Bushings for carb butterfly shaft?

[earthquake]

I am getting ready to re-bush a set of Kadron carb throttle bodies, I know you should not use "Oilite" bushings because the gas will leach the oil out and they will leak air but what about "SAE 841" graphite bushings? will the gas eat graphite? Mark Harney said he used cast bronze "alloy 932" bushings but they are way more expensive then 841 graphite bushings. If I had a lathe I would make my own, I have all kinds of 360 brass rod laying round.

Casey
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[flyinglow94]

I use valve guides that I machine to size. i know they will hold up and just a little honing for a nice fit on the shaft.
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[vwracerdave]

http://www.thesamba.com/vw/forum/viewtopic.php?t=401869&highlight=kadron+bushing+shaft
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[modok]

Good to use hard bronze, but remember almost anything will be better than the soft alloy the carburetor is made of.
Some types of high silicon or heat treated aluminum may last longest of all!

How much press fit can you put on a graphite bushing?? does loctite stick to it? How do you ream one? I really don't know. I mainly work with metal.

[nsracing]

Just use an old VW pushrod. Of course you need a lathe to make the bushings. Free!

I do not think you will ever wear them out.

Best way is to ream the bores on the carb. Then machine the bushing to that size plus the small bearing crush. 0.0005 is plenty.

Also, I was going to do a 'write-up' on the way to make the transition but have so much on my plate right now.

[Chickensoup]

Ive run out of usable plastic bushings for my carbs. So im going to trim some down on the lathe. What material is recommended? preferably a self lubricating material? Also, what kind of fit should the ID be? I assume a very slight interference fit for the OD. Its for solex carbs.

thanks
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[oprn]

How about Teflon or Delrin? I have a pair of type 3 carbs that need to be re-bushed.
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[Chickensoup]

[Brian_e]

McMaster Carr has tons of different size bushings, all different ,materials. Cut down valve guides are also very easy, and cheap. Nick mentioned old stock push rods. That is good quality aluminum, and will most likely last forever.

I don't think this would be a good place for plastic. Lots of temperature change, lots of different chemicals, and lots of movement.

Brian
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[Vanapplebomb]

Plastics of old, poor choice.

Plastics of new, often more durable than bronze.

Look at the Igus T500 engineered plastic bushings. They are phenomenal. Much better than bronze for a lot of applications. Anything from simple carb bushings, to full on industrial automation equipment. I have been phasing out old school bronze bushings for these engineered plastic bushings in a lot of applications.
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1800 Type 4 Berrien 295

http://www.thesamba.com/vw/forum/viewtopic.php?t=487021

[scrivyscriv]

I hard a hard time finding anything that fit right, without making something on a lathe.. you might consider milling the body for an O-ring. I'd be happy to drop you a handful of o-rings in the mail, I ordered a pack of 100.

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[oprn]

I won't be doing the carbs for a few months yet, other projects in the fire right now. I'm just in the planning stages in my mind. I have lots of Delrin and Teflon and a lathe to turn them on as all is well. I don't think the carb will ever run hot enough to effect either one... short of an engine fire.

The O rings are a nice touch!
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[Vanapplebomb]

Felton and Teflon are not great materials for throttle shaft bushings. Good wear resistance, but hey cold flow over time. So, even though they won’t wear much, they get sloppy after a while because the material deforms.

That’s why we use engineered plastic bushings designed for high loads, heat, and harsh environments these days. They don’t cold flow and deform over time the way things like nylon, Teflon, UHMW, and Delrin do. Also, the engineered plastic bushings are self lubricating because they are a composit with solid lubricants diapered in the material. This is why I have been moving away from bronze, which has poor lubricating properties on pivoting shafts, or environments where oil washout is inevitable… both of which are conditions present in carburetors.

Another bonus with plastic is they are largely electrical insulating, which keeps galvanic corrosion at bay. Steel throttle shafts provide cathodic protection to the copper alloy bushings. In doing so, the steel shaft is sacrificial, and corpses away. I frequently see steel throttle shafts that have corroded away more than the bronze bushings are worn. Even with new on size bushings, it won’t fix the problem because the steel shaft is now several thousand smaller where the bushings were than the rest of the shaft. Plastic bushings put an end to this.
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1800 Type 4 Berrien 295

http://www.thesamba.com/vw/forum/viewtopic.php?t=487021

[Vanapplebomb]

Link to Igus T500 material specs.

[url] https://www.igus.com/info/iglide-material-t500[/url]

Enjoy.

Often, because of the galvanic corrosion of the steel throttle shaft used in copper alloy bushings, I use undersized bushings. 5/16” vs the original 8mm, polish down the shaft so it is all a consistent diameter, and ream to fit. Sometimes a 5/16 drill bit is all that is needed to clean it up. Other times it will need to be teamed. It helps to slide the shaft of the reamer through both bushings, then back it out. This helps align it as you start, so you don’t go crooked. I also open up the throttle body so I can use 3/8 or 1/2 long bushings. Just don’t blow through into the throttle body bore.
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1800 Type 4 Berrien 295

http://www.thesamba.com/vw/forum/viewtopic.php?t=487021

[raygreenwood]

[Chickensoup]

thanks yall for the SUper helpful responses. I was thinking the delrin would be ok with being able to handle 250F but i didnt know about its chemical incompatibilities.

And now that i know igus, i dont need to think about the delrin.

Thanks again! ill order some rod from mcmaster and turn them down on the lathe.
_________________
-'85 c10 5.3 LS, 222 cam, long tubes, x pipe, 3 inch spin tech's
-'05 B5.5 TDI Wagon 17in sport rims ;EGR + BSM + ASV Delete, Stage-2 Tune, straight pipe
'65 Tourist Delivery Build
'66 RIP
'69 RIP
Hosea 4:6 "My people are destroyed for lack of knowledge"

[AlteWagen]

Van posted this way back and I added it to the Solex page on the carb thread

https://www.thesamba.com/vw/forum/viewtopic.php?t=662593



https://www.thesamba.com/vw/forum/viewtopic.php?t=572107&start=15
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[Michael Ambrozik]

Try using Beryllium copper, it only down fall is it presents a toxic inhalation hazard during manufacture or machining. It is also a bit pricey.

[Vanapplebomb]

[oprn]

Interesting about Delrin. I have some shaving from it on my lathe bed yet. I will put them in a jar with pump gas and see what happens. My stock of Delrin is from used displacers that were in service in oilfield vessels that were filled with crude oil and in some cases natural gas condensate so I am a bit sceptical about Delrin not being compatible with gasoline. We have used it extensively in this service for many decades.
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We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age)