The Stovebolt Site Forums The Shop Area Engine Shop Heat riser repair

I mistyped the that sentence (oh noes! An error that is clear to anyone NOT trying to simply be contrary!)

I posted PREVIOUSLY that the riser on the CCKW (my truck) is MANUAL, and the setting is either OFF, ON, or BEST GUESS. I even posted a link to the pages that said so.

The THEORY of how the riser should work vs the REALITY of what they do are two separate things. The Handy video clearly shows that at the time they thought two things were happening: one being the intakes on a Siamese port manufold with vastly different running lengths could somehow guarantee 'EQUAL' amounts of fuel charge to the cylinders is laughable. The other that the riser was boiling fuel into vapor. The former is wrong, the latter is somewhat correct, but not for all operating conditions.

And yes, I could see how a heat source could vaporize fuel. That HOW YOU VAPORIZE IT, by raising the temp to the boiling point. But unless you get direct contact with the metal, the air is not in the intake long enough to have any significant rise in temperature. Also, fuel pooling at the bottom of an intake box, with the choke on accelerator pedal down and VERY COLD air (like a cold star on a cold day) is a common problem. But at that time the riser is as cold as the outside air, and there is no chance of any boiling as its not warm enough to do so.

The most significant difference between atomized and vaporized fuel is the size of the fuel droplet. If you take a common hand pump like a bottle of Windex and set the tip to 'spray' you get that cloud of atomized Windex that you can clearly still see, and promptly falls to the floor. The droplets are large and heavy. Vaporized fuel is like steam from a pot of boiling water... light and small.

Of the two, which ones one would be more efficient to burn and transport through a metal tube? The steam as it will not fall out of the air, and also liquid gasoline does not burn, the vapors do. This is most noticeable with diesel fuel. You cannot light raw diesel fuel. You can drop a lit match on the stuff and it will put out the fire. But heat the diesel up till it gives off a vapor and ka-pow! Fire!!!