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    Results 1 to 5 of 5
    1. #1
      Join Date
      Nov 2004
      Location
      Colorado
      Posts
      1,260
      Country Flag: United States

      EFI Cam/Manifold matching question

      I'm trying to figure out what a good cam replacement for my ASM TPI 468 would be. Right now I am running a 218/228 114 LSA 55x" lift hyraulic roller.
      The cam choice at the time was dictated by the fact that I was running a MEFI 3 controller and an automatic trans. This controller is now running a TPI 350 in my K5 Blazer, and I have purchased a WB dual sync Gen 7 Accel to run the Camaro, along with a T56.
      My thought is with the increased resolution and scalable tables around the idle RPMs that I can get away with less idle vacuum, thus I can run a bigger cam.
      I have access to a GM zz502 cam 224/230 55x" lift 110LSA and also a 234/244 600" lift 114LSA roller. Which of these would be a better choice for my engine? The ASM TPI has a 13" runner length, the engine is a 468 with GMPP aluminum oval ports (the zz502 heads).
      Any advice from the EFI experts here would be appreciated.



    2. #2
      Join Date
      Apr 2001
      Location
      The City of Fountains
      Posts
      16,117
      Country Flag: United States
      If you change cams, how will the MEFI III computer compensate? Isn't the fuel map set on those?

      Andrew
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    3. #3
      Join Date
      Nov 2004
      Location
      Colorado
      Posts
      1,260
      Country Flag: United States
      Quote Originally Posted by andrewb70
      If you change cams, how will the MEFI III computer compensate? Isn't the fuel map set on those?

      Andrew
      I can program the MEFI 3s. Its a eeprom based calibration like the LT1 PCM.

      Maybe my post is confusing, I am switching to a Gen 7 Accel ECM. It should deal with a bigger cam better I'd think.

    4. #4
      Join Date
      Aug 2004
      Posts
      582
      This is really more of an engines building question than an EFI question. Having a well matched combination of heads, cam, intake, and exhaust will make any EFI tuning WAY easier than just selecting the biggest cam that you think you can get away with.

      For instance, usually tuned port intakes are designed for midrange performance, and if that's the case with the ASM unit, would you really want to select a high RPM cam? You could possibly lose a ton of low and mid range torque, and may be dissapointed by the top end gains. Ask a big block guy (or ASM) which combo would make the most sense for your application, then worry about the fuel injection tuning later.

      I will note that the second cam with the wide LSA may salvage a decent idle.

    5. #5
      Join Date
      Nov 2004
      Location
      Colorado
      Posts
      1,260
      Country Flag: United States
      Quote Originally Posted by Fuelie Fan
      This is really more of an engines building question than an EFI question. Having a well matched combination of heads, cam, intake, and exhaust will make any EFI tuning WAY easier than just selecting the biggest cam that you think you can get away with.

      For instance, usually tuned port intakes are designed for midrange performance, and if that's the case with the ASM unit, would you really want to select a high RPM cam? You could possibly lose a ton of low and mid range torque, and may be dissapointed by the top end gains. Ask a big block guy (or ASM) which combo would make the most sense for your application, then worry about the fuel injection tuning later.

      I will note that the second cam with the wide LSA may salvage a decent idle.
      You are absolutly right about this being an engine building question. My thought is that the EFI comes into play in terms of LSA duration etc. Also what is a "high RPM cam" for a 468? I don't know, the zz502 noses over at 5500, is that high?
      There is alot of discussion on the gen 3 motors about cams, and some folks are getting away with cams that would never work under a carb.
      With the 6 speed my car will want to RPM more that it does with the automatic, so bumping power band up is not a bad thing.
      Maybe install the 234/244 114 advanced 4 degrees?




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