Manifold Studs

[RedMeanzGo]

Hello, I have decided to swap out the almost 40 year old studs used for my exhaust manifold. I have noticed there are several different material options for replacements. I want to avoid galvanic corrosion, but I want a material that is strong, and will last. I've read so many conflicting reports about stainless steel studs, and aluminum. Can someone please recommend either the stainless, or the yellow zinc coated... Or if there is another option all together ? My head is spinning. Thanks !!

[Tom]

I'd just use factory studs -- metric 8.8 yellow zinc, along with factory washers and nuts. Stainless isn't as strong as 8.8, can gall easier, and increases the galvanic corrosion potential. See the galvanic corrosion scale below. The further apart the metals, the higher the potential for galvanic corrosion. Note how close aluminum alloys and mild steel are; and how much further away stainless (and copper) are... That's not to say stainless wouldn't last a long time in the right environment, but if your goal is to minimize galvanic corrosion, the chart speaks for itself.

galvanic scale.png (1.77 MiB) Viewed 213 times

[JamesM]

I used stainless, My reasoning was that they shouldn't need to come out of the head since they last so long and I can pull the exhaust headers off whenever I want with ease and not have to worry about twisting a nut or stud off. At the very least I expect them to last as long as the head would be on the engine and I can deal with them off the block with heat and oil if they ever got stuck.

[RedMeanzGo]

Thank you for the kind, and thoughtful responses along with the diagram !

[Belgian951]

I used the Rennbay kit. Bought from Pelican Parts. Installed them on NYE, and so far so good.

[Tom]

I used the Rennbay kit. Bought from Pelican Parts. Installed them on NYE, and so far so good.

The Rennbay kit has the added advantage of the hex key on the end, which is nice. I'm sure they will last a very long time! My comments above were really just focused on the galvanic scale question.

[icb]

I used stainless studs as well, I believe I used M8 stainless set screws from Belmetric, along with the extra thick yellow zinc washers and copper lock nuts. I was initially concerned about galvanic corrosion too, but I read somewhere that because the surface area of the block (the anode in this case) is huge and that of the studs (cathode) comparatively small, there would be little, if any, noticeable galvanic corrosion.