replacement heads

Discussion in 'Engine, Fuel and Exhaust' started by fwcole, Apr 21, 2011.

  1. fwcole

    fwcole Active Member

    Friend of mine has a 89 evo(bottom breather) with serious attention needed for the heads. we have a set off a 97 model and we were wondering if they would work. thanks for any help

    BUBBIE Well-Known Member

    Don't know for sure, 8 years and a lot of changes. I think they would.. BUT I don't know about the oil breathers and oil back to motor..

    Hoping for one like Chopper or TBones, HDDon, Jack K, and many more that will know for sure...

    I had a 97 EVO FXDS and it was Nice...

    Hold by the forum and check back as an answer will come..

  3. Jack Klarich

    Jack Klarich Guest

    They would work tho you would have to plug the breathers or re route them, what is wrong with the original heads?
  4. HDDon

    HDDon Experienced Member Contributor Retired Moderators

    I'm not sure how the oil breather would work or if there is some difference in the timing of the oil screen in the cam chest. I guess if you plugged the heads and retained the bottom vent you might make it work.
  5. Jack Klarich

    Jack Klarich Guest

    One other note your original heads were tapped to hold the A C back plate on, these were blind holes, with the new heads these holes are the breathers and would certainly pass oil to the air filter Don is correct the breather would have to be altered in the cam chest a lot of extra work IMO
  6. Breeze3at

    Breeze3at Well-Known Member

    My '92 is a bottom breather. Evidently the mfg. date of this bike was during the transaction to head breathing. My stock heads had the breather passages, and the rocker boxes are cast for the umbrella valves, but the bolts from heads to air filter bracket were/are solid 1/2" thread. It breathes through the plastic valve in the cam chest, and out to a tube going up to the air filter. I bought and installed Edelbrock Performer heads that were made to be head breathers, but I just bolted them on. I have often thought about putting umbrella valves in the rockers, and having dual venting, but never found anyone that could give me a definitive answer of possible negative effects of dual venting. Seems like it should work.
    So IMO yes, the '97 heads should work. You will need to modify the air filter bracket for the larger diameter bolts.
    Last edited: Apr 21, 2011
  7. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

    Same as Breeze3at my 92 softail has the breather heads and a crankcase breather solid bolts hold the air cleaner backplate in place and block the head breathers so the breathing is done through the crank case so i would think those heads will work fine with the rest of the engine as long as you have solid bolts in the head breathers