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Stainless steel exhaust manifold bolts

Discussion in 'GM 6.5 Diesel Engines' started by Mikey von, Jan 14, 2010.

  1. Mikey von

    Mikey von Member

    Nov 3, 2009
    Burney, CA
    While reading MaxPF's CTD build tread, I noticed he uses stainless steel bolts on his exhaust manifolds. I would like to use new hardware on my exhaust manifolds and I am thinking of using stainless steel.

    Anyone see any issues with this? Is there a special type of stainless that needs to be used?

    Here is MaxPF's response to someone questioning the use of stainless steel bolts;

  2. SmithvilleD

    SmithvilleD Active Member

    Mar 2, 2009
    St Joseph, MO
    ARP makes some very nice exh manifold studs in their stainless 300 alloy (if memory serves). They're both strong & don't have corrosion issues. Don't know if they make them in the right size for the 6.5?

    The bolts/studs that mount the exh manifolds to the heads are a unique thread shape. Don't know if the corresponding thread in the heads is unique? Would seem logical the unique thread is to keep the bolts from loosening while at the relatively low torque spec & resulting clamp load used to hold the manifold sealed to the head. Prolly low clamp load to allow some expansion/contraction movement btwn head & manifold as things heat & cool.

    Another thing worth remembering w/ many exh system studs, is that the nut is often some type of locknut (often copper/brass, or some alloy of that color). So they're somewhat designed to grab onto the stud - to avoid exh leak warranty claims. Also some OEM applications used some locktight type thread sealer. So a little torch heat to release that may be in order. Some stock engines are assembled w/ locktite on the studs in the heads. Don't know if this was done on the Cummins heads? If so, again a little torch heat may be in order to release the thread sealer. Probably want to search factory service manual, etc., to confirm if they used threadsealer & if they suggest heat to release it.

    For the manifold to cross-over studs, I used reg steel replacement studs, & stainless steel nuts. This avoids some of the tendency of the stainless stud/bolt combo to gall on themselves. Obviously the stud can still corrode, but it doesn't "grow" together like the stock steel stud/nut.
  3. btfarm

    btfarm 300,000 Worth Staff Member Moderator

    May 12, 2008
    Sandwich, Illinois
    Let me jump in here on stainless bolts. I design meat processing equipment so I only use stainless fasteners on them. 300 series stainless fasteners are referred to as 18-8 (for chromium & iron content) and they are equivalent to 304 or 316 stn. st'l. There's nothing wrong with them on exhaust systems but you really can't put any serious torque on them because they are much lower tensile strength than alloy steel. They will stretch more so have to be tightened more than once after break in (in this application. They aren't likely to gall because of the disimilar metals you are threading into. If you want to use stainless I would recommend studs with "matching" nuts. Meaning 300 series studs and 400 series nuts (to avoid the galling issue). Believe me, you gall up a stainless to stainless fastener and you'll wish you hadn't. I've been in that predicament at 0100 hrs in a meat plant when morning startup is at 0400. NOT FUN! If ARP has some suggested stainless hardware, that would be the way to go. I've found also that stn. st'l bolt heads have a bad habit of losing their head at inopportune times when subjected to heavy vibration and high stress. I know they rust but you can never go wrong with proper alloy steel "header" bolts. Use stainless at your own risk and check them often. In any case, a good copper permatex thread compound is important to use.
    Sorry for such a long post but I thought it was important.
  4. NVW

    NVW Well-Known Member

    May 5, 2008
    Castor, AB.

    Stainless also distorts (stretches) much more than steel, possible leaks?
  5. SmithvilleD

    SmithvilleD Active Member

    Mar 2, 2009
    St Joseph, MO
    Here's a link to ARP's catalog site.


    Click on:

    Metric exhaust/acc. studs

    And it will bring up the page showing the exhaust studs I've used & can vouch for the quality & strength. They're not cheap, but I've found them a close to permanent solution to exh stud issues.

    They refer to their material as ARP Stainless 300, but it isn't remotely comparable to the common alloy stainless fasteners that lack adequate tensile strength.

    The common stainless alloy fasteners polish up nicely in a vibratory (like ammo cartridge) polishers & stay looking nice. But they're only for non-stressed applications - sort of underhood dressup stuff.
  6. bk95td

    bk95td 6.5 nut job/addict

    Nov 26, 2008
    I use all stainless bolts on my exhaust manifolds. I believe fastenal called them A-8. They are supposed to have more tensiI strength than the 10.8 bolts they replaced. I used A-8 threaded rod for the bolts where the glow plug heat sheilds go. I wouldn't pay over $5 a bolt for the crap that was on it originally. I paid less than that for the stainless.

    Attached Files:

  7. btfarm

    btfarm 300,000 Worth Staff Member Moderator

    May 12, 2008
    Sandwich, Illinois
    That's a beauty!:thumbsup:
  8. bk95td

    bk95td 6.5 nut job/addict

    Nov 26, 2008
    I loaded about 60 more pics on my album last weekend. Take a look.:D
  9. Missy Good Wench

    Missy Good Wench Wild Blonde from Cloud Mt

    Nov 19, 2008
    Newberg Oregon
    For whatever it's worth.

    I have coaxed more damned broken manifold and crossover pipe bolts out of 6.2/6.5 engines than I care to think about.

    I have tried stainless steel and the comments that have been made about the breakage and loosing their heads, Oh yeah.

    I personally would use the stock replacement rolled thread bolts just like the beast came from MA General.

    Slop the hell out of them with never seaze and let er rip.

    These stock factory bolts are designed with a tri lobe swage in the threads that help keep them tight. (It works well) Just use plenty of Never seaze and your good to go.

    There may be a type of stainless bolt that is better than whats available at the hardware or parts houses but Im sure they come at a steep price too.

    My vote is for the stock set of bolts with the stud tops where needed.

  10. chevyinlinesix

    chevyinlinesix Eyre Flow Headers

    I am using stainless A2-70 grade fasteners, they have a 102,000 psi tensile strength, and a 65,000 psi yield strength. Also, the threads of the original bolts/studs are a common metric size and pitch. I use Never SeezĀ® nuclear grade nickel Special Anti-Seize for anything real important.
  11. :iagree: I think that's one the key which make things easier : anti seize...

    my favorite one is the hi-temp copper one from loctite

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