clogged preheater

[2Dokas]

My intake manifold preheater is clogged. I have never even thought about this happening, but reading the vintage how to rebuild a 36hp I thought I would see if it was clogged and it is. I can get almost to the middle from one side but only about 8" in on the other.

While I intend to get it cleaned out, a thought arose that maybe someone can answer.

If they were both clean and hot exhaust was being pushed into both ~ equally, why would a clog in the middle matter? The hot gas has no escape route and I don't know how cooled gas can be replaced by hot gas under pressure.

I guess the clog on the short side would impact heating the fuel unequally side to side.

anyway, just curious

aways something with me and this engine.

Peter
_________________
87 Doka 2WD Ej22,
56 Convertible

[billb]

"Use this method:
Take an old clutch cable and chuck the threaded end in a drill.
Cut the other end off just long enough so that it will pass all the way through the heat riser tube.
Then slowly feed one end into the tube while the drill is spinning.
It will slowly spin through the carbon until the end pops out the other side.
Has worked for me several times."

from here:
https://www.thesamba.com/vw/forum/viewtopic.php?t=150565&highlight=manifold+cleaning

[Mark Evans]

[Snort]

The way it works is that one side, usually the left side has a pipe that goes inside the muffler and sits in front of the tail pipe outlet. That creates a low pressure on the left side of the heat riser and the exhaust moves from right to left through the heat riser. With any blockage in the heat riser you don't get exhaust flow so you only get conductive heat from the mechanical connection which is not enough to do the job.

There are lots of ideas on how to clean out the heat riser. The one that has worked for me is using 4-5 different lengths of cable on a drill motor and various solvents and lubricants. Start with a short one and change to larger size when you make some progress. Keeping the length of cable that is outside the heat riser short helps prevent kinking. I use a leather glove on my hand to help keep it straight when it's turning. Only run the drill one direction, whichever prevents the end of the cable from unraveling.

[fes]

I've used the cut off cable method and also a sheathed length of aircraft cable in a chuck..I like the aircraft cable because it doesn't fray, only the bit at the end you expose,whereas the donor clutch cable, you only get one shot before it hits it's obstruction,binds and uncoils..
Some times you get one so clogged,that there's no other choice other than drill in a 3/8"hole in the horizontal part of the tube past the bend and knocking out straight through with a rigid piece of rod, then welding the hole back up...
I have a whole shelf of various manifolds that I've been meaning to get at because Repops are junk, and the originals are becoming more valuable every day..
One thing to mention, If the heavy carbon builds up unchecked to the extreme, it can actually rust through into the manifold carb neck itself,essentially rusting from the inside out and causing an internal air leak,try finding that when the car is idling poorly,and you've tried all the methods to find a leak..spraying carb cleaner,starting fluid and even a smoke box wont find it
This condition is rare, but it has happened, best to keep them thar risers clear for a multitude of reasons
Good Luck
-Matt
_________________
'68 Campmobile-Pedro
'15 Golf-Stella Blau
'56 Oval-The Turd (for now)

[catahoula lou]

Here's a link to my approach:

https://www.thesamba.com/vw/forum/viewtopic.php?t=666181&highlight=

Best,
Thom
_________________
1 great wife
2 Catahoula Leopard Dogs (Mahogany Star and Spartan) - RIP Lucy, Braveheart, & Dusty!
1 1959 mango green Ragtop Bug (the "Mango")
1 1958 pantina red Lowlight Ghia (the "Chili Pepper")

Still looking for:
(1) My Dad's 1955 356 (he raced it amateur-class at Riverside and other courses during 1950s),
(2) My parent's black 1955 hardtop bug (CA license plate FWC 201 or FWG 201), and
(3) My parent's agave green 1957 ragtop bug (CA license plate LFK 734).