'93 K1500 5.7

Are the stock TBI intake manifold bores feeding a common plenum chamber or does each bore feed four intake runners?
Question is raised as our 'burb is under performing these days (no pulling
power on hills Canadian Rockies around 4000 Ft asl).
There is a natural power loss with altitude that pilots of normally aspirated piston engine aircraft know too well. This under performance can best be described as lack of accelerating power though the engine runs smoothly and has not set any codes.
The truck will bury the speedo needle on level roads without skipping or missing a beat. Just seems to take until next year to get there! Plugs, when last pulled were white with hard deposits at the base of the ground probe. Possible too lean I'm guessing . I'm not afraid to ask as I'm more familiar with turbine engines than piston engines. Timing? Injectors/pulse width? filters? fule pressure vs fuel flow? Thanks in advance Rolf
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nozel wrote:

    It should be a open as you call commen plemiumn intake manifold. For the spark plugs find a "service" book that has a pictorial of spark plug in different damage/deposit types. From that you can identify what you saw.
    If you don't know how many miles are on the fuel filter, they don't cost much to replace. You can check the fuel pressure with a TBI adapter and a stanard EFI fuel pressure test gauge.
    You should also check your spark plug wires, distributor cap, and rotor for wear, carbon tracking, arc out.
    At altitudes that high Gear Ratio makes a huge differance in perfromance. In the glovebox will be a decal with a buch of codes on it. Swing by a dealership and ask someone to find your Axle Ratio code for you, and what it translates to. Also ask them if you have the code for a "Locking Rear Differential or Gov-Lock". Charles
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Charles Bendig wrote:

Elderbrock make a nice replacement manifold for TBI engines. Stock manifold is very restrictive and stock 350 TBI are pretty gutless about 3500 RPM because of this. You might wind them well past that but they are not making any good torque and what they are making drops more and more as RPM increases. Stock TBI engines do their best work below 3500 RPM or so regardless of what paper ratings may say
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