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Discussion Starter #1
I have a sample set of Spica to Weber conversion plates, and a CNC mill to make as many more as I want.

I notice fairly regular "Want to Buy" for the kits.

Worth doing?

What would a fresh set of CNC billet Weber/Dellorto adapters be worth?
What issues if any should be corrected or improved on?

Looking for items to make as my CNC mill sits idle too often.

Richard,
[email protected]
 

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I have ... a CNC mill to make as many more as I want. I notice fairly regular "Want to Buy" for the kits. Worth doing? What would a fresh set of CNC billet Weber/Dellorto adapters be worth?
I haven't done any market research on this, so these are just my guesses:

Spica to Weber adapters have been on the market for decades. Anyone who wants a set of these adapters probably already has them. The Alfa market was never large, and now that these cars are 40+ years old, it is miniscule.

Back in the day, when these cars were close to worthless, it was cheaper to cobble up an adapter to bolt a set of Webers onto the Spica manifold than it was to fix the Spica. But today, 1970's Alfas have some value and the trend is originality, so owners tend to either retain the Spica, or use a European carburetor manifold to do a carb conversion. Bottom line: I doubt the market for adapters is very large.

What issues if any should be corrected or improved on?
If you are bound and determined to do this, the two weak points of the original Shankle design are:

- Throttle linkage using a bent rod attached to the spica cable drum. Adapting the original-style carburetor bellcrank beneath the manifold would be a cleaner solution, since the rods could be straight.

- The isolator-seals used between the adapters and carburetors never worked very well. If you could come up with a design that used a better part, that might create some demand.
 

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I would echo Jay's comments. Frankly, there are an abundance (relatively) of euro intake manifolds that are as cheap or cheaper than the SPICA conversion kits and more elegant IMHO.

If you wanted to keep the CNC humming I would suggest looking into hard mounts for Webers. I know that's a bit controversial (replacing the rubber mounts) but I've got hard mounts on two motors without any issues. My logic in favor is as follows:


  • Rubber mounts are perishable and vary in quality from different vendors. I don't know how many manufacturers there are but I doubt more a a couple. Making these things is a difficult process and with low volumes it is difficult to maintain the quality (I'm in this business so I do know a bit about the pitfalls). Anyone with a CNC (or a simple Bridgeport for that matter) can produce a hard mount that will last the life of the motor.
  • Rubber mounts are just as costly as hard mounts.
  • You could easily add a vacuum port for balancing on a hard mount.
  • You can also easily port match the mounts to the manifold and carbs.
  • I don't buy the vibration argument - rubber mounts would only attenuate vibration across a specific frequency range which would vary based on many factors. For the vast majority of conditions a hard mount would perform as well and I would argue better over the long haul.
I think there is a market for such things.

I would also look into Burman boxes...

My $.02...
 

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Hmmm, alloy Burman box is a critical component, high liability.
Would have to make them a bit thicker for strength if the original iron castings are shattering.
7075 for yield strength or 6061 for a bit of elasticity?
And of course I would have to fit one to my own car to demonstrate faith in the product.

"Hard mounts" are clearly less liability.
With or without grooves for an O ring?
Simply copy the rubber mounts?

A few years ago I inquired here for Alfa parts that are needed and not readily available.
Unfortunately virtually all replies involved replacing parts that are stamped or were originally plastic injections that would have to be cast.

So I'm still looking for parts to do that are Milled or Turned as it's a CNC mill and lathe pairing that I have.
I also have a sinker EDM but see little application for it to making Alfa parts.
 

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Rubber mounts are perishable and vary in quality from different vendors. I don't know how many manufacturers there are but I doubt more a couple.
I'm getting off-topic a bit here, but I think the stock carburetor soft mounts are a pretty good design. Yes, you need to change them once a decade or so; like other rubber parts (i.e., belts and hoses) they don't last forever. But I think that on a 4-cyl engine, with its inherent vibrations, isolating the carburetors to prevent fuel foaming and cracking of the mounting ears is a good idea. Of course, the "O-ring + thackery washer" style of mount provides some vibration isolation as well.

Richard/SIA said:
alloy Burman box is a critical component, high liability. Would have to make them a bit thicker for strength if the original iron castings are shattering. 7075 for yield strength or 6061 for a bit of elasticity?
Richard: The stock Burman case is cast aluminum, not iron. You'd have to make replacements out of styrofoam for them to be any weaker than the stock parts! But yea, there are some considerations:

- Liability is an issue if you are making any steering/brake/suspension components.
- The tolerances in Burman cases are a lot tighter than on carb mounts.
- I'm not sure there is an end-user market for replacement cases. Fitting the internals from a cracked Burman into a new case requires a lot of measurement and shimming. This is a job for a specialist with access to shims, presses, reams, measuring tools, ....
- Alfaholics already offers replacement Burman cases.
- Later-model Alfa spiders came with the more robust ZF boxes. I know the Burman has that nice, ball bearing feel, but swapping in a ZF would be much simpler/cheaper than performing a case transplant on a cracked Burman.

Still, I don't want to come across as negative, and agree gprocket has suggested an interesting idea. Solutions for replacement steering boxes are more in demand than Spica --> Weber conversion parts.

Alfaholics has done a great job of engineering replacement/competition parts, many of which are built on CNC equipment. They have also adapted 21st Century technology to our mid-19th Century cars. So one way to generate new product ideas would be to scan the Alfaholics website, looking for niches they have overlooked.
 

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... But I think that on a 4-cyl engine, with its inherent vibrations, isolating the carburetors to prevent fuel foaming and cracking of the mounting ears is a good idea...
I think this is urban legend stuff. Let's start a thread in the carb section and debate this a bit more.


Richard: The stock Burman case is cast aluminum, not iron. You'd have to make replacements out of styrofoam for them to be any weaker than the stock parts! But yea, there are some considerations:

- Liability is an issue if you are making any steering/brake/suspension components.
- The tolerances in Burman cases are a lot tighter than on carb mounts.
- I'm not sure there is an end-user market for replacement cases. Fitting the internals from a cracked Burman into a new case requires a lot of measurement and shimming. This is a job for a specialist with access to shims, presses, reams, measuring tools, ....
- Alfaholics already offers replacement Burman cases.
- Later-model Alfa spiders came with the more robust ZF boxes. I know the Burman has that nice, ball bearing feel, but swapping in a ZF would be much simpler/cheaper than performing a case transplant on a cracked Burman.

Still, I don't want to come across as negative, and agree gprocket has suggested an interesting idea. Solutions for replacement steering boxes are more in demand than Spica --> Weber conversion parts.

Alfaholics has done a great job of engineering replacement/competition parts, many of which are built on CNC equipment. They have also adapted 21st Century technology to our mid-19th Century cars. So one way to generate new product ideas would be to scan the Alfaholics website, looking for niches they have overlooked.
Styrofoam:grin2::grin2::grin2:

Personally I don't think the Burman design is that bad. I think that aging is more the culprit coupled with lack of maintenance that is taking it out on the stress points. Did these tend to fail when younger? I've not heard that to be the case (pun intended). But man, I'm finding it harder and harder to find a non-cracked box these days.

Were it me, I would send a box to China (gulp, sorry) and have them sand cast A356 and then do the final machining on your CNC. I think a decent CNC with the right tools could hold the tolerances.

Alfaholics is making a beautiful piece but at +$1,000 I think there is a lot of room for another source.
 

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Personally I don't think the Burman design is that bad. I think that aging is more the culprit coupled with lack of maintenance
Probably true. I don't think that "lasting for 50 years" was one of Mr. Burman's design objectives back in the 1960's.

I would send a box to China (gulp, sorry) and have them sand cast A356 and then do the final machining on your CNC....Alfaholics is making a beautiful piece but at +$1,000 I think there is a lot of room for another source.
I suspect the problem is the low unit volume. Whether you have them cast in China, or machined from billet (as Alfaholics do), the tooling is going to be significant. Spreading that tooling expense over only a few units adds a big component to the final price.

You probably understand manufacturing costs better than I do, but I would think that the tooling cost for a billet machined part would be < the tooling cost for a cast part.
 

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Discussion Starter #8
I was thinking machine from a solid billet, then bead blast the exterior for a "Cast" finish if desired.
Molds are so expensive that I do other items from billet as the machine time comes out cheaper.
But none of this addresses the internal components and rebuilding.
 
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