Flywheel Finish?

[Bill75]

Just received a new GM flywheel for the ZZ4 and was a little suprised at the finish. I was thinking is would have been a very smooth surface but it isn't, I can feel the machining marks when I run my fingernail across the surface.
http://i29.photobucket.com/albums/c251/Bill75/Flywheel.jpg

Is that normal and usable as is. Never had a brand new unused one of these, mine are usually full of microcracks!:eyerole

Also, I was reading some old threads on flywheels..........a mention was made that these engines are balanced with the flywheels in place and changing them might be an issue. Sounds a little strange since a flywheel could be changed at any time but hought I'd ask.

Edit...........Just thinking last night, these things don't come with a flywheel, they have a flexplate, so that has to be a crock!
Thanks

 

[JohnZ]

Just received a new GM flywheel for the ZZ4 and was a little suprised at the finish. I was thinking is would have been a very smooth surface but it isn't, I can feel the machining marks when I run my fingernail across the surface.

That's EXACTLY how it's supposed to look.

 

[Bill75]

That's EXACTLY how it's supposed to look.

Hi John. I was just thinking the surface would have been very smooth as the pressure plate is. This is somewhat like an old record in that you can feel the grooves. Why aren't they ground as smooth as the pressure plate?

Bill

 

[craig32]

If it was too smooth (polished) it wouldn't have much grip, like when brakes get glazed. . .

 

[pws69]

Hi John. I was just thinking the surface would have been very smooth as the pressure plate is. This is somewhat like an old record in that you can feel the grooves. Why aren't they ground as smooth as the pressure plate?

Bill

No - what John said....

 

[JohnZ]

Hi John. I was just thinking the surface would have been very smooth as the pressure plate is. This is somewhat like an old record in that you can feel the grooves. Why aren't they ground as smooth as the pressure plate?

Bill

Here's a typical ($$) steel billet flywheel with the correct non-directional surface finish; the pressure plate surface should look the same.

 

[Bill75]

Ahh Ok, I see what you meant about the finish. I can clealy see the non directional machining and I would understand why it's that way. Mine looks just like a record, as if the face was finished in a lathe, in fact I'm sure it was. If you put his thing on a turntable you could play it like an old 78 record! I'll try to get a better picture.

See if these show it any better.........

http://i29.photobucket.com/albums/c251/Bill75/Flywheel2.jpg

http://i29.photobucket.com/albums/c251/Bill75/Flywheel1.jpg

 

[JohnZ]

Either machining method will provide satisfactory results as long as the surface roughness spec is the same, although non-directional surface grinding is the preferred method for surfacing flywheels and pressure plates (vs. doing it on a lathe).

 

[Bill75]

Well, I guess it's OK then. I like the directiion of the surface grinding on yours better, it makes more sense to me not to do it uniformally in a circle like mine.

As always, Thanks for everyone's input.

Bill