Balancing the bottom end... how far would I have to go?

[Ross]

Been doing some thinking and researching recently on how to 'make peace' with the avant. I want to achieve what I'd set out in my mind a few years back, but with a toned down approach.

Other than the alloy refurb/replace and drone-free exhaust I've been banging on about, I want to get the bottom end balanced. I need to replace a very rattly clutch release bearing, so the engine is going to come out for that. I miss the smooth and responsive engine I had previous, I have fitted a zero-balanced 3B flywheel but it's not quite as smooth as i know it could and should be. If it was a high-miler I'd be sold on the 'replace everything and rebuild' but at 95,000 she's only just broken in!

So what would be neccesary to replace? It runs well with no oil use so I'm reluctant to strip it down and do everything... save that for 150k miles in about 5 or so years! Effectively I just want to pull the rotating parts out, take them down to BDB and re-fit. If I have to take the head off I'll do ARPs and a new HG of course, but is it worth doing valve guides at this mileage? I'm not wanting to 'short cut' but as it running well and using no oil at present I'm hoping to keep it simple and have enough funds to fit an RS2 EM in the process.

My goal is RS2/hybrid, 350hp/600NM so I plan on sticking with stock rods, although that is a temptation.

Ross

[A80Avant]

oh no.. ross getting back in the game?

[mcandmar]

Oh dear, thats a bit like opening pandoras box. In order to balance the crank you have to remove everything and send it to Philip, crank, rods, pistons the lot. Once dismantled you will need new gaskets, rings, bearings, and bolts to put it all back together. And to do that properly you will need a quick skim and hone done on the block. Unfortunately its a full rebuild or leave it alone, there is no half way point.

[knobstar]

JP gives a great explanation of what he's done here: http://www.s2forum.com/forum/showthread.php?t=43652

[JP]

Your lack of smoothness comes from the fact you have fitted a zero balanced flywheel to an externally balanced crank assembly that uses the flywheel as part of the balance. Unless you internally balance the crank you can't just add a flywheel that's zero balanced and expect to get away with it. Saying that manufacturers standards are so loose that 90% of the time you can, it just will miss that little edge that you are seeking.

Anyway as mcandmar says it is pretty much a full rebuild at that point unless you leave it alone.

[A80Avant]

i was going to say, good info that, as i did something similar by fitting a 7A flywheel non balanced to my crank specifically, but used it as it is. Is that any different than zero balancing?

unfortunatelly in Greece there is noone that can balance a 5cyl crank.

[JP]

i was going to say, good info that, as i did something similar by fitting a 7A flywheel non balanced to my crank specifically, but used it as it is. Is that any different than zero balancing?

unfortunatelly in Greece there is noone that can balance a 5cyl crank.

Not really but probably a higher chance in the law of averages to being more suited. As for balancing, V6 RS4 crank assembly rods and pistons flywheel etc from Italy to UK and back worked out at approx 100Euros. Something to keep in mind if you are doing a full on build.

[Ross]

Vas it feels a bit like throwing myself 'back in the game' but more about refinement than power. My most fun to drive S2 was my coupe after the engine had been rebuilt, 1.5bar map on the K24; the GT3071 was amazing but not a path I'd go down now.

I did fear it would be an 'all or nothing' approach. Was hoping perhaps I could avoid having to fully strip the block and just replace gaskets, belts and bearings. My other option is to refit the dual-mass flywheel and leave the engine well alone! But, the coupe felt transformed after a rebuild... gives me something to think about. I just have to decide how important the 3B flywheel and a smoother engine are to me.

Mark - it does help that Philip's workshop is on the other side of Swindon, I guess the convenience of that aids temptation! He was 1st class when he balanced my coupe internals.

Cheers for the comments.

[Jamo]

Ross if you go this route buy a separate ABY block and have it built and balanced at your leisure, you can then do a swap when your ready.

For you go Rs2 or K26/K27 and keep it simple

[Ross]

Ross if you go this route buy a separate ABY block and have it built and balanced at your leisure, you can then do a swap when your ready.

For you go Rs2 or K26/K27 and keep it simple

That is something to consider. Was trying not to add to the hassle by sourcing parts I already have but it would of course save hassle in other areas... just weighing up the options regarding the engine at present but for turbo it's either Sonic's hybrid (only concern is mapping - need to see what Paul can do) or RS2. Would prefer the hybrid.

[Acidburn]

out of interest what bits do I need to take for balancing when I do mine soon. Got a rough idea but want to check 100%

[mcandmar]

out of interest what bits do I need to take for balancing when I do mine soon. Got a rough idea but want to check 100%

Everything. Pistons, rings, pins, clips, rods, bearing shells, crank, flywheel, pressure plate, front pulley, and all the nuts and bolts that hold them together.

AFAIK the process starts with matching the piston weights, then the rods are matched end to end. Rings, pins, clips, and bearings are needed so he can calculate the bob weights to attach to each crank throw. Then front pulley and flywheel are bolted to the crank to balance the rotating mass. Adding the clutch pressure plate is optional.

[jogi730]

oh no.. ross getting back in the game?

Hey Ross,
I understand fully. You were so close to getting your car to exactly where you wanted it and your dreams were shattered by an 'expert'.
I'm so glad the spark has been reignited and hope you get things to where you want to be in the near future.
Good luck.
Chris

[Sonic]

Do it Ross!

Sounds like a lot of work to get the bottom end rebuilt though, certainly with the mileage, maybe it if had 150k like mine you'd possible consider it, but 90k...

[Jamo]

I agree sonic that why it would be buy a seperate new bottom end for me, for the money it would cost to buy it would save in hassle of having the car off the road and the timescaling of the project.

When mine was done swapping ( with the help of a few forum members ) was done in a weekend there wouldn't have been downtime if I hadn't had to do a few other things