Shaft that holds butterfly in throttle body?

tbitz · 12-19-2003, 03:59 PM

Part of the CIS to EFI kit I'm working on requires modifications to the shaft that holds the butterfly in the throttle body. I would like to get a handfull of these which would be pre-fabricated for the kit.

It's not just a simple shaft, it has a slit down the middle which the butterfly slides in and it bolted down. Not easy to make from scratch.

Anyone know where I can get them? I tried our sponsor, but no go.

Tony

project935 · 12-22-2003, 08:40 AM

No idea of a parts source, but the best way to have them made might be to have the slot EDM'd rather than machined - could be cheaper.

tbitz · 12-22-2003, 09:15 AM

EDM eh?

A DIY EDM machine has always been on my list of things to build. I just never got around to it. The problem with EDM is it takes forever to "machine" anything. Great for one-of prototypes, but I don't think it can meet any production volume.

If I can't source the shaft, I'll have to come up with another solution.

Thanks,

Tony

cowtown · 12-22-2003, 10:17 AM

Tony, you have a fantastic website and EFI project!

I'd try these two parts dismantlers. Partsheaven usually has what I need for used parts. I've never bought from Silver Star.

www.partsheaven.com
www.silverstarrecycling.com

BGCarrera32 · 12-22-2003, 10:35 AM

Most likely the way to machine that is once properly fixtured and oriented you hit it with a slitter saw in a milling machine...how wide is the slot?

Sounds like a 5 minute job...

HawgRyder · HawgRyder's Garage

That's what I think too....
Start with brass shaft of the correct diam...drill and tap the holes for the screws...thread end/mill flats...slit the shaft....de-burr....voila.
Bob

911pcars · 12-22-2003, 01:27 PM

I believe PMO had this same issue when they were in the prototyping stage. The slits must be in perfect alignment otherwise idle is imprecise. Not sure if there's a reference on the shaft end to recognize. The factory weber carbs use a two-piece throttle shaft with a coupler to align the third throttle plate with the first two. Not sure on an MFI throttle shaft. I believe EDM or equivalent is probably the most accurate and precise method of making this cut. Do a search on the internet. There might be a faster process using EDM.

Sherwood
http://members.rennlist.org/911pcars

tbitz · 12-22-2003, 05:13 PM

Thanks for the input guys.

I'll take my throttle body out and measure the shaft and get a drawing made of what I need. Then I'll get some quotes from machine shops.

Zendalar · 12-23-2003, 02:39 AM

I believe firm called Hestec sells whole throttle bodies, and spare parts. I was planning getting the shaft with bearings and the butterfly from them.

Its a Finnish firm and here is their email: info@hestec.inet.fi

BGCarrera32 · 12-23-2003, 05:14 AM

There is NO way in the world that Porsche EDM'd those shafts. That would take an insanely long amount of time. Some sort of high speed machining op with a production cutter in a 3/4 axis screw machine...

jhelgesen · 12-23-2003, 06:01 AM

Why not call some of the aftermarket throttle body companies and see if they have something on the shelf, or could make you the parts?

You're looking at a slot that needs to be cut on a surface grinder with a thin disc installed.

Any good machine shop can make them with a print.

tbitz · 12-23-2003, 06:08 AM

Thanks Zendalar. I will shoot them an email.

HawgRyder · HawgRyder's Garage

A trick in sealing shafts is to put an Oring in each side of the shaft bore.
I usually overbore the holes and press in 2 bronze bushings...the first into the hole goes all the way to the venturi bore....the second goes in to leave a gap in between the 2 bushings.
Then, when assembling, you put a Oring in that slot to seal the shaft.
If sized properly...almost no extra drag on the shaft....an no more leakage of air.
Bob

911pcars · 12-23-2003, 11:25 AM

"....the second goes in to leave a gap in between the 2 bushings.
Then, when assembling, you put a Oring in that slot to seal the shaft."

Bob,
Once the second bushing is installed, can the O-ring be replaced at a later date w/o destroying the bushing?

Sherwood

HawgRyder · HawgRyder's Garage

Sherwood...yup...just remove the shaft and go in with a small pick (I use one with a little bend at the end)...pull out the old Oring and push in a new one.
The Orings go in sort of figure eighted and then open up and sit correctly.
This fix is particularly good for old carbs that are just unavailable anymore....and the fix works on the old original shaft.
Bob