Chatgpt - manifold nuts

S

smlav

Senior member
Location
Shropshire UK
I’ve have an issue with SF1 exhaust manifold coming loose. So I’m refitting today and using loctite 5926 as recommended on a thread I found in forum, and I have some copper coated self locking exhaust manifold nuts, but I wasn’t sure if I should use a washer with these. Rather than search or ask the forum, I tried chatgpt, which gave this -


Short answer:
✅ Generally no, you don’t use additional washers with self-locking exhaust manifold nuts unless the manufacturer or service manual specifies them.

🔎 Why?​

Self-locking exhaust manifold nuts are designed to:
✅ Resist vibration loosening (critical on exhaust systems)
✅ Clamp securely against the flange or manifold directly
✅ Maintain proper torque without backing off

Adding washers:
❌ Can change the clamp load / torque relationship
❌ May reduce the locking feature’s effectiveness
❌ Can increase the chance of loosening (if wrong type used)
❌ Can interfere with thermal expansion design

✅ Exceptions (when washers are used)​

✔️ Some OEM designs do specify washers, typically:

  • Special hardened or heat-resistant washers
  • Conical spring washers (Belleville washers) to maintain tension with heat cycling
  • Sealing washers (rare on exhaust manifolds, more on turbo flanges)
✔️ Some aftermarket studs/nut kits include them intentionally

➡️ Always follow the manufacturer’s spec for your engine.

✅ Best practice​

✔️ Use new self-locking nuts if the manual says (they often have prevailing torque or deformed threads that wear after use)
✔️ Torque to the specified value
✔️ Don’t substitute random washers

⚡ Bottom line answer:​

❗ Typically you don’t use any washers with self-locking exhaust manifold nuts, unless the engine manufacturer specifically calls for them.
Stick to OEM recommendations for best reliability.
Click to expand...
If you tell me:
✅ Which engine or vehicle you’re working on
✅ What hardware you’re using (OEM vs aftermarket)

I can give you a more specific recommendation!
 
Loctite only makes them a PITA to remove in the future.

Try to source titanium lock nuts as used on F1 engines, you'll never look back. ;) These are all-metal and usually have a flange, no washers required.

If you're having problems keeping the nuts tight, you should maybe look into the cause, most probably because the entire system is moving around too much. Correct headers with cross-over pipe fitted? Wobbly silencer mounts?

piet
 
They need nipping up after new seals have bedded, then basta.
If you've junked the crossover, keep a 13mm spanner in your pocket at all times.
Paul
 
Thanks, will see how it goes. There is a crossover under engine, not OE. All was fine until I removed to fit clutch extender and after refit the exhaust nuts (brass nuts with spring washers) kept coming loose, and oil started coming out. I found the thread below where it sounded like Keith N recommended the loctite route, so will see how that goes. The loctite won’t be on the nuts, just the header itself. the nuts I bought are BMW exhaust specific and are oval so they distort and lock, and have flanges. Will see how it goes. The titanium sound good, I’ll get some of thise for tge GTL - it’s SF1 I’m playiing with today
Sean

1971 SF a couple of questions please - Updated

Having recently acquired Shaun's lovely 71 SF during lock-down I used the time off the road to strip, clean and fettle the bike. It's my first bike for over 30 years. Having previously had Hondas the mechanicals seem very familiar although the robust materials and quality of engineering are a...
laverdaforum.com laverdaforum.com
 
Paul Marx said:
They need nipping up after new seals have bedded, then basta.
If you've junked the crossover, keep a 13mm spanner in your pocket at all times.
Paul
Click to expand...
Junked my junction box in 1975 - been through std headers, then custom headers, then a factory SFC 2/1 and now my own custom 2-1-2. The SFQ has the brass nuts that came with my SF1 from the factory - have never had one nut come loose, commuted, raced, toured etc for a total of probably 300,000km. I don't doubt some people have trouble with theirs - I've musta just been very lucky!
 
Yeah, I. Ever had any trouble with the GTL OE brass nuts and spring washer in 41k Mike’s, and just reused the original nuts and washers when I swapped from OE exhaust to a Marvin 2:1.
 
smlav said:
Yeah, I. Ever had any trouble with the GTL OE brass nuts and spring washer in 41k Mike’s, and just reused the original nuts and washers when I swapped from OE exhaust to a Marvin 2:1.
Click to expand...
Don't the OE brass nuts have an interference type of thread that once removed and reinstalled a couple of times could lose its interference fit?
 
Fabricated mine out of imperial hex brass stock, tapped to internal M7, use two custom height nuts per stud if you must. Depends on the modern era mechanical adaption in parts, such as the crush washers.

( not ) Like spark plug torque, tighten until you crush the seal washer flat as a pancake, then read the box that said, tighten to finger feel then 1/4 turn.

Doubt any fastener adhesive will stand for the elevated temperatures of the studs. The usual types will fail above 90C. Perhaps NASA type are different?

As the cognisant here point out, its not usual to have the nuts loosen unless other contributing issue or combination of issues. HTH j.
 
I make them longer than that and have a closed domed end, I have supplied about ten sets to friends around the globe, they are also wired on after having done 2 or 3 heat cycles and be retightened, I have previously lost a few on the road and on both twins and triples and know of quite a few who have had the same, one of them resulting in a cracked alloy rose, due to overtightening the remaining nut, I no longer carry spares, the studs do not rust (not exposed) and I am very happy with them, I posted a photo somewhere but cant find that or the photo anywhere, someone might have it, since forum members were very critical that the lockwire crossing the pipe from nut to nut was considered by many to be a disaster in that it will cut the pipe, break, vibrate etc, none of that has happened and they are still good. Just like all who said that my "around the wrong way" calipers on TOG for my four piston calipers will cause uneven pad wear............. it hasnt.
CLEM
 
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at least I understand the floating fork system, and mine fit without locking the front wheel !
CLEM
 
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