After how many miles the heat riser got clogged?

[Ofir]

After how many miles the heat riser in the dual port manifold got clogged?

How often need to remove the manifold and clean/open the heat riser?

Thanks

[Danwvw]

I think they usually clog more over time. Perhaps 10 years! Usually they are good for the first and second rebuild. Kind of depends on gas you use!
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1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

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It also depends on if the engine is burning oil, and/or how rich the jetting is.
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[Ofir]

After I opened and cleaned my heat risers with drill and clutch cable which were completly clogged, how many miles I can expect till it will be clogged again?
It took me hours to remove most of the junk in there, I believe it was never cleaned in the last 40 years!

My engine doesn't burn oil, I used 95 RON fuel.

Now that the heat risers are open and function, what's the difference I'll notice?

[bluebus86]

I got a single port motor and the manifolds are hard to comeby these days. they not only get clogged, but also rust out, then they are shot.

I have driven a lot with the manifold heat raiser totally clogged and cause of my weather condition I have not had icing problems. I imagine in cold climates the problems are worse.

My last manifold on my 1300 motor where clogged and rusted, they had pin holes after cleaning. I got a replacement manifold and cleaned it but noted rust pits on the inside, so I elected to block off the heat raiser with a solid gasket and run without manifold heat, seeing as I never had a problem before with totally clogged manifolds. this way I hope to not have them rust out internally. It was hard enough finding the correct used manifold now, I'd hate to be searching for replacement ten years from now.

I am in preservation mode now.
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[Howard 111]

Ofir, you may not notice any difference. But it's purpose it to help warm the manifold and carb faster on a cold startup.
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[Danwvw]

Bet it gets better gas milage!
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1960 Beetle And 1679cc DP W-100 & Dual Zeniths!