I'm picking up my Twin Weber Head this week from the machine shop. I'll need to do something to permanently seal the steel flanges to the head. Someone once mentioned whatever the rotary folks do for bridgeporting their engines (Devcon, I think?)
Steel flanges visible here:
Right Stuff.
Devcon is basically concrete. You don't seal flanges with it, you fill water jackets. (With rotaries, Devcon is used to fill the water jackets for bridge ports so large that they pass through the jacket area. Or to fill the intake ports when you build a peripheral port engine. I have always used JB Weld for this, not Devcon)
There are other flange sealants you can use, like the stuff used to seal Volvo and VW block halves and cylinder head halves together, but in my experience Right Stuff works better and is easier to work with.
Welder? And don't you want three carburetors? lol
Jeez... DUH. Metal glue gun. OK, Braze.
Are you going to bolt them on? I would use flat head allen screws into threaded holes in the head and use some thick epoxy as well if the surface of the head is less than perfectly flat. J-B is as good as anything in this application. RightStuff is less than happy with fuel in my experience. Lots of small screws if the wall thickness of the "port" is thin.
TurnerX19 said:Are you going to bolt them on? I would use flat head allen screws into threaded holes in the head and use some thick epoxy as well if the surface of the head is less than perfectly flat. J-B is as good as anything in this application. RightStuff is less than happy with fuel in my experience. Lots of small screws if the wall thickness of the "port" is thin.
I don't think I have any clear pictures anywhere, but I plan on bolting them in place with two bolts per; one to the front of the engine and one towards the back per plate. There isn't really room to do anything to the sides
Head is decently flat where they'll be mounting, I milled the spots smooth.
If they'll be bolted in place, why not just use some gasket material?
In reply to stuart in mn :
There's enough room for a viscous material to seal it, but I wouldn't trust a paper gasket. Take a look at this pic and you'll get a rough estimate of how much room there is. I'd also like to have the metal flanges be semi-permanent to help prevent any long term issues.
I have looked at brazing already, and actually tried with a previous head, but it ended up cracking all over the damn place because I couldn't get enough even heat throughout. Even when I tried putting the head in an oven to bring the whole head up to a workable temp
How close are the mating surfaces?
I've used Yamabond with good success on 2 stroke crank cases, but those mate up almost perfect. The way we checked for leaks was to let the sealant cure and then fill the cases up with premixed gas overnight to see if there were any leaks, so fuel shouldn't be an issue.
In reply to No Time :
The surfaces are parallel and milled smooth on the same machine. May be some roughness from the end mill, but they're good mounting surfaces.
I think I've used Yamabond before with an outboard, I may have a tube somewhere.
Loctite 518 or 573.
JB Weld, clamp in place for a day, and they are there forever. If you want to remove them without grinding them off, then pick up a sheet of Mr Gasket header gasket material.
How thick is the cast iron around your new holes> The picture makes it look less than a quarter inch, in which case I would want to drill and tap a whole bunch of machine screws around the openings to hold it.
They say Right Stuff is not good for sealing head gaskets but they's lyin'.
I use it to seal NPT fuel fittings where Teflon tape tends to get dissolved...
Right stuff is my vote
If welding or brazing isn't an option, I'd JB weld and bolt it. It's pretty permanent stuff.
Welding or brazing cast can be done but it is going to require lots of heat. I usually put the piece on my turkey cooker burner to bring it up to temp. Turn off burner and weld. Relight burner on high and gradually bring the temp down over 30-45 minutes.
JB Weld would possibly work, but the head would heat up while the adaptors would not heat up as much, so there will be some shear forces on the joint that a "hard" epoxy would not tolerate.
The joint sealants that OEs use stay somewhat flexible to accomodate this small amount of motion.
With a good look at this I think you need 4 screws not 2. The surface finish you have is good enough for Yamabond for sure. I would personally use a soft paper .050" gasket with old fashioned Permatex from the can on both sides of the gasket. Offsetting the adapter/head screws from the adapter/carb screws may be a challenge....
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