Plating case through bolts a good idea ???

[Dpmulvan]

I’ve seen a bunch of engines assembled with zinc/ cad plating case through bolts and I’m wondering if that’s such a good idea.
I do my own plating and I’m thinking about just plating the bolt head, I’m pretty sure that this stuff could possibly flake off being exposed to oil and high temps possibly plugging up a piston squirter.
Anyone else have an opinion on this??

[reclino]

I am in the process of rebuilding a 1986 930. I just got my hardware back from CAD plating. My engine from the factory did not have the through bolts plated. The nuts.and washers were plated. I did not plate the bolts, but did the nuts and washers. High strength steel (above 145 ksi tensile strength) can suffer from hydrogen imbrittlement as a result of any electroplating process.
https://www.imetllc.com/training-article/hydrogen-embrittlement-steel/
I did not check the hardness (quick test for tensile strength) of the bolts but assumed that if the factory didn't want to plate them then I would not. Hydrogen imbrittlement can be mitigated by specifying a bake out process right after plating, but unless your there to verify it's done how do you know?
I have enough unknowns, this being my first engine build, I don't need to add more.
David
Performance EngiNerding

[Dpmulvan]

I’m aware of hydrogen embrittlement did a lot of reading when setting up the plating system. I also wasted time and money trying to make my own plating solution. Didn’t realize how hard it is to make a bright zinc plating solution.

[reclino]

Yes, I have also made a zinc plating setup, it's not bright, but for some parts it's good enough as a prep for painting.

[Dpmulvan]

Originally Posted by reclino

Yes, I have also made a zinc plating setup, it's not bright, but for some parts it's good enough as a prep for painting.

I went through several patents on the chemistry and still couldn’t make the magic sauce for the zinc bath. The brightener is the key. I admitted defeat and bought some replenisher chemistry from caswell stuff is excellent.

[Harpo]

Baking immediately after electroplating has been very successful to prevent HE

[Dpmulvan]

Originally Posted by Harpo

Baking immediately after electroplating has been very successful to prevent HE

Yup about 4 hours at 400 ish.

[Harpo]

At Chrysler our specification was 60 minutes and many of the small electroplating shops could not get the barrels in the baking oven in time. Nowadays they have continuous baking ovens and the barrels dump the parts on the conveyer belt for an 8 hour bake (8.8 - 10.9) and consequently we have nearly eliminated HE.

[Flat6pac]

You really want something in with the oil and to what end.
No one is going to say, nice electroplated through bolts......
Bruce

[911S_1975]

But are case throw bolts high strength steel? I´ve seen many people selling case throw bolts plated and I was just wondering.
I´m not related to this advertisement I just post it as an exmaple:
https://www.ebay.es/itm/372932263316?hash=item56d47ebd94:g:F0MAAOSwfJheMGm Z

[reclino]

As an engineer, I thought about it, and decided the benefit did not outweigh the risk.
Just because someone else on the internet has done it is reason enough for you to consider that it's better?
Porsche decided not to plate the through bolts, the surface finish on mine was pretty rough with visible marks from the screw machine that turned them, maybe the cutting tools we're getting worn when my bolts were made in 1986, Or the tool marks are like those I see on high strength steel parts that resist forming a chip and cutting cleanly. I lightly improved this surface finish by chucking them in the drill press and using some fine scotch Brite on them. If I am feeling OCD I may bead blast and clear coat the heads of the bolts.

[Dpmulvan]

Originally Posted by Flat6pac

You really want something in with the oil and to what end.
No one is going to say, nice electroplated through bolts......
Bruce

Plated case bolts add about 20 hp!!

[911S_1975]

Originally Posted by Dpmulvan

Plated case bolts add about 20 hp!!

so you get the ultimate killing machine!

I´m an engineer myself as well and the fact that porsche didn´t plate them in first place tells you something...

I was just surprise why if so why people was still plating them without even wondering

[reclino]

People do things without wondering all the time. I have a job reworking the most expensive products in the world cause someone thought of this cool procurement strategy and dreamed up the name "concurrent design and production"

[Walt Fricke]

Doesn't take an ME degree to figure that a steel fastener bathed in oil (or, if not, separated from sources of water) doesn't need some kind of surface plating. You can't even really see the bolt heads, or the washers and nuts for that matter - the air guides surround most of most of them.

Ever seen one, in normal or racing use, so rusted it failed?

[Walt Fricke]

Here is another cad plating thought.

After years of DIY, I had a skilled engineer with a shop rebuild my stock US 82 SC engine, and do some suspension work. It ran great - despite being too tall for bolted in place seat, he test drove his work until he equaled the class lap record for the track he used and called it good.

About mid-way through its first year back on track, the #4 intake rocker shaft came loose, as evidenced first by an oil leak leading to smoking. I was unable to tighten the shaft enough for it to hold. The hardware had been plated. The bolt head bound somewhat in the special beveled part. I replaced the hardware with regular stuff, and for extra protection (this was a race weekend) cut a piece of hex stock so it fit between the chain housing and the fastener, so the shaft could not move toward the rear of the engine (which is what it had been doing). No further issues.

Well, last weekend in Utah the same thing happened with the #5 intake, noticed for the same reason. This time I didn't have spare hardware, but was able to get things tight enough. Back home I replaced the plated hardware with the regular stuff from my trove of used parts. And I noticed that there was some extra friction between the bolt head and cup. I also noted that spinning the nut further onto the plated bolt's threads had extra resistance when I spun it further down.

My suspicion is that plating affects the friction between nut and bolt if it includes - as was the case here - the threads. More thread friction means less bolt stretch, which means less force expanding the ends of the shaft outward, which is what holds it in its bore.

Porsche didn't plate these shafts. They are a torque critical part. I suppose the platers just toss these small parts in the bath or whatnot, and don't cover over the threads.

And they are not exposed to the kind of moisture (short of a flood) that other external fasteners could be.

So yet another reason not to mess around with unneeded plating, perhaps.

I did notice that there is some rust on my valve cover studs - down well below where the washer and nut are. Perfectly harmless there. The effort/expense of removing these studs, plating them, and replacing them would seem to be a pretty low return on investment. As would, to a lesser degree, replacing them with new ones absent rust having eaten away at the diameter or something otherwise obvious. Running a new nut all the way down to the cam carrier surface and a little anti-seize ought to deal with aesthetics and worries about the future.

So this is my additional $2 (inflation and no cents key) on the issue.

[Henry Schmidt]

25 year or so plating case through bolts just because it looks good. Never any issues, maybe 250 engines.
We plate in-house so cost is relatively low and we like everything as clean as possible. Plating shows us flaws in the surface as well.
One caveat: Plating adds thickness and plating the nuts can leave internal rust issues. Buff the threads to ensure proper torque and double check the nuts for rust.




On this 906 we went with black oxide.