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Thread: BBC Merlin heads keep cracking!

  1. #1
    Q-ball
    My brother-in-law has a built 468 in his V-drive, here is the problem; the merlin heads he bought keep cracking along the casting seam.(2 heads so far, 1 on each side of the engine) the first one cracked when he was tourqing it down with the proper sequence. The other one lasted about 10 hrs. It's getting pretty expensive, any help would be nice.

  2. #2
    230EAGLE
    IN SOME CASES THE HEAD HAS BEEN MILLED CROOKED FROM THE FACTORY OR THE CASTING HAS BEEN COOLED OFF TOO RAPIDLY ANOTHER POSSIBLITY IS THE BLOCK COULD BE WARPED ALSO YOU COULD HAVE A TORQUE WRENCH THAT IS NOT READING ACCURATE P.S I HOPE THIS HELPS YOU

  3. #3
    DOHARA
    Q-BALL, What kind of head bolts are you using? I would recommend the ARP, the ARP's stretch when torqued. If you use old worn out stock bolts they don't allow anymore stretch and you get false torque readings. I also use the merlins and ARP head bolts and haven't had any problems. 230 EAGLE has a point too it could be a bad surface job on heads or the block needs to be checked too. Has the engine been machined or recently built? if so I would take it to another machine shop to have the other guys work checked. The machine you used may of screwed it up.
    DANO

  4. #4
    Q-ball
    Thanks for your help guys, we will check all that stuff.

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