costpenn

I need to change out by exhaust manifold bolts and fat washers on the 70 455 I'm doing since they are too badly pitted/wasted to reuse. I see ILT sells a kit but the bolt finish they have is the black plating. Is this correct?
Also, what is the correct finish for the two alternator bolts and one nut?

costpenn

ttt

Run to Rund

dark gray phosphate

ROCKET VAPOR

FWIW, I have noticed that GM used a lot of either bare steel or clear zinc finish on electrical component hardware (i.e. starter mounting, alternator mounting and adjustment, battery cable to engine block ground).

Also, a lot of the hardware from INT that appears to be dark gray phosphate is actually some sort of shiny black plating, simulair in appearance to black anodize.

I hope this helps

jensenracing77

X2.


I think Ron Memmer found a supplier for the exact bolts and washers and carries them. The intake bolts and washers I seen looked to be exact. I assume he would have the exhaust manifold bolts also.

Mike77

Finally a piece of useless information I discovered last week that I can talk about.
The "fat washers" are called Williams Washers. Nothing too exciting but at least I got to tell someone.
Mike

Kevin W

I always thought that the engine bolts were Black Oxide and body fasteners were black Phosphate, not including the zinc and cad plated ones. My 2 cents.

dc2x4drvr

AMK Products has a large selection of fastners in various finishes. The engine fastners I've seen didn't look like they had any finish after mfg.. I doubt if black oxide was used much originally, it starts rusting quickly unless the parts are coated with oil, or another sealant, giving the parts a shiny finish. Gray phosphate was used on the body shims, and a few other areas, it does stand up to corrosion fairly well.

costpenn

Thanks for all the responses. You guys were right. I found the shank of the bolt that is stuck in the head has signs of that black coating on it. All the others I had already wire brushed the surface coating along with corrosion off the bolt. Here is a pic of the worst bolt, RH center, along with the best one LH front that also goes through the P/S bracket showing the EWF marking.

Kevin W

Interesting topic, didn't realize I had it wrong. I was under the impression that black oxide has a sheen to it and that black phosphate has a dull finish. I believe that black oxide is a more expensive process and has better corrosion properties than black phosphate. Thats why I thought that fasteners used on engine components and to mount all the engine brackets used the slightly better oxide finish unlike the body bolts that use the black phosphate. Similar to the use of yellow, blue and black CAD finishes on steering and brake components, higher manufacturing cost but a better corrosion protection.

2blu442

I knew there had been some old threads discussing this. I did the search function and came up with one. I'm sure there was another where the person was heating the bolts, then dipping them in oil to get the right color. Anybody else remember that one? John


https://classicoldsmobile.com/forums...on-finish.html

dc2x4drvr

Black oxide is just a coating very similar to gun blueing. I haven't seen black phosphate, only gray. I think all of the engine brackets, pulleys,etc., were painted.

Kevin W

@dc2x4drvr, Sorry, I wasn't very clear, I was referring to the bolts that mount the brackets, yes the brackets are painted.

My understanding, that black oxide is similar to gun blueing as well. I know there is two different methods to apply Black Oxide, hot tank and cold. Gun blueing has a hot tank and a cold method as well (ie: BirchWood casey), results are the same, one with a sheen and the other flat.