Black oxide bolts

[FABombjoy]

Vibratory polishing technically, walnut media, plastic tub. Principally affected the AC compressor bolts. Should have been nice and gentle!

The 7mm hardware seemed to weather things ok. Amazingly the local Home Depot has a usable selection of 7mm zinc-plated bolts.

[David T]

S/S hardware is not graded like carbon steel and should not be used in a high stress location. Allen head bolts are high grade (not sure what it is exactly but it is not ordinary). You should not substitute fasteners unless you know what you are doing. Painted ones are not necessarily any good. Just the action of tightening it with a tool will nick the paint and it will rust, that is why they are plated. To some extent plating is self-healing til it eventually is degraded due to sacrificial corrosion. If you are into refurbing hardware check out Eastwood, they sell tumbling and plating stuff to refurb old, original hardware. Also look up "Hydrogen Embrittlement" before you decide to do any plating.

[hippieman9]

I had replaced my axle bolts with Allen cap black oxide bolts. But with less than 100 miles the heads of those bolts are completely rusted. So I found zinc bolts at MaterCarr. I also mostly use stainless flat washers and lock washers since there is no real strength needed for those. I did see where one owner had used SS washers on his transmission bolts and they fell out after use. I don't see how SS washers caused that since the harness is the same as carbon steel.

Not sure is all black oxide bolts corrode like that but I'm not going to use them on any exposed locations anymore.

I just re greased my C/V joints and installed new boots and put all new Stainless bolts (6pt hex head) and lock washers in. Weird thing was the bolts that were in the C/Vs were all 17mm heads (wench size) except one joint had all 16mm heads. Needless to say, I figured good time to replace them all so they match with stainless.

[dn010]

So I found zinc bolts at MaterCarr.

Do you have a part number for this? I'm about to do my clutch and would love to change those bolts to something that won't rust immediately.

[Bitsyncmaster]

Do you have a part number for this? I'm about to do my clutch and would love to change those bolts to something that won't rust immediately.

1 90128A292 Zinc-Plated Alloy Steel Socket Head Screw, M10 x
1.5 mm Thread, 60 mm Long, Packs of 10
3
Packs
3 0 8.30
Per Pack
24.90
2 94241A560 316 Stainless Steel Split Lock Washer for M10
Socket Head Screws, 10.7 mm ID, 16 mm OD,
Packs of 50
1
Pack
1 0 10.56
Per Pack
10.56

[dn010]

Great, thank you! I just placed my order. Cant wait to ditch the hex head bolts.

1 90128A292 Zinc-Plated Alloy Steel Socket Head Screw, M10 x
1.5 mm Thread, 60 mm Long, Packs of 10
3
Packs
3 0 8.30
Per Pack
24.90
2 94241A560 316 Stainless Steel Split Lock Washer for M10
Socket Head Screws, 10.7 mm ID, 16 mm OD,
Packs of 50
1
Pack
1 0 10.56
Per Pack
10.56

[dn010]

Wow! Ordered yesterday and arrived today. Guess I am close to their warehouse. Looks like a clutch job this weekend, fun times...

[Bitsyncmaster]

It seems the DeLorean torque spec of 30 ft/lbs is light. Recommended torque for a 10 mm 8.8 bolt is 40 ft/lbs. dry. I know some people are using locktite but that was not stock from factory. I think I remember one guy found his bolts were loose but he thought someone tried to steal his axles.

By the way I think I know what the plates used on the two bolts are for. I'm guessing they just work as flat washers but since we use a split lock washer which bites into the plate, single flat washers would just spin loose but with two bolts they can't spin.

[David T]

Actually, for bolts subject to rotation, they should be safety wired. At the least you can put inspection marks on them like a drop of nail polish. Yes, the plates can only act as fancy flat washers. Really doesn't seem to be much of a problem if they are torqued to spec and inspect the undersides of the car once in a while. If they all loosened up you would notice it right away I would think!

[DMC-81]

It seems the DeLorean torque spec of 30 ft/lbs is light. Recommended torque for a 10 mm 8.8 bolt is 40 ft/lbs. dry. I know some people are using locktite but that was not stock from factory. I think I remember one guy found his bolts were loose but he thought someone tried to steal his axles.

By the way I think I know what the plates used on the two bolts are for. I'm guessing they just work as flat washers but since we use a split lock washer which bites into the plate, single flat washers would just spin loose but with two bolts they can't spin.

That reminds me of my very first car (a 1982 Volkswagen that had very similar drive axles). I had to replace the engine short block. The mechanic tightened the drive shafts without Loctite and after a while, both shafts loosened enough to separate from the output flanges. After that, I always apply Loctite when working on these.

Actually, for bolts subject to rotation, they should be safety wired. At the least you can put inspection marks on them like a drop of nail polish. Yes, the plates can only act as fancy flat washers. Really doesn't seem to be much of a problem if they are torqued to spec and inspect the undersides of the car once in a while. If they all loosened up you would notice it right away I would think!

David, that may apply to aviation, marine, or racing applications, but I have never seen a bolt safety wired on a street car. For everyday use, we have Loctite. On the Delorean, I have seen Red Loctite specified/recommended for the flywheel, wheel hub nuts, transmission shaft nuts etc., and Blue for clutch pressure plate bolts , drive axles etc.