Vako's AAZ rebuild

[air-cooled or diesel]

according to manual maximum non-flattness of the head when it does not need any resurfacing is 0.1 millimeters and it seems not to hurt camshaft.  it worked like this (deformed from years of service for more than 3 years and 25 000 kilometers) and camshaft (and camshaft bearing in the head) is still as good as new 

I don't mean to be arrogant (im not), but listen to your self; you say 0.1mm is max for resurfacing, you say (unless im wrong or you didn't give correct info) you took 0.18mm off cyl head to make flat/straight, that sounds to me like a whole different ball game??, in any case you've put a lot of money and work into cyl head already,, hope you don't pay for it more,,,

[vako]

according to manual maximum non-flattness of the head when it does not need any resurfacing is 0.1 millimeters and it seems not to hurt camshaft.  it worked like this (deformed from years of service for more than 3 years and 25 000 kilometers) and camshaft (and camshaft bearing in the head) is still as good as new 

I don't mean to be arrogant (im not), but listen to your self; you say 0.1mm is max for resurfacing, you say (unless im wrong or you didn't give correct info) you took 0.18mm off cyl head to make flat/straight, that sounds to me like a whole different ball game??, in any case you've put a lot of money and work into cyl head already,, hope you don't pay for it more,,,

generally if the head is bent only on 0.1 mm-s it's ok to use it again, and it does'nt need any resurfacing. if the deformation is beyond that figure you should scrap the head (on diesel engines), but on petrol engines you can and have to resurface the block if you have deformation 0.06mm-s or more (it seems that cam journals do not deform so hard, because they are way far from head gasket surface), still i do not know why the do not recomend resurfacing on diesels at all (enev at 0.4 mm deformation for example )  in the machine shop when i told about the reccomendations in instruction manual they said that they have resurfaced tons of vw diesel heads and did not have any issues so far, also they told me that even if the head was within 0.1mm deformation specs leaving it that way would probably cause head gasket sealing problems and cost me another set of head bolts and head gasket



today i have disassambled lower end,    rod bearings were original  with VW and audi emblems on them and probably std size, and all the crank surfaces were as good as new  .  main bearing were 0.25mm undersized (according to emblem they were king bearings) and crank surfaces were little bit scored, but still were in good condition.   so i will have my crankd machined  for 0.25 oversizedrod and 0/50 oversized main bearing. i will be using kolbenshmidt bearings for the crank   and clevlite for intermediate shaft.     if everything goes according to my plans i will have crank machined on monday or tuesday + tdi style spocket fitted.


pistons all seem to be originals (i will remove N1  piston tomorrow i have not seen it removed yet), without excessive scoring or wear, so i will reuse them. they have some play in cylinder bores but that will not be a big issue if i use new ring (i will check ring gaps tomorrow and deciide to buy new ones or not) + i will hone cylinders

[Gizmoman]

. . . but on petrol engines you can and have to resurface the block if you have deformation 0.06mm-s or more (it seems that cam journals do not deform so hard, because they are way far from head gasket surface), still i do not know why the do not recomend resurfacing on diesels at all (enev at 0.4 mm deformation for example ) 

I've read of guys machining IDI heads with success. Possibly the reason to not do so is the super hard pre-chambers (which have a tendency to fall out) might loose their fit during the process? A surface grinder would definitely be easier on them as opposed to a fly-cutter on a mill.
As for the cam journals, if the head is warped, they are as well - makes no difference how far they are from the had surface as it's one chunk of aluminum. In other words, it doesn't 'grow" at the ends or "shrink" in the middle - it simply turns into a banana .

If you shaved the head, make sure you check your highest piston against the deck height ("piston protrusion") before you order the gasket There's a good section in the FAQ on this.

[vako]

. . . but on petrol engines you can and have to resurface the block if you have deformation 0.06mm-s or more (it seems that cam journals do not deform so hard, because they are way far from head gasket surface), still i do not know why the do not recomend resurfacing on diesels at all (enev at 0.4 mm deformation for example ) 

I've read of guys machining IDI heads with success. Possibly the reason to not do so is the super hard pre-chambers (which have a tendency to fall out) might loose their fit during the process? A surface grinder would definitely be easier on them as opposed to a fly-cutter on a mill.
As for the cam journals, if the head is warped, they are as well - makes no difference how far they are from the had surface as it's one chunk of aluminum. In other words, it doesn't 'grow" at the ends or "shrink" in the middle - it simply turns into a banana .

If you shaved the head, make sure you check your highest piston against the deck height ("piston protrusion") before you order the gasket There's a good section in the FAQ on this.

thank you for you reply (y)

hea gasket and bearings are the things i have not to order from abroad   after resurfacing (only for removing old gasket parts) i will measure piston protrustion and buy cyl head gasket accordingly  i think machine shop will not work on the weekend so i have to wait for monday ((

[vako]

i'm interested if TDI timing belt spockets vary from year to year? what year/model spocket should i look for (are thore tdi style psocket used in gasoline engines?). i'm planning on buying one tomorrow

[libbydiesel]

You need to get one for an AHU or 1Z.  The ALH sprocket is different. 

[vako]

thanks  already bought the spocket for 13$ today, removed from used engine but in very good condition.



i have another very important question to you guys.

today i took my engine to the engine shop and the mechanic told me that the block is worn too much. it has very noticialble edge on the top of the area where cylinder rings move.   on the first cylinder it cylinder walls were so worn that i am still unable to take out the piston + i have broken 1 ring on 2-nd piston while measuring the ring gap       my crank is also machined to .25 mm on the main bearings.  new pistons cost more than 200$ + honing, boring and resurfacing the block 60-70$, new bearings + crank machining will cost another 70-90$.

for 90$ i am able to buy complete short block for later AAZ (that came with metalic head gasket , maybe is 94 or newer). it doesent have noticiable scoring on cylinder walls, pistons have much less lash in bores and it does'nt have very noticealbe edge on the top of the cylinder bore.  i have not checked the crankt but seller says that it is most likely not machined, and must be in STD specs. the onlu problem is the cause why they disassambled the engine, timing belt had snapped and pistons met the valves.... seller showed me the head and 3 valves were bent there 

will this kind of failure harm the short block? should i stay away from that engine or buy it (after checking the crank and internals for shure)?

if i buy that engine i will probably have to hone it and install old pistons and rings. because even on my old engine most rings were within pecs... 

[Rock3tman]

If some of the valves have hit the pistons, it's possible that some other damage has occured - - like bent
connecting rods.   Measure the piston protrusion very carefully to see if it's the same between all cylinders
when they are at TDC.

[vako]

yes i will check piston protrusion carefully before purchasing . and i will check cylinder bores from top to bottom

i'll be the happiest man if that engine has good crank and bearings, so that i will not have to change or machine them

[vako]

and now the news


today i bought AAZ short block for 90$ cylinder walls still had honing marks on them and crank was in perfect condition for AAz i have never seen siming spocket in such an good condition.    but when i started the teardown, i found out that mainc bearings were changed.... and there was 0.25mm oversized bearing isntalled. n4 main bearing had bearing with oil passage on both sides (it is a good desicion for vw engines as i know. but bad things appeared when i removed the pistons... :| n1 & 4 pistons were in perfect condition, all the rings moving and no scoring at all, but 3 and 2 pistons had some scoring marks on the sides where pistons pin goes in  scoring marks were on cylinders too.  also pistons mentioned above both had first compression ring stuck, on the sides where the scoring was present.

 i knew that easiest & cheapest way of finding oversized pistons was to find the used ones with good rings...        i measured the new pistons, and yes, they were oversized  80mm, every piston except for the third one has rings with perfect gaps.... on third psiton second compression ring has some signs of scoring from cylinder wall, but i can get those rings for dirt cheap


sooo the decision was made to overbore  my old block for the "new pistons" and buy 1 set or new rings for the third cylinder (i'me very tight on budget )


pics coming soon

[vako]

first three pics are of the piston that is scored the most, scored second ring is also seen.
4-5 pics ar of the best pistons , no scoring or wear marks.
last two pics are from the piston damaged less, that has good rings. what do you think? were they worth 90$ , i recieved engine block rods and crank as a bonus

[vako]

another and less expensive option is to deep hone my new block and put these pistons in their own places



this is N3 cylinder bore.


my goal is 30-40 thousand kilometers not more. if i will not have starting issues because of these little scratches on the wall then using this block will be the best 9and the cheapest) option for me :|

[Gizmoman]

Your piston scoring looks very much like mine did. My issue was too much heat on a long steep grade (melts the piston which smears itself on the barrel walls like peanut butter). I was watching water temps as I had no EGT gauge - a very bad decision
Hopefully you already have one, but an EGT sensor and gauge are a must - even on a tight budget.

Good move on the re-bore choice

[CrazyAndy]

It would be better if you over-bored your original block and reused the second engine's pistons; I think deep honing con't get that all out, and even if it did I think you might be at your limit of ring end gap.  If the damage on the piston(s) is not too much then see if some light-grit wet sandpaper helps at least deburr the scratch marks.  If after that they don't move around in the bores excessively, I wouldn't feel too bad about reusing them.  Check them very thoroughly for cracks, though, after giving them an equally thorough cleaning!  Don't forget about measuring the engine connecting rods, have you checked that they are straight after the valves have come into contact with the pistons? Also is this just going to be a mild power build?

[745 turbogreasel]

Also the ring groove has to  still be square, if the ledge is  tapered,  new rings may not help much.
In California,  the parts motor wold almost certainly have been $400, even with the damage disclosed.