Engine: Exhaust Manifold Bolts On 55 C-Body V-8

[3x2stude]

I tore down a really rusty but less than 80K mile 55 C-body president I got from Nick H. two years ago and I was intrigued with the finish on the exhaust manifold bolts. I have attached a couple of photos to illustrate. It appears that the bolts were nickel plated. Several of them have a silver luster after all this time, some are just rusty. They are highly magnetic as if plated carbon steel. I did a simple magnet test with and a grade 5 plated bolt, an 18-8 stainless bolt and the '55 bolt. The '55 bolt seamed equal in attraction to the CS bolt so I drought it is stainless. '55 bolts are on the left, #4 is plated CS and #5 is 18-8 SS.

Did Studebaker nickel plate them to prevent galling? Just curious.

JK

[rkapteyn]

Studebaker used brass nuts on the exhausts.

[3x2stude]

RK, I had a foopa on the first entry, no photos. Its the bolts to the head, not the outlet.

JK

[Dwain G.]

Monel maybe, although you wouldn't expect it to be 'highly magnetic'. Very expensive unless you have access to military shop stores, aircraft or marine industry.

[3x2stude]

Monel, is not very strong and would be a poor choice for bolts. The dairy industry used it for threaded tubing connections, (the nuts), for years because it did not gall but 3A made them go all stainless.

JK

[StudeRich]

Yes they appear to be Nickle Plated on the earlier Engines, but not after about 1957.

Another special thing about these Exhaust Manifold to Head Bolts is they use thick, solid cast Iron Flat Washers only very slightly larger than the Bolt Heads, with Inside Lock Flat Washers.

[doofus]

I believe they are stainless steel and i have found some with a "toothed" lock washer under the head. reason for stainless is a guess ,while in military i have found exact same bolt in hardware bins. they were exhaust manifold bolts for m151 "jeep" and were identical to each other! yes i have a few extra! Doofus

[jackb]

I was always advised "not" to use a lock washer on these applications. ??? Clarification ?? Rich ??

[oilnsteel]

They are stainless steel. 400 series ss is cheaper in most cases and most alloys are magnetic, 300 series can be magnetic after cold working. Split lock washers are not effective on a Stude exhaust manifold, in my experience the star type are.

JT

[3x2stude]

Oil,

As rusty as some are I was reluctant to assume they were a not plated carbon steel. It is a no brainer that they are not a 300 series austenitic, non-magnetic stainless. However, whether it is a ferritic or martensitic 400 series would need to be tested. I have some options. Take one to work, (a stainless steel equipment manufacturer), and put some nitric acid pickle paste on it. If the silver gets better, its stainless. If the silver burns off and it rusts again in minutes its carbon steel. If it appears to be stainless I will send it to one of my nearby cronies with a "Niton" gun and get a print out of the alloy's makeup. For those that are not familiar with the device it is able to tell you the make-up of an alloy as to its percent of ingredients, carbon, nickel, etc. An amazing machine, small, about the size of a hair dryer, but in the 30K range so we do not have one where I work.

JK

[doofus]

Hey 3x2 buy one at your local hardware store and do a back to back test.Doofus

[Alan]

They are 410 stainless.

[StudeRich]

I was always advised "not" to use a lock washer on these applications. ??? Clarification ?? Rich ??

I believe what someone warned you about was using the standard Split Type Lock Washers, you could not go wrong with the Factory flat, inside Lock Type.
I have no idea why that was said, but I would never use the Split Type because they are wrong.