Bore and crank dimensions - AAZ rebuild

[Gizmoman]

I am very slowly getting through my AAZ rebuild.
I spent all morning getting the dimensions on the bores and crank journals and am posting a snapshot of the spreadsheet -  take a look and let me know your thoughts.
I hope it posts OK (so it is readable).
I used the Bentley extensively.
Something you may notice is that a few spots in the bores are actually "under" stock dimensions.
Trust me, I checked my mic to the standard in the box and it is under by .0005". I took this into account in my numbers.

My hope is that I don't need to bore the block or grind the crank. Not because I can't afford to but if it's within spec, why take a chance on a machine shop possibly messing things up instead of improving them .

Also, this is the third thread I have started related to this motor. I don't want to break the rules and am not sure if starting a new thread is proper but during the build I have veered off topic (started with a blown head gasket ("I thought"). I could keep the old thread going with updates - if that is preferred by the moderators.

Let me know what you think of the numbers. The #4 piston is shot but the rest may be OK - I have to mic them yet though. Defiantly will need new rings and a hone of all four barrels as they are all quite polished. However, before my mis-hap, the motor used zero oil.

I hope this screenshot is readable 

[theman53]

I forget the amount of taper but if it is within that I would say that the #s look in spec. for the bore diameters. You must have a fairly fresh engine as all of the ones I went through have way too much taper and wear to be able to hone and ring. Good luck sir.

[Gizmoman]

Thanks for the quick feedback.
Not having all the info from the original owner all I can do is guess. . .
I think he started out with a great concept - to build a Westy with a bio-fuel/diesel set-up that had more power than the stock NA 1.6. The block may very well have been new (not sure where he may have found one though). He fabricated a huge custom aluminum bio-fuel tank, custom heaters, dual filters, dual pumps, heated fuel lines, relays, etc, etc. He did a pretty tidy job considering, but there was a few issues with the bio-fuel and I think he just gave up. He sold it to a dealer/friend and I found it on the web for sale.

I never used the bio side and still need to drain the tank and remove all the stuff. The van was in Northern CA and Bio is available there in many stations - not so much here in San Diego. Maybe someone here will want all the bio stuff after I remove it

The thing would still be running if I had only listened to someone on this site (maybe you) who highly recommended I install an EGT sensor and gauge. You see, I upped the turbo to 15 psi and added some fuel with the screw - nuf said - I sorta melted #4.

I'm having a tough time finding every part I need to get the rebuild done correctly. So far I have most of it listed on another spreadsheet and there are over six different resources so far . I read on a thread in here that Giles was in the VW parts business as well. I may just send my list to him (along with my 1.6 pump ).

Thanks again for you input - makes me feel better about not boring the block. I think the crank is fine as well (except I am definitely taking your advice on the "D" sprocket machining)

[libbydiesel]

Like I said in your other thread, I think your piston melted from having the valve leak out the boost air resulting in an over-fueled situation with piston melting temps.  Unfortunately if it's an exhaust valve leaking, an EGT will still register normal in this situation because the leaked air cools the exhaust stream resulting in normal or even low EGTs.

15 psi will result in cooler temps than stock boost of 9 or 10.  Upping the fuel a little didn't melt that piston unless you were seeing a fair bit of smoke.

[Gizmoman]

Like I said in your other thread, I think your piston melted from having the valve leak out the boost air resulting in an over-fueled situation with piston melting temps.  Unfortunately if it's an exhaust valve leaking, an EGT will still register normal in this situation because the leaked air cools the exhaust stream resulting in normal or even low EGTs.

15 psi will result in cooler temps than stock boost of 9 or 10.  Upping the fuel a little didn't melt that piston unless you were seeing a fair bit of smoke.

I didn't see smoke during the long climb but to be honest, I wasn't looking for it.
I have been reading the FAQ and chasing threads on this site for hours and hours trying to get a "feel" for this motor and it's quirky nuances. I really want this re-build to be strong and dependable - now I'm having serious doubts that it's even possible. From what you are saying, I can burn a piston because the gate on the turbo is leaking?(if that is the "valve you are referring to). That installing an EGT won't tell me that anything is happening? -man that really has me worried. I took the valve out and the seat was coked up but nothing like others I have seen.
I removed all the carbon from the port seat and did the polish thing that was suggested in the FAQ. However, I don't think it's going to seal perfectly as the surface is pitted a bit. I had it set up in my mill and was going to try a spot-face but decided the casting was too hard and I may just mess it up. The bevel of the valve is 22.5 degrees BTW.

The rod on the valve was sticky when I pushed it in - could this be part of the issue? Pushing it an while turning the valve seems to have freed it up nicely. If what you say is true, having to rebuild this motor because the valve on the turbo leaked boost is pretty crappy design don't you think? Any suggestion as to how to make this not happen again? From what I have read, this is a pretty good turbo for my application - maybe I should switch to a VNT? I will be adding an intercooler from Frozen Boost and an external oil cooler as well but that's just an expensive band-aid if I have a leaky valve.

OK, I found your post from the previous thread - sorry I misread your meaning of "valve" and just started rambling on about the waste-gate

Another possibility is that the exhaust or intake valve on that cylinder leaked and let out the boost air.  The resulting over-fueled situation got the piston too hot and it started to melt.  That would be pretty easy to check.  Tip the head on it's side with the ports up and pour/spray some solvent in there.  If it leaks out on the combustion face, your valves were leaking.  Any impressions on the piston tops?

You were talking about an intake valve leaking and I didn't find that to be the case after doing the "leak-test" you suggested. I did find quite a bit of burnt crud on all the intake ports though which I still don't understand - as it makes me think all the intake valves were "leaking". Is this possible? - Possibly a timing issue?

I my have mentioned this in one of my earlier posts - when I took off the intake manifold, every bolt was just slightly over finger tight. This could certainly "dump" boost and prevent it from providing the cooling effect you mention.

What do you think of the numbers from the engine and crank? If this was yours, would you bore and grind?

[Gizmoman]

I forget the amount of taper but if it is within that I would say that the #s look in spec. for the bore diameters. You must have a fairly fresh engine as all of the ones I went through have way too much taper and wear to be able to hone and ring. Good luck sir.

Is there a "taper spec" in the Bentley or is it somewhere else (possibly posted in here somewhere)? I'd like to check it again.

[theman53]

There is a spec somewhere that says if the cylinder is tapered so far then it should be rebuilt. I don't know what it is though.