Can or should the cylinder head be resurfaced with the pre-cups in or out?
My mechinist told me that after resurfacing, they are wanting to fall out or won't stay in now. :evil:
myself , i prefer to have the head ground with a stone , with the precups in place .
then afterwards carefully peen around each precup to hold it in if it gets loose .
From what I know of machining these heads, there are 3 methods:
1) Remove the pre-cups and mill it as you would any traditional aluminum head. Grind (with a sander) the pre-chamber inserts and re-install separately.
2) Put the whole head on a belt sander (NOT recommended)
3) Put the head on a grinder (rotary sanding wheel) with the cups still in.
It depends on what shop you go to as to what they prefer, but options 1 and 3 are probably the best options. Frankly, I prefer option 3, but no-one around here in TN has the proper tools to do it, so I go with option 1
If they try (tried) to MILL the head with the cups still in place, you might as well throw the head away now. The cups are hardened and when you try to mill the head with the cups still in place, the blades rip the cups out since they're too hard to mill. If the blades hit the cups, chances are the cups got yanked out, and did damage to the their recess in the head. Once that happens, you'll never get the cups to stay in there, short of filling (welding) the head, and re-milling it for the cups.
If the shop did this (milled with cups in place), you should be able to get them for a new/replacement head. If they did not know to take the cups out before putting it on a mill (with cutting blades), then they had no business working on your head, or claiming they knew how to. ALL diesel heads with pre-chamber inserts are the same. So, if they're worked on one diesel head, they'd know this.
just to be clear , when i said to have the head "ground " i was refering to a milling machine with a very large stone grinding wheel .
and the precups can be safely left in place when being ground .
a conventional milling machine using a cutting bit will either break when it hits the hardened precup , or gouge the aluminum after it leaves the precup and enters the aluminum .
thus the precups need to be removed , and resurfaced seperately .
( i've seen this done on a magnetic flywheel grinder , all at the same time ) .
also a ground head provides a better finish for the head gasket to seal against .
for any who try a belt sander .... you have just ruined your head .
Can or should the cylinder head be resurfaced with the pre-cups in or out?
My mechinist told me that after resurfacing, they are wanting to fall out or won't stay in now. :evil:
I want to know how he surfaced it!
Here's what happened to my pre-cups 1000 miles after resurface on grinder (pre-cups not removed)
Read more about it here....
http://www.vwdieselparts.com/forum/viewtopic.php?t=7799&highlight=
myself , i prefer to have the head ground with a stone , with the precups in place .
then afterwards carefully peen around each precup to hold it in if it gets loose .
my head guy ground mine,but staked the precups in first
we have a "grinder" and a standard "milling machine"
the grinder is better for reasons others have listed
stake it in a star pattern to clear the wire ring in the head gasket
(5 punch marks with the top point of the star at the whisle side of the prechamber)