Inside the Callaway Twin Turbo Corvette

At first glance, those unfamiliar with these rare TORQUE MONSTERS think that it is just a good looking body kit. However, not all Callaway Twin Turbo Corvettes are equipped with the Aerobody as it added some $12K to the cost of the car, making them the ultimate sleeper corvettes.

Those who are familiar with the Callaway name know it is much more than unique, cutting edge styling. For those who are not, this page seeks to familiarize the public as to the "Powerfully Engineered" work behind the massive power and torque of Callaway Twin Turbo Corvettes.

The first and most obvious change is apparent upon lifting the hood. As you can see in the picture below, the most noticeble change is the Aluminium air-air Intercoolers which connect to the throttle body through an M shaped tube called the Rams Horn. The purpose of the intercoolers is to cool the compressed air (which heats up during the process of compression) as it leaves the turbo's.



At the tip of the Rams Horn, two additional fuel injectors provide extra fuel when the turbo's go into boost so the engine does not starve for fuel as more air is forced through the throttle body. The fuel injectors are wired to a device located under the instrument panel called the Microfueller which monitors the distributor and tells the additional fuel injectors when to provide extra fuel. A very large Bosch fuel pump replaces the standard fuel pump in the tank to provide the extra fuel pressure to the 295 lb/hr fuel injectors.

Another visible difference is a rectangular shapped device between the fan and the upper radiator hose. The purpose of this device is to remove any air bubbles which may enter the oil stream. The turbo's are both oil and water cooled since they get quite hot as exhaust gasses pass through the exhaust side of the turbos via a turbo oil sump tank and pump.

Other visible items in this picture (slight variations exist in earlier models) include the black wrinkle finish paint on the runners and upper intake cover, heat shielding of various hoses and lines to protect them from the extra heat, blue anodized finish on various hose fittings and A/C condensor, and polished tubing.

Additional Engine work done in the conversion process and not visible include: Engine block 4 bolt main caps, splayed bolt style; Michigan Engine Bearings; Forced Gas Nitrided Crankshaft, 60Rc Journal hardness; Proprietary Mahle Forged Pistons with 7.5:1 compression; Plasma Moly Ring package; High Volume Oil pump; Engine Oil cooler; Stainless Steel inlet and exhaust valves; up-rated valve springs; Steel Roller Camshaft & Hydraulic roller lifters; Specially hardened distributor drive gear; Dry sump pump for turbo oil scavenge; and polished air inlet castings. Balance and Blueprint operations include: Magnaflux Block and crank assembly; cranshaft journals cross drilled and micropolished; aluminum cylinder heads decked; line bore main bearing caps and block; decks squared to crank centerline; all galleries cleaned and replugged; valve springs shimmed for equal pressure; and all threads chased. My car benefits from aditional boring, sleeving, custom pistons, porting, heads decked, special Callaway stainless headers, turbos ported and heavy duty wastegate springs installed, and a custom 2.75in mandrel bent and laser cut exhaust with less restrictive/high flowing random technologies catalytic converters, a Centerforce clutch and single mass flywheel.



Some vehicles are also fitted with Coilover suspension, Center Exhaust, and ultra light weight Callaway/Dymag Wheels.



Yet another difference upon further and close inspection (beginning with 1991 models) is the addition of the Wonderbar. The Wonderbar is a modification to the air intake system in which the front frame is modified and used as a duct to route air to the turbo's. This modification provided greater air flow to the turbo's which resulted in an increase in power.

Looking below the engine, you will obviously notice the Rotomaster T04b Turbo's on either side just in front of the catalytic converters. The turbo's are wrapped in shielding material to protect them from sudden temperature changes (water splash) which might cause the housing to crack when hot. You can also see the exhaust and turbo air up hoses as well as the additional coolant and oil lines to the turbo's. The oil lines are connected to a triangular reservoir located just in front of the oil pan.





Another modification of interest here is that the starter is repositioned due to the placement of the passengers side turbo. The starter is placed upside-down from its original location and mounted on the visible blue anodized adapter. Additional heat shielding is also installed.

In the front of the engine, one of the pulleys is converted to an oil sump pump to provide added oil pressure to the turbo's. By converting the pulley to a pump, this increased the length of the serpentine belt making the belt a custom size. (See picture below)




About Luigi's B2K

For Luigi it all started after selling one of his two 1987 Buick GNX's.  "I remembered that the only thing American that could touch the Grand Nationals in the late 80's were the famous Callaway Twin Turbo Corvettes. But honestly, I didn't know too much about them. After doing a bit or research, I was in awe over the engineering work done for the turbos, the mean look of the intercoolers, and I absolutely fell in love with the Aerobody cars. I knew I had to have one and it had to be a convertible."


Luigi had seen various ads for Callaways but as it turned out he had a business trip to LA where several Callaways were for sale at Corvette Mike. They had a black 87 coupe, turquoise 91 Aerobody convertible, and the Yellow pearlscent Speedster.

"Honestly, the ad for the turquoise 91 wasn't the most appealing and I never went with the intention to buy her but, when I saw the car in person and I drove her, I knew I was not leaving without her. The pictures I had seen had not done the car any justice." With a deal made, off to South Florida she was shipped.

Luigi's car is a 1991 Turquoise Convertible, #26 of 62. He is the second owner. The car was delivered new from Callaway to Anderson Chevrolet in Menlo Park, California. When he bought her in 2000, she had just over 10K miles. Luigi says that he had the most pleasant surprise during the purchasing process. Corvette Mike put him in contact with Callaway Cars in Old Lyme, CT. Joanne Mercer as always, was very friendly and offered to send me whatever paperwork was available on the car he was buying. It was then that the best surprise of all was discovered.

In 1993, the prior owner had sent the car back to Callaway for a 475 HP (634 Ft. Lb Torque) upgrade. His car had the same engine upgrades that had been installed in the Speedsters, a nearly $10K upgrade from its 1991 price of $100,884. His car also sports the same OZ 3 piece wheels optioned with Speedsters, which Corvette Mike had chromed. The car also has a ZF 6 speed manual transmission, Adjustable Ride Suspension, a Bose Concert Sound system, and rare optional hardtop as well.

"Since then I have not only enjoyed the pleasures of this magnificent car but I have become a complete Callaway fan. In 2002, I drove her from so. Florida to/from the Callaway Reunion at Corvettes at Carlisle and occasionally reunite with the Callaway Owners Group to talk, share, and photograph these awesome cars."

It should be mentioned, that this B2K was selected by Corvette Mike, at the 2002 Callaway Reunion at Carlisle, for his “Celebrity pick” award. Luigi’s Callaway was one of a select few cars picked to parade around the grounds and receive this distinguished award out of all the Corvettes on the “Fun Field”. It has also been featured in the Callaway Owners Group – Corvette of the Month, Twice featured in Corvette Enthusiast magazine, and was part of “The Special Collection XX, The Corvettes of Reeves Callaway” during the 2004 Bloomington Gold Corvette Show.


RPO Codes from Luigi’s 1991 Callaway Twin Turbo Corvette

1YY67 – Base Corvette Convertible
AC1   6 way Power Seats – Passenger
AC3   6 way Power Seats – Driver
AJ3    Front Seat Inflatable Restraint
AQ9   Passenger/Driver Reclining Seats
BGR   Bowling Green Assembly
B2K    Callaway Twin Turbo (Console Lid RPO option code) 
C05    Convertible Folding Top
C68    Electronically Controlled A/C
DL8    LH/RH Heated Sport Mirrors
D3X    Speedometer Driven Gear (25513049)
D8I     Speedometer Sensor (10456089)
E5Z    Delete Speedometer Adapter
E9Z    Delete Speedometer Key
FE1    Soft Ride Suspension
FX3     lectronic Ride Handling
GM3   3.45 Ratio Rear Axle
G87    Ring Gear 8.50 Inch
IL3      Interior Trim Design L3
J55     Heavy Duty Brakes
KC4    Engine Oil Cooler
K68    105 Amp Alternator
L98     8 cyl 5.7L Engine
ML9    ZF 6 speed Transmission
MN6    6 Speed Manual Transmission
NA5    Federal Emission System
NK4    Sport Leather Steering Wheel
NN5    California Emissions compliance
QA1    17 x 9.5 Aluminum Wheels
R8T     Control Sales Item 69
UX0     Delco Bose 6 Speaker System
U1F     AM/FM Radio w/CD & Cassette
U52     Electronic Instrument Cluster
U75     Power Antenna
VG8    Vehicle Label-Notice to Buyer
V73     Vehicle Statement Certification US & Canada
XAU    P275/40ZR17 Tires Front
YAU    P275/40ZR17 Tires Rear
Z5G     Callaway Conversion Option (as listed in Build Sheet)
1AY     Stock Order
1SB     Marketed Option Package 2
191            Black Interior Trim

193      Black Leather Trim
199      Black Seat Belt
41T      Black Convertible Top
42U     Turquoise Metallic Color

Callaway Installed Options:
B2K   Callaway Twin Turbo
Aerobody Kit
475 HP upgrade (same as Speedster)
3pc OZ Wheels (same as Speedster)
KoolOff Windshield

Copyright 2001-2003, Luigi Automotive Productions
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