So I bought a Shurflo diaphragm pump for my water injection system, and its mounting base has 4 rubber posts.


Due to the rubber, I can't tighten the 4x mounting screws so much... I don't want to oversquish the rubber (even though I will use washers).

My dad pointed out that due to lack of tightening, the screws might back out, especially as the pump vibrates some.

Hence, I ordered some cross-drilled screws from eBay:


Since I am a noob regarding the use of safety wire, I have a few questions:
1. What diameter of wire should I use? What is a good general purpose diameter?
2. Stainless steel or regular steel?
3. Do I need to (or should I) buy special pliers?
4. What's the correct twist rate?
5. Right-handed twist or left-handed? Is it a matter of twisting such that the wires won't unravel?
6. Any recommended online guides that I should read?

I think your going overboard...we're not in aviation here.

Stainless steel is best, just make sure to connect the wire to a solid bracket.

Have the wire tensioned towards the clockwise direction so the bolt won't back off loose.

You don't need to have special pliers, but aviation mechanics do; because they do it all the time.

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fierogt28

88 GT, Loaded, 5-speed.
88 GT, 5-speed. Beechwood interior, All original.

Leaving the bolt loose, will allow it to rock in the nut and it will eventually wear down and snap off.

If there is a metal sleeve inside the rubber bushing, you can fully tighten the bolt (so it won't back out) and still allow the rubber bushing to do its job.

You can also spend about $15 and get some rubber isolation mounts that are designed to do exactly what you are looking for: This is a crappy pic, but there is a stud on 1 side, nut on the other, and only rubber connects the two ends.

Here is a link.
https://aviation.stackexcha...asoning-behind-the-w

It is easier to do than it looks. Just make sure you keep your twists tight. Use .026 or .032 wire and make sure you loop it the right way.

What are you bolting the pump to? Are there going to be nuts on the other side? If so, why nut use lock-nuts?

quote Originally posted by Blacktree: If so, why nut use lock-nuts?

I think you meant... why nut use lock-nots? No wait, that's nut not quite right either.

Alright, so I think I'll purchase a spool of 0.032" stainless wire, and I'll twist it using the vise-grips I already have.

I decided to count the pixels on the eBay photo of the screws, and the drilled holes measure about 0.057", so the standard wire should fit.

quote Originally posted by fieroguru: Leaving the bolt loose, will allow it to rock in the nut and it will eventually wear down and snap off. If there is a metal sleeve inside the rubber bushing, you can fully tighten the bolt (so it won't back out) and still allow the rubber bushing to do its job. You can also spend about $15 and get some rubber isolation mounts that are designed to do exactly what you are looking for: This is a crappy pic, but there is a stud on 1 side, nut on the other, and only rubber connects the two ends.

Yeah, I'm not so hot on the idea of leaving screws not too tight. I may just try really large washers; I may be able to get decent torque this way without destroying the rubber bushings.
If that's not enough, I'll press in metal sleeves, slightly shorter than the rubber. The local hobby shop has thin brass tubing that would do the trick.

Even if the bolts are tight enough not to require safety wire, I've already ordered the drilled bolts, so I'd like to take the opportunity to add a new shop skill to my repertoire... which is one of the reasons I have a project car.

Shock mounts would work too, but I'd have to modify the pump mounting base, which is something I'd prefer to avoid (not a hard requirement though). When the pump bites the dust, I want replacement to be a drop-in affair.

Strangely, Holley doesn't tell you how to mount their (relabeled Shurflo) pump:
https://www.holley.com/prod...onents/parts/557-100
In their photo, there are some normal-looking bolts, but I'm not sure how developed that solution is...

quote Originally posted by Blacktree: What are you bolting the pump to? Are there going to be nuts on the other side? If so, why nut use lock-nuts?

The pump is mounted to the water tank. The water tank is made of 3/8" and 1/2" rigid PVC foam (for weight savings vs solid) panels, cemented together.
PVC foam can strip "easily" if screwed into directly, so wherever there are fittings or bolts going into the tank, I made some threaded bushings made of solid PVC, cemented in place.

The result is 4 blind threaded holes in solid PVC plastic for the pump.