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Old November 6th, 2019, 13:48   #6
Join Date: Nov 2019
Location: Denmark
Fuel Economy: Bad it's chipped and driven hard..

As I said, I am not familiar with the twin cam PD's, but the nut and the tensioner for the rest of the PD's and virtually every other belt driven TDI Might SAY they are TTY, but I don't think so.

Just like the engine mount bolts, that are supposed to be TTY, they are actually 10.8 bolts, which are 1) not that hard and 2) only stretch from intentional abuse...+1/4 turn. We never liked the business of the preload +1/4 turn. That is actually a manufacturing thing, for their convenience, not yours. I have a torque wrench and use it.
These are TTA or Torque To Angle bolts, i have also heard different terminology. Standard bolts being stretched into the plastic zone.
Depending on the safety factor they can be reused, just not officially.
You can't readily measure the stretch, it's too small. But they do stretch.
In my experience the smaller TTA bolts have a smaller safety factor and these break often. But the big ones like the engine mounts will take more of a beating.

I'm not sure if the tensioner stud is actually TTA or VW just prefer to go the safe rute and have the tensioner tightened with a set angle. I think it is.
Either the stud was reused to many times and was too weakened, or the mechanic overtightened it (he used the double spanner technique) but i think it was a combination. The stud over time was allowed a tiny bit of play which started to oscillate and worked the aluminum thread loose, resulting in engine failure.

Bronze guides are finicky. When installed the guide will compress on the O.D. and close up the I.D. It's not just that driving them will cause a distortion, it's the physics of the material. We intentionally make our guides slightly large on the I.D., and have a very close tolerance on the O.D. It must press in, but carefully.
Interesting! The guides i can source are 5,99 mm ID, could this indicate that reaming and honing is expected?

I will not soon forget when Febi stopped using S. Africa and switched to China for guides. Our employee, who had done hundreds of cylinder heads, shoved guides in just like he always did... Broke 5 Cylinder heads... We gave away a lot of heads that week; new ones. And made sure that never happened again. We started making our own guides.
So what happened? Bad tolerances or bronze?

So, measure close, freeze the guides and heat the head. They go in easier that way.
Got it!

Some people think when it comes to head work I have OCD... actually it's CDO... I have to alphabetize it...
During my apprenticeship i was working alongside skilled machinists. I know your type! I don't expect this to be factory quality, but it should be durable.
If i had the time and money i would go the 'OCD way' but i'm short on both However i'm not putting this engine together to have it fail again.

Is pressing in the valve guides even considered possible by DIY? Am i insane?


If this project is hopeless i can buy a new core with premounted guides, source the parts individually and assemble it myself (i guess this is the budget OCD way, sorry i meant C. D. O ). But as i said i'm trying do this on the cheap. Of course a budget is not a budget if the engines dies again ...
tdidk75 is offline   Reply With Quote
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