211 replies to this topic

[bigdaddylee82]

gilber33, on 25 October 2010 - 12:28 PM, said:

What exactly do they all do to the rotating assembly when they balance it?

The main thing will be chucking the crank up in a "fancy machine" that's kind of like a hybrid of a lathe, mill, and tire balancing machine (thats' about as best as I can think of to describe it). The machinist will spin the crank in the machine and it will give a read out of the weight difference along the crank. Based on the machine's readings, the machinist will use the milling/drilling part of the machine to drill out/remove material from the bob weights of the crank, i.e. the fat ends to either side of where the connecting rod attaches. This is assuming, of course, that simply removing material from the bob weights will be enough for balancing, some times weight will have to be added, so a similar procedure will be used to drill a hole in the bob weight, but that hole will be "plugged" with a dense metal plug usually made of Mallory. Other difference when adding weight is that the bob weight will be drilled horizontally, i.e. parallel with the crank.

For the piston/connecting rod assembly each piece will be weighed and material removed from non critical areas until all are within a certain range of one another.

After sleeping on it, would assume that as modern and technologically advanced as these engines are, that they are likely internally balanced. I've never had a Volvo manual trans off, only worked on autos, so I don't know if the flywheels are weighted, and I can't remember seeing weights/alignment marks on the flexplates I've had my hands on. I know that the crank pulleys have balancing holes drilled in them, but I can't remember them having specific alignment marks on them. All this would lead me to believe that both the pulley and flywheel/flexplate are neutral to the rotating assembly, or balanced by themselves. So this makes me think that you wouldn't have to have them to balance the crank.

After having said all of this, if it were my investment, I'd still have the rotating assembly balanced, and use whatever method my experienced machinist recommended.

I'll caveat all of the above with the disclaimer that all of my experience with the subject is from American V8s, SB 400s and 350s have flywheel and crank/dampener weights. My LT1 stroker project's factory balance is internal front external rear, so the rotating assembly is balanced with a neutral crank pulley, and weighted flywheel.

Balancing the rotating assembly at the machinist I've used in the past is ~$125 YMMV.


- Lee

[BlackT5]

[ozzimark]

bigdaddylee82, on 25 October 2010 - 04:53 PM, said:

After sleeping on it, would assume that as modern and technologically advanced as these engines are, that they are likely internally balanced.

They're not.

My personal opinion? Get it balanced. You're doing a performance build, you're gonna be spinning faster than stock, and revving it frequently. For what it involves, it makes no sense not to get it balanced out.

[gdizzle]

Balancing isn't an expensive investment.

[ozzimark]

Exactly. It's like not checking bearing clearances when you put the engine together.

[Volvo5.0]

BlackT5, on 25 October 2010 - 04:07 AM, said:

Crank vents ftw.

I was confused, I had heard them called block vents. Plus it took me all afternoon to figure out the "ftw". I guess I'm getting old lol (laugh out loud....right?)

[Volvo5.0]

Black Betty, on 25 October 2010 - 02:34 AM, said:

FYI, I've used burtonsville Machine shop off old gunpowder for my machining needs. I've never had an assembly balanced but give them a call and they might be able to.

Got everything back from Burtonsville Machine. Wallet is a little lighter but I think it probably was wise to get the balancing done. They also checked the RSI rods and did some minor adjustments to get the clearances where they wanted.

While they had everything I also had them give me all the data I needed to accurately calculate the static CR. It turns out that with the new R pistons and the machine work I had done on the block and head, it will be 8.7:1. If I had used the original pistons from the XC it would have been just under 9.2:1, which probably would have been fine, but the new ones are so purdy ....

[gilber33]

So pretty. How much did the balancing run you if you don't mind me asking?

[Volvo5.0]

gilber33, on 03 November 2010 - 02:05 AM, said:

So pretty. How much did the balancing run you if you don't mind me asking?

It ended up costing a little under $300. It would have been less, but he didn't have the spec for Volvo to know what percentages they use for the bobweight. Bub at Butonsville Machine is a perfectionist and he didn't want to assume that they used 100% of rotating mass and 50% of reciprocating mass for the bobweight. He even called the manufacturer of the balancing equipment and they weren't sure what the spec was, so he asked me to give him 1 old rod and 1 old piston, he used the weights from them to make a bobweight, and spun the crank to verify that it was indeed balanced using 100%/50%. Then he used the weights of the new rods/pistons to make another weight that he used to actually balance the crank.

[gilber33]

Not bad, I would say it was totally worth it then.

[matt b]

Will you clean/prep the outside of the block at all ?

[ozzimark]

gilber33, on 03 November 2010 - 02:49 PM, said:

Not bad, I would say it was totally worth it then.

I was gonna say the same thing. I bet you feel a lot better about having it taken care of now

[gilber33]

bigdaddylee82, on 25 October 2010 - 04:53 PM, said:

The main thing will be chucking the crank up in a "fancy machine" that's kind of like a hybrid of a lathe, mill, and tire balancing machine (thats' about as best as I can think of to describe it).....

Woah, I just noticed that you wrote this. Cool, thanks for explaining it , I kinda figured it was something along those lines, but wasn't 100% sure, then I figured after I posted, I could have just googled it.

[Volvo5.0]

matt b, on 03 November 2010 - 02:55 PM, said:

Will you clean/prep the outside of the block at all ?

Yeah, it looks like hell doesn't it I guess bead blasting must be part of a valve job because the head looks like new. Maybe I should have had it all blasted, but I didn't. I'll clean the bottom end up and throw a coat of engine paint on it unless anyone thinks that would cause problems.

[mdlimy]

Volvo5.0, on 03 November 2010 - 07:04 PM, said:

Yeah, it looks like hell doesn't it I guess bead blasting must be part of a valve job because the head looks like new. Maybe I should have had it all blasted, but I didn't. I'll clean the bottom end up and throw a coat of engine paint on it unless anyone thinks that would cause problems.

just use a high temp paint and a good high temp clear and you should be fine.

[gilber33]

And clean the shit out of it before you paint it. I thought I had cleaned my valve cover extremely well before I painted it, however, the paint peeled right off when I touched it.

[ozzimark]

Volvo5.0, on 03 November 2010 - 07:04 PM, said:

Yeah, it looks like hell doesn't it I guess bead blasting must be part of a valve job because the head looks like new. Maybe I should have had it all blasted, but I didn't. I'll clean the bottom end up and throw a coat of engine paint on it unless anyone thinks that would cause problems.

It probably got a hot dip. Bead blasting an engine part isn't the smartest idea, unless they are VERY careful not to get the media on any internal parts.

[Volvo5.0]

Lots of scrubbing with a small wire brush (some paint also ) and now this....



finally looks like this....

Edited by Volvo5.0, 06 November 2010 - 02:41 AM.

[matt b]

There you go, that's what I'm talking about!

Is this the S70 that will get the ECU I sold you a little while ago ?

[mdlimy]

ozzimark, on 03 November 2010 - 10:53 PM, said:

It probably got a hot dip. Bead blasting an engine part isn't the smartest idea, unless they are VERY careful not to get the media on any internal parts.

hot tank, media blast, hot tank, paint