Re-machining 308 cam covers after fire | FerrariChat
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Re-machining 308 cam covers after fire

Discussion in 'Technical Q&A' started by luckydynes, Feb 27, 2006.

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  1. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
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    pit bull
    #1 luckydynes, Feb 27, 2006
    Last edited by a moderator: Sep 7, 2017
    Hey chatters,

    I've attached a lousy pic of the cam cover misalignment on a 308 motor I'm rebuilding . . . the centerlines of the cam journals and seal c'bores were pretty much right in line with the exception of the seal bore for the air pump drive . . . it's off about .01".

    There was also misalignment on the distributor mount "faces" which I'd heard about when fitting "non-factory" cam covers . . . this was easy to fix.

    So to fix the misalignment of the air pump drive, should I:

    1. Not worry about it . . . drill & tap "the end" of the head and cam cover and make a cover plate since I don't care about the air pump drive . . . murphy's law might need it later though for triggering or????

    2. Re-machine just the valve cover c'bore as close to the head c'line as possible . . . it'd be "right on" on one side (the lower side which would matter more I guess) of the cover but the "high side" of the c'bore will be about .005 bigger where it mates with the head.

    3. Re- machine the head and valve cover for a larger seal.

    4. Drink a few beers and put if together as is . .. I'm "kinda" joking when I say this but sometimes I like to find out "what'll work". When I was having problems with multiple rear main seal leaks on a newer P car, I got it out of the factory tech that they consider .008" misalignment on crankshaft/seal centerlines acceptable . . .


    It's interesting that this is the only seal c'bore that's out . . . like it was setup and machined later which I guess might make sense for the U.S. market.

    Thanks,

    Sean
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  2. Artvonne

    Artvonne F1 Veteran

    Oct 29, 2004
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    Paul
    #2 Artvonne, Feb 28, 2006
    Dont know what to tell you. To fix it correctly the cover probably has to be milled from the gasket face, and line bored to match the cylinder head bores. Lot of screwing around. But I found the hard way that I couldnt use silicone sealer on my cam seals. No one said, I just thought it would help hold them before i put the cam cover on. All they did was push out over and over again until I took it back apart and cleaned everything up. They have to go in dry. I guess I would waste a few seals. Try bolting the cover down on the head, and tap in a seal. If it fits tight, it will probably work as it is. Otherwise, maybe take some metal out of the stud bores to see if you can shift the cover over a few thou.
     
  3. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
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    #3 luckydynes, Feb 28, 2006
    Guess I'm not as concerned about the seal staying in as I am it leaking . . . because the seal c'bore centerline is off, it seems like it's going to distort the seal a little . . . the pic really sucks, sorry.

    Anyway, I can pick up the cam centerline and remachine the seal c'bore for a larger o.d. seal, but I seem to recall a "reputable" service guy telling me he's seen this particular seal c'bore off from the factory . . . this story came up after he had done a major service and this seal was leaking . . . anyone else seen the factory misalignment?

    Paul, your seal was loose as opposed to misaligned?

    Thanks,

    Sean
     
  4. Verell

    Verell F1 Veteran
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    May 5, 2001
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    Verell Boaen
    #4 Verell, Feb 28, 2006
    I tend to agree with artvonne. 0.01 s/b within the seal lip's ability to accommodate & still seal properly.

    Do you know of a history of problems here?

    If the seal doesn't hold, then your #2 alternative s/b fine. You can use a thin smear of anaerobic sealant like loctite 515 flange sealant or 518 to ensure that the 0.005" gap is sealed tight. Either of them will seal a gap of at least 0.25 mm.

    http://68.72.74.113/TDS/product515.pdf
    http://68.72.74.113/TDS/product518.pdf

    The anaerobics are a lot less slippery than RTV which makes a slippier a greased pig look downright sticky (been there too). However, as with any sealant, less is better.
     
  5. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
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    #5 luckydynes, Feb 28, 2006
    Thanks for the info. . . . . the only "history" of problems is with the engine that's currently in the car right now . . . a "reputable" mechanic told me he'd seen these c'bores way off and causing problems . . . guess no one else has really seen this misalignment on a factory cover/head combo and maybe he'd only seen the problem when people had done what I'm doing.

    Anyway, I'll probably just run her as she is and avoid the rtv's!!!!

    Thanks,

    Sean
     
  6. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    #6 Matt Morgan, "Kermit", Feb 28, 2006
    Last edited by a moderator: Sep 7, 2017
    I would suggest this trick I have used on 2 and 4 valve motors. Take a small sharp punch or an engraver to "dimple" the seal surface. This helps greatly in keeping the seal in place. If you are useing rubber clad seals you shouldn't have any problem
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