The question of 'What engine do I have?" seems quite
common around here, so this should help out the new members.
These 4.3's are 90 degree even-fire engines, with a 1-6-5-4-3-2 firing
order.
4.3L translates to 262 cubic inches, and 4293cc's.
Bore is 4.00" (101.6mm) and stroke is 3.48" (88.39mm) with a 5.7"
connecting rod.
All have overhead valves, with two valves per cylinder.
Cylinders are: 1-3-5 (Driver's side front to back)
2-4-6 (Passenger side front to back)
Almost all 92+ engines have an internal balance shaft to help reduce
vibration.
The VIN engine digit is the 8th in the code. RPO list is in your
glovebox.
The heads and blocks of these 4.3's are cast iron.
TBI (Throttle Body Injection)
1988-1995
Vin: Z RPO: LB4
160 HP/ 230 ft/lbs
Compression Ratio: 9.3-1
TBI is very similar to a carburetor, but much easier to maintain and
more versatile. It has two injectors in a pod above the throttle plates.
Injectors are batch-fired. Late model TBIs may have CPI (L35) Vortec
heads (usually identified by plastic 'Vortec' valve covers) raising
horsepower to 165 and ft/lbs to 235.
Turbocharged MPFI (Multi-Port Fuel Injection)
1991 (Syclone pickup)
1992-1993 (Typhoon SUV)
Vin: Z RPO: LB4
280 HP/ 360 ft/lbs
Compression Ratio: 8.35-1
Boost: 14 psi
Turbo-MPFI is the most powerful 4.3 released by GM, but it was only
available in the Syclone and Typhoon trucks. A Syclone runs the 1/4 mile
in roughly 13 seconds at 100 mph. 0-60 time is about 4.8 seconds. The
block and cylinder heads are the same as the LB4 TBI, with the exception
of lower-compression pistons and nodular iron main caps. Boost is
provided by a Mistubishi TD06-17C at 550 CFM. Fuel injectors and
throttle body are borrowed from L98 Corvette/F-body V8's. The fuel
injectors are fed through fuel rails and are batch-fired.
CPI (Central Multi-Port Fuel Injection)
1992-1995
Vin: W RPO: L35
195 HP/ 260 ft/lbs
Compression Ratio: 9.05-1
CPI operates very similarly to TBI with a central injection assembly
mounted in the intake manifold. It uses single batch-fired injector
feeding six poppet valves located at the intake ports. It has a
dual-plenum manifold (upper and lower) with variable tuning with a
manifold tuning valve to equalize pressure.
CSFI (Central Sequential Fuel Injection) or just SFI
1996-1998
Vin: X RPO: LF6
175 HP/ 240 ft/lbs
1996-2003
Vin: W RPO: L35
190 HP/ 250 ft/lbs
2002-2004
Vin: X RPO: LU3
190 HP/ 250 ft/lbs
Compression Ratio: 9.2-1
Maximum Engine Speed: 5600 RPM
The heads on the CSFI engines are the best-designed for the 4.3 to date.
They flow much higher CFM than any other head, and have a better
designed combustion chamber. CSFI uses six individual injectors and a
fuel pressure regulator that pulses fuel through six orifices through
flexible nylon tubes. These tubes run to poppet valves at the intake
ports. In 2002, GM began installing the new "Multec 2" injectors,
upgrading the system to "Multi-Point Flexible Injection". This new
system uses actual injectors and does away with poppet valves. GM is
offering an upgrade kit through dealerships for 96+ engines with CSFI.
Horsepower numbers differ slightly depending on vehicle configuration:
(T Series) X=180/245 W=190/250
(S Series )X=175/240 W=180/240
