TurboJew

So here's where I stand with my S4 refresh. I am at a crossroads. I have the front subframe off the car to replace the front subframe bushings and all the other rubber down there and to be able to access the oil pan and replace piston rings. The quesiton is, do I replace the rings? I'm gun shy when it comes to taking apart the rotating assembly of my motor. This whole process started due to a smoking/low compression issue. The original cylinder head is cracked to hell on all 5 cyls and will be replaced with a head from 034efi. Looking at the cylinder bores, the bores look damn near perfect with no noticeable ridge at the top of the cylinder. What would you do in my situation?

Bill the Cat

But - But - But...

I argued with myself on this one. (It's much easier on someone else's engine.)

You are this far - the cost of rings and bearings is not that great - and - although a little time consuming - not difficult to do. (Plastigauge your bearings before ordering new - but you will probably need std bearings. REALLY clean the lands of your piston grooves out.)

Why not zero out the age of the engine? Eh?

The 'rotating assembly' is not that bad a thing to get into - easier than a (this one, at least) head R&R.

Ring it!

HTH!

TurboJew

Relative to how skittish I'm gonna be about pushing this thing after its back together. Is that extra few percent of improvement worth it? I dont know. The bores look good from my inspection and the severity of the head cracks lead me to believe that was the real cause of the bad compression. Plus, my bankroll is being severely stressed by this whole thing.

Bill the Cat

As you are supplying the labor...

(I'll loan you my cyl hone. You do your own ridge reamer.)

TurboJew

but this would be my first bottom end work on a motor that i intend to reassemble. I've torn apart stuff before but nothing of value like this. GAHHHH!!!! I'm gonna go finish replacing the motor/trans mounts and think it over... When all is said and done at the very least the car will have:

-New motor mounts
-New trans mounts
-New subframe bushings
-Replaced/rebuilt cylinder head (7A modded to AAN specs)
-RS2 exhaust manifold

The rest of the front suspension (control arms, swaybar bushings, etc...) was done a bit over a year ago at a garage.

Bill the Cat

Really - the bottom end is actually simple.

Like I said - plastigauge every bearing - all in specs? (they will be - but check anyway) Cool - replace all bearings with stock.

And plastigauge again with the new bearings - Time consuming - but you will sleep the sleep of the just.

Ridge reaming is not difficult - just time consuming.

And clean those ring groove lands. Break your old rings into pieces - an use 'em to scrape every bit of crud out of the grooves.

You will have a zero time engine.

Pistons ( as opposed to pist - offs - sorry - BMW MC boxer engine humor) - pins - and rods last forever- barring other calamity.

es-car-go

Don't cut any corners if you open the bottom end. And do all the steps Bill The Cat mentioned.
If you're running out of money, get more money.

It's tough to coach Turbojew on engine rebuild via email, but he seems careful and patient about it. Keep everything very clean when you reassemble.
The plastigauge steps tell you the tolerances are maintained to Audi spec.

Keep going.
Posto

Bill the Cat

And you will end up with a (worlds first?) Kosher AAN.

S4-Fireblade

2nd, and I should had done it too!

TurboJew

How's your compression after the head rebuild?