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Alternative to Exhaust Donuts on the 308?

Discussion in 'Technical Q&A' started by Wayne 962, Feb 22, 2004.

  1. Wayne 962

    Wayne 962 Formula Junior

    Nov 27, 2003
    434
    I've researched the archives, and it seems that there are some people who believe that the 30+ year old design of the "fiberglass" donut exhaust gaskets don't really last too long. I replaced this type of gasket on my BMW the other day with a soft metalic one. I was wondering if anyone has any cross-reference to a newer-style gasket that can be used in place of the older fiberglass one. I'm not against paying for the original ones ($100 for a set of six), but I want to make sure that there's not something better out there that I can use. Seems to me that a bunch of people have had trouble with these gaskets distintegrating (all six of mine were in very poor condition, or missing altogether).

    Thanks in advance for your suggestions,

    Wayne
     
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  3. Wayne 962

    Wayne 962 Formula Junior

    Nov 27, 2003
    434
    #2 Wayne 962, Feb 22, 2004
    Last edited by a moderator: Sep 7, 2017
  4. Steve Magnusson

    Steve Magnusson F1 World Champ
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    I think most of the trouble with the "stock" gaskets is caused when using an improper flange design (per Dave Handa's comment in the earlier thread). I've not had any trouble with the stock donut gaskets when using the stock flange design that compresses/protects all three sides of the donut. Is the joint in your jpeg, or the joints you've had trouble with, 2-sided or 3-sided?
     
  5. jselevan

    jselevan Formula 3
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    Nov 2, 2003
    1,854
    Wayne - is original stock part "fiberglass" or asbestos?

    Jim S.
     
  6. f355spider

    f355spider F1 World Champ
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    May 29, 2001
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    As Steve alluded to, the stock asbestos type gaskets are not designed to take direct hot exhaust gases, the typical union will include a metal "sleeve" that protects the gasket itself from the direct exhaust gases. The gasket is purely assisting with the seal. If the system has been modded at all, such as with an incorrectly (that is not identical factory type flange) designed flange for a "test pipe" or something, then yes, the sintered or metal impregnated type gaskets will be the only way to go for proper longevity, as they can take the heat of the direct gases.

    All of the 308 sized donuts can be purchased at any muffler shop. I got mine at Midas. I just showed them the old ones and they matched them up.
     
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  8. Wayne 962

    Wayne 962 Formula Junior

    Nov 27, 2003
    434
    Great suggestion - I hadn't thought of that. I will head there tomorrow!

    -Wayne
     
  9. Wayne 962

    Wayne 962 Formula Junior

    Nov 27, 2003
    434
    They are the stock 3-bolt ones that are on the stock 308 system...

    -Wayne
     
  10. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Remarkable -- I usually have the other problem with the stock 3-sided arrangement that the donuts are so well protected that you can't get them off the side with the ID protection/compresssion sleeve (but I'd agree that the primitive "asbestos"-over-metal-foil-layered type donuts don't re-use easily in any case).
     
  11. Wasco

    Wasco Formula Junior

    Dec 9, 2003
    486
    Salem
    Full Name:
    Randy
    Are you guys using lock nuts (heat resistant) or just lock washers on your exhaust. I took my 308 in for a alignment and found only one bolt out of three on one side. I since replaced the other two only to find a nut on my garage floor two days later.

    Any ideas?
     
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  13. Steve Magnusson

    Steve Magnusson F1 World Champ
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    The stock "stud + coil spring" design is best IMO because it lets you fully tighten the nuts on both ends (with the coil springs developing the flange clamping load rather than the nuts). When you try to use a simple "bolt + nut" at the exhaust flanges, you can't really fully tighten the nuts because this increases the load on the donut (which is why conventional washer locking methods don't work too well for that). Probably adding a jam nut on top of the primary nut would work OKish (at least preventing things from falling off) if you stay with the bolts, but you could still have exhaust leaks since the preload in the bolt (a few thousandths max) really can't accomodate dimensional changes in the relatively "soft" gasket.
     
  14. Wasco

    Wasco Formula Junior

    Dec 9, 2003
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    Randy
    I think when the previous owner put the Headers on they must have tossed coil spring system. I am not familiar with this so any photos or suggestions on where to purchase. Does sodacoms or Dennis Mcaan carry these do you know?
     
  15. Wayne 962

    Wayne 962 Formula Junior

    Nov 27, 2003
    434
    I used exhaust flange copper nuts that are slightly oblong so they are self-locking. The copper helps to minimize any rust or corrosion. We sell these for our Porsche customers all the time as the recommended exhaust nut.

    Not sure about the design of the donut flange - doesn't the inner tube butt up against the opposite side and prevent extreme compression of the donut?

    I went to Pep Boys yesterday and they had an good fit replacement for the gaskets. I'd rather use something newer than the older design which people mentioned they had problems with. I think the exhaust leak is gone now, but I can't be 100% sure as the exhaust is so loud that it's truly tough to tell...

    I still have backfiring though - now I'm convinced it's the carbs. I have a new tool that is a tail-pipe plug-in wide-band O2 sensor and handheld monitor (very cool) that I've been testing and will hook up to the Ferrari...

    -Wayne
     
  16. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Wasco -- Unfortunately, I don't have any good sources for the stock 308-2V exhaust hardware at reasonable price (even FerrariUK want ~$822 for the set!). The SPC illustration is a little messed up (the washer between the flanges actually goes against the shoulder on the other end of the stud), but might give you an idea of the basic form:
     
  17. Peter

    Peter F1 Veteran
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    Dec 21, 2000
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    B.C., Canada
    I'm going to experiment with the spring-bolts...

    ...I have just placed an order with FofUK. I did some searching and found that the 288 GTO exhaust bolts are much less (at 0.60 versus 10.50UK Pounds for the 308 versions!). Be aware this is an experiment of mine, but it should work.

    I cobbled-up some bolts and springs obtained from a hardware store before and they've lasted, but alas, since they're plated steel, they're all rusted to s---'s now. Looking forward to seeing how it'll work with these GTO bolts.
     
  18. Wasco

    Wasco Formula Junior

    Dec 9, 2003
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    Randy
    I have a little backfire going on during heavy dexcelleration I assumed fresh air was entering the exhaust at the header exhaust pipe contection allowing for combustion of unburnt fuel. I think I will go with the brass nut idea, as I have used those before with good results.
     
  19. Wasco

    Wasco Formula Junior

    Dec 9, 2003
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    Randy
    Steve,

    Many thanks for the detail view! What a complex fastening system!
     
  20. Wasco

    Wasco Formula Junior

    Dec 9, 2003
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    Randy
    On second thought it wouldnt be hard to fashion a bolt spring system.
     
  21. Steve Magnusson

    Steve Magnusson F1 World Champ
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    I think you're right! TRs are done that way -- using a bolt, a coil spring with a washer at each end, and a slotted-squished-all-metal-lock nut. I still like the 308 design better, but not at those costs. (Peter that L10.5 price is for the 2 slightly longer 308 studs -- the 16 shorter ones are L14.4 each!)
     
  22. Robert Johnson

    Robert Johnson Karting

    Dec 8, 2001
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    Robert Johnson
    Unless you're going to the car show, the basic design premis for the 308 is this: The engine goes North, South. The exhaust system goes East, West. So, you better have some flex. I have found that exhaust "dounuts" from NAPA and the surviving springs & bolts from the OEM set up along with stainless bolts & springs from GT Car Parts work just fine. This is not magic or rocket science, you just need some flex in the system (read, a spring on every bolt and do not bottom out [coil bind] the springs).
    Do what you want, this works for me on an old 308.

    Regards
    Robert
     
  23. Wasco

    Wasco Formula Junior

    Dec 9, 2003
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    Randy
    Robert,

    The car came to me without the bolts and spring set up. I think several have suggested GT Car Parts, is that a vendor? do you have contact info?

    I really want to go with the spring set up but dont want to go around to parts stores sizing them up.
     
  24. Lloyd

    Lloyd F1 Rookie

    Aug 25, 2001
    2,703
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    #21 Lloyd, Mar 2, 2004
    Last edited by a moderator: Sep 7, 2017
  25. Wayne 962

    Wayne 962 Formula Junior

    Nov 27, 2003
    434
    Yes - that's them. They look the same as the ones on my 308...

    -Wayne
     
  26. Peter

    Peter F1 Veteran
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    Dec 21, 2000
    6,389
    B.C., Canada
    #23 Peter, Mar 5, 2004
    Last edited by a moderator: Sep 7, 2017
    Here are a few pics of the 288 GTO bolts I received from FofUK yesterday. I now know why the GTO bolts were so inexpensive compared to the 308 ones... These look to me like they're galvanised steel. No complaints, since if these rust out, I'll replace with stainless, or I may just end up starting off with S/S and keep these on the shelf for something else.

    These should work fine for my 308. I'll post pics in the future when I have them installed on my car.

    Notice how the nuts have a simple locking mechanism - they have a fine slit through and are squished. As the nut is tightened, it spreads and this load is what locks down on the bolt. Neat. Also shown next to the nuts are the chromed spacers that fit inside the spring. The washers are dished slightly (add pressure when tightened?).
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  27. Wayne 962

    Wayne 962 Formula Junior

    Nov 27, 2003
    434
    My 308 didn't have the spacers - the nut bottoms out on the threads and then won't turn any more.

    -Wayne
     
  28. Wasco

    Wasco Formula Junior

    Dec 9, 2003
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    Randy
    Peter,

    Great post, what part number was that for the kit?

    A pic of them installed would be spectacular!
     

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