D4400 Head Flatness spec

I usually use a precision straight edge and .001 feeler gauge. I know this is good and flat.

No daylight under a straight edge works for me.

Well mine appears to have a bit of a hump in it. Sounds like I better just have it flattened. Doing everything else. Thanks.

Mike, I have never considered having the head resurfaced without removing the PC chambers first. I can see that eventually if carried to extremes, the chamber tips might hit the piston, but every piston I have seen has a well under the chamber so I think that is unlikely.

Mike, I have never considered having the head resurfaced without removing the PC chambers first. I can see that eventually if carried to extremes, the chamber tips might hit the piston, but every piston I have seen has a well under the chamber so I think that is unlikely.

The guy here in Australia sent his head off to be reconditioned and apparently the shop tried to remove the precoms before machining but even with heat applied they were unable to get them out, as you know Jim those old precoms can be very tight and when I removed them from my D4400 heads I needed a 4 foot cheater bar to get them loose and the heads were still sitting on the engine blocks, it would be really difficult to get the precoms out with a head just sitting on a bench or on the floor.

My thought is the precom tip takes up space in the combustion chamber at TDC and if it is machined off during a head shave it is possible the compression pressure will be lowered, I remember discussing this with Eddie Bedwell awhile back and he mentioned those valve head protrusion dimensions are fairly critical if you wont to avoid hard starting.
regards
Mike

Mike you are very correct about the valve protrusion specs. It is very critical with a diesel engine. As they recess it lowers compression. That is why there is a spec stated.

Yes I have the old head. Haven't tried removing the PC Chambers but I'll try.