some head questions

[highest_vision]

First up, the machine shop dude put my heads on the belt sander. IH says no surface work is to be done to the head surface. Am I screwed? I don't know why he did, he couldn't get .004 to go anywhere and they weren't warped.
The heads I took off my truck (I have four) have grooves in a few places where the fire ring ate into the head (this may explain the belt sander and I hate to see what I will find on the deck). My head gaskets were coming apart, so apparently that ring had been moving for some time. I had a known compression leak between cylinders, and this is where one of the grooves is. Any thoughts?
What is the ********* ring in the head gasket kit? Foamish, about 2" OD, maybe 1" ID, 1/2" thick.
Last question is regarding valve stem oil shields. Read a bunch of archival stuff somewhere but didn't really get a definitive answer as to whether or not intake valves get shields.
Thanks
James

 

[aaklingler]

I'd find a new machinist, you don't use a belt sander on heads, they make milling machines or head machines to do that.

Minimum head thickness (from "deck" to valve cover surface): 4.7950"

 

[riphip]

Don't remember the ring seal right off, but the white (nylon) seals go on the exhaust & the dark (viton) go on the intake stems.
The only ring I can think of that would look like that is the CDR to Intake seal. That should be in the Intake set tho.

 

[highest_vision]

He said he stuck them on the belt sander because the prechambers are 'too hard a material to be machined.' Seems to me I have read that before, so it didn't raise an eyebrow. My precups are also cracked a bit, but according to IH are within spec. I think I remember reading only the latest generation of cutting heads can cut precups in-head. I am also NOT a machinist I asked him specifically to check head thickness prior to doing anything, he said he would do that first (after the hot tank, they were nasty )
Thanks Rick, that's what I wanted to hear. Plenty of the shields to go around!
Thanks
James

 

[aaklingler]

You can cut the head with a mill, it's a pain in the ass since the pre cups are harder, but a bet the belt sander didn't do much to the pre cups either.

 

[sle2115]

When we did these heads, we removed the pre-cups, milled the head with a Carbide Cutter-Broach, then reset all the pre-cups to the factory spec by installing them, measuring the seated height, and grinding the face of the pre-cup and a very fine tool grade diamond stone wet stone separate from the head. Having surface ground around 1000 heads in my machine shop career, it would scare me to death to do a head with them installed. If that little carbon puck caught one of these, it would destroy the head and probably the machine.

Also, the old surface grinders used a set of stones. The easiest way to tell if it has been sanded or stoned is to look at the way the grind occurred. Across the surface of the head is stoned, lengthwise is belt sanded. There is a performance shop not to far from me that does the belt sander type surface grinding, not to scare you, but it rarely works well. The problem is that you can grind the surface flat, but sloped to one end or the other. The pressure applied to each end has to be exactly the same, you can't get "exactly" the same by holding it. Our machine, just like most good machine shops, held the head in a fixture which would support many tons of force on the head. The head was leveled and then ground, .001 at a time.