034 ARP Mainstuds and line boring/honing?

[V6quattro]

Hy,

I have a set 034 ARP mainstuds. As said on the 034 site i torqued them down at 65 ft/lbs (audi manual says 48lbs). But when the ware torqued down the clearnesses ware off. So i took the engine to my machine shop and the measured it and said it needs a line hone.

Bud i never read anything about a line hone and ARP's. So do i have a engine made out of chocolate or is this so normal nobody talks about it?

[JP]

It varies from engine to engine. Torque'ing down the caps using a mains girdle can often distort them into oval requiring a line hone. Mainly due to the fact the blocks are not machined 100% true at factory on the sump. So when you pull a girdle over it, it flex's the block resulting in distorted mains.

If an engine has had excessive torque put through it you can also distort the caps. It would be interesting to see if the mains are distorted on your block using stock bolts and stock torque settings.

The reason you don't ever hear anyone saying anything about linehoning is because most people don't realise It's something you have to check, although on most builds It's very rarely out. However a proper engine builder will always check for ovality on all caps to see if it is within tolerance, if not you either machine it true or if cheaper use another block.

Hth JP

[V6quattro]

Just get the block back from the machine shop. The bores ware all .006 mm off. The crank turns very smooth now.

[JP]

You'll notice it revving up much nicer. Especially if it is all 100% balanced.

[terrybullwon]

You'll notice it revving up much nicer. Especially if it is all 100% balanced.

Here here....... Mine revs real nice

[Error404]

even if the tunnel bores are all round is it ever possible that they are not aligned with each other?

[JP]

No not if it is line honed with the correct machine. This is why it is called LINE boring and honing. It's how all the cam journals perfectly align and your mains from factory. As it literally finishes in a perfect straight line.

[Error404]

Thanks JP, so basically what i meant I suppose is if all the tunnel check out ok when measuring for roundness then no real need to have them checked for alignment?

[JP]

Yep use a bore gauge to check roundness. If ovalled line hone. If they are out alignment you will see it in the crank when you polish the journals/balance it. Realistically it is very rare unless the engine had a real big failure although not unknown.

[Error404]

cool thanks for the useful info as always