I put in new SS downpipes last summer on my 88 V12. I replaced the original tall bronze helicoil nuts with new of the same. But as i was torquing, one nut stripped, and another one deformed. Not liking how soft the bronze was, i decided to install with SS nuts and SS lock washers.
Well, since then I’ve learned that SS is not such a good choice for exhaust nuts. They can loosen, and can corrode with the steel studs. The lock washers can also become ineffective from the heat.
So today i replaced with brass nuts and steel star lock washers. These should be good, little corrosion and no loosening. Copper plated steel is also a good choice, but is very hard to find in 3/8"-24 fine thread. Brass is about same strength as SS.
My SS nuts were still tight, but i did see slight corrosion with the studs. I was able to get nuts off, but there was a bit of resistance after only 8 months.
I used anti seize (now and last summer) and torqued the brass no problem to 18 ftlbs. (Supposed to be 25 ftlbs dry)
Greg,
Not the stainless steel is your problem but cheap chinese nuts from eBay, because these are from eBay - right?
You would never say how big difference quality product makes. I noticed that when using hydraulic version of these (3/8 UNF). All you need to protect the studs is a Loctite copper stick.
By the way… At least 10 years ago it was scientifically proven that spring washers are making no difference…
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
7
For those of us who have seen the difference, please provide verification.
As an experiment, about 5 years ago, I double nutted my exhaust manifold (I6) with SS and brass on each manifold, nickel & copper ant-seize, and SS spring washers
It didnt hold tight, and I am going with long brass and nordlocks (I think they are SS)
Many years ago, I encountered an absolutely superior exhaust fastener
turned out to be Caterpillar stuff, presumably a plant mechanic had owned the vehicle before me, as they were not readily for sale
12 point nuts and bolts, a dark grey SS, they never showed the slightest sigh of wear or galling, and came on & off easily a few times
That’s the modern teaching about mechanics. I found out from the guy who finished primary school much later than myself. They’ve dropped it almost entirely apart from flexing materials/plastics Maybe, there are too many aspects to control or maybe these work slightly contrary to tribe knowledge we obtained. Somehow it is really difficult to find those on modern cars. I was certain that these are making difference, so I took the risk of stop using them and I can see no difference…
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
11
The problem is – and always has been – the length of the bolt. If the bolt (or stud) is long enough to develop some stretch when torqued, no lock washers necessary. If the bolt is short, though, some sort of locking scheme will be needed. At P&WA there were no lock washers because 1) short screws normally screwed into nuts, and the nuts were locking type with a pinched area in the threads, 2) screws that didn’t screw into nuts were lockwired, and 3) longer screws relied on bolt stretch.
It wouldn’t surprise me too much to learn that modern cars are designed largely the same way.
It’s also worth noting that apparently tablocks have gone away. They need to be soft metal, and having the soft metal tablock under the hard bolt head didn’t work, the tablock would give a little and the bolt would get loose without turning. This was reportedly a serious problem on the rear hubs on a 427 Cobra. Reportedly, anyone working on cars old enough to call for tablocks is today advised to leave the tablocks out and rely upon Loctite to keep the fasteners from loosening.
On all the work I have done to my recently acquired 2006 Land Rover I have yet to find a lock washer.
I have done only superficial mechanical stuff, but have dismounted almost all of the interior.
What seems to be the norm is flanged bolts and nuts.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
14
Yeah, flanges seem to be the fad, don’t they? Are we seeing flanges with little serrations around the edge, or are they just flat?
They were just flat.
I have to add, comparing with all the different cars I’ve worked on, that Jaguar at the time had a serious obsession with securing the nuts and bolts. There is almost no one screw without a lock washer, star washer or nylock nut.
I also have a striped brass manifold nut and need a replacement.
Do you have the link for the right ones you got from McMaster-Carr ?
Was it UNC, UNF or BSF?
