Oh ya you will hear them. And like others have said, it will sound like a sewing machine.
An aggressive cam profile (opening valves to max lift quickly and then snapping them shut) generally makes this sewing machine noise more pronounced simply because of the fact that the valve is being accelerated back up into the valve seat at a higher velocity before it hits the seat. This gives it a nice ticking noise that is oh so lovely

 

You know, for the most part my 918s are pretty quiet. I can hear them if I have the hood up and listen. I am running a .563 lift cam and titanium retainers with hardened 7.4" pushrods. Sometimes the noise is a little louder than other times, not sure why. Most of the time when I hear something, its a distinct tapping from the passenger side only, not so much the sewing machine effect.

 

APE heads with 918s and Ti retainers 220/550 114LC,sounds like a sewing machine(buddys denali).If I ever change cams I will go with late yellow LS6 springs.I like quiet.With the small cam I have and blue LS6 springs my valvetrain is completely quiet more so than the stock 5.3 ever was.This maybe due to the heads shaved .020 tighting the preload.

 

Like Ryan said, I think it has more to do with the cam shaft than the springs. However a spring with higher seat pressure coupled with an agressively lobed cam will bring the valves in harder producing a little more noise that a the same cam with a softer spring. On the same note, a stiff spring with a lazy lobed cam could be very quiet.
With that being said.. my FMS cam w/918s has some pretty sugnifficant valve train noise.

 

bigkid what fms cam do you have: mine is the 220/220/114 +4. at times the noise does seem to be louder than others who knows. i will bring the truck back to allen futural and let him look at it and tune it again, then run it tills it blows up.

 

No noise from my 918's.

Mark

 

Allen and I put our heads together and came up with a 214/216 .535/.545 113+4

 

you have to really listen to hear mine
same as above sewing machine sound

 

Mine are no louder than stock.

 

Mine is loud its especially noticable when I pull up next to something. More preload, longer pushrods will quiet it down though you run risk of more wear.

I have a aggressive cam 222/222 .566/566 lingenfelter gt2-5