Allis Chalmers HD7 with 3-71

[khyron]

I am currently getting an Allis Chalmers crawler from the mid '50's running. It has a 3-71 2 valve in it and the injectors are stuck in the down position. I see how to get the injectors out (or do i?) but they are not coming out easily. I have moved the rocker out of the way, removed the clamp that holds down the injector, and taken off the fuel lines. I am thinking about tapping it with a piece of wood to "help" it out.
What does the group think about that. I don't see how to get a puller on it.

Thanks in advance
Chris.

 

[NCWayne]

If you've got the fuel lines off, the rocker arms out of the way and the clamp off the back side of the injector that's all you need to do before it comes out. If their stuck I'd first let them soak overnight with PB Blaster or some other penetrating oil. If there's any carbon built up between the barrel and the injector tube (caused by combustion gases leaking by the sealing surface) this will help loosen it up. Also it's not gonna hurt anything to take a wood block and gently tap it back and forth to break the injector loose in the injector tube. If you do this tap side to side using the body of the injector where the lines connect. Another thing when I've run into one that doesn't want to come out easily I've always had luck using a ladys foot/ ladies slipper type pry bar. Simply hook it under the edge of the injector and pry it straight up and out while working it side to side. The injectors stay covered in oil when the engine is running so unless the engine has been setting for awhile and has had water in it they shouldn't be stuck "that tight". Usually burnt oil/carbon from leaking cumbustion gasses is gonna be the worst thing you'll run into. Good luck.

 

[khyron]

Appreciate the quick reply. It has been sitting for a number of years, and is currently in a tractor museum in San Diego.
I will post more when i attempt to start it up.

 

[Chuck Hilton]

Many times you can free up the plungers without removing the injectors. Use penetrating oil then tap and pull on the plunger or possibly a screwdriver between the spring coils. Be sure everything works smoothly before starting though. If you do remove the injectors you will need to reset the fuel rack or engine may not shut down and/or RPM may be uncontrollable. Its best to have a Co2 fire ext handy when starting an unknown Detroit. If RPMs get out of control a shot of Co2 will shut the engine down without doing any further damage.
Chuck