Crossfire & TBI distinction...if any?

Everything Else Cadillac

  1. tlake

    tlake LVC Member

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    I have heard the terms used interchangeably, but what is the tech difference between Vette / F body Crossfire and TBI on humble 4 cylinder Cimarron, Fiero etc cars?:confused: Thanks.

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    Iron Duke
     
  2. CBODY67

    CBODY67 New LVC Member

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    TBI is throttle body injection. One TBI unit is needed on 4cyl and V-6 engines. Placement wouild be similar to what a carb would have been on those motors

    CrossFire on the Corvetrte and F-body engines uses two TBI units, one for each bank, located opposite from the bank of V-8 cylinders it feeds.

    The CrossFire engines were not a performance engine, by observation, but looked the part with their "cross-ram" style intake, similar to many later '60s drag race engines. With the intake manifold off, the port sizing was even smaller than for a 4bbl V-8! The later Tuned Port Injection (TPI) motors were MUCH better in all respects!

    CBODY67
     
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    • tlake

      tlake LVC Member

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      Thanks, it must have been a terrible feeling to have bought a late 1984 Corvette, only to find the improved TPI 1985 car just around the next corner!
       
    • CBODY67

      CBODY67 New LVC Member

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      Actually, the CF appeared on the 1982 Corvettes and late-intro 1982 Z/28s. Until the 1982 Camaro Z/28 Indy Pace Car edition cars were built, the CF305 Z/28 didn't happen, with only the normal 305 4bbl available in those cars, initially.

      Due to some flaky engineering, the Camaro CF305s all suffered from "water intrusion" into the air cleaner (and intake manifold areas!). Many amusing incidents resulted! Plus several TSBs for band-aid fixes, by observation.

      Many of the CF305 induction systems were replaced with aftermarket 4bbl intakes and 600cfm carbs, resulting in a car that ran better. The Camaro Z/28 with the L69 4bbl was the best performing one of the bunch, until the Tuned Port Engines appeared.

      Enjoy!
      CBODY67
       
    • CBODY67

      CBODY67 New LVC Member

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      The CrossFire 350 and 305 were never marketed as a performance" engine, by any means. When people raised the hood on the Corvette, seeing something that looked similar to a later 60s cross-ram intake (as some Chrysler HEMI race engines used), they automatically presumed "max performance". In reality, that system was more of a transitional toward the later EFI engines, more than anything else. With the capabilities of the engine to be able to run at sub-2000rpm levels in OD on the highway with improved emissions and such.

      No performance< per se? The lower half of the intake, which had the ports in it, had ports that were about 75% as tall as a normal 4bbl intake. A big ledge at the bottom! I suspect this was a band-aid fix for the fact that a bit too much unvaporized fuel would be in the ports, so the ledge was there to induce some turbulance to get the larger droplets back into the air flow and more vaporized as a result. At the lower rpms, that added turbulance helped the mixture, but didn't affect part-throttle power and response.

      When we got the first ones in, I took off the air cleaner to look at it running. Large fuel droplets were in evidence. Such that I laughed and said "Throw a match in there and cook weinies". Obviously, the spray pattern was not what it should have been, but "good enough". No doubt, the later TBI units, especially the 2bbl versions, had much better spray patterns and atomization characteristics such that they were "bulletproof" in reliability and performance.

      Enjoy!
      CBODY67
       

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