ScaryFast

Looks like these relevant options for the LS6:

918848 - 25% UD with AC
918847 - 25% UD without
917279 - 10% UD without AC

Do I want 25% UD or the 10% version? Obviously I don't have A/C...

Where's the best place to get one, Jegs?

Scooter70

Jon - Send an e-mail to jcbuncc@gmail.com and ask if he has any blemished units. I just got a 10% UD one for $250 shipped. James is the damper development guy for ATI and sells the blemished ones out the back door and on eBay.

geerookie

You have a few more options but this is the most practical:

918849 - 25% UD with 60% UD AC serpentine pulley for dry sump or Alternator relocate.

You can also get this with a Gilmer drive instead of serpentine.

Yes Jeg's has good prices. That is where I bought the 918849 above.

travisnd

I have the 917279 on my car. Steel hub, aluminum damper shell, 10% underdrive w/o AC. I went with the 10% because for a long time ATI wouldn't make a 25%. Word on the street was that they couldn't achieve the dampening characteristings they wanted out of the smaller damper and they finally started making them because that's what the drag racing crowd demanded. However, I've seen a few road race guys using the 25% one now w/o issue.

96CollectorSport

no need to go 25% too many chain issues with these cars because of bad harmonics. Just stick with the heavier 10% set-up.

geerookie

I would agree with this unless you are running a lightweight clutch. When they were doing testing for the ASA motors GM said the harmonics were within acceptable range with no damper when using a 7.25" clutch and they added the smaller damper for that application.

ScaryFast

What would you know about my clutch?

So with the SPEC clutch I should go 25% UD? Can, or should? I don't need harmonic issues, I've had enough with the LT1 for the last 6 years. BTW, the cause of my problems "back in the day" was a failed ATI damper (in 2008) which cost me a motor. However, that was my stupidity for buying the aluminum hub instead of the steel hub, I do not blame ATI for that, although they should never have offered it as an option...

Anyway, getting the one with the AC pulley allows alternator relocation - not sure if this is necessary yet. I'm going to keep the Caddy location which is very similar to the 'vette.

BTW should I add the LS2 chain immediately? The motor I have only has 15k miles on it.

ScaryFast

Man that sounds dangerous, Eric...blems, not defects? It is the damper, after all...I'd hate for it to be out of balance.

geerookie

Could go with it, not should.
There are many things that can go into the decision about how much under drive.
In my case on track I spend a bunch of my time with the revs between 4.5k and 6.8k so under driving the water pump has benefit since it tends to cavitate when it is spun above 5400rpm. 25% UD is like spinning it up to 5100rpm. But then it does pump less water at lower rpms so you need to make sure that won't cause issues for your use.
It's also a huge benefit no matter what for the power steering.

I run my alternator off the 60% UD AC pulley and have a small pulley on it so it spins perfect rpm.

I'm running a 7.25" QM clutch.

If the rpm issues are not a problem then the 25% UD would work fine with the lighter weight clutch. Big difference between 57lbs and 31lbs.

LS1 chain is an inexpensive insurance policy. I ran my stock '99 LS1 chain for 115k miles with no problems. Of course when I went to replace it I could almost take it off without removing the cam shaft gear

The LS2 chain is a big difference when you compare them.

ScaryFast

While we're at it, confirm this is the correct LS2 timing PN:

CLOYES Part # 94205 Pitch: 3/8 In.; Links: 60

Do I need the sprockets or does the chain work with the LS6 gears?

geerookie

I just used the GMPP chain. Otherwise I believe you need to change the sprockets as well.

PART# 12586482

http://sdparts.com/details/gm-factor...parts/12586482

Scooter70

Blemishes = scratches in the paint finish. Quality is the same as if you paid full price at Summit/Jegs.

travisnd

I just run the OEM LS2/3 chain. It has supersceded the old LS1/6 chain. I use the OEM timing gears. Make sure you use red loctite and torque to spec on the upper gear.

Wish I'd known about a blem option. It's not like they stay pretty over time. They get some surface rust on the bolts etc.

trackboss

FWIW, I have a '99 and when I replaced the timing set I used a cloyes hex-a-just for an ls2 (3 bolt) simply because it was what TPIS had in stock. At the time cloyes still made an ls1 set which had no cam sensors. That cam sprocket had holes all the way around. The chain to me looked identical to a stock ls2 chain. There was no need to replace the sprockets, but since I purchased the kit I chose to install them. I had to make my own crank sprocket puller and installer. If your sprockets are in good shape and you don't want to go through the trouble of replacing the crank sprocket then replacing only the chain should be fine. The one thing that I didn't do, but is a good idea, is to drill the cam sprocket bolt heads (3 bolt) and safety wire them.
I used an ATI standard 10% balancer with the a/c pulley. The a/c pulley just slips over the back. One nice thing about the ATI is its modular so you install the mandrel on the crank and the balancer can go on afterwards. If you need to remove it for some reason it just ubolts and you leave the mandrel on so no need for a puller/installer.
Do yourself a favor and spend the measly $20 to get an arp crank bolt. It's re-usable and you can use a normal style torque wrench rather than the torque to yield factory stuff. Put silicone behind the washer to not only get the proper torque, but also to seal. The ATI mandrel has a keyway in it and the factory crank does not have a key so there is a possiblity that oil can leak through that channel. I pinned mine, but the pin will not seal up the keyway like a proper key.

travisnd

^ Interesting. I used an ARP this go around as well and have the crank pinned. I used ARP's moly lube on the washer and the bolt threads per their instructons. Have never had any issues with oil seeping past the pin on either of the ATIs I've installed.

One nice thing about pinning it and using the ARP bolt is that you can just torque it to some normal value and be done with it. I think I torqued mine to 160 ft/lbs. No need for super human torque values when you're not relying on the interference fit anymore.

I did the following:

1. Install the ATI with a pulley install tool which is basically threaded rod, washers, and a nut.

2. Install the old bolt and torque it to 200 ft/lbs to fully seat it

3. Remove and install the ARP bolt and torque to 160 ft/lbs.

trackboss

I wouldn't recommend using the bolt to seat. You can damage the threads in the crank. Just use a hardened length of M16x2 all thread and a nut/large/heavy washer. Jam two nuts on the end and locktite to hold the rod. I also used a bearing from another install kit to reduce the friction, but greasing the washer will work as an alternative. The arp suggested torque value is well over 200ft.lbs. with their lube.

travisnd

I use the crank pulley install tool to get the balancer installed and seated, but old bolt to 200 ft/lbs afterward to ensure it's fully seated. Not sure how you'd ensure it's 100% seated using the pulley install tool?

As for the ARP torque. The specified torque is for an un-pinned balancer that's still relying on an interference fit. Once you pin it there's no need for the super high torque value.

davidfarmer

I don't know if you are looking at aluminum or steel, but I always ran the lighter aluminum. However, make absolutely sure you pin the crank. Also, torque the attachment bolts properly (that fasten the 2 parts of the damper, not the crank bolt), as over-torqueing them will "lock" the damper and it will vibrate off!

We did this during an emergency camshaft change trackside, and the damper stayed on about 3 laps!

ScaryFast

Why do I need to pin the crank on a basically stock motor?

geerookie

You don't It is for when you run a super charger because that is the drive belt and at higher rpm there is a lot of drag.

Absolutely no need without a super charger but some people do it because.