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Thread: Crack in head?

  1. #1

    Crack in head?

    Has anyone had this problem? Good news is my 67 FLH is back on the road and running real good. Bad news is there appears to be a crack on the rear of the rear head. It is directly above the head bolt. It is leaking oil and dripping on the rear pipe (I have true duals on it). You can see it in the middle of this pic where the oil is seeping out between the second and third fin from the bottom. It was cleaned with brake cleaner before the picture was taken.



    Is it possible to weld with the head on the bike? If I remove the coil it is accessable, but of course reaching between the fins would probably be tricky.

    Thanks, Stan

  2. #2
    It would be best to remove the head.
    Chris Haynes
    A.M.C.A. Member
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  3. #3
    Weld it on the bike? Good luck with that! Why don't you just put some silicone, or other sealer on it? If it isn't a high pressure leak, that should help. But for the little bit of work it would be to remove the head and do it right.........
    Mike

  4. #4

    Re: Crack in head?

    Finally got around to taking the heads back off after riding it for a season and a half (hated to do it 'cause it was running so good) & wanted to tell what I found in case someone else has the same problem.

    I was able to seal the crack with JB Weld and it seemed to hold up well. When I removed it I had to chip & scrape it off. There was a small area that came off clean, but most of it was still bonded tight.

    When I removed the heads, it was apparent that the head gaskets had been leaking. What I found was the head bolt inserts on both sides of the oil return hole (on both heads) had pulled out just enough that my fingernail would catch and the head gasket would not seal. I called Don's Custom and Donny said he had seen this before, but not too often; that the inserts have a bulb at the top to hold them when they are cast in. He said he had a place he sends them for repair, so I took them to him. I believe the leak was caused by the insert pulling out, since it appears to be right at the top of the insert.

    I got them back and Donny said they didn't replace the inserts, but torqued all of them to 85 ft/lbs to make sure they would not pull any further, then milled the heads & sealed the leak from the inside. I don't know how they sealed the leak, but Donny said they assured him it was done. Gettin' it back together now so I sure hope they're fixed.

    BTW, there's about 125K on these heads.

    Stan

  5. #5
    Join Date
    Aug 2008
    Location
    Winter Garden, Fla.
    Posts
    6,589

    Re: Crack in head?

    Sounds great, Deacon! And thanx for getting back to the forum with the 411. Sounds from you description like the headbolt insert with a bulb at the top, inside the aluminum, could pull out, but only so much. Makes sense. That was enuf to allow the part that stuck out to act like having a washer/spacer on the bottom of the head and keeping it from torqueing all the way down. Good to know that a simple head-milling solves it. See if you can find out the rest of the process they used, if you can, for the forum, here. Thanks alot!
    Sarge, Gerry Lyons, Fla.
    F.O.G. member: http://flatheadownersgroup.com/
    www.37UL.com
    "It's a 1937, and the downside is, it's out of warranty"

  6. #6
    Join Date
    Jul 2009
    Location
    nashville tn
    Posts
    1,170

    Re: Crack in head?

    I USUALLY GO ONE STEP FURTHER and MILL DOWN THE INSERTS A COUPLE THOUSANDTHS SO THE WHOLE HEAD IS PULLED DOWN AND NOT JUST THE INSERTS. THIS IS A PAN HEAD BUT SHOVEL IS THE SAME I JUST DON'T HAVE ONE TO PHOTOGRAPH. NEVER HAD A HEAD GASKET LEAK YET THIS WAY. THIS WAY YOU DON'T USUALLY HAVE TO MILL THE HEADS OR AT LEAST NOT AS MUCH. MILLING CAUSES PERMANENT DAMAGE WHEN YOU REMOVE MATERIAL LIKE THAT SO LESS IS ALWAYS BETTER. MOST SHOPS I SEE ONLY CARE ABOUT THE JOB AT HAND AND DON'T THINK ABOUT HOW MANY TIMES IN THE FUTURE REPAIR MIGHT BE NEEDED. HOPE THIS HELPS

    Last edited by flat-happy; 01-26-2011 at 09:38 AM.

  7. #7

    Re: Crack in head?

    I USUALLY GO ONE STEP FURTHER and MILL DOWN THE INSERTS A COUPLE THOUSANDTHS SO THE WHOLE HEAD IS PULLED DOWN AND NOT JUST THE INSERTS.
    I thought about using a counterbore to remove a few thousanths, but didn't. If it happens again I'll do that. I hope they didn't take too much off when they milled them. Thanks for the info flat-happy.

    See if you can find out the rest of the process they used, if you can, for the forum, here
    Donny didn't say who did the work and I didn't press him. I can give his phone # to anyone that would like to talk to him about it.

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