Thread: 300 efi heads

Results 1 to 5 of 5
  1. 06-14-2019, 03:16 PM #1
    Wendy lou
    Wendy lou is offline
    Member
    Join Date
    Jun 2017
    Location
    Baton Rouge LA
    Posts
    179

    300 efi heads

    2001 mercury 225 EFI

    Is there any difference in stock 225 or stock 250 heads?
    Reply With Quote Reply With Quote
  2. Gamblinman
    Gamblinman is offline
    Major Flagelator Gamblinman's Avatar
    Join Date
    Jun 2004
    Location
    Yantis, TX
    Posts
    4,121
    #2 06-15-2019, 06:22 AM
    No difference in combustion chamber volume.
    "Better to remain silent and be thought a fool than to speak out and remove all doubt."
    Reply With Quote Reply With Quote
  3. bkeenom
    bkeenom is offline
    Member
    Join Date
    Nov 2005
    Location
    Mcloud, OK
    Posts
    5,189
    #3 06-15-2019, 06:28 AM
    Quote Originally Posted by Gamblinman View Post
    No difference in combustion chamber volume.
    But there is a difference when you go up to 300. You can have your current heads shaved to increase compression. I did this and it was the biggest reason for my speed and holeshot gain. But if you do this you must change to a 4-hole intake and computer changes are recommended.
    Reply With Quote Reply With Quote
  4. Mr.Miyagi
    Mr.Miyagi is offline
    Member
    Join Date
    Oct 2017
    Location
    Collingwood, ON
    Posts
    44
    #4 06-15-2019, 07:04 AM
    Don't forget to add high octane fuel and hang on !
    Quote Originally Posted by bkeenom View Post
    But there is a difference when you go up to 300. You can have your current heads shaved to increase compression. I did this and it was the biggest reason for my speed and holeshot gain. But if you do this you must change to a 4-hole intake and computer changes are recommended.
    Reply With Quote Reply With Quote
  5. Tinbanger1979
    Tinbanger1979 is offline
    Member
    Join Date
    May 2016
    Location
    Ellwood City, PA
    Posts
    19
    #5 06-15-2019, 05:43 PM
    This is about what I have done to my 1996 250 EFI motor. The heads are cut to 300 ProMax specs by Black Magic Racing, 300 ProMax ECUs, mine came with 4 butterfly intake. I wish I would have had Simon program my fuel ecu to 250 XB, instead of 300 ProMax. It seems that is the way to go on the fuel ECU. Midsection is relieved, but not sure if that matters or not? At least it sounds like a big block inboard/outboard boat with above water exhaust through the no wake zones. LOL
    Reply With Quote Reply With Quote
« Previous Thread | Next Thread »