i was thinking about getting some sort of modification package or something to switch from glow to deisel, but i dont fully understand what it being changed except that the carb and head are being replaced or something like that, what exactly is mechanically different about a glow engine converted to deisel.

Check Davis Diesel
They are dirty and they raise a stinkl

All you do is change the head and use a different fuel. Some people get a different connecting rod and change crank shafts.

um yea, i already checked out davis deisel, didnt answer my question. i mean do you acctually know what is different about the head

The head for a diesel has the ability to adjust the compression of the engine. And of course, there is no provision for a glow or spark plug.

If you've been to Davis Diesel, then you've seen their pictures. The thing sticking out of the head is basically a bolt. Turn it and that changes the compression of the engine.

You have to adjust the compression of a diesel to match the "weather" encountered. You adjust it as well as the needle valve.

The physical differance in many diesel heads is: frequently a contra piston is used. This thin free sliding piston within the head is located directly above the crank piston and is free to slide up and down. The compression screw above the head (can be a knurled nob or a T bar for turning) will push the contra piston down to increase the compression when the adjustment screw is turned in and vice versa.

With a dedicated diesel (not a conversion) the crankcase and head hold down design will be of a bit stouter construction as well as the head itself compared to a glow engine of similar displacement.

John

Besides the mechanical difference, you will want to ask about the fuel difference. These conversions don't just run on straight diesel fuel. You must mix in a percentage of ether or something.

Best wishes,
Dave Olson

Sorry double post

And like outlaw said, they are messy and they stink!

so what ignites the fuel

Compression - The act of compression of any gas produces heat. A diesel produces considerably more compression than a comparable glow engine and that in turn is why a properly designed diesel will have more stoutly constructed upper end.

Also the reason on the first start of the day you must open the compression screw before the first start and adjust. Hitting an overcompressed diesel with a starter will destroy an engine in a flash in exactly the same manner as hitting a hydrolocked glow engine with a starter. Also the reason many diesel flyers prefer hand proping. Once a diesel is properly compressed and needle set will start far easier than any glow engine.

Glow engines actually are considered a semi diesel with a little extra help from a glow plug. That is why you can control the ignition timing of a glow engine with plug heat. A hotter plug will advance the ignition timing BTDC and a colder plug will retard ignition timing.

A hot glow engine if conditions are just right and the state of prime just right subject to many varibles such as engine port design can start accidently with no glow heat attached. Yes I have seen this occur on more than one occasion.

John

is this the way real deisels work in real trucks and everything? i always thought they had soem sort of spark plug

Some automotive diesels use glow plugs for starting in cold weather. Used to mix my own fuel. 1/3 each of kerosene, ether, and castor oil and a few drops of amyl nitrate which is an ignition retarder. Without it you will get the broken crankpins,rods and wrist pins from the timing being to far advanced. If you try it, you still need a very strongly built engine. I tried a diesel head on a Royal 40 quite a few yrs ago. Flew it for about half a gallon of fuel but got tired of the black glop all over the plane. Switched it back to glow but wouldn't run right. Noticed it wet with raw fuel under the engine. Turned it over to check it out and there was a crack in the bottom of the crankcase from front to back. So much for that engine. [&o]
PS If you do try it, you'll need fuel tank fitting and lines made for gasoline as this is a petrolium product.

If you want to learn about model diesel engines there is one book on the subject. Go to http://www.cafes.net/doctordiesel/DDaccessories.htm

> is this the way real deisels work in real trucks and everything? <

Big diesels do not have a contra-piston and model diesels do not have fuel injectors. Quite a big difference there.

The injector in a truck diesel are timed for injection because as soon as it is sprayed into the cyl., it ignites just from the heat of compression. Comp. ratio is much higher than on a model engine and one of the the reasons they have to be built much heavier. The pressure in the cyl after ign. is much higher also.

Great tag line! I might change mine to "Dreamed I was eating a giant marshmallow... woke up and my pillow was gone..."

Isn't this thread more suited to the Engines forums?

Best wishes,
Dave Olson

Just snorted coffee out of my nose and fell out of my chair laughing. That tag line is even better. Be great on a cooking forum. I stole that one from the blond, can't remember her name, on Golden Girls.

it probably is a question more suited for the engine forum but i figured i would get more hits here and i was feeling kinda lazy to find where the engine forum is at, im on this one enough i can scroll right to it.