Hi Guys,

Newbie here, bit long winded so please bear with me 👍

I bought a 2007 A4 3.0 tdi with a snapped cam chain on the left side (cyl 4-6).

I removed the head to find no valves were bent but seats/guides were worn so gave head to cleasbys in Durham. Got head back with 12 new guides and 6 new exhaust valves.

Head refitted with all new genuine Audi head gasket, bolts, all 4 new genuine timing chains, guides and tensioners.

Bought a set of timing pins for this ASB engine and I have access to a genuine Audi workshop manual.

Everything timed up but when I crank the engine over by hand there's no compression in cylinders 4-6, the side I had the head off! I have compression on cylinders 1-3.

With the cams removed I have compression on 4-6.

I started doubting the exhaust camshaft, wondering if the lobes had moved when the original chain snapped (thinking that was why no bent valves) so purchased a 2nd hand one. I didn't actually fit it cos the camshaft was scrap so sent it back. However I put them side by side and the cam lobes looked in identical positions.

My next theory was the camshaft timing. I'd only painted my own timing marks on the cams before removing them so I decided to buy the Jig required to time the cams up (£600!) to be 100% sure, and yep, my cam timing is spot on but still no compression.

Has anyone any idea why I'm having so much hassle? Something I'm overlooking or something I'm not doing correctly?

Started even wondering if the new valves are the correct spec/size!!

Be grateful if someone can put me out of my misery 😀

Thanks for taking the time to read this and for any help.