[DeTomaso] Stainless steel hardware and aluminum complications

[Charles Engles]

Dear Ken,

              ARP's engineering and technical staff know much more than I do, but I would never use stainless steel bolts in an aluminum crank pulley.    :-)

                            Warmest regards, Chuck Engles


-----Original Message-----
From: Ken Green [mailto:kenn_green at yahoo.com] 
Sent: Saturday, July 27, 2024 11:47 AM
To: detomaso at server.detomasolist.com; Charles Engles
Cc: 'B Hower'; Asa Jay Laughton
Subject: Re: Stainless steel hardware and aluminum complications

ARP says to use an anti-seize on the stainless fasteners, do you think that resolves the issues?






On Saturday, July 27, 2024 at 06:26:41 AM PDT, Charles Engles <cengles at cox.net> wrote: 






Dear Ken,
 
            Your comment about using stainless steel studs and hardware on the ZF, reminded me of a lesson I learned from another Pantera owner and a very experienced Ford Motorsports and Rousch Industries engineer.   After my friend’s Pantera began making troubling noises, it was determined that the culprit was the aluminum crank pulley secured with stainless steel bolts.  Ultimately, it required major mechanical efforts to remove the cold-welded stainless steel-aluminum from the balancer.   The pro told me to never use stainless steel in aluminum because of the tendency to galling and worst case scenario---cold welding.   I had *no* idea.
 
           Just yesterday I was working on a Windsor engine with an aluminum intake manifold.  My brother told me that on its previous iteration, the front nose (?) piece on the intake manifold coolant snout was very problematic to get watertight.   Short story: I found that the two *stainless steel* bolts did not completely thread down.  Each was blocked at a different depth.   A thread chaser was a big improvement, but I re-tapped both and finally got both bolts to seat properly.  Then, it dawned on me that the snout-intake had been assembled, at least, two or three times before I got it.   The problem was the stainless steel bolts galling the bolts holes.  I also replaced the SS bolts with common steel bolts.
 
          In addition to the SS-aluminum galling propensity, there is also a potential for electrolytic reaction of SS-alum to produce “tea staining” of the *stainless*steel fasteners.
 
          Information links:
 
              Galling:   https://www.pencomsf.com/articles-updates/galling-of-stainless-steel-fasteners/
 
              Staining:  https://www.marshfasteners.com/can-stainless-steel-and-aluminum-be-used-together/#:~:text=When%20using%20stainless%20steel%20fasteners,also%20called%20'tea%20staining'.
 
 
                      Metallurgically yours,  Chuck Engles