Mach 1 Weird Power Loss during tuning

Discussion in 'Special Production' started by Flysquirrel29, Oct 27, 2011.


  1. Flysquirrel29

    Flysquirrel29 New Member

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    Hey everyone. I'm a new guy so if this post is in the wrong spot, please let me apologize in advance and I promise to learn quickly.

    Okay. So I HAD a 2004 Mach 1 until I put a P-1SC on it (8#s) and promptly threw a rod through the block... talk about carnage. I'll try and upload pics that'll make you laugh at me or cry for me as soon as I figure out how to. Rebuild went well (or so I thought):

    -Old teskid block, had it honed and cleaned up.

    -8.8 manley pistons

    -h-beam manley rods

    -Re-used heads

    -Re-used crank but had it polished and balanced

    -Valve job (replaced bent valves on number 4 and the machine shop said the rest were good... later I found out that shop has a less than perfect rep)

    -Had the whole thing balanced from the harmonic balancer to the pressure plate.

    -Built it using the factory disc and all the specs for an '03 cobra.

    Then I dropped it in and drove 500 miles with break in oil without even coming close to boost. Changed to 5W30 synthetic and drove another 500 miles. Changed oil again and threw her on the dyno.

    Now I have 39# injectors and I tried to go down to a 3.5 inch pulley (10 to 12 pounds of boost I think) and the guy tuning it said probably going to need 42 pounders. Set that aside for now, not the issue.

    Did the initial fuel curve, everything looked fine, then went for a full power run. Made 9.7 pounds boost at 5800 rpm and ONLY 285 HP?!?!?!?! Then the boost climbed steady all the way to 11 or so at 6500 and between 5800 and 6500 RPM it dropped almost 100 HP.

    I am totally stumped. Any and all help would be much appreciated.
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