Initial start of LS without full exhaust system?

Discussion in 'High Tech Retrofits' started by Goat, Jul 2, 2018.

  1. Goat

    Goat Veteran Member Lifetime Gold Member

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    Just about done with the wiring and wanted to try and fire the engine to make sure all was hooked up correctly. Right now I just have open headers. I was going to trailer it to a place to have ss exhaust installed from the headers back after the initial start.

    But, I was re-reading the GM engine control harness instructions and it said the exhaust system must be properly sealed or the oxygen sensors may not work right. I currently have a 'start-up' tune on the ECM and was planning on a dyno tune when all was ready. I don't want to take a chance of dumping too much fuel or not enough because the sensors are not reading right.

    Is this a concern? Should I have the exhaust system finished before firing it up?

    thanks.
     
  2. nobreaks254

    nobreaks254 Veteran Member

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    If you really want to run it you could hook up 3 feet of pipe to you headers and you should be fine. That should be long enough to keep the o2 sensors happy
     
  3. Mike-78 Z-28

    Mike-78 Z-28 Veteran Member

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    I'm going to say properly sealed means no exhaust escaping through blown or no gaskets so the O2's can read the entire mixture.. I'm sure it'll run fine just for a trip to the muffler shop.
     
  4. bigkat_83

    bigkat_83 Member

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    Is this a new crate engine? When I did mine I had a very hard time getting the engine oil pump primed. In the GM instructions they say to do it with the starter. I had to pump it thru one of the oil ports. Finally got it primed and then could see oil pressure with the starter.
     
  5. badazz81z28

    badazz81z28 Veteran Member

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    I started mine with open headers. I wasn’t going to drive down the road with it like that, but I surely did start it. Good thing too because it caught issues I would have wanted to fix in the garage, not at the tuner. Such as...it wouldn’t start lol.

    The o2 sensors don’t do anything and anyways until they are hot.
     
  6. Goat

    Goat Veteran Member Lifetime Gold Member

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    Thanks guys for the replies.

    Nobreaks, we just got back from a 3 week camping trip. Spent five days in South Dakota. What a beautiful place...
     
  7. Goat

    Goat Veteran Member Lifetime Gold Member

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    Not a crate engine. It's been broke in already on a dyno...
     
  8. Knuckle Dragger

    Knuckle Dragger Mayor of Simpleton Staff Member Lifetime Gold Member

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    Heated O2s get hot pretty quick. You'e into closed loop within seconds any more. I wouldn't hesitate to start it. The only issue I can see is if the exhaust pulse allows air to be sucked into the exhaust near the O2. If your sensors are near the open collector this might be an issue, but I doubt it will have a catastrophic effect of major over fueling.
     

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