If you replace the stock balancer unit with an ATI Superdamper you'll find that it is a bit larger in diameter. The stock belt won't fit. Go to your local auto parts store and grab a 68" Gates Micro-V belt. It will JUST fit (I consider it a perfect fit).

Reference this to a 1996 model.

No reply needed. This is mostly just for me when I forget exactly which belt I used.

 

Don't have time to dig into this now.......but my ATI damper was approximately a 10% underdrive and the diameter would have been just a bit smaller not larger than stock???

 

Mine's smaller too but they also have a couple that are larger. And this is what the major parts houses want to stock, why I don't know. I had mine drop-shipped directly from ATI through Doug Herbert.

 

Looking at an ATI with 10% underdrive. Subscribed for future reference.

 

Just for reference, the ATI damper I used is PN 917274. Oddly enough, I just checked the website and they list a 917275 and a 917273 for the Y-body LT1 but no 917274.

I just checked the box and the PN is correct with the correct description (Y-body LT1).

The alignment is perfect. I've put several hundred miles on my latest combination with mostly hard runs (~7K shift points) and the belt looks great.

My engine builder provided this piece and called ATI directly to get the right part. Perhaps a call to ATI is in order.

 

Summit shows a 917269, 274 & 275 for the Y body but not the 273. Mine is the 917275 which is 6.750" with aluminum shell and steel hub. The other two are 7.500" & 7.530" diameters. Stock is a bit over 7 inches.

 

I just installed the 274 yesterday on the 388 I'm building.

Someone asked me to post on how the installation went, but I can't find the post to respond. If you're reading this, "gimme ahollar".

Took a little creativity on my part to press on the hub.

Jake

 

I'd like to know what was required to install the 274. Could you go ahead and post a write-up?

Thanks!

 

The 274 is a two piece unit and arrived with them bolted together.

I first read all the directions that accompanied the unit and found that you'll need a TORX head bit T40=PLUS! That sucka wasn't available at any of the auto parts stores - NAPA, AutoZone, PepBoys, Advance or even SEARS. It's available on SUMMIT's website though.

So that was the first wrinkle.

I disassemble to two pieces to be able to press on the hub then re-bolt the damper itself.

The OD of the HUB is 2-1/2", so in order to press it on I needed something made of stiff metal that is wider than that. Had to come up with a 'work-around'. I found what I needed at Menards in the plumming section. I'm not sure what it's called, but it's 3-1/2" in diameter with four holes in it (I guess it's designed to be screwed/bolted down to something) and a raised threaded end. Worked perfectly.

My installer is the type that has one end that screws into the crank snout (same place the the damper bolt mounts) and has a large nut (bigger than my largest socket which is a 34 mm). So rather than buy yet another tool that only has once use, I decided to use a pipe wrench.

I screwed in the installer WITHOUT THE NUT ATTACHED, the slide on the HUB, index the broached opening in the hub with the WoodRuff key in the crank then threaded on the nut. At first, the nut would not go one because not enough instaler threads were exposed for the nut to grip, so I hit the HUB once or twice with my 4 lb hammer just enough to move the hub to expose a few moe threads.

Once I had enough threads exposed to allow the nut to, Ah, thread on one turn, I began cranking on the nut with the pipe wrench.

I kep doing this until the crank began to turn; so I installed all six of my flex-plate bolts into the rear of the crank; then wedged one of my largest flat tip screw driver between two of those bolt against the engine stand to prevent the crank from turning. This solved the crank turning problem.

So, here we go again: I, using the pipe wrench, kept cranking on the NUT and the HUB SLOWLY moved onto the crank snout.

Being unfamiliar with LT1's, all this was strange and different from L98 stuff, so with the HUB sitting so far forward gave me moments of concern. I'm use to seeing the damper fitting MUCH closer to the timing chain cover than what I saw with the LT1 HUB.

So rather that take the chance that everything was "OKAY", I removed all the timing chain cover bolts so that I could actually SEE how close the HUB had moved.

With the cover unbolted, I slid it forward just enough to allow me to see (WITH THE AID OF A FLASHLIGHT)

 

The 274 is a two piece unit and arrived with them bolted together.

I first read all the directions that accompanied the unit and found that you'll need a TORX head bit T40-PLUS! That sucka wasn't available at any of the auto parts stores I visited- NAPA, AutoZone, PepBoys, Advance or even SEARS. It's available on SUMMIT's website though. REMEMBER T-40 PLUS

So that was the first wrinkle.

I disassembled the two pieces to be able to press on the hub individually then re-bolt the damper by itself.

The OD of the 274 HUB is 2-1/2", so in order to press it on I needed something, made of stiff metal, that is wider than that. Had to come up with a 'work-around'.

I found what I needed at Menards in the plumbing section. I'm not sure what it's called, but it's round, 3-1/2" in diameter with four holes in it (I guess it's designed to be screwed/bolted down to something) and has a raised threaded end. Worked perfectly.

My installer is the type that has one end that screws into the crank snout (same place the the damper bolt mounts) and has a large nut (bigger than my largest socket which is a 34 mm). So rather than buy yet another tool that only has once use, I decided to use a pipe wrench on the NUT.

I screwed in the installer WITHOUT THE NUT ATTACHED, then slide on the HUB, index the broached opening in the hub with the WoodRuff key in the crank then threaded on the nut.

At first, the nut would not go one because not enough installer threads were exposed for the nut to grip, so I backed off on the amount the installer was threaded into the crank JUST ENOUGH to expose the additional threads I needed to start the NUT.

Once I had enough threads exposed to allow the NUT on the installer to, Ah, thread on one turn, I began cranking on the nut with the pipe wrench.

I kept doing this until the crank began to turn; so, it was time for yet another "work-around". I installed all six of my flex-plate bolts into the rear of the crank; then wedged one of my largest flat tip screw driver between two of those bolts and against the engine stand to prevent the crank from turning. This solved the 'crank turning' problem.

So, here we go again: I, using the pipe wrench, kept cranking on the NUT and the HUB SLOWLY moved onto the crank snout.

Being unfamiliar with LT1's, all this was strange and different from L98 stuff, so with the HUB sitting so far forward gave me moments of concern. I'm use to seeing the damper fitting MUCH closer to the timing chain cover than what I saw with the LT1 HUB.

So rather that take the chance that everything was "OKAY", I removed all the timing chain cover bolts so that I could slide the cover forwad to actually SEE how close the HUB had moved.

With the cover unbolted, I slid it forward just enough to allow me to see (WITH THE AID OF A FLASHLIGHT) how close/far the HUB was from the Crank Position Sensor RELUCTOR.

I continued turning the NUT with my pipe wrench until I could FEEL and SEE that the HUB had moved as far as it could. One more GRUNT with the Pipe Wrench to make SURE and I was satisfied.

I then cleaned off the silicone sealant that I'd used to install the timing chain cover; wiped the cover down with a rag soaked with brake cleaner, then used my finger-tip to apply a fresh coating of Sensor Safe Silicone Sealant. I then bolted the cover back to the block.

I then removed the installer.

I re-fitted the damper, aligned and indexed the bolt holes and, using BLUE Lock-Tight, torqued the Damper bolts back in place.

I installed the new Opti and finally the new water pump.

Today I first determined the seat pressure, then I installed my new Crane double valve springs/retainers and locks. I set the lifter pre load, using the E/O I/C method at ONE FULL TURN FROM ZERO.

That's about it. Hope this helps.

Jake

 

This perfectly explains why mine needed a slightly longer belt. It's the 7.5.