Nuts bolts and washers

[Wangler]

I've never been happy with the 8 plain nuts and split washers on my S3 used to secure the intake trumpets in the air filter box. I assume they are the originals. I changed the air box gaskets recently and the nuts were definitely not as tight after 700 miles as they were when I carefully did them up. The gaskets must have compressed just enough to take some of the gripping pressure off the nuts.

The obvious potential for catastrophic damage from one working loose seems to me to be too high without a better locking method. I was wondering what the best way to eliminate the danger is. Nylock nuts perhaps, Loctite or flange nuts, or maybe those expensive, clever, but very highly rated Nord-Lock washers.

Any thoughts or experience welcome.

[dhla40]

I have used nylocks and split washers as belt and braces for ten years no problem.

Sean

[waterman42]

A useful post, just checked mine and was pleased to find nylock nuts, couple of them accepted a very slight tightening.

But what I also observed was the inefficient "re-entrant" plain ended intake tubes. For these the hydraulic loss coefficient is about 0.8 V²/2g, whereas without any tube, ie straight into the carb choke from the plenum chamber is better at 0.5. I'm wondering why they have these tubes, perhaps something to do with the shape of the plenum chamber, who knows. Is there an after-market bellmouth fitting? That would be an improvement on the plain tube. The ideal would be a rounded bellmouth entry with no projection but more costly to arrange on a production engine.

[Richard Fridd]

 Removal of the baffle in the plenum chamber has caused problems in the past. Not sure why?

  Richard

[dhla40]

I think the stack pipes combined with the baffle make a longer inlet path to improve torque?

Sean

[fay66]

I've had my series 1 2c Berlina since 1997, in that time the original fixings have never fallen off, even though they have been removed numerous times.
I have Dellorto 32  Dhlb carburettors in place of solex 32s. But use exactly the same fixings.
Unless series 3 carburettors are significantly different to series 1, I fail to envisage a scenario where a nut or washer could conceivably enter a carburetor,
You'd need both nuts and spring washers to fall off after climbing uphill on the threads, before the trumpet could move to allow ingress.
But as the bottom of the airbox is lower than the bottom of the trumpet, they would fall lower than a carburetor throat, they are fiddly to pick up if you drop the nut ot washer, so I find such a scenario improbable, and that's without considering how the trumpet would climb up the threads and fall clear.
 Perhaps there's a case for changing the spring washers, but I think we're looking to find a solution to a problem that in my experience doesn't exist.

[Jai Sharma]

When I was racing a Fulvia I did have one nut ingested which made a proper mess of the head. But the air box was modded and that may have altered the risk, too.