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Double manifold gaskets?

Discussion in '60-Series Wagons' started by RHON, Dec 16, 2006.

  1. RHON

    RHON Regular Member

    Messages:
    204
    Location:
    Las Vegas, Nevada
    Getting ready to install a header on my 60, I've been told by a couple of people to double up the gasket, I know it sounds just plain wrong but they insist it will reduce the chances of the infamouse cruiser exhaust leek, and works well on stock manifolds as well, I don't know, I do know I don't want to pull it back apart later, the leek I've got now is absolutly annoying and am going to surface the intake as I'm sure it is warped also.....any thoughts about this double-up?, And it would be great to hear from someone that has actualy done this.Any advice would be helpful.
  2. Mace

    Mace rock scientist.. Staff Member s-Moderator

    Messages:
    17,859
    Location:
    Las Vegas
    I do it routinely with headers.. It should not be necessary. But it does help..
  3. Mark W

    Mark W New Member

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    6,166
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    The Greatland
    I do it all the time. I tend to do it on almost every rig, just to be safe. Don't know why it sounds wrong to you. It provides more crush space to help seal irregular surfaces.


    Mark...
  4. 60wag

    60wag SILVER Star

    Messages:
    1,843
    Location:
    Boulder, CO
    It does provide more crush space but there's a reason the gasket isn't thicker to begin with. All gaskets, (well all except steel shim gaskets) creep a bit. Creep being loss of clamp stress. If you torque the bolts to a given level and then heat cycle the bolted joint for a while, you can go back and measure the amount of torque or clamping stress that the bolts have retained. Actualy the bolts haven't moved but the gasket under them has collapsed. Gaskets that retain 80% or more of initial stress are generally pretty good. The bolts are acting as really stiff springs. Torquing the bolt stretches the bolt and puts load on the gasket. The gasket collapses and the load goes away. The the joint leaks - especially exhaust gasket joints, head gaskets too. If a 0.03" gasket creeps 20% the bolt loses approx 0.006" of stretch. If a 0.06" gasket loses 20%, then the bolt loses 0.012" of stretch. ie thicker gaskets creep more and leak more. You want the thinnest gasket that will do the job. Also, and just as important, is what the gasket is made out of. Some materials creep more than others. The Grafoil material used in the Fel-Pro manifold gaskets creeps less than mosts other materials when run through the wide temp range of an exhaust manifold. You might be able to get as good performance with 0.08" of Grafoil as "0.04 of some "Kevlar" loaded material.
  5. jgordon

    jgordon New Member

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    823
    Location:
    NYC, NY
    60wag, try to know at least something about a subject before you post. Dang.

    :beer:
  6. rat

    rat Regular Member

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    78
    Location:
    South Africa
    60wag... I like it!
    how about a bit of high temp silicone sealant on both sides of the gasket? that's what I used the last time I had my headers off - no problems so far... did re - torque after a thousand miles or so.
  7. Mark W

    Mark W New Member

    Messages:
    6,166
    Location:
    The Greatland


    That's why you have to retorque the manifolds. ALWAYS retorque the manifolds.

    Thinnest gasket you can get may sound good in your explanation here. Makes sense to me, but in the real world it just doesn't work like that.

    I've installed... a shitload... of F/2F intake/exhaust gaskets. Doubleing the gaskets simply does not promote leakage. Many many times it prevents it.


    Mark...


    Mark...
  8. DaveWest5150

    DaveWest5150 New Member

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    570
    Location:
    North West Arkansas
    I dont have any manafold gaskets on my sbc...........
  9. pvidrummer

    pvidrummer Regular Member

    Messages:
    192
    Location:
    Puerto Rico
    You don't have any gaskets but you have lots of leaks...
  10. RHON

    RHON Regular Member

    Messages:
    204
    Location:
    Las Vegas, Nevada
    Mark- It sounds wrong to me because putting two parts on a space disigned for only one of the same part seems to be going against what the original engeneers seemed think would work best, but that's why I'm asking around because what works best is simply just that. So OK , so far I think I'll probably try the two gasket aproach,.......but with 60Wag's scientific annalysis of all this , I'm even more uncertain than ever, Thanks for all the input,but i could still go for some more.
  11. cbmontgo

    cbmontgo SILVER Star

    Messages:
    2,836
    Location:
    Colorado
    Not trying to hijack here, but I have my carb off right now and thought about replacing my intake and exhaust manifold gaskets while I am in there. Is this a major PITA to do? I have always had a minor exhaust "tick" down there...

  12. RHON

    RHON Regular Member

    Messages:
    204
    Location:
    Las Vegas, Nevada
    In my opinion -yes, I put a rebuilt carb. on my 60 back in July, I had a small exhaust leek at the time that went away when the engine warmed up,now it's a full time nuscence, I wish I did my exhaust back then, remember it won't get better but only worse as the gasket starts to burn. BUT, if you want to go wth one or two gaskets is up to you- let us know what you descide upon.
  13. Mark W

    Mark W New Member

    Messages:
    6,166
    Location:
    The Greatland
    There are a lot of things that we do tho these rigs that are different than what the original designers did. It may be blasphemy to some, but... Toyota did not get everything right. They did not anticipate the rigs being used as long as they have been and continue to do and they had no way of knowing some of the uses that the rigs would see.
    Double gaskets on the exhaust/intake is simply a way of addressing a problem. It works. Not much more I can tell you. This is not exactly a high precision connection here. Rocket science it ain't. ;)


    Mark...
  14. RHON

    RHON Regular Member

    Messages:
    204
    Location:
    Las Vegas, Nevada
    Okay, good advice there, My 60 is 25 years old and pushing 187,000. , We do need to wonder if the guys that invented these things would invision such longevety. If it works better with two and you know from experiance ,that is reasuring to me.Think of all the expansion and contraction the manifolds have been thru all these years. Nothing lasts forever, but in my universe., I will probably never part with my wagon.
  15. RHON

    RHON Regular Member

    Messages:
    204
    Location:
    Las Vegas, Nevada
    Hey ctbmongo- about the PITA part, one thing you should be careful of is to mark the emission hoses for re-connection later, other than that it's really not too hard.
  16. 60wag

    60wag SILVER Star

    Messages:
    1,843
    Location:
    Boulder, CO
    I know Mark has boatloads more experience with this particular engine than I do. I used to design OE gaskets in a previous life. When the block and the manifold are within OE tolerances of flatness, the thin gasket should work best. If you're working with a header and an intake that are different thicknesses and questionable flatness, two gaskets might be a good choice. Personally,I'd go with the highest quality gasket you can find, not the one that came with the header.

    The sharing of a bolt between the two manifolds has to be one of the more questionable design decisions I've seen on the 2F. The one that really blows me away is the unbolted outside end of the exhaust manifold on cyls 1 and 6 on the early 2Fs. At least they added the outboard bolt on the later ones. We used to test different materials and gasket designs by clamping something like carbon paper in the joint. You wanted to see an even line smashed into the marker paper all around the joint. By adjusting the density of the gasket material and the thickness of the metal grommets stamped in the gasket, you had a good deal of control over the distribution of the stress. I can confidently say that one bolt one one side of the exhaust port would have been a major PITA to deal with. The funny thing is, there's plenty of room for a second bolt as it was added later. There were plenty of engines that suffered from a lack of bolts because there simply wasn't room. Head gaskets on some of the early dual overhead cams were way underbolted.

    As for goop on the gaskets? You shouldn't need any. It won't hurt on these metal reinforced gaskets. On plain paper one though, like water pumps, the silicone can actually help the gasket get pushed out of the joint with repeated heat cycling.
  17. Mark W

    Mark W New Member

    Messages:
    6,166
    Location:
    The Greatland
    Yep, if we were dealing with new, OEM condition parts, there would be no need for this discussion even. ;)

    You can get the manifold remachined to true them out and remove any pitting. The head surface usually doesn't have any deterioration. But it can be difficult to find a machine shop that can/will do a decent job of machining this manifold combo.

    The single bolt arangement of the end exhaist port is particularly agrevating when using headers. Especially after the header has some age on it. Especially especially if the header is less than top of the line quality to start with.

    I recently gad to deal with an F engine (single bolt end port) with an old header. When all was said and done I had to *masage* the ears around the bolt in order to get both the header and the intake to line up correctly on the prts . Actually had gaps around the edges where the sealing bead of the header did not cover the ports when it came in.

    I only use the Felpro gaskets. Thick, soft single material all the way through with flame rings around the ports. Victor and some others use a sandwiched foil approqach which is mush less satisfactory.

    Stay away from the "Kevlar" gasket that SOR sells. JUNK!


    Mark...
  18. DaveWest5150

    DaveWest5150 New Member

    Messages:
    570
    Location:
    North West Arkansas
    NO I do not have ANY leaks...
  19. Micah

    Micah New Member

    Messages:
    674
    Location:
    Lubbock, TX
    so seriously i really dont see why so many people have manifold/headers leaks. i have headers on mine and when i put them on i did not want to mess with taking the intake off so i just put them on with out putting a new gasket on and have had no leaks and they have been on for 2 years now.

    but now that i have said something about the no leaks thing i will probably have alot of leaks this week...

    that is just my luck. oh well.
  20. RHON

    RHON Regular Member

    Messages:
    204
    Location:
    Las Vegas, Nevada
    What brand header did you install if I may ask?...................Knock on wood about the leaks part.

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