Friday, February 5, 2021

First All-Wheel-Drive Drag Racing Performance Success: GMC Syclone and Typhoon



GMC Syclone and Typhoon Era: The Dog Days of Sports Cars

Back in 1991, the dogs days of the sad, slow, so-called economy-efficient sports cars were starting to come to an end. The days of the poorly performing 350-cu.-in. Tuned-Port Injection (TPI) engine setups that General Motors were using for their unimpressive performing sports cars were about to be replaced by a much more stout performing LT1 350-cu.-in. engine.

'91 GMC Syclone

But before the change, the GMC truck division of General Motors made an interesting move to get involved in some of the performance hype GM was encouraging at the time. GMC made a move and signed a contract with a company called Production Automotive Systems (PAS) which in turn started the creation of the fastest production trucks of its time: the '91 GMC Syclone pickup truck and '92-'93 GMC Typhoon SUV.

The Pass Company was no stranger to this type of work. Pontiac called upon them to help build the very famous
20th Anniversary 1989 Pontiac Trans AM

1989 Turbo Trans Am 20th Anniversary Edition. Oddly enough, they just went with a drive train that was already tormenting all of the sports cars on the streets, the V6 3.8-liter Buick turbo intercooler setup.  

Originally Buick's Idea

Originally, Buick came up with the idea for the turbocharged truck, but not to cause any conflict with the GMC truck production branch, they handed the idea over to them. GMC was hesitant to take on the project at first since they already had a similar black regular cab pick-up truck on the market with a 454 cu.-in. engine. 

But some forward-looking engineers and designers saw the potential in smaller engines. Assuming Buick could make it work in a G-Body grocery-getter car with much success, doing the same in a truck and an SUV should work just as well, and to nobody's surprise, it did.  

Different Turbo Setup For The Syclone and Typhoon

The PAS company engineered a 4.3-liter Vortec engine equipped with a turbocharger and an intercooler to fit in both the Syclone and the Typhoon.

To efficiently transfer engine
'91 GMC Typhoon
power, both models would receive the four-speed 700R4 automatic transmission, the same trans the Corvette and the Buick turbos were using at the time.

The First All-Wheel-Drive Technology Used For Racing Performance

What made the Syclone and the Typhoon so unique from other trucks is that they used a very performance-efficient all-wheel-drive system. That technology helped these trucks that had an underrated, unofficial horsepower rating of 280 get down the quarter-mile with times that could stop the clocks somewhere in the high-to-mid 13-second range. 

Since the technology was so similar to the successful 3.8-liter turbos, aftermarket part dealers and car enthusiasts knew exactly what easy upgrades could be made to make these trucks amazingly performance efficient. I've personally seen Typhoons run in the high 10-second range and Syclones being lighter in weight, stop the clocks in the 9s. 





GMC Syclone and Typhoon: Unbeatable Deal

With great gas mileage, great performance, and the fact that they were limited production, the GMC Syclone and Typhoon were and are still collector items for all car enthusiasts alike. 

With production numbers of only 2,998 '91 Syclones, 2,500 in '92, and 2,200 '93 Typhoons built, the price tags on these rare trucks still stay up in the $15,000 to $25,000 range for the ones that are still in good condition.

Unfortunately, the PAS company based in Troy, Mi., that was responsible for the GMC Syclone and Typhoon's engineering and design would go out of business after GM decided not to go forward with any more specialized GMC vehicles at the time. 

The decision was mostly due to the progression of the Corvettes, Camaros, Trans Ams, and the need to focus on the new technology of eclectic vehicles. That may have sounded silly then, but now, all auto companies have moved into the electric vehicle direction, and GM predicts by 2035, the only vehicles they will be producing are going to be all-electric vehicles. 
             

Syclones and Typhoon GENERAL SPEC

4.3-liter turbocharged intercooled











Type:      V6
Disp.:      262 C.I. (4.3L)
Horsepower:   280 BHP @ 4400 (Syclone) 285 BHP @4400 (Typhoon)
Torque:     350 lb-ft @ 3600 (Syclone) 350 lb-ft @ 3600 (Typhoon)
RPO:       LB4
Bore:      4.00
Stroke:     3.48
Comp. Ratio:   8.35:1
Firing Order:  1-6-5-4-3-2
Oil Pres. (Min) 6 psi@ 1000 RPM, 18 psi@ 2000 RPM, 24 psi@ 4000 RPM

CYLINDER BORE
Diameter:    3.9995-40025
Out of
Round:      .001 (production) .002 (service)
Taper:      .001


PISTONS:
Clearance: .0015-.0030
PISTON RING: Compression: Groove Clearance: .0012-.0032 Gap: .010-.020 (top) .010-.025 (2nd) Oil: GC: .002-.007 Gap: .015-.055 PISTON PIN: Diam: .9270-.9273 Piston Clearance: .0002-.0007 Rod Fit: .0008-.0016 Interference

CRANKSHAFT:
MAIN JOURNAL: Diam: #1 2.4484-2.4493
#2 #3 2.4481-2.4490
#4 2.4479-2.4488
Taper: .001 max
Out of Round: .001 max
MAIN BRG. CLEARANCE: #1 .0010-.0015 #2#3 .0010-.0025 #4 .0025-.0035
CRANK END PLAY: .002-.006
CRANKPIN: Diam: 2.2487-2.2497
Taper: .001 max
OOR: .001 max
ROD CLEARANCE: .0013-0030
SIDE CLEARANCE: .006-.014


CAMSHAFT:
LIFT +- .002 Intake .357 Exhaust .390 Journal Diam: 1.8682-1.8692 End Play .004 -.012

VALVE SYSTEM:
Lifter Hydraulic Rocker ratio 1.5:1
Lash Adj. One turn down from zero Face Angle 45 deg.
Seat Angle 46 deg.
Runout .002 max
Seat Width 1/16 to 1/32 Stem clearance .0010-.0028 Spring length 2.03 Valve Spring Pres. 76-84 lbs @ 1.70 in Closed 194-206 lbs @ 1.25 in
Open Installed height 1 23/32"
Valve Spring Damper: Free Length 1.86 # coils 4