Aaz head salvageable? - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• Aaz head salvageable? by oblique on 29 Oct, 2023 19:48
• Just thought id get a second opinion. Precups are perfect, cracks minimal but looks like it had a bad head gasket leak for a while...some of the valleys look quite deep..
  
  
  Also general question: if precups are supposed to protrude past head a few thou how does any head get milled ever?
  
  
  
  
  
  
  
  
  
• #1 by RabbitJockey on 29 Oct, 2023 21:23
• looks salvageable to me. i'd just make sure who ever resurfaces it is familiar with doing aluminum idi heads.
• #2 by RustyCaddy on 29 Oct, 2023 21:35
• The precups can be machined flat when the head is resurfaced but you need to trust that the machinist knows what they are doing.  We are fortunate to have a local shop that takes it into the zone of art and has done possibly hundreds of VW diesel heads; a couple of weeks ago had 4 new precups actually planed down as they were about 10 times above spec when completely seated. Resurfacing runs around $60 USD in these parts so if that is similar for you maybe your local shop could give it a try just to see how the pitting turns out? Shame to scrap a salvageable AAZ head. My $0.02:)
  
  
• #3 by fatmobile on 30 Oct, 2023 01:23
•  I've heard the prechambers are supposed to be removed first.
  
   I've had several heads surfaced that didn't have them removed and still worked fine.
  
  If the cam rocks in the saddles and you have it surfaced,
  the cam will rock when it's bolted down
• #4 by oblique on 30 Oct, 2023 05:39
• My machinist is good but has not done a lot of IDI work. I am pretty much all of his 1.6/AAZ work.
  
  What's the correct procedure to assess then possibly work on it? How would an equipped machine shop remove precups?
  
  1. Check flat
  2. Remove cups
  3. 1st pass plane
  4. Assess?
  
  
  I also have a 1.6Td head with no cracks between valves but absolutely shot precups...not sure how that happened but would love to replace just the cups on it
• #5 by RabbitJockey on 30 Oct, 2023 12:18
• they should should remove the cups and then make the head flat with a good clean surface, then cut the precups the same amount. the precups can protrude a few thousandths, which is good because of the different expansion rates of the aluminum and steel or inconel inserts.
  
  they can also mill the head with the precups in it with a stone/grinder. but they should be very thoughtful with it because the aluminum head is much softer than the inserts, i am no machinist but my understanding is that they run the machine slower to accommodate for the different materials.
  
  in both cases it would be good to cut the valve seats deeper into the head so that they are receded the same as stock, and the machinist may have to also shorten the top of the valve to compensate for the valve sitting higher in the head closer to the lifters. great time to get a 3 angle valve job.
• #6 by oblique on 30 Oct, 2023 17:41
• Hmmm so the valves and cups would have to be moved back by the amount the head is cut.
  
  Question: under ideal timing what is the closest a piston comes to an open valve? Obviously this would be even closer at high rpm where inertia prevents the valve from springing back as fast and then slight variations in cam position.
• #7 by fatmobile on 30 Oct, 2023 20:57
• Since the valve wears the seats, they are probably low enough just by being freshly machined.
  Somewhat common for the valves to need shortened, just 10thou off the top.
   I always put them back together myself, without the valve seals and check the shim clearances,.. so I don't get charged for that work.
   
   It's damn hard for me to get the prechambers out.
   I set a lifter shim on the face of them and smack them a couple times in hopes of loosening them up.
   Then tape them over and fill them with salt to distribute the pressure,
  before putting a rod on the injector hole and hammering them out.
  
  1.5 prechambers will fit most TD heads.
  I haven't tried heating/cooling parts.
  
  They used a stone grinder on one of my heads and a piece of stone popped out,
  maybe because the prechambers were so hard,
  and scratched a gouge across the head, from cylinder to water jacket.
  They had to do it again.
• #8 by oblique on 05 Nov, 2023 15:42
• I am going to toss the head, if anyone is interested i think its about 150 to ship it.
• #9 by fatmobile on 05 Nov, 2023 19:31
•  You going to try to pop the prechambers out and save them?
• #10 by oblique on 07 Nov, 2023 18:49
• Nossir, I've tried to remove precups before and I think I gotn1 out of 8 to come out without me denting it up...because it wasalready loose
• #11 by RustyCaddy on 07 Nov, 2023 21:30
• Please someone take Oblique up on his generous offer!  If i thought i could possibly use this would be on it but have a freshly resurfaced cylinder head on the shelf.
• #12 by oblique on 14 Nov, 2023 22:02
• It's been curbed. Some of those pits were quite deep.
  
  What to do with older carb-only gas heads? I have a rebuilt one thats been sitting for probabaly 30yrs.
• #13 by fatmobile on 15 Nov, 2023 23:18
•  I'd probably put an ad up on the samba or the vortex to get rid of
  something like gasser parts.
   maybe craigslist and hope for something local.
   
   Finding a carbed rabbit with a bad head would be the long path, ha.