Intake manifold heat rise clogged with carbon

[Frenchy Dehoux]

   For those of you buiding stock VW engines such as 36 HP 40 HP and 1600 CC engine we know that there is an issue with the carbon build up in the heat riser area of the intake manifold what are you doing to unclogged this area are you using acid or blasting it until it is open from one end to the other. Or what are you doing to clean this area out let me know.


Thanks
Frenchy

[drumbum68]

Chuck a length of  old clutch cable in a drill. Flexable reamer made  long enough to get to the center from both ends.

[Rocket-Racing]

Another tip concerning the same issues.
People have a tendency to forget that the heat riser gaskets are supposed to have a large hole on one side (same size as the hole in the intake/exhaust) and a smaller hole on the other side. Most of the exhaust gasket sets sold nowadays have the large hole in both gaskets.. To work properly it really needs to have a smaller hole on one side to get the warm air moving from one side to the other. Big difference.

[karl h]

you can carefully use a torch to burn the carbon out...Careful!!!

[Martin S.]

Another tip concerning the same issues.
People have a tendency to forget that the heat riser gaskets are supposed to have a large hole on one side (same size as the hole in the intake/exhaust) and a smaller hole on the other side. Most of the exhaust gasket sets sold nowadays have the large hole in both gaskets.. To work properly it really needs to have a smaller hole on one side to get the warm air moving from one side to the other. Big difference.

I thought that the small hole gasket was used when you wanted to limit the pre heat in warmer climates. VW recommended blocking off the preheat when not needed as a hot manifold decreases performance.

[Rocket-Racing]

I thought that the small hole gasket was used when you wanted to limit the pre heat in warmer climates. VW recommended blocking off the preheat when not needed as a hot manifold decreases performance.

I hear what you're saying and it almost makes sense. But having the same size hole in both makes the air stand almost still and not move from one side to the other.
I just tried.. And you really need the heat risers in most climates. At least here in Norway with a summer temperature of about 20 degrees celsius, blocking the heat risers will instantly get you a soaking wet intake manifold from the carb downwards and a bogging and coffing engine.. It's not so much the outside air that is cold but the vacum in the intake that makes the air on the inside of the intake a lot colder than the one on the outside (that is, in a warm engine bay) and condensation is bound to happen if the intake is not heated..
Of course this is not a problem on "ordinary" engines or when using dual carbs as the intake will be mounted on a warm part of the engine and get the needed heat there.

[Doktor]

you can carefully use a torch to burn the carbon out...Careful!!!

That really works !
I have done it that way...

[56BLITZ]

a summer temperature of about 20 degrees celsius

 Frenchy doesn't get to enjoy that very often! 

[Frenchy Dehoux]

     I am building a 1600 CC engine for an early bus going to Switzerland wanted to make sure that this intake manifold has the heat riser working properly before it leave my garage after all my name is on that engine.


Thanks for all responses
Frenchy

[JamieL]

I think a stock exhaust is the key, regardless of gasket hole size - the plumbing is set to come straight out the exhaust port and into the preheat pipe on the 1/2 side and then the 3/4 side flows through to the collector. There should be a pressure drop between the two areas thereby creating the "flow" that you need...