# New Holland Cylinder Head Design



## BradS (Aug 14, 2012)

We just changed the rings and are ready to put the head back on a TC55DA. My friend, who is doing the work, has informed that the "pre-combustion chamber plugs" that are in the head(where the fuel injectors go in) are loose and can pop right out. Before putting the head on he wants to make sure this is normal and the plugs are not suppose to be pressed in. He is used to working on diesel trucks and has never run across this kind of a design. Any help would be appreciated.


----------



## sixbales (May 18, 2011)

I found the following on the internet:

*What is Pre-Combustion?*
The Pre-Combustion system is found mainly on the diesel engines. It uses a classic injection pump, that contains pistons which main function is to push the fuel to the tubing, separate for each engine cylinder, where the fuel enters a nozzle (one for each cylinder) and they pulverized the fuel into the Pre-Combustion Chambers mounted on the engine head. It's on the Chamber where the combustion begins. The combustion comes out as fire from the PreChamber into the cylinder. There are incandescence plugs or heaters mounted on the Pre-Combustion Chambers that heat the air in order to get a better engine ignition.

*Damage caused by Pre-Combustion Chamber wear.*
The Pre-Combustion Chambers in diesel engines suffer extreme changes in their structures, and with time they tend to crack, they sink below the engine's head's surface, and they also get loose. Due to constant air-fuel combustion's they wear, and sometimes they crack, and if they are not change they can damage the engine's block surface. This happens because if they are loose when there is an explosion the PreChamber hit the block's surface, causing damage.

*Abnormal Combustion Due To Crack on the Pre-Combustion Chambers.*
When there is a combustion inside a crack Pre-Combustion Chamber, it sometimes leaks some of the fire from the crack to the cylinder creating abnormal combustion due to Non Uniform Flames.

*Installation of the Pre-Combustion Chamber.*
When Pre-Combustion Chambers are installed they should be above the head's surface, about 0.001" to 0.003", this is necessary to compensate for the head gasket thickness, in order to avoid, damaging it. 

HTH. Your pre-combustion chambers are loose, therefore, they must be changed.


----------



## BradS (Aug 14, 2012)

Thanks for the info


----------

