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Rally Pack 2000

Nuts and Studs for Pinto Head Exhaust Manifold

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Fitting a new exhaust manifold I thought maybe I should change the studs in the head as they havent been changed since 1979? Probably wont come out I bet.

 

Im a bit rusty on the metallurgy of things, but f I remember correctly you can use stainless studs but you should never use stainless nuts with them as you get some kind of reaction but rather copper plated nuts that are self locking are best. (Although some say use brass instead?)

 

Then there are fancy stainless Aerotight nuts but they would have to be used with conventional steel studs if you are to avoid the stainless on stainless combo. Some sellers even offer stainless allen key studs!

 

Who knew simple nuts and studs could be so involved!

 

So whats the best non seize combination that people would suggest? Or just keep the old studs and get some new nuts?

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colr6    1,271

Oe type studs and nuts have survived this long so why change, inspect the studs and replace any corroded ones. Replace nuts with oe type. Jobs a good un.

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katana    210

Original studs will be a type of 'ordinary' carbon steel and by its nature will rust and when fitted in a carbon rich cast iron casting will naturally lock together hence removal is difficult - they are effectively designed to never be removed. Using steel nuts will also rust to the studs which transfers the removal torque to the stud which is tightly held by the head and so either strips the thread or snaps the stud!

If you can break the cycle between one pair of these components - removal will be easier. Personally i'd either stick with a steel stud and use a plain brass or copper nut with spring washer to act as a locker, or use a stainless nut, lubed with copperslip and a spring washer again. With a cast iron manifold I wouldn't use a stainless steel stud, they are slightly weaker in tension ie clamping force and in shear ie. hanging a heavy object off it. Also they expand less with temperature so as the head and manifold expand the clamping force within the stud increases which can snap them whilst they are torqued up to 'book recommendations'. If using a lighter fabricated manifold gives the stainless studs or screws an easier time.

The other benefit with the brass nuts is they are 'soft' and less likely to damage stud threads. SS nuts + SS studs without a form of barrier lubricant send to gall leading to difficulty in disassembly hence general non recommendation. Steel and brass nuts tried and tested......................its also cheaper!

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