It took a couple of days to do a good job of it, but I have the intakes nearly finished.
I rough cut the flanges one at a time with a sabre saw, then clamped them together and ground them to shape as a unit. I marked and drilled one plate, then clamped them together again to drill the mounting holes and a pilot hole for the center. I hole-sawed each center hole separately.
I was rolling along so well that I forgot to photograph the pipe cutting and brazing. The “before brazing” photos are actually of the prototype, which you may notice has the pipe off center and does not have the taper referred to next. Anyway, for the pipe, I had already cut a threaded end off, so I slightly tapered that end of the pipe and wire brushed the factory coating off. I used a standard plumbing-type pipe cutter and cut a segment about 1.2 inches long. This makes a rough and slightly distorted end, but it’s square to the end of the pipe. I cleaned up the cut edge on the grinder and set it aside.
I clamped the first flange and used a deburring tool to slowly increase the diameter of the center hole until it made an interference fit over the tapered end of the pipe segment. The flange was gently hammered all the way down to the non-tapered end of the pipe segment, making it as flush as possible to the end of the pipe.
I then put the assembly on a brick (I recommend a real fire brick for this; my brick will someday pop off shards of hot brick that will land either in my eye or on Toni’s trike. I think I’d prefer it land in my eye, for that would probably hurt me less.) and brazed the seam.
If you haven’t done brazing, it’s really just a solder that melts at red hot. It’s about as easy (to me, anyway) as electronic or even plumbing soldering and I find it much more forgiving to the novice than welding and is often more appropriate anyway. The joint almost always stronger than the materials being joined and the relatively low temperatures are less likely to alter the physical properties of the materials. It’s not appropriate for joining really big pieces, but it is good for joining dissimilar metals, like copper to steel, etc. Welding copper to steel is very difficult because copper melts away before steel reaches welding temperature. Enough about that…
My prototype intake was seriously flawed in two ways. Earlier I mentioned that the center hole was not indeed centered. It could theoretically affect the flow of fuel-air mixture, but the net effect would probably be pretty minimal anyway because we’re going from the throttle body into a short rubber reducer, the small end of which is clamped to the intake. The turbulence from a 1/16″ offset would probably not be noticed with all the other obstacles!
The other flaw on the prototype is that I attempted to use a standard air-MAPP torch for the brazing. It does get it hot enough, just barely, so it made a good seal and a mechanically sound joint, but it was lumpy. I think I could have suspended it on wire or some such and heated it uniformly enough with that torch to reflow the joint, but I was going to replace the unit it anyway. This time, I used a MAPP-oxygen torch, which gets way hotter. The result is that the piece heats up faster, flows the filler better and does it fast and efficiently enough that the brick isn’t heated all the way through in the process.
Then I did three more just like it.
The only flaw in the new ones is that the mounting holes ended up ever so slightly too close together, but at least all four are the same! I will slot them a bit and that should be that. What’s left is to surface grind/file/sand the flange face that mates with the engine, apply some black engine paint to hide my beautiful brazing and find gasket material to cut for them and they are ready to bolt on.