Where to buy Si/Br nuts? (for exhaust)

pgsandiego · 07-25-2004, 09:11 PM

Im installing a premuffler and want to use SS bolts and Si/Br nuts to ease future work. No problem with SS bolts (Lowes). Where do you find the Si/Br nuts?

Per Wil's much earlier posting:

Replacement nuts/bolts for cat:
5/16" x 18 pitch, 1.5" long under head, partially threaded 316 Stainless bolts.
Matching nuts are Si /Br ( Silicon Bronze). These have 1/2" heads and work with 12 or13 mm wrenches. Very close dimensionally to stock 8mm x 40 mm long regular steel bolts.

Thanks!
Patrick

Jim Sims · 07-26-2004, 04:18 AM

If you're willing and able to switch back to a metric thread (shouldn't be too much of a problem finding an 8mm SS bolt) then Pelican has 8mm by 12 mm wrenching hex flanged self locking nuts that are either a copper alloy or are copper plated (designed to work with exhaust studs). These will be plenty strong for matching to stainless steel bolts and will be corrosion resistant. The Pelican part number is BW-11-62-1-711-954 (it's a BMW part) and last time I checked they were $.53 each. If you search the web you may be able to locate the Si/Br nuts but they likely won't be cheap and you may have to buy a whole box of 100. Jim

pgsandiego · 07-26-2004, 06:59 AM

Thanks Jim.

How about brass nuts on SS bolts? Would that hold up at exhaust temps and be easy to remove later? I'd like to start this project today....

billyboy · 07-26-2004, 07:15 AM

Mc Master -Carr carries them, item # 93439a030, I believe. They are available in quantities less than 100. Phone #(562) 692-5911

Wil Ferch · 07-28-2004, 12:14 PM

Since I'm partially to blame for this ! ...

I got a box of 50 from McMaster Carr. Not terribly expensive, either, as I recall...maybe under $10. Si/Br is *the* way to go and the head size works with stock metric 13mm wrench....as original, since the 5/16 nuts have 1/2" heads.

--Wil

david.avery · david.avery's Garage

Hi guys

Just trying to buy a set of these nuts and bolts, and I find these from Mcmaster-carr. I found the bolts easily enough, but the nuts are a mystery... The part referenced by billyboy doesn't work, and this is the closest I've found...

93439A620
Silicon Bronze Hex Nut 5/16"-18 Screw, 1/2" W, 17/64" H, Alloy 651
$ 8.93 per Pack This item is only sold in Packs of 50

The problem is that this is the non-locking variety, and Porsche uses some type of locknut... anyone have the proper mcmaster-carr part# for the locking nuts?

Thanks,

DMA

RoninLB · 07-28-2004, 02:36 PM

Si Br are really nice.. but I use metric stainless on the exhaust studs and marine stainless on the SSI to muffler. stainless needs a bit of technique to maintain its torque properly on the exhaust system.

thomschoon · 07-28-2004, 03:22 PM

The best exhaust nuts I have found are (gulp) Datsun/Nissan 240-280Z exhaust manifold nuts. They are about 3/4 long, SS, and well made. They cost about $.75 from your local nissan dealer and I havent had a problem on any of the cars I have used them on.

billyboy · 07-28-2004, 04:18 PM

I think Thom is on the right track. You maybe want to use lock nuts and high temperature never seize with the stainless. I think any type of jam nut will give you major grief after the heat has been on them awhile. Mc Master has an online catalog with lots of options. Stainless nuts do "gall" and then are impossible to remove.My Cummins engine uses titanium nuts and bolts with neverseize to hold the turbo on.That operates frequently at 900+ degrees.

RoninLB · 07-28-2004, 04:29 PM

Quote:

Originally posted by thomschoon
The best exhaust nuts I have found are (gulp) Datsun/Nissan 240-280Z exhaust manifold nuts. They are about 3/4 long, SS, and well made. They cost about $.75 from your local nissan dealer and I havent had a problem on any of the cars I have used them on.

cool..
ss can be great or a pia. I usually bring a small magnet with me when I'm window shopping. You kinda get a drift on them after awhile. The local Home Depot has great quality imo. They don't suck to the magnet. If you ever have to work with an open end wrench you don't have to worry about rounding the nut. The Si/Br mfg that uses high nickel gives a tougher nut than the low nickel mix that's wonderful with heat and corrosion.. and you get a better feel for your tightning torque and no constant rechecking after install than ss.

all that said the copper plated nuts PP sells used with anti-seize, is a great act. Not much attention after install, wrench great, durable, and designed to do a good complete specific job. They're a little more delicate than this subject nuts so I'd probably flip to a new set on the 2nd/3rd/etc re-use.
All only imho.

RoninLB · 07-28-2004, 04:50 PM

Quote:

Originally posted by Jim Sims
If you search the web you may be able to locate the Si/Br nuts but they likely won't be cheap and you may have to buy a whole box of 100. Jim

I've searched for hours for metric Si/Br. I'd drop a $100 for a simple assortment tonight if I could find them. I spent real big bucks rebolting an outdoor wooden deck lounge in Si/Br fastners. I got those from a marine store.
I can't find metric Si/Br.

david.avery · david.avery's Garage

Quote:

Originally posted by RoninLB
I've searched for hours for metric Si/Br. I'd drop a $100 for a simple assortment tonight if I could find them. I spent real big bucks rebolting an outdoor wooden deck lounge in Si/Br fastners. I got those from a marine store.
I can't find metric Si/Br.

I did see metric si/Br on the mcmaster-carr site Ronin... have a look.

-DMA

pgsandiego · 07-28-2004, 09:52 PM

Thanks for the replies everyone!

I made some calls and found that most marine hardware stores should carry the si/br nuts or can get them in a few days. I think I remember a quote of ~$0.25/each for the nuts.

From my understanding of the posts, I can use regular 5/16", 1.5" long Stainless Steel bolts from Home depot ($0.14/each) with Si/Br nuts to ease future removals.

Nut summary:

Most marine hardware stores have 5/16" Si/Br in stock.

OR

From the McMaster Carr website I found:
Part Number 93439A620
$8.93 per Pack of 50 (only sold in packs of 50)
Nut Type: Machine Screw and Hex Nuts
Material Type: Silicon Bronze
Thread Size: 5/16"-18
Width: 1/2"
Height: 17/64"
Thread Type: Standard Threads

McMaster contact information (LA area):
9630 Norwalk Blvd.
Santa Fe Springs, CA 90670-2932

Sales Desk and Customer Service:
(562) 692-5911

As for locking nuts: I didnt find any that came in Si/Br. (I am going to try the $0.10 lock washers from Home Depot)

Tomorrow, I'll find out how rusted the original bolts are! (Ive been soaking them with PB blaster for a few days).

Cheers!
Patrick

RoninLB · 07-29-2004, 12:27 AM

Quote:

Originally posted by david.avery
I did see metric si/Br on the mcmaster-carr site Ronin... have a look.

-DMA

thanks.. but last time I checked there was a limited choice..
I'll check again.

KTL · 07-29-2004, 05:35 AM

Another option is to forego the lock nuts and just use the standard Si-Br nuts with Si-Br lockwashers. That's what i've got. Got them from McMaster-Carr.

But I don't think the Si-Br lockwashers are necessary. You can use standard steel/plated lockwashers since the washers are unlikely to cause any stuck fastener issues, even when they do start to rust?

I'm curious why others use locknuts on the cyl. head connections of the exhaust system? On my 87, the original hardware is standard hex nuts and the inhex barrel nuts. Neither of these two nuts are the locking type. Seems to work fine. Just be sure to use a little antiseize on the studs. The torque spec for these fasteners is kinda low at 18 ft-lbs/25 Nm, so I can see why locknuts might be a good idea. But i've never heard of these connections coming loose? I'm no expert by any means, so take my comments with a grain of salt.

Wil Ferch · 07-29-2004, 08:53 AM

Lots of posting traffic here....

1.) I too couldn't find metric Si/Br....that's why my original post used stainless 5/16 bolts with Si/Br nuts...what's so important about metric anyway, when the tool used to remove / install is the same? "Correct" metric is 8mm x 40mm, and the 5/16-18 pitch x 1.5" long are nearly identical. In either case a 13 mm wrench works.
2.) Don't need lockwashers for exhaust service. I found that with the bag of 50 I got from McMaster-Carr, I simply double-nutted everything, and even at that....it wasn't required, as everything was splendidly tight even after a few thou miles with one nut.
3.) If you insist on stainless, go for a different alloy nut compared to bolt. It's when the chemistry is exactly the same, that you could see galling.
4.) All these methods allow dry assembly / disassembly without messy anti-seize compounds.
5.) Magnet is not a reliable indicator of whether the material is stainless. Only the austenitic grades ( 304/316..."3XX") are not magnetic, while the martensitic grades ( "4XX") exhibit a slight degree of magnetic properties.

---Wil

RoninLB · 07-29-2004, 01:28 PM

Quote:

Originally posted by Wil Ferch

5.) Magnet is not a reliable indicator of whether the material is stainless. Only the austenitic grades ( 304/316..."3XX") are not magnetic, while the martensitic grades ( "4XX") exhibit a slight degree of magnetic properties.

Not to indicate If it's stainless.. but to determine the quality of the stainless. I think the better stainless has a higher nickel content?

and I've seen cheap stainless being noticablly magnetic.. it varies.

Randy Webb · 07-29-2004, 05:25 PM

What's wrong with those copper (or copper colored) nuts that Porsche sells?? 6 of them are not a lot of $$ -- or is it some other factor?

Jim Garfield · 07-29-2004, 06:56 PM

These guys are pretty good with marine fasteners-
http://www.jamestowndistributors.com/eserv/eclipse.ecl?PROCID=WEBPROC.WOE.AUTH&AUTOLOG=YES%26SEARCH%3Dsilicon+bronze+nuts&TRACKNO=0

RoninLB · 07-29-2004, 08:41 PM

Quote:

Originally posted by Randy Webb
What's wrong with those copper (or copper colored) nuts that Porsche sells?? 6 of them are not a lot of $$ -- or is it some other factor?

Randy.. come onn. From my previous reply,
"all that said the copper plated nuts PP sells used with anti-seize, is a great act. Not much attention after install, wrench great, durable, and designed to do a good complete specific job. They're a little more delicate than this subject nuts so I'd probably flip to a new set on the 2nd/3rd/etc re-use.
All only imho."