Itinerant Air-Cooled

I have discovered my manifold preheat tube or pipe is clogged so I want to clean it out. Any amazing tricks? This is for the single port 1600 on my ghia which has the stock single port manifold with preheat pipe coming off the muffler to heat the intake manifold.

It's frequently said that a piece of steel stranded cable spun in a drill motor, with the business end splayed out a bit, makes for a good reaming tool.
I've found that repeated tapping/banging on the pipe with a big rubber/plastic mallet will cause a steady rain of rust/carbon chips to drop out the ends,
and worked better for me than the cable-reaming technique. Do not be surprised if holes appear in the preheat pipe, as clogged pipes are usually
clogged mostly with rust, and many are rusted nearly all the way through.

How clogged is it? With carb cleaner or water dripped in one side over night, will it run out the the other if you leave it propped up accordingly?

If so, you can get lucky cutting up an old clutch cable into 4, 6, 8, 12, and 16" sections and running bits through in a drill. Make sure the drill is on "reverse" as you'l quickly unwind the cable otherwise. Once a cable goes through, mangle the end of it so it grabs more carbon on the next pass.

From there, I usually take mine to the local sandblast shop and have them blast it from each side for a few seconds. Too long and they'll blow a hole in it though, so I usually take a trash manifold with me to have them practice on first.

There is also the oxy-acetelene trick where you fill it with gas and light the torch to blow the chunks out, but I've never seen it done in person…

Good luck!
Robbie

i went through all robbies suggestions except for the sandblasting.
All that and it was still supper clogged, i couldn't get any air through it. I must have spent 3 - 4days working on it.
I ended up having to drill a hole on the side of one of the tubes so i could drill horizontally through the blockage. Brazed it up and all is well.

Advice I had with my 2 stroke motorbikes in the UK was to use caustic soda to dissolve the carbon. I never did try it - would that work?

tommu wrote: ↑

Wed Nov 29, 2017 11:35 am

Advice I had with my 2 stroke motorbikes in the UK was to use caustic soda to dissolve the carbon. I never did try it - would that work?

I would not use caustic soda.It can dissolve the alloy sandwich that holds the heat riser to the intake manifold.
Colin

Any more discussion of the oxy-acetlyene method would be appreciated. My guess would be that a VERY large percentage of heat risers on single carb type 1 engines are plugged. It was a normal needed fix clear back in the 1960's.

69doublecab wrote: ↑

Sun Nov 15, 2020 1:42 pm

Any more discussion of the oxy-acetlyene method would be appreciated. My guess would be that a VERY large percentage of heat risers on single carb type 1 engines are plugged. It was a normal needed fix clear back in the 1960's.

Air flow-through is what allows oxy-acetylene to clean through. A blocked riser dams up the heat at the blockage.
Colin