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Thread: V6 Engines: ID's and Specs

  1. #1
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    V6 Engines: ID's and Specs

    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

    Some dyno charts I've found for the LF6 and L35's:

    LF6



    L35





    (Courtesy Matt 4.3 TBI)
    Last edited by BlazinLow_inORE; 12-14-04 at 02:37 AM.


  2. #2
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    ::The 60 degree v6::

    The 60degreev6 came in 3 different displacements

    2.8L From '81 to '91
    3.1 from '91 to '93
    3.4 from '93 to '96 when production on RWD ended
    The s10 did not come with the 3.1 or the 3.4, and only came with either carb or TBI. The info on the other displacements and injection systems are for swap info only. Also note that the FWD blocks will not work with the RWD ones, although you can update injection systems. An upgraded fuel injection system will require a different intake manifold and heads (aluminum).

    Here are the engine specs

    2.8 V6 (RWD 82-85)

    Engine Description (LB6) 2.8L 60 degree V6
    Horsepower (HP@RPM) 110@4800
    Torque (ft-lbs@RPM) 148@2000
    Block Cast Iron
    Heads Iron
    Valves 12
    Displacement 2.8L (2800cc, 173ci)
    Bore 89mm (3.503")
    Stroke 76mm (2.992")
    Compression Ratio 8.5:1
    Intake / Exhaust valves 1.60" / 1.30"
    Valve lift .347" / .394"

    2.8 V6 (RWD 85-93)

    Engine Description (LB6) 2.8L 60 degree V6
    Horsepower (HP@RPM) 125@4800
    Torque (ft-lbs@RPM) 150@2400
    Block Cast Iron
    Heads Cast Iron
    Valves 12
    Displacement 2.8L (2800cc, 173ci)
    Bore 89mm (3.503")
    Stroke 76mm (2.992")
    Compression Ratio 8.9:1
    Intake / Exhaust valves 1.725" / 1.425"
    Valve lift .393" / .410"


    2.8 (LB8) Multi Port Fuel Injected
    Horsepower (HP@RPM) 135@4900
    Torque (ft-lbs@RPM)160@3900

    3.1 V6 (RWD) 90-92

    Engine Description (LHO) 3.1L 60 degree V6
    Horsepower (HP@RPM) 140@4600
    Torque (ft-lbs@RPM) 180@3600

    3.4 RWD (93-95)

    Engine Description 3.4L 60 degree V6
    Horsepower (HP@RPM) 160@4900
    Torque (ft-lbs@RPM) 200@3600

    ::Other 60v6 facts::

    1986 the s-10 recieved TBI in Addition to large valve heads (flat not splayed).

    1987 recieved full serpentine belt system (water pump rotates opposite way than before) a one peice rear main seal and an internally balanced crankshaft.

    1988 recieved lathe turned pistons and piston weights reduced

    ::Cam specs on pushrod motors and cast iron cylinder head valve size and design::

    Stock Cam
    (one of the best thigns you can do to these engines is get an aftermarket or GM performance cam. The stock cam duration is very short duration for low end power but doesnt allow the engine to breath well)

    centerline ATDC=109 on both sides
    Duration at .50= Intake-196 exhaust-203
    Max lobe lift at .50= intake-.263 exhaut-.273
    Rocker ratio= 1.5
    Gross lift= intake-.395 exhaust-.410
    Lobe seperation=109

    ::Cast Iron Heads::
    CARB HEADS
    Intake valve size-1.60
    exhaust valve size-1.30
    Compression 8.5:1
    EFI HEADS
    Intake valve size- 1.72
    Exhaust valve size- 1.42
    Compression 8.9:1
    Approximate average port diameter (estimates for reference)
    intake 1.33
    exhaust 1.2
    (the intake port is a rounded rectangular shape and the exhaust is round)

    (stock exhaust manifold has about a 1.3 inch inner diameter at the port)

    Chamber design- Flat 59cc with spark plug in the center

    RUNNER LENGTHS(these are approximated and might not be correct, but will give you a good starting point with dyno software)

    ::TBI::

    Intake= 8 inches
    exhaust= 10 inches

    ::2bbl Carb::

    Unkown
    (email me if anyone knows or has a good estimate)

    (Courtesy JJWalker)
    Last edited by BlazinLow_inORE; 12-14-04 at 02:37 AM.


  3. #3
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    2.8L Engine ID's

    The 2.8L engines are 60 degree engines, with a displacement of 171 cubic inches.
    The firing order is 1-2-3-4-5-6
    The cylinders are numbered 2-4-6 on the driver side bank, and 1-3-5 on the passenger side.

    2bbl Carbureted 2.8L
    RPO: LR2 VIN: B
    1982-1985 (S-trucks)
    110 HP 148 ft/lbs
    Compression ratio: 8.5-1


    TBI (Throttle Body Injection) 2.8L
    RPO: LL2 VIN: R
    1986-1993 (S-trucks)
    1987 is the last year for 2.8L's in Blazer/Jimmy
    125 HP 150 ft/lbs
    Compression ratio: 8.9-1


    MPI (Multi-Point Fuel Injection) 2.8L
    RPO: LB8 VIN: S
    1985-1992 (Third Gen F-Bodies)
    135-140 HP 165-180 ft/lbs
    Compression ratio: 8.9-1


    MPI (Multi-Point Fuel Injection) 2.8L
    RPO: L44 VIN:
    1984-1988 (Fiero)
    135 HP 165 ft/lbs
    Compression ratio: 8.9-1


    MPI (Multi-Point Fuel Injection) 2.8L
    RPO: VIN: W
    1987-1995 (FWD)
    130 HP 160 ft/lbs
    Compression ratio: 8.9-1


    -Still in progress. If anyone has any of the missing info, PM me.


    (Courtesy Matt 4.3 TBI)
    Last edited by BlazinLow_inORE; 12-14-04 at 02:36 AM.


  4. #4
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    Here's a reference chart of TBI injectors, since it comes up from time to time:

    Flow is lb/hr @ 13psi

    GM Part # / Engine ////// Flow //// TBI bore

    5235430 /// 2.8L ///////////// 33 ////// 35mm

    5235203 /// 4.3L ///////////// 45 ////// 43mm

    5235279 /// 5.0L ///////////// 40 ////// 43mm

    5235206 /// 5.7L PU //////// 55 ///// 43mm

    17084327 // 5.7L Police //// 65 ///// 43mm

    1708430 /// Late BB PU //// 80 ///// 51mm

    5235231 /// Early BB PU /// 90 ///// 51mm



    (Courtesy Matt 4.3 TBI)
    Last edited by BlazinLow_inORE; 12-14-04 at 02:36 AM.


  5. #5
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    Ways to SIGNIFICANTLY improve your 2.8L's performance. (also applies to 4.3's and any other motor for that matter)

    Exhaust: The stock exhaust is restrictive.Just for sake of explanation, MOST of the exhaust that expelled through the exhaust port is NOT pushed out by the piston. The extremely hot exhaust gas has lots of pressure and will expell itself when the valve opens. The piston only has to work to push what little is left after. So basically the less restriction the easier it is for the exhaust to expell itself and makes the motor work alot less to push the remaining exhaust out. This is why headers make such an improvement over manifolds. Manifolds usually only have 2-4 inch runners. The exhaust gas slams into the abrupt enlargment or "log" of the manifold and in turn causes quite a restriction.

    Basic rule of thumb says design your exhaust to flow 180% of your engines ACTUAL CFM at redline. Actual CFM is what your motor is actually breathing. For reference the approximate actual CFM of a TBI 2.8 is 200 CFM at 6000rpm's. This is assuming it is stock but has a free flowing air cleaner assembly.


    Intake: The intake manifold of TBI motors is very restrictive as well. It is best to beef up your intake before your exhaust.Although it is more expensive than exhausr,it is easier to design your intake to accomodate future exhaust upgrades than it is to design your exhaust for future intake upgrades. There aren't really any aftermarket manifolds available, but a Longer duration cam makes ALOT of difference in intake flow. You can also get your intake manifold polished ( not much room for porting ) if your feeling froggy, but it is slightly on the expensive side. The throttle body should be also on the list of upgrades and Holley does make a 400 CFM TBI to put in place of the Stock 235CFM TBI.

    Do what the pro's do! Take advantage of the Thermodynamics of the internal combustion engine!


    It is impossible to get more than 100% volumetric efficienvy from a naturally aspirated motor. There is one exception. If you can make the exhaust and intake flow a little more than what the engine will suck in and expell and on top of that get a good cam with high overlap, you can cheat the system.

    It is posible to use the vacuum that exhaust creates due to its high velocity leaving the exaust port that it naturally forces the intake charge into the cylinder. It actually creates the same effect of forced induction. You will lose a small amount of fresh intake charge into the exhaust, BUT that is good becuase that means there is 0% residual exhaust in the cylinder. This also means your getting 100% of your available displacement. It is also possible to take advantage of tuning your motor to the vacuum pulses within the intake manifold, but if you can afford to do that you shouldnt have a 2.8 in the first place.

    Doing the above would theoreticaly create 200+ HP and 250-270ft lbs of torque out of 173 measily cubic inches! This also applies to a 4.3 as well. Imagine adding forced induction to that!

    Free + some cheap mods:


    Now the above is probably out of league for most people (even me). Adding a little timing advance can put a significant amount torque in the bottom end with only sacrificing very little in the top. The theoretical sweet spot of a 2.8 is 14* advance at base timing for low end torque and HP. Higher than that will take away from the upper RPM's.


    EGR of course puts inert gas into your cylinders. This effectively reduces detonation and NOX emissions. The bad thing is it also effectively reduces your engines displacement.

    Summary- Get rid of it if you can.







    Maybe more will added later but my broken hand hurts and I am tired.



    (Courtesy JJWalker)





  6. #6
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    Re: V6 Engines: ID's and Specs

    Factory 4.3L Cam Specs
    * '96-'00, VIN W, w/ balance shaft
    - Lift (I/E) - .415/.429
    - Dur @ .050 (I/E) - .191/.195

    * '93-'96, VIN Z, w/ balance shaft
    - Lift (I/E) - .376/.402
    - Dur @ .050 (I/E) - .183/.193

    * '92-'95, Vin W, w/ balance shaft
    - Lift (I/E) - .432/.440
    - Dur @ .050 (I/E) - .208/.208

    * '91-'93, ZR9/Z79, Syclone/Typhoon
    - Lift (I/E) - .351/.386
    - Dur @ .050 (I/E) - .179/.195 (Ductile)

    * '90-'91, VIN Z, Astro/Safari
    - Lift (I/E) - .403/.450
    - Dur @ .050 (I/E) - .202/.213 (Steel)

    * '87-'94, Vin Z, w/o balance shaft
    - Lift (I/E) - .351/.386
    - Dur @ .050 (I/E) - .179/.195 (Ductile)

    found this on s10 forum

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