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Hot Rodding a P71

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  • Hot Rodding a P71

    Is it possible to hot rod the P71 2003 and still pass muster with "The Man"?

    My car is a pig since Ford decided not to bump up the compression after converting to CNG. What are my options and still be able to pass the smog patrol.

    Thanks.

  • #2
    Re: Hot Rodding a P71

    I'm sure you could bump the compression up and easily pass smog, but It's a lot of work just to get a few more horses. There may be some street legal exhaust options. A cold air kit or K&N would help too, the K&N on my Civic made a big difference in performance. I wonder if anyone has put nitrous on a NGV?
    BLUE 09 GX

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    • #3
      Re: Hot Rodding a P71

      I would think crowned ("pop up" pistons in mullet speak) pistons would give you the compression you are looking for. I'm not sure on price as you would end up needing 2 head gaskets and a oil pan gasket at the minimum to change pistons. Plus the cost of the pistons.

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      • #4
        Re: Hot Rodding a P71

        And, I do believe the CNG crown vics DO have s lightly higher compression ratio.. just not as high as it COULD be. At least on the 97, the stock CV ran at 9.1:1, and the CNG is like 10.1:1. Not a huge gain, but it is SOMETHING. For the cost, you might be better off looking at a dual-exhaust setup, and some intake mods.

        If, for some reason, you were going to be rebuilding the engine anyways, it might be worth looking swapping out the pistons, but I'm not sure you'd gain that much for the amount of work involved.
        Last edited by CraziFuzzy; 08-28-2008, 03:06 AM.
        1997 Factory Crown Victoria w/ extended tanks ~~ Clunkerized!
        2000 Bi-Fuel Expedition --> ~~ Sold ~~ <--

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        • #5
          Re: Hot Rodding a P71

          did some more looking, and it does indeed look like when they bumped the compression up to 9.4 for the stock engine in the later model years, they decided that they could just use that for CNG as well.
          1997 Factory Crown Victoria w/ extended tanks ~~ Clunkerized!
          2000 Bi-Fuel Expedition --> ~~ Sold ~~ <--

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          • #6
            Re: Hot Rodding a P71

            I have modded my 2001 CNG vic a little bit. They are limited in terms of acceleration mainly by the 2.73 gear ration and the fact that the shift too early in the rpm band at WOT, along with the extra 500lbs of tanks in the trunk. One easy mod is to remove the intake snorkel on the airbox and replace it with a 3" rubber pvc pipe connector. This opens up the intake and took around 3 tenths off my 1/4 mile time. I replaced a muffler with a pipe and the sound is perfect, even though it is still single exhaust. I half-shafted my throttle body, which gave me a little difference, prob. a tenth of a sec in the 1/4. When I unbolted the exhaust after the cats, it also took around another 3 tenths off my time. My car stock ran a 18.999 at 72mph. Now it runs 18.5's at 75mph still with the single exhaust bolted up.
            Last edited by jefo; 02-09-2010, 12:43 AM.

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            • #7
              Re: Hot Rodding a P71

              Reduce weight, buy performance chip for shift points, 3.55 or 3.78 gears in axle. Only other mod that might work is to add a supercharger designed for the 4.6.

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