Need help with harmonic balancer
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Joined: Apr 2024
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From: MS
Need help with harmonic balancer
Hello all,
I spent months researching how to replace my harmonic balancer on my 2013 GS Manual (dry sump). After watching a lot of videos and reading on this forum I thought I had selected the correct pulley, a Summit C2501. However after going to all the trouble to do the installation I got it on the car it will not line up with the belts. It is clearly NOT the correct pulley. Summit even TOLD ME it would work when I asked them!!!!
So now I need a different puller kit to get this paper weight off and can someone please tell me the absolutely, positively, without a doubt what the CORRECT pulley is???? Does Summit even make one????
I spent months researching how to replace my harmonic balancer on my 2013 GS Manual (dry sump). After watching a lot of videos and reading on this forum I thought I had selected the correct pulley, a Summit C2501. However after going to all the trouble to do the installation I got it on the car it will not line up with the belts. It is clearly NOT the correct pulley. Summit even TOLD ME it would work when I asked them!!!!
So now I need a different puller kit to get this paper weight off and can someone please tell me the absolutely, positively, without a doubt what the CORRECT pulley is???? Does Summit even make one????
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Joined: Apr 2024
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From: MS
Almost certain it was. The end of the cranksahft was almost flush with the securing surface of the pulley, just like the OEM one I pulled off and it was not even close to lining up with the belt drive system. In addition, the back side of the pulley was very close to the crank case so it was not even possible for it to go any further without bottoming out.
I called Summit customer service and this time the guy told me that the C2501 will not fit a dry sump LS3 so I guess the other person did not know what they were talking about.....
He quoted me a Fluidamper brand, which is more expensive than the ATI. So I am going to wait and talk to an ATI person and order one of those that everyone on here says is the best....
On top of that, the ATI bolt they sold me is shorter than the OEM and I can assure you it is not long enough to have enough thread engagement, especially when you put the washer under the head of it...good grief, what a waste of time.
Again, any insight offered is appreciated. My ignorance on this subject cost me.
I called Summit customer service and this time the guy told me that the C2501 will not fit a dry sump LS3 so I guess the other person did not know what they were talking about.....
He quoted me a Fluidamper brand, which is more expensive than the ATI. So I am going to wait and talk to an ATI person and order one of those that everyone on here says is the best....
On top of that, the ATI bolt they sold me is shorter than the OEM and I can assure you it is not long enough to have enough thread engagement, especially when you put the washer under the head of it...good grief, what a waste of time.
Again, any insight offered is appreciated. My ignorance on this subject cost me.
Intermediate
Joined: Oct 2008
Posts: 30
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From: Concordia KS
Almost certain it was. The end of the cranksahft was almost flush with the securing surface of the pulley, just like the OEM one I pulled off and it was not even close to lining up with the belt drive system. In addition, the back side of the pulley was very close to the crank case so it was not even possible for it to go any further without bottoming out.
I called Summit customer service and this time the guy told me that the C2501 will not fit a dry sump LS3 so I guess the other person did not know what they were talking about.....
He quoted me a Fluidamper brand, which is more expensive than the ATI. So I am going to wait and talk to an ATI person and order one of those that everyone on here says is the best....
On top of that, the ATI bolt they sold me is shorter than the OEM and I can assure you it is not long enough to have enough thread engagement, especially when you put the washer under the head of it...good grief, what a waste of time.
Again, any insight offered is appreciated. My ignorance on this subject cost me.
I called Summit customer service and this time the guy told me that the C2501 will not fit a dry sump LS3 so I guess the other person did not know what they were talking about.....
He quoted me a Fluidamper brand, which is more expensive than the ATI. So I am going to wait and talk to an ATI person and order one of those that everyone on here says is the best....
On top of that, the ATI bolt they sold me is shorter than the OEM and I can assure you it is not long enough to have enough thread engagement, especially when you put the washer under the head of it...good grief, what a waste of time.
Again, any insight offered is appreciated. My ignorance on this subject cost me.
I ran into this myself about 2 months ago. I have a 2007 Z06 that I ordered a Fluidampner for. When I installed it, it would not fully seat (ran into the timing cover). I found out the dry sump engines have another oil pump that causes the timing cover snout to be much larger. I had to remove it and send it back and get an ATI- don’t ever trust Summit fitment chart.
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From: MS
When I compared the OEM to the C2501 I see now how to tell it will not work. I guess all those threads I read I just really did not understand.
Can you share with me which part number of ATI you used? Everybody says 'ATI' but no one ever says the part number.
Can you share with me which part number of ATI you used? Everybody says 'ATI' but no one ever says the part number.
Safety Car
Joined: Dec 2006
Posts: 4,592
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From: Pearland / Houston Tx
Lesson learned trusting someone on the other end of the line. My first site when looking for a hard part is Rockauto. It is pretty good at helping make sure you get the right part. See link below with With and Without dry sump notations. That means the balancers are different. Second link is CF help with ATI part number.
The C2501 on Summit's site states: "Application Notes: Integral harmonic damper and crank pulley design. Fits short spacing pulley kits only."
I guess you are supposed to know that short spacing indicates Wet Sump.
RockAuto
Search results for ATI dry sump
ATI application page for C6 dampers
The C2501 on Summit's site states: "Application Notes: Integral harmonic damper and crank pulley design. Fits short spacing pulley kits only."
I guess you are supposed to know that short spacing indicates Wet Sump.
RockAuto
Search results for ATI dry sump
ATI application page for C6 dampers
Last edited by C6ToGo; Feb 15, 2026 at 09:04 AM.
Safety Car
Joined: May 2016
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From: Erlanger, Kentucky
Because you have the dry sump engine, it is easier to search for a harmonic balancer for the LS7 engine or C6 Z06. A lot of websites make no distinction between the wet and dry sump LS3's which causes a lot of confusion.
So just searching Summit, my search shows that Summit doesn't make a balancer for the dry sump engines. My search only came up with ATI, Powerbond, and Innovators West balancers.
I personally am using the Powerbond balancer in my 2011 GS with dry sump. Cheapest price for the Powerbond is from RockAuto.
ATI part number - ATI-918620 (there is a part number ATI-918620U which I think is the underdrive version).
Powerbond (Dayco) part number - PB1503SS
Innovators West part number - INW-852
So just searching Summit, my search shows that Summit doesn't make a balancer for the dry sump engines. My search only came up with ATI, Powerbond, and Innovators West balancers.
I personally am using the Powerbond balancer in my 2011 GS with dry sump. Cheapest price for the Powerbond is from RockAuto.
ATI part number - ATI-918620 (there is a part number ATI-918620U which I think is the underdrive version).
Powerbond (Dayco) part number - PB1503SS
Innovators West part number - INW-852
Intermediate
Joined: Oct 2008
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From: Concordia KS
Use ATI-918620- do not use the underdrive version.
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From: NC
Thread Starter
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From: MS
As a follow up to my original post. I will give kudos to Summit. I contacted them about the mixup and I got a reply that yes, it was their mistake to tell me the C2501 would fit a dry sump car. They sent me a return label and will not charge me a restocking fee. I ordered the correct ATI 918620 yesterday for my dry sump car. To the other poster on here asking. The ATI website has very clear listings of the part numbers for the various engines and specifically separates the LS7 and LS3 dry sump engines.
The C2501 should work on a regular wet sump LS engine BUT do not take my word for it, do the research and talk to someone who knows for sure.
The C2501 should work on a regular wet sump LS engine BUT do not take my word for it, do the research and talk to someone who knows for sure.
Intermediate
Joined: Oct 2008
Posts: 30
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From: Concordia KS
Intermediate
Joined: Oct 2008
Posts: 30
Likes: 0
From: Concordia KS
It should work with or without a dry sump. It's larger on the back pulley and will accomodate the larger snout on a dry sump timing cover but should fit the wet sump timing cover as well.
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From: MS
As I understand it the 'U' designation means it is a different diameter than the stock diameter and you should not use this under normal conditions. Call ATI and talk to them. They are knowledgeable and will be able to explain differences. I will say this, the dry sump arrangement is different from a wet sump and I would not expect the same HB to work on both, they are different. The issue is the lining up of the accessory belt that drives all the other things on the car. The C2501 would fit the crank but when it was bottomed out it still had an inch or so to go before it would line up with the serpentine belt that drives all the other stuff.
Like I suggested, call them, they will help you get the right one for your corvette.
Like I suggested, call them, they will help you get the right one for your corvette.
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From: NC
The way I understand it is that the U is for underdrive. So if the ATI-918620 is the LS7 / LS3 dry sump HB, then the ATI-918620-U is the 10% underdrive of that same HB. I've already decided this is the HB I'm going with (after many hours of research) so if there are any issues with that I will report back. For my cam swap, I anticipate that my idle will increase by 10-15% and redline will increase by around to 5% and the car already sees a lot of high rpm driving. So this should keep me from spinning anything faster than originally designed. At least that's my theory.
Intermediate
Joined: Oct 2008
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From: Concordia KS
Instructor
Joined: Oct 2023
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From: NC
That is good to know, although something doesn't seem right in your photo. The back is for the A/C, that should be standard size. The front that drives the acc is what should be 10% undersized.
Last edited by 11GSCoupe; Feb 18, 2026 at 12:39 PM.