[oupa]

Last month I made a nylon replacement for the rubber cam chain roller. Today while waiting on parts to arrive I decided to tackle another missing part I need. Also originally rubber. The intake manifolds.

My new carbs came with rubber connectors but without the flange for attachment to the cylinder. This is a pretty simple part to make. It's what I made it from that may raise some eyebrows.

First up was creating a pattern of the intake port. A tracing with paper was transferred onto stiffer cardboard for the working pattern. The base, the part bolting to the intake port, was made from a 1/2" pipe flange. The flange was sprayed with dykem and the pattern transferred.


Bear with me kids. This isn't going to look so dumb in the end... I think.

The extra bits were cut away with a angle grinder and then the flange milled to final contour.


Next the inner lip was beveled in the lathe and the center of the flange cut away.

Since the bevel is on the inside, it looks pretty rough in this photo.

Appearently I didn't take photos of that process but next up was drilling the base plates for the 6mm mounting holes.
Then I cut two 3/4 inch lengths of one-inch (I.D) iron pipe for the spigots.


I'm not much of a welder but I'm satisfied with the attachment of the spigot to the base.


The last machine operation was to chuck the spigot in the lathe and take a finish cut off the back of the plate to assure the spigots are square to the mounting surface... not that it is super critical since the carbs will be attached by a rubber sleeve. :-?
They will of course require separate gaskets unlike the original rubber units, but that's a simple fix to. I ran out of time for today, but they need some serious cleaning up. The interiors will be polished as smooth as practical.

 

[Boomer343]

Be interesting to see if heat transfer is an issue compared to the OE.

Otherwise carry on .... give a man a lathe and a welder and the world becomes a different place .... damn I miss that fully equipped shop I used to run ...

 

[oupa]

Be interesting to see if heat transfer is an issue compared to the OE...

I may be wrong, but I'm not terribly concerned with that. First off there is still a rubber sleeve connector between the carbs and manifold as well as the gasket - I intend to use neoprene. Additionally, the air/fuel mixture is the coolest thing entering the engine, so there is that constant cooling effect. AT least that's how I envision it. :-? :grin:

 

[Rob Axel]

Heat.. well taking a page out of Triumph's book, well (from the collection of crap In my garage), their 650s (50s-mid 60s) the heads had a "pipe" as a intake manifold.. well bonniviles did (dual carbs) Tigers has a single.. and the Amal carbs were mounted with a rubber hose/boot between the two. Later (67-later) the intakes has a flat flange with studs pressed in. There was a recess cut into some carb flanges for a "O" ring.. The studs had a shoulder, allowing the carbs to not get over tightened and bend the flanges (didn't work that well).. lately I have seen "spacers" offered for this flanged setup.. stating "aid with heat".. they look like the same epoxy polymer spacer my shovel head had for a S&S carb...
If u are concerned about heat transfer.. look into these or similar products.. couldn't hurt..
oh.. here is a thought.. tap those intakes for vacuume ports.. will make balancing the carbs a whole lot easier..

 

[oupa]

They're not pretty, but they should be functional.



Robaxel, yes this is kinda sorta somewhat like the Triumph intake. I didn't take any photos but cut (+/- 1/16") neoprene gaskets for between the intakes and heads. There is a rubber mounting sleeve between the carbs and intakes. I suppose there will be some heat transfer. That's going to happen whenever you attach anything to something hot. The carburetors will be isolated (by the rubber sleeves) at least as much as with the original rubber intakes. The length of the intake (between carb and head) will increase slightly, but then so is my carb size. The spigots are short enough that the rubber sleeves fit close to the flange so the increase in length isn't that much really. The part is 1" overall length. The pipe is basically just a rigid mounting to tighten the rubber sleeve against. As I mentioned previously, the constant flow of "cool" air/fuel through the part will have an effect as well. I may be wrong, but I just don't see heat being a problem so long as the engine doesn't overheat generally.