1990 CHEVY SYCLONE PROTOTYPE

During the stages of the GMC Syclone’s development into production, many prototype trucks were built from already existing  trucks which were converted to test mules for various areas of testing. One such truck is the 1990 4.3SS Chevy Syclone Prototype.

VIN’d as a 1990 GMC S-15, the 4.3SS was one of the trucks used in engine and drivetrain testing for the GMC Syclone development. The 4.3SS could be considered your standard sleeper truck as its unassuming appearance both on the exterior and interior wouldn’t give way to the truck’s potential and power. That is until you notice a logo on the fender in gold vinyl lettering that states – “4.3SS Turbo”, a hint that GM and PAS were up to something.

Cladded in forest green paint, the exterior is what you would find on most production S-Series trucks. The rubber wheel arch flairs, tonneau cover, steel front and rear bumper, and a 1-piece grille are how the truck was built before it was chosen as a test mule. No cladding is on the truck. The only visible outside change to the truck is it wears production-style Syclone/Typhoon rims wrapped in Firestone Firehawk SVXs (what the production SyTys came with). Instead of the standard GMC emblem center cap, Corvette crossed-flags center caps were used. We can assume this was before the GMC center caps were ready for production.

The interior of the 4.3SS remains untouched with no signs of post-production alterations. A light gray cloth bench seat, manual roll-up windows, and the standard analog gauge cluster with a column shift setup is about as interesting as it gets. There is non leather wrapped “X-pattern” steering wheel and no logo emblem resides on the glove box door. The truck does have the standard cassette player with an optional equalizer radio.

Underneath the hood is where the action starts. The 4.3SS truck is complete with a 4.3 turbo V6, its visual appearance the same as a production Syclone only with one missing element; a blank upper intake with no “Syclone 4.3 Turbo” machined into it.  The intercooler reservoir does have the cosmetic cover plate on it – a piece not found on the production Syclone but on the Typhoon. The exhaust system is the same as production with a dual muffler setup and pipe exits. Also like the production trucks, it has a 700R4 4-speed automatic with an AWD setup.

Today, the truck is privately owned and makes regular appearances at the SyTys@Carlisle event during the Annual Carlisle All Truck Nationals located in Carlisle, Pennsylvania. It is one of the few remaining verified prototype trucks that still exist and in driving condition.

1990 4.3SS CHEVY SYCLONE PROTOTYPE HIGHLIGHTS

• 4.3SS Turbo Vinyl emblems
• 4.3 V6 Turbo Engine (blank upper intake)
• 700R4 4-spd automatic trans with AWD
• Bench Seat (light gray cloth)
• Column Shift
• Analog Gauge Cluster
• Cassette player radio with optional equalizer
• Manual Roll-up Windows
• Forrest Green
• No Cladding
• Production Syclone Wheels with Corvette Center Caps