossed on the accessory code section of the cowl
tag. Some cars that are documented did not have any accessory codes,
and some had only the Q to designate the W-style motor.
The high rise nature of the intake
manifold made proper air delivery to the carbs a main concern. Each
car was equipped with a cowl plenum induction system. Chevrolet had
experimented as early as 1961 with a carb fresh air system that
utilized the cowl grille high pressure area at base of windshield.
This technique was used prior for the flow through ventilation system
to the rocker panels to reduce rusting in that area.
The Z-11 did not have "as many believe"
an extra link on the upper suspension, although many were added
later.
The rear axle assembly probably was the
weak part of the entire Z-11 package. Many were replaced with Pontiac
rear axle housing, Etc. because of breakage. To the best of my
knowledge there was a special set of axles made to reduce axle
breakage. This was a help as in 1963 N.H.R.A. began to allow full
slicks in A/FX for the first time. Chrysler-type spider gears allowed
large fine spline axles.
WHERE, OH WHERE
Did all this "Z" business come from
anyway? Well, in 1963 Chevrolet adopted a special alphanumeric coding
system to include any car with special equipment such as a high
performance option of limited production. Option codes of this nature
were given the Z prefix. Thus was born the Z-11 option, the first of
the rare desireable Z cars which later gave way to early Z-28's, and
also ZL-1's, Z-16's, etc.
Z-11 FACTS
Produced only in 1963
The R.P.O. Z-11 option was an additional
$1240.00
Shipping weight-3245 lbs.
Curb weight-3405 lbs.
57 Z-11 Impala's were produced
Only 7 are known have survived
Modified 409 engine rated at 430hp@6000
RPM's. (Actual horsepower was 480-525)
Block casting #3830814. Code "QM"
Head #3837731
2 piece Intake manifold #3830623
(top)-#3837733 (bottom)
Cam #3837736 Duration/lift-325/.556
Distributor #1111023
Coil #1115107
Generator #1100628
Starter #1107274
Special cylinder heads
3.65" piston stroke
4.3125" bore (same as 409)
13.5:1 compression ratio
2.20" intake and 1.73" exhaust valves
Special cowl induction air cleaner
#6418986, #3839764 (duct)
Tachometer (redlined at 6200 rpm's)
Borg Warner T-10 4 speed transmission
(close ratio)
Special posi rear with 4.11:1 rear gear
ratio
Sintered metallic brakes with vented
backing plates
15 X 5.5 wheels with 6.70 X 15 bias ply
tires
Deleted sound proofing and insulation
Deleted front sway bar
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