OutdoorKing Repair Forum Forums Finding and Swapping Idle Chatter Homemade Manifold - Southern Cross Engine

I am short of a manifold for another Southern Cross mower restoration and have given up looking for one. So I got to work on the weekend and made one! Not sure if it will work, but it is pretty close to the original. Just made out of scrap - cut up bits of plumbing fittings, stainless steel pipe, alloy for the carby end and mild steel for the piston block end. The hardest part was to make the two connecting ends. The material seemed a bit weak at a major join in the middle, so just to be on the safe side I decided to bind the entire pipe with fibreglass exhaust tape and epoxy resin. Then when it dried I re-coated it with another layer of epoxy resin. This should be "hella strong" once it is fully dry. Then will sand it off smooth and paint it. One problem I might have is that epoxy resin is said to be highly flammable, and the pipe does come pretty close to the exhaust. But I have the pipes on other Southern Cross manifolds painted with ordinary enamel paint, and they've never shown any signs of being bothered by the heat. Should I put some fibreglass between the exhaust and intake pipe just to be on the safe side?

Inlet manifold is drawing in outside air and a mist of fuel so this helps keep the inlet cool

Not sure what your point is there Norm?

Intake or inlet? It's the manifold pipe that connects the carby with the piston block. Strange how it runs so close to the exhaust, but I can't do anything about that. That is the way it was designed.

In the manual from the 1960s they called it a "carburetor to piston block elbow".

Depends on what part of the world you are from I guess, intake manifold,inlet manifold,carb to block elb same thing

I'd imagine there would need to be a lot o radiant heat hitting it for there to be a chance for it to catch alight and as NormK said, the cold air and fuel mix passing through would have an active cooling effect on the elbow from inside which should have some effect on the resin's temperature. It's almost like a built in cooling system.

Thanks for explaining Mowerfreak. Hence the term "air-cooled engine". This rings true, because even though the intake pipe runs alongside the exhaust you can still put your hand on it after the mower has been running. Unlike the nearby exhaust of course. lol!

The problem is my homemade one runs even closer to the exhaust than the original, and almost touches it at one point. I guess I will just have to keep an eye on it.

Suitable replacement manifolds are hard to find and also hard to make. I spent a lot of time searching online for a replacement. Lots of generic ones out there for go-karts, mopeds, scooters, but nothing that would fit. Also the shapes were completely wrong. Another problem: The connections on the Southern cross are 42mm between hole centres. Most modern ones are 45mm and have wider diameter intakes. The modern ones also have different spacing on the carb mounts to the block mounts. So the only solution was to make one. Took a whole day. A word of caution: epoxy resin is noxious stuff, even if you are wearing a respirator! Work with it outside in the fresh air, not inside in the shed... or house. lol!

hi vint mow
as long as its all air tight it should work ok, just make Shure its not too close to muffler.
I would let the mower run for 10 minutes shut down and see watt happens. that's when your manifold will get to its highest temperature with motor stopped, as heat from the engine block and muffler creep into the manifold no longer cooled from atomised fuel.
maybe jb weld epoxy would have been a better choice as it can with stand highest of engine temperatures ,
good on you for having a go, hope alls good

Thanks freebird. I reckon there is a good chance that it will work. In point of fact I came across a relative today who tells me he made his own manifold for a 2-stroke. He showed it to me - just a couple of old galvanized plumbing fittings threaded together and a bit of rolled tin. lol! Looks rough but the engine starts and runs well.

The epoxy stuff I used is called Pro-weld, which is a close cousin of JB Weld. Maybe not quite as heat tolerant, but I have used it in the past to repair broken heat fins off engine blocks and it has never shown any signs of melting or letting go. Very strong stuff! In one case I rebuilt the entire lost fin out of Pro-weld and 6 months on it is still there. I've also just been told that most epoxy welds are only flammable in the wet state. As soon as they set hard they lose most of their flammability. So when dry it is probably no more flammable than dry engine paint.

Still, I will be watching this manifold closely and maybe try a bit of fibreglass insulation if it looks like overheating. Will let you know if it works. :-)

Put the motor back together with my homemade manifold. Started first pull and runs great.

G'day vint_mow

That is great news and it offers reward to SC engine restorers.

Cheers
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Jack

Thanks Jack, The only problems I had was the original manifold has the connection for the throttle cable on the side, which I could not reproduce, and the original bolts would no longer fit so I had to improvise with some bolts and short lengths of thread. It took a bit of fiddling to find another location for the cable connection in order to push and pull the governor spring correctly. If I ever make another one I will weld a small piece on the side for this purpose. This one was really only a trial. Like always, we learn from our mistakes. :-)

BTW, I'm told the Honda CT-50 and CT-70 have manifold connections which are identical to the Southern Cross mowers, being 20mm ID and about 42mm between the mounting holes (centre to centre).