VW cylinder head machining - increasing compression ratio

Well this guy came to the shop with two VW cylinder heads that he wanted some machining done to. The idea was to remove 2 mm from the combustion chambers in order to raise the compression ratio. Not being a specialized VW shop, or a car engine machine shop for that matter, here's one way to do it:

First, find a a big faceplate for the lathe. Somewhere there's bound to be an old one with a roughly 4" by 4 tpi mount, so make a threaded stub shaft that fits, generously loctite the threads and assemble with a cheater bar and BIG hammer. Machine a slug with a centre hole. Make it so it just fits the cylinder seats, toss the faceplate-on-a-shaft in the three-jaw, pinch the cylinder head against the faceplate with a live centre pressing against the slug inserted in the cylinder seat, bolt it onto the faceplate with suitable fasteners and it should look like this:

Big faceplate with VW cylinder head - iPhone 5s

Remove the tailstock and slug, indicate the cylinder seat and tap it around a bit if you need to, tighten the bolts, mount some scraps to balance the faceplate, and bore 2mm deep. Paint the first bore with a magic marker so you can touch off and set your dials for diameter and depth, then bore to size and depth on all four.

Of course you need to use the slug and centre on all four holes while setting up. It's so much easier when you don't have to fight gravity. Depending on how flat the faceplate is you may also have to use shims. I did not want to add that fuss so I took a skim cut after assembling the stud shaft and faceplate. Next time around though, I might have to shim since I don't want to turn the faceplate into chips. It's only so thick to begin with.

Well the job was a success and I made myself a faceplate that can go in both of the big lathes without removing their chucks. Fun stuff!

iEngineer - handy pocket reference

...because you have your iPhone in your pocket, don't you?

And when you stand there wondering about what the recommended torque for a M12x1,5 grade 10.9 bolt is, whip out your iPhone and start iEngineer:

Start-up screen - iPhone 5s screenshot

And then select your bolt size:

Easy selection of screws - iPhone 5s screenshot

Hey, it even shows the pitch diameter! Nice! But swipe sideways on the top half, and soon you'll see

Ahh, there's the torque - iPhone 5s screenshot 

There! Now just oil the threads, set your wrench to 92 Nm and pull. What are those funny numbers instead of the signal strength bars? Field test mode!

Interesting that a bolt of this size and thread clamps five tons!

I find this app well worth having, packs a lot of useful info into your already crowded iPhone!
Couple this with MechTab if you need more thread data, like if you need to cut a thread in the lathe and don't have dies or taps. Those two apps can really make mechanical work easier.