stainless exhaust manifold bolts ?
 

Hi all,

I am replacing my two exhaust manifolds (2002 Ex) and was wondering if stainless steel bolts is a good idea.

If so, does anybody have any source or specification for a stainless bolt?

Thanks very much and happy holidays !!

Dave

Scribing. You would think as much as Ford charges for new ones they were gold. I like the idea, but for some reason thinking there is some stretch properties involved.
I am sure someone better quailified will chime in soon.

Stainless can and is used all the time. Stainless does gall and is brittle and will break if to much torque is applied.

http://www.genuinesaab.com/catalog/images/manstuds.jpg

I had bad experiences with s.s. bolts. ive learned to use only when absolutely have to. due to the galding effect you wont get the clamping force needed,and they can be a pain to drill out when broke off in castings.

You're using the wrong stainless bolts for the application if you keep breaking them.
Most all stainless bolts you get at the hardware store and even parts stores are "grade 3" or "household" bolts. They are NOT ment to be used for important stuff.
You CAN buy good stainless bolts from ARP and sometimes places like fastenall and grainger probably.
Problem with stainless is the expansion rate vs regular hardened steel. The more carbon the less expansion. Meaning you'll lose clamping force with stainless bolts more than hardened steel bolts from the 1000* heat of your manifolds.

I'd stick with the correct bolts or studs. It's not like you're taking the manifolds on and off 2-3 times a year and need the ease of removal.

If you get ss bolts for an application that you'll be removing and reinstalling the bolts more than a few times I have found that running a die over the bolts when new and lubing them with moly lube stops them from galling.

SS bolts and nuts don't have "grades". The only difference in different SS fasteners is the ss they are made out of, anything from 409 to 316 ss. The ss expansion rates are null with such short fasteners. The expansion rate would make a difference however if the bolts were say 6" long or longer.


Materials

Stainless Steel
Stainless steel is an alloy of low carbon steel and chromium for enhanced corrosion characteristics. Stainless steel is highly corrosion resistant for the price and because the anti-corrosive properties are inherent to the metal, it will not lose this resistance if scratched during installation or use.
It is a common misconception that stainless steel is stronger than regular steel. In fact, due to the low carbon content, stainless steel cannot be hardened. Therefore when compared with regular steel it is slightly stronger than an un-hardened (grade 2) steel fastener but significantly weaker than hardened steel fasteners.
Stainless steel is also much less magnetic than regular steel fasteners though some grades will be slightly magnetic.
18-8 Stainless
18-8 refers to any stainless steel containing approximately 18% chromium and 8% nickel. This is the most common stainless designation for hardware. For information on 18-8 stainless steel material properties see our Material Grade Identification and Properties Chart.

I would use the OEM bolts, they seem to hold up just fine. The 6.4's use stainless and they are breaking very often, and when they break they are a total PITA to get out.

I will admit I was pleasantly surprised to only have to cut one bolt when I recently replaced my manifold. PB Blaster comes through again. I did go back together with anti seize on everything.

I used the "grade" term to compare it to a regular steel bolt. Most people are not aware of material properties like you and I, so we need to use terms most people understand.
I've snapped off many 5/16 stainless bolts with a 3/8drive ratchet. And others I've impacted tight, or had to use a long breakerbar to remove.
You are correct in saying the exact material dictates its strength. (But your stainless example said exactly what I did as far as grade goes)