1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

F134 Overbored?

Discussion in 'Early CJ5 and CJ6 Tech' started by Shawn M, Jul 5, 2007.

Page 1 of 2
  1. Jul 5, 2007
    Shawn M

    Shawn M Member

    West Seattle
    Joined:
    Jun 7, 2006
    Messages:
    51
    Exactly how far can I bore a F134. At some point a previous owner bored to 030, which is fine by me, but he also left the jeep sitting for a long time. The bore is pitted near the top. and needs to go 080 over. Can this be done safely?
     
    Shawn M, Jul 5, 2007
    #1
  2. Jul 5, 2007
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    12,381
    Mine is .060 over, which I've heard is maximum so I don't know about .080. Have you considered sleeves?
     
    Glenn, Jul 5, 2007
    #2
  3. Jul 5, 2007
    Shawn M

    Shawn M Member

    West Seattle
    Joined:
    Jun 7, 2006
    Messages:
    51
    I"m thinking about them. My machinist says the 080 over won't be a problem due to the very thick casting.
     
    Shawn M, Jul 5, 2007
    #3
  4. Jul 5, 2007
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    12,381
    I've heard that too. Was kind of torn about going to .060 on mine.
     
    Glenn, Jul 5, 2007
    #4
  5. Jul 5, 2007
    Shawn M

    Shawn M Member

    West Seattle
    Joined:
    Jun 7, 2006
    Messages:
    51
    I should have a talk with my machinist about just how I intend to use my Willys. I don't want anything flexing or whatever nasty thing I don't want to think about.
    Is 080 over going to reduce my already low compression ratio?
     
    Shawn M, Jul 5, 2007
    #5
  6. Jul 5, 2007
    Mcruff

    Mcruff Earlycj5 Machinist

    Albertville, AL
    Joined:
    Sep 22, 2002
    Messages:
    5,349
    Overboring will increase compression not lower it. By boring you are increasing the volume that you are cramming into the head chamber, therefore increasing compression. Minimally but none the less you are increasing it, not decreasing it.
     
    Mcruff, Jul 5, 2007
    #6
  7. Jul 5, 2007
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    12,381
    No it won't change the compression ratio. If the head is shaved at all the ratio will actually increase.
     
    Glenn, Jul 5, 2007
    #7
  8. Jul 5, 2007
    w3srl

    w3srl All-around swell dude Staff Member

    Port Orange, FL
    Joined:
    Nov 6, 2002
    Messages:
    4,275
    The biggest risk with overboring is overheating, not flexing. There is a LOT of iron in that block! Before I'd go .080 over though, I'd investigate sleeves. YMMV. ;)
     
    w3srl, Jul 5, 2007
    #8
  9. Jul 5, 2007
    Shawn M

    Shawn M Member

    West Seattle
    Joined:
    Jun 7, 2006
    Messages:
    51
    Overheating because of having a bigger fire? The cooling surface area doesn't change. If the bigger fire is big enough to cause overheating, won't it also change my gas mileage?
     
    Shawn M, Jul 5, 2007
    #9
  10. Jul 5, 2007
    w3srl

    w3srl All-around swell dude Staff Member

    Port Orange, FL
    Joined:
    Nov 6, 2002
    Messages:
    4,275
    NO, overheating due to more surface area inside the cylinder to absorb heat, and the same amount of surface area OUTSIDE the cylinder to shed the additional heat.
     
    w3srl, Jul 5, 2007
    #10
  11. Jul 5, 2007
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    12,381
    I have always assumed that the thinner the cylinder wall the more that heat is able to radiate through the wall and be absorbed into the cooling water, also causing overheating, or running warmer at least.
     
    Glenn, Jul 5, 2007
    #11
  12. Jul 5, 2007
    Shawn M

    Shawn M Member

    West Seattle
    Joined:
    Jun 7, 2006
    Messages:
    51
    How much should I worry about the F134 over powering the stock radiator? I didn't have a lot of time driving the jeep, but I did drive it a few hours on a nice sunny warm day with the needle near the bottom of the temp range.
     
    Shawn M, Jul 5, 2007
    #12
  13. Jul 5, 2007
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    12,381
    I don't know if there's a good answer to that question, we can only tell you potential problems to consider.
     
    Glenn, Jul 5, 2007
    #13
  14. Jul 5, 2007
    gasman

    gasman Member

    mariposa calif...
    Joined:
    May 13, 2007
    Messages:
    61
    those blocks had alota iron in them I,ve got an F-head the is .80 over they used to bore chevy small blocks .125 thousent,s over stock.
     
    gasman, Jul 5, 2007
    #14
  15. Jul 5, 2007
    Shawn M

    Shawn M Member

    West Seattle
    Joined:
    Jun 7, 2006
    Messages:
    51
    Gasman, how do you use your jeep? Have you had any overheating problems 80 over?
     
    Shawn M, Jul 5, 2007
    #15
  16. Jul 5, 2007
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    12,381
    Another thing to consider however is any corrosion over the years of the water jacket side of the cylinder wall.
     
    Glenn, Jul 5, 2007
    #16
  17. Jul 5, 2007
    gasman

    gasman Member

    mariposa calif...
    Joined:
    May 13, 2007
    Messages:
    61
    no problem over heating I do a lot of crawling temp stays about 180 oil pressure at 55 Psi I did put a radiator out of a DJ in it 3 ROW . Always slow speed 3 to 5 mph no shroud stock 4 blade fan.
     
    gasman, Jul 5, 2007
    #17
  18. Jul 5, 2007
    Shawn M

    Shawn M Member

    West Seattle
    Joined:
    Jun 7, 2006
    Messages:
    51
    thoroughly tanked. Clean and pretty
     
    Shawn M, Jul 5, 2007
    #18
  19. Jul 5, 2007
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    12,381
    Decisions, decisions. :)
     
    Glenn, Jul 5, 2007
    #19
  20. Jul 6, 2007
    w3srl

    w3srl All-around swell dude Staff Member

    Port Orange, FL
    Joined:
    Nov 6, 2002
    Messages:
    4,275
    I guess you'd have to weigh the cost of sleeving vs. the cost of possibly having to do it twice. Either way you are looking at the cost of a set of pistons, since you will want to go back to stock specs if you sleeve the block.

    Decisions, decisions!
     
    w3srl, Jul 6, 2007
    #20
Page 1 of 2
New Posts