decking a cylinder head

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rpainter

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Ona 24v head what is the max you can deck the head and still be in cummins specs??
 
My service manual (1998 model year) says not to exceed 1.00mm (0.03937") but it doesn't distinguish between 12 and 24 valve so I'm not sure if its the same for both.
 
depends on what you are doing- mine is @ 40 thousands now-- going to 70 thousands total per motor/cam guy
 
Well the reason why I was asking is a guy called me and wants a aftermarket drop in cam installed in his 24v motor. The head has been decked .018" with the stock head gasket. I was worried about clearance issues before I start the project.
 
jsf350 said:
depends on what you are doing- mine is @ 40 thousands now-- going to 70 thousands total per motor/cam guy
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I'm curious, is there a reason to do this? Since there is no combustion chamber in the head I don't see where you could make a gain :what:

rpainter said:
Well the reason why I was asking is a guy called me and wants a aftermarket drop in cam installed in his 24v motor. The head has been decked .018" with the stock head gasket. I was worried about clearance issues before I start the project.
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As long as he also had the valve seats cut and valve depth reset to stock he should be fine, the adjuster will take care of the depth change.
 
White Knight said:
I'm curious, is there a reason to do this? Since there is no combustion chamber in the head I don't see where you could make a gain :what:



As long as he also had the valve seats cut and valve depth reset to stock he should be fine, the adjuster will take care of the depth change.
Click to expand...

I think Hamilton said something about surfacing the head .080" and letting the valves protrude a bit more than stock. Had to do with air flow IIRC.
 
better low/mid lift airflow and also puts the fuel in the piston bowls better

pistons will have to be reliefed (lower compression)- but decking the head brings the compression back up

per Zach
 
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Cummins won't tell you how much you can take off. They will tell you what the minimum thickness of the head can be. Sometimes there is a machined boss on the upper front or back of the head to use for measuring. In our case, we probably just use the valve cover sealing surface. They have .010" and .020" head gaskets to help out if you have to wack that much off. Valve recess and injector tip protrusion have to stay in spec. as well. It's been 9 years since I left the machine shop so I can't remember the minimum cylinder head thickness, sorry.
 
White Knight said:
I'm curious, is there a reason to do this? Since there is no combustion chamber in the head I don't see where you could make a gain :what:



As long as he also had the valve seats cut and valve depth reset to stock he should be fine, the adjuster will take care of the depth change.
Click to expand...

That is what I am worried about. The machine shop never reset the valves just decked the head and shipped it out.
 
SHughes said:
I think Hamilton said something about surfacing the head .080" and letting the valves protrude a bit more than stock. Had to do with air flow IIRC.
Click to expand...

morkable said:
It also will allow the injector to sit deeper in the bowl.
Click to expand...

jsf350 said:
better low/mid lift airflow and also puts the fuel in the piston bowls better

pistons will have to be reliefed (lower compression)- but decking the head brings the compression back up

per Zach
Click to expand...

Interesting. Thanks

rpainter said:
That is what I am worried about. The machine shop never reset the valves just decked the head and shipped it out.
Click to expand...

You might want to talk to the cam manufacturer, it could be a little tight. When you put in the cam I would check piston-=valve clearance just to be sure
 
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