Anybody put on a FMF 4.1 Slip on to stock header?

3 replies to this topic
  • CO_Rider

Posted July 18, 2007 - 04:42 PM


Just a quick quesiton. I get a 4.1 slip on for my 07 450 and was reading thru the instructions and they said to use one of the adaptor peices if you are using it on you stock header, but NOT to if you are running a FMF header. Well when I went to put it on I could only fit it not using an adaptor peice so I just mounted it on that way but want to know if anybody has this pipe on their stock header and ran into the same thing or did you actually use one of their adaptor peices to put on? It seems to fit good but don't want to run into an exhaust leak problem. Thanks

  • KJ790

Posted July 18, 2007 - 05:03 PM


FMF changed the midpipe on the factory 4.1 half way through production. Some of the older ones have a midpipe that fits perfectly on the stock header and then have a small step after that. The newest ones (built in the last couple months) have a midpipe that is quite a bit larger than the header and you have to use the adapter, and this acts like the step on the older ones. Sounds to me like you got the older style, you should be fine. If you needed an adapter you would know it, the midpipe is way to big for the header.

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  • CO_Rider

Posted July 18, 2007 - 05:09 PM


Ok thanks I appreciate it. Yeah must have got an older one then because it fits really good on the stocker without the adaptor, but the instructions said different. Didn't know if there was a typo or something or I just didn't know how to put on a slip on :crazy:

  • TapptOut

Posted July 21, 2007 - 10:18 PM


Ya hes right, the first generation if you will, of the slip-ons were made to fit-stock headers and/or fmf ones.

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