General consensus on the notorious bottom end failures

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  1. #1

    Default General consensus on the notorious bottom end failures

    As we all know the 4.6 4V motor has all the ingredients of greatness. Yet they never seem to go beyond 100+k before the bottom end gives up. What gives? Anybody decoded the flaw? I spoke with a few car builders and they absolutely hate to do the swap because of that. I guess I didn't realize how poor reliability reputation this engine has in the custom car circles...BTW IMO Ford threw in the towel in 2003 when they went with the cast iron block for the supercharged Cobra....

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  3. #2
    Senior Member Array cobraracer46's Avatar
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    The factory motor in my 2001 Cobra has made it past 100K without issue.

  4. #3

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    That's wonderful, congrats. I meant the general consensus however. Many fail and that's the reputation this engine has in the builder circles...

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    Senior Member Array cobraracer46's Avatar
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    My guess as to what is killing some of the cobra short blocks is the factory oil pump with an aluminum backing plate that causes a loss of oil pressure as RPM's exceed 2500. The following video shows this quite nicely:

    https://youtu.be/6QPahVJJqFw

    To solve this problem, install a 2013 Shelby GT500 oil pump with a billet steel backing plate. While your at it, install billet oil pump gears as well.

    Finally, I believe that the 99-01 Cobra engine is reliable and although pure speculation on my part, the majority of bottom end failures you find on the Cobra motor
    can be traced to people doing stupid things like letting the engine run low on oil or loading too aggressive of a tune into the PCM.
    Last edited by cobraracer46; 08-27-2019 at 01:07 AM.

  7. #5

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    Thank you. I did suspect the oil pump. That sounds like a good start. I just saw another cobra on CL with a spun bearing.

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