Nut selection for carburetor repair

[Quickstep192]

I’m getting ready to replace the covers and diaphragms on the accelerator pumps on my Weber 40 IDA 3Cs. These things are fussy because the cover is pot metal and tends to warp if the attaching nuts are over tightened. If not tightened enough, they leak gas. The usual process is to tighten just enough to compress the lock washer, but then they tend to loosen over time.

I suppose the nut/lockwasher solution might have been an economical decision by Weber.

Economics are not a concern for me when buying 8 nuts, and I have options.

I can use lock washers and regular nuts as Weber did, or I can use nuts with nylon inserts or I can use nuts with nylon inserts and serrated flange.

What do you think is the ideal solution?

 

[Codyboy]

Some guys have luck with flattening out the cover.
http://forums.pelicanparts.com/pors...e-buy-parts-leaky-accelerator-pump-cover.html

 

[Skyman]

Perhaps a little blue Loctite?

 

[BurtEggley]

I would avoid nylocks. If the nuts grab the studs you may start having issues with the studs backing out instead of the nuts. The issue is that no one making these type carbs ever thought that people would still be using them for 30 -40 years on some model sportcars.

 

[four.cycle]

After trashing a perfectly good pair of 28mm Solex one-barrel downdrafts on my Opel 1.1L attempting to do something along this line, I would advise against making ANY deviation from the original set-up, but that's just my lousy opinion.

photo is not my engine.

 

[Quickstep192]

I just got turned on to Nord-Lock. They seem like a better lockwasher solution than a split washer.

 

[RoninB4]

-For carbs I try to use the low strength (222 purple) Loctite, it's made for small diameter fasteners that don't require much torque but still prevent the fastener from backing off. Been using for years of motorcycle carbs, no problems.

 

[Squankum]

Don't ya wanna do something elaborate with wingnuts and safety wire?

(Kinda joking. Those Nord Locks look tempting.)

 

[finn]

Lock washers are garbage, and a sign of a poorly designed joint. They don’t work.

A proper joint relies on bolt stretch, and a gasketed joint should have a compression limiting feature.

These old carburetors have none of that, so you’ll be best off with hardened flat washers and a low strength loctite .

 

[garfunkle24]

If by lock washers you mean spring type split washers, they are garbage and do nothing. Nylocs or stover type lock nuts, loctite or (as you mentioned) nordlocks are all vastly superior but still no replacement for proper torque/tension.

 

[LXCam]

I just got turned on to Nord-Lock. They seem like a better lockwasher solution than a split washer.

I’ve been using nord lock washers for a couple decades on problem assemblies prone to expansion/contraction issues. They just work.

 

[CraigStu]

I have often used a small dab of UltraGrey sealer globbed onto the bolt head and carb body.

 

[Craig Balzer]

I’ve been using Nord Lock washers for a couple decades

If those who are not familiar with them, they are installed in pairs

/
The serrations on one side of each washer grab each other, preventing loosening from vibrations and hot/cold cycling.
They come in various sizes based on the size of the bolt/stud being tightened.

 

[garfunkle24]

If those who are not familiar with them, they are installed in pairs

/
The serrations on one side of each washer grab each other, preventing loosening from vibrations and hot/cold cycling.
The come in various sizes based on the size of the bolt/stud being tightened.

To further clarify, the sides I would call 'serrated' go away from each other. The sides with larger ramps go together so that to overcome said ramps the washers actually have to spread, increasing bolt tension in the process, to loosen off.

This could well be what you meant but I thought your terminology a little confusing for the uninitiated.

 

[Recoveryman]

I hav'nt had much experience with small carbs, but as an old machinist, I never had a lot of love for split lock washers. But RoninB4 sounds like the voice of experience. It's kind of hard to ignore someone who's done it before.
Recoveryman

 

[Quickstep192]

I used Nord-Locks and torqued to spec. So far, no leaks.

The gasket, or more accurately, diaphragm is very thin, so requires some compression to seal. To make matters worse, the fasteners are only at the corners, inviting distortion. I sanded the covers dead flat to help improve mating.

Time will tell.