Custom Norton carburetor spacers

I've been working on this project for a good long time now, and it's finally starting to pick up the pace. My goal, was actually to find some original longer carburetor spacers like the Norton Works Dept, used on the Domiracer and the Daytona race bikes, but they simply aren't available. I've been lucky enough to see some in person, but they were mounted to an original machine. All others, have only been seen in photos. So I've decided to make some of my own, I've taken a lot of time to clean up the lines on the shape, and matched it up to an Amal monobloc carburetor flange.
I've designed them with my Solo Motorcycle Works logo to be inset into just one side of the casting. That way, they can be turned in and faced down, should I not want to see the logo. That would give a traditional look, but still allow all the benefits of the longer inlet tract.

I'll produce them to be a straight fit, with stud holes at 2" apart on center. The center bore will be 1 1/8" and the thickness of the spacer overall is 2 1/8".

I'm sourcing studs at the correct length, and will sell the spacers, longer studs and nuts, as a complete bolt on kit. I'll likely offer them for sale in bare cast finish, as per original, as well as polished, and polished with the inlay painted.

Another nice bonus is that once finished, they can be milled down should they be slightly longer than needed. Anyone interested, should consider the spacing on their particular machine. For instance, a featherbed machine, with the stock battery box and oil tank, will not allow enough room to make use of these longer inlet tract spacers. You'd need a central oil tank, or some other modified set up.


Finished cost for a set of the spacers, is unclear at this point, and will basically depend on the mold cost and tooling, plus the cost of the studs. I'm not exactly taking orders yet, but if you're interested, please send me a message, as it'll help me to gauge overall interest, and guesstimate quantities with the foundry. I'll only make a small batch of these, and selling them is intended to allow other enthusiasts a chance to get them and offset a portion of my cost. I'll be having these produced by a foundry and professionally machined, so it's not some sort of back yard operation. Also worth noting is that these will be produced in the USA. With the extent that I'm taking this project, my final goal is to have them made properly. So if you've got any interest, please message me.

Lastly, I'd like to add that this is a passion project for me. I'm not starting a business, but figured if I'm going thru the trouble, perhaps others would like some as well. The specs I gave are to suit what I'm building and as I said, this is personal preference for a personal project. I don't really want to start a huge debate about the topic or the specs, so hopefully we can keep this a positive thread.

I've got some photos of a 3D printed positive part I made, and I can share the photos of it, as well as how it looks in comparison to stock parts. I can never seem to figure out how to post photos here. You can see the photos and read more about it, on my blog, if you're interested:

https://solomotorcycleworks.blogspot.com/2018/12/norton-amal-carburetor-spacers-project.html

Looks like nice work!

I hope you find enough interest. Not for me ..... my velocity stacks are mighty close to the oil tank and battery box.

The long intake track was supposed to boost hp. Any data on how much boost? That data would be good marketing info.

Slick

Thanks Slick, appreciate your kind words.
I honestly don't know the data on what HP increase would look like. I think there's quite a bit of precedent for the benefits of longer inlet tracts. It was at least a portion of the equation in taking the Domiracer to 100mph average speed at the TT. I've seen longer inlet tracts work very well on Douglas MaCrae's bike, and he's talked about that in the past. And of course Manx Nortons use a long inlet tract. And guys like Paul Dunstall made some back in the day as well. I think that most of the issue on stock machines is the lack of space due to the battery box. I'm sure that played a part in how thick the spacers could be.
I agree with you that that info would be good marketing, and I look forward to tuning and development once I get them made and the bike finished.

Leo Geoff determined the long norton manifolds to be VERY long. I don't remember 4" 6" or 8"?
"Paul Dunstall made some back in the day as well." sorry OT ?

I doubt he made them, but I do have an original set on my 68 atlas (Dunstall sold and prepped). Finned and 1-1/2" long-32mm bore with balance tube fittings. Probably British aftermarket hotrod norton parts.
68 had concentrics, 2.75 long carb but monobloc are 3" long.
http://atlanticgreen.com/dunstall.htm
good luck

Thanks Dave, I appreciate that. I've got a set just like your Dunstall spacers as well. They're finned and are really nice. The ones I'll be making are longer than that, but you're right as the distance from the carb needle to the valve, will vary based on application and which carbs are used. I'm looking forward to messing around with the tune, spacer distance, needle position, jets and even the length of the velocity stacks, once the bike is finished.
Cheers
Jeff

Would it be possible to cast them longer and then cut/machine to size as needed? Complicates the studs, but the vast majority of the cost has got to be the labor, rather than the size of the object cast, yes? Different lengths would also allow some tuning on a dyno (by someone, somewhere) to get down to the nitty gritty of those legendary Daytona bikes.

Anything is possible, in regards to the casting, but the whole thing isn't going to be cheap. To be honest, machining each set to a custom order, isn't something I want to get into. I'm making them long enough that I can't imagine anyone would want them longer. So once they're made to my specs, it'd be easy for anyone to skim off a 1/16 or an 1/8 or whatever, to get to where they'd want to be. But the sheer cost and logistics, plus the issue with stud length, would just be more than I'm looking to do.
I fully agree with what you're saying though. I'm just not doing it as a business, so it's not really worth it to me to make it more complicated / expensive than it already is.
There's also the cost of a set, just as they are now. I'm imagining that a set of the spacers, and studs, will likely be $250-$275, and I'm not sure what most people's threshold would be.

Fair enough. It's easy to get sucked in.

I made some for someone’s 750 as he wanted to use 32mm carbies, so they were taped from 32 to 28 mm on the bore. I often wonder if the 500 will take bigger bore carbs.

I agree with you, and doubt that the bigger carbs would be beneficial for a 500