After 600 miles, I got 2 cracked main caps. What the heck.

[Gizmoman]

I didn't say they broke, I was implying they let loose or stretched a bit more. Guessing is all I am doing. Without knowing exactly how long the bolt was going in and how much it would grow being TTY there is no real way of knowing if they grew a bit or not. I would still love to know which length bolts were installed.

Also, from what I gather the aaz and ahu have the same exact crank, block, and rods. Is your crank hurt or are you thinking that the TDI will be stronger or something?

That's really sad news, especially as you were off on an adventure - such a nice rig too.

Im no expert but I have to agree with theman53. You said you rebuilt it (I think). Did you install new bolts or use the originals? As TTY or stretch bolts, that generally means one time use. If that were the case, they simply gave in and stretched more (without breaking). The resulting gap allowed the crank journals to smack the cap like a hammer and bingo.

If you know they were new and you torqued them properly, then I have no idea.

[410]

Man, I just noticed how long your main cap bolts are!  Obviously mine were the short ones in comparison but I wonder if the bolts had bottomed out in their holes?  

[TonyTDTruck]

I didn't say they broke, I was implying they let loose or stretched a bit more. Guessing is all I am doing. Without knowing exactly how long the bolt was going in and how much it would grow being TTY there is no real way of knowing if they grew a bit or not. I would still love to know which length bolts were installed.

Also, from what I gather the aaz and ahu have the same exact crank, block, and rods. Is your crank hurt or are you thinking that the TDI will be stronger or something?

I just measured the bolts and they are 80mm long. Not sure if they bottomed out 410.
It's possible that the crank is busted. I'm just trying to stay ahead of the game in case it is. I was told that the crank could have been damaged in the process.
I just got a hold of a guy who has a TDI crank and main caps.
410 Is it true that a TDI crank will work on an AAZ? I had my AAZ crank notched to fit the TDI pulley.

Gizmoman they were new botls. Did I torque them properly? I hope.
 

[410]

The tdi crank will work in the aaz.  It just has a reluctor ring on it.  I would be a little nervous putting money into that block though.  It might have been a blessing that both my blocks scattered. 

[Gizmoman]

I've no doubt you torqued them properly.

410, Would there be a feasible way he could check the block before scrapping it?

[410]

I've no doubt you torqued them properly.

410, Would there be a feasible way he could check the block before scrapping it?

If it has to get line bored, I'm sure the machinist can make the call.  Other than a really good visual check there's not much you can do imo.

[CRSMP5]

 cannot you use 1.6 main caps?? lots of them vs 1.9...

[theman53]

Yes, They would have to be lined bored as well, but I had a pic of a 1.9 crank in a 1.6 block. I think that means they share the same size journals.

BTW, I wasn't thinking when I posted about the AAZ and AHU crank. I was more meaning the forging and sizes are the same, but yes the AHU would have the D and the ring for the crank sensor.

[Jetmugg]

Here's the thing about any TTY bolt - once they are properly torqued the first time (generally at the factory), there is no way to "torque" them properly again.  When they are installed the first time, they are permanently deformed (lengthened) by stressing them above the yield point of the material.  This is by design. 

You cannot "yield" them again safely.  It's a one-time deal.  If you somehow manage to get above the yield point again, but don't break the bolts, then the load on the fastener will not be correct.

If you tighten them again, but don't exceed the yield point, then you will not have enough clamping pressure.

From my view (I'm a metallurgical engineer by day), the only correct solutions are to buy brand-new TTY bolts and torque them per the manufacturer's specification, or install conventional bolts or studs which are not intended to be taken above the yield point.

That's for future reference.

For now, if you manage to save the block, you are indeed lucky.  Take the whole thing to a good machine shop, have them check the crank, check the block for cracks, then take a seat to brace yourself for the machining bill for them to fit new main caps, line bore/hone them, install ARP studs, grind the crank if necessary, and get back on the mend.

Steve.

[RabbitJockey]

should he take a seat or find a second job

[TonyTDTruck]

should he take a seat or find a second job

I'm actually laying down on the garage floor. After all of this, with a TDI crank, ARP head bolts, ARP crank bolts, all new bearings, new ported cylinder head, Giles pump, complete rebuild. What would this engine be worth?
I'm wondering if it would be a better idea to go with a TDI engine. Call me stupid but what are your thoughts?

[theman53]

My machinist would only charge about 100.00 to do the line bore. 100-130 he said. No way would I do the swap to tdi if that is all you had with some gaskets and such. Now if it was anywhere close to the cost of a TDI swap then yes I would do it that way.

The way I see it this is a perfect opportunity to get some Billet steel chunks and have them rough milled down then your machinist finish them. Since you are basically starting from scratch and you need these pieces why not upgrade. I would ask Jetmugg what would be the ideal tool steel chunk of billet to make it from, but after you do that it should be bullet proof. Some alloys take vibration better than others. Too hard I know is bad as well as they are brittle. I would guess you would have less than 500.00 in getting it back on the road. Forged would be better but finding a forging close would be the problem there.

From what I have seen in the casting world I would bet that VW had some issues with ductile iron getting a bit close to the 7 minute mark on these main caps. Somewhere around there it turns from ductile to grey and had less vibration resistance and strength...from what my casting guys have told me anyhow.

[Jetmugg]

What Theman is referring to is ductile iron "fade".  The potency of inoculants used in the ductile iron processing decrease with time.  It's important to pour ductile iron within a certain amount of time after the iron is inoculated.  That time varies based on the quantity of iron, temperature, etc.  However, as he referred to, 7 minutes is probably too long.

Billet steel caps would have a very high cool factor.  Something like a 4340 alloy, which is fairly common, would offer somewhere in the neighborhood of 4 times the strength of an equivalently sized ductile iron cap.

Anything more exotic than 4340 is probably just spending money that wouldn't be necessary.

The factory main caps are probably more than adequate with the correct fasteners.  For an added level of security, a bottom end girdle could be added to spread the load around.

On some engines, it's relatively common to mill the bottom of the main caps flat, then use a bar of something like 4340 to add support to the individual main caps.  I'm not saying that it's common to VW diesels, but it's certainly possible.

Steve. 

[theman53]

I like the idea of adding the tool steel to the cap. Around the front and rear main it might be an issue to keep it all stock, but since he needs it all I figure why not. 4340 is fairly attainable and not completely unreasonable to machine, especially if you are talking about 5 caps. That is what I would do. I figured you, Jetmugg, would be better suited to give out a tool steel grade than I as I am just a salesman and dabble in it. You deal with it for real LOL.

[hillfolk'r]

Huh, didn't know they were TTY.
ARP studs anyone?

Raceware makes studs. Im runnin em in my ahu.
I dont know if arp does.  I think they said if you use studs you want to check your clearances again to be safe