still workin on this 6.9

[JeffMoss1]

Hi guys, still workin' on this engine. Need some help.

Question 1

What the heck is a "pre chamber?" And should I really have been worrying about it falling out when I installed the heads? I came across this in the manual, but I honestly have no idea what that means.

Question 2

I installed the heads and then found these "coolant grommets" that were maybe supposed to fit on the gasket somewhere. Oops. Why do these exist? Do I need them?

Question 3

The heads are on, and I'm looking down into the ports where the injectors go and the surfaces down there look a little cruddy. I'm trying to think of how I could clean them off with out letting the crud fall into...maybe the "pre-chamber???"...or whatever that little hole down there leads to Anyone have any ideas?

~Jeff

 

[JeffMoss1]

Another couple questions I forgot

Should I use some sort of thread sealer on the glow plugs?

What torque should the glow plugs be tightened to?

What do I do if my new injectors fail the pop test, return them?

 

[h2odrx]

Another couple questions I forgot

Should I use some sort of thread sealer on the glow plugs?

What torque should the glow plugs be tightened to?

What do I do if my new injectors fail the pop test, return them?

thread sealer... NO

torque = 12ftlbs

POP test?

 

[Diesel JD]

Its not a bad idea to pop test(pressure test) and check the new injectors for spray pattern, if they fail, try to take them back. No thead sealer on the glow plugs, that torque value is right, but just snug is okay as well. If they are beru they already have some antiseize like compund on them, a little dab of that might be okay on other brands, which are not usually recommended for this application. You may be in trouble if the grommets came out of your head gaskets, but if they are and were separate from the gaskets, you should be alright...maybe somebody knows more. What brand of head gasket? The prechambers have a specification for their protrusion. Falling out or loose prechambers are mentioned in the Haynes manual, but I bet you would notice if they were loose. If they are in spec for protrusion and not visibly looser, they ought to be just fine. If they protrude too much, you will not be able to get a good seal, but I doubt that will be a problem unless your heads were milled. Good luck!,
JD

 

[JeffMoss1]

JD,

I did have the heads resurfaced, but I still don't understand what the prechambers are. I see on the mating surface of the heads: intake valve, exhaust valve, and a little hole right next to them. Is that little hole where the prechamber is?

Anyway, the head gaskets were felpro. Nothing came off the gaskets, I just put them in as they were. Then I found this little baggy of "coolant grommets." Doesn't make sense to me. I wish I took a photo of the gasket before I put it on.

 

[69oiler]

Jeff

the prechamber is that little hole by the valves. if you look closely there is a seperate round disk (around 2" diameter give or take) that has a notch in it, the notch is the hole you see. the disk covers the prechamber and is machined to be flush with the head so it is not obvious when you look at it unless you are looking for the line around the edge of the disk. the firepower comes out thru the hole and pushes the piston down.

the prechamber disk is held in place by the head gasket and block. also it's a tight fit in the head. the disk only sits about half over the cylinder, the other half is squashed between the head and the block. the prechamber is what makes the engine an IDI. the fuel is injected into the head and not directly into the cylinder. that's about as good as i can describe it.

i wish i could remember what i did about coolant grommets when i did my heads. i remember i called Mel and he told me what to do but i dont remember if i ended up putting the gaskets on as is or if i added grommets.

 

[JeffMoss1]

Alright cool...starting to make sense. Maybe I misunderstood how these engines work all along. I always thought IDI injected before in the intake valve instead of directly into the cylinder, so that the intake stroke sucked it in.

But i guess in retrospect, maybe that doesn't make so much sense.

Well at least I'm getting this cleared up for myself now.

~Jeff

 

[Michael Fowler]

On IDI engines there is a spherical chamber ( pre combustion) in the head. here is a small hole that connects the pre chamber with the cylinder. During the compression stroke the piston pushes all of the air in the cylinder into this small sphere, creating a lot of turbulence as it swirls around inside. The air also gets quite hot during this compression. It is at this point that the injector squirts the fuel into this same small space. The air is hot enough that it ignites the air-fuel mix. As it burns, the increased pressure forces the burning mixture out of the precombustion chamber and into the cylinder, forcing the piston down, and eventually turning the wheels in our trucks.

The fuel is NOT injected at the valves, nor the piston, but into the precombustion chamber. It is called pre-combustion because the burning process only starts there. It continues as the moisture is forced out of the precombustion chamber into the cylinder where is burns almost completely.

 

[JeffMoss1]

Thanks for the clarification. I was thinking about it wrong.

 

[Agnem]

Here is a picture to go along with the explaination. The pre-cup is the area below the red painted section.

You must be registered for see images

 

[JeffMoss1]

wow, that picture is awesome.

 

[JeffMoss1]

Does anyone have an injector seat cleaner that I could borrow?

Or know of a good alternative to clean that mating surface down there?

~Jeff

 

[typ4]

Hey Mel ,nice pic. where didja get that head piece. Just kidding, that is exactly the reason I cut it up ,to answer questions for folks.

 

[RLDSL]

Does anyone have an injector seat cleaner that I could borrow?

Or know of a good alternative to clean that mating surface down there?

~Jeff

A shotgun bore brush works nicely for cleaning that up if you can't get ahold of the official tool

--------Robert

 

[JeffMoss1]

A shotgun bore brush works nicely for cleaning that up if you can't get ahold of the official tool

--------Robert

Shotgun bore brush. Cool thanks.

Yesterday though I decided to just take a 5/8 flat endmill to it (just turning it by hand) and a lot of carb cleaner. Got the job done good enough for me. hopefully it doesn't screw stuff up too bad...i don't think it will.

Thanks for the reply.

~Jeff