91 L98 Harmonic damper replacement
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Racer
Joined: Sep 2021
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91 L98 Harmonic damper replacement
I've managed to install a new harmonic damper on my 91 corvette and it wasn't as har as I thought it would be. The reason for replacing it is because it was an 8" diameter, that came with my crate engine. Initially it didn't rub the frame but after working on the transmission it started to rub and when I chencked the timing it was 10deg off. It was much larger. Before that I've bought a new <<fluidampr>> HD and a puiller-installer kit from Summit that works very well, To create the required access to the pulley and damper I've taken out the coolant hose, air snout and also the belt tensioner which was easier to remove than the steering pump pulley. You also need to remove the water pump pulley, and losen the steering pump hidraulic line as they say in the manual. The space is a bit tight but it's not that bad.
To remove the crank bolt many recommend to cranck the engine with the starter motor after securing the ratchet in place. My bolt is about 15.5mm hex head. So instead of cranking I simply put the transmission into the 6th gear and pushed the car but turning the front tire. The force is greater when you turn wheel by hand and you can also see what happens to the ratchet and when it gets loose. Everything worked perfectly here. Anytime you need to spin the engine it is much easier this way, unless you have the car on a lift which btw, is not necessary.
Next step - remove the cranck pulley.
Next -removing the HD. Nothing special here, just follow the instructions. The force required is moderate, a 12" long spanned has enought force.
Make sure you measure the bore and keyway of both dampers or other visual checks, and lubricate the areas required, also the puller needs lubrication.
The next step you have to be very careful about how you align the damper with the shaft key. On my first try I've screwd it up. The instructions say if you encounter sudden resistance (except when it gets fully seated) you must stop. I've proceeded with the insrtallation and put the HD on then tried to find its orientation by rotating it until I thout it was aligned. The I started to push it with the installer. pretty quickly the force became too high for my 12" spanned so I decided to chech the alignment even using a borescope but couldn't see anything wrong. However, I've setup the puller and removed it. The HD has a hald a mm indent from the key and the key was pushed half way down the keyway. So this is were you have to be very careful because you can ruin your parts. On my second attempt things worked pretty good. I've rotated the crannkshaft so the keyway was at 12 o'clock, placed the key after testing the fitment with the keyways, You need to have good visibility. I recomment a flashlight. You need to alingn it very carefully. You push it by hand, may tap it with a very small hammer I think. After you think it is in place watch what happens to the key and the snout of the damper as you tighten it. The key is D shaped and can rotate so make sure it stays almost parallel to the axle. If it gets pushed realign it using a round rod so you don't scratch the seal. The force required was similar to when I removed the old shaft. You should see how the HD is pushed. If the force is high you can risk breaking the crank bolt adapter so even if it takes some more time it is better to just stop, remove it and retry. When it was originally installed. The builder used silicone to glue it to the shaft, which should help, But I've just used engine oil, and shoud be ok "afaik".
from there just follow instructions, should be easy. PS. just realized the pulley needed to be installed before the main bolt. smh. for now I've only torqued the main bolt on the crank. I've did this incremently to have more control. I've set it to 50Nm initially to have a sense of how much force is required tthen 60, the added 5Nm each try until 95Nm/70lb ft.
This is beter "imo" because in case something is wrong with the torque wrench you know you only needed a bit more force to produce a click and if it doesn't happen the something could be wrong with the wrench. I've already went through this when tightening some spark plugs that is how I thought of this.
Be careful that I've only discussed some of the steps, this is not a full tutorial
The idea of this is maybe I can help other members avoid problems when installing a damper or someone may spot something I actually did wrong so feel free to comment.
Thank you.
To remove the crank bolt many recommend to cranck the engine with the starter motor after securing the ratchet in place. My bolt is about 15.5mm hex head. So instead of cranking I simply put the transmission into the 6th gear and pushed the car but turning the front tire. The force is greater when you turn wheel by hand and you can also see what happens to the ratchet and when it gets loose. Everything worked perfectly here. Anytime you need to spin the engine it is much easier this way, unless you have the car on a lift which btw, is not necessary.
Next step - remove the cranck pulley.
Next -removing the HD. Nothing special here, just follow the instructions. The force required is moderate, a 12" long spanned has enought force.
Make sure you measure the bore and keyway of both dampers or other visual checks, and lubricate the areas required, also the puller needs lubrication.
The next step you have to be very careful about how you align the damper with the shaft key. On my first try I've screwd it up. The instructions say if you encounter sudden resistance (except when it gets fully seated) you must stop. I've proceeded with the insrtallation and put the HD on then tried to find its orientation by rotating it until I thout it was aligned. The I started to push it with the installer. pretty quickly the force became too high for my 12" spanned so I decided to chech the alignment even using a borescope but couldn't see anything wrong. However, I've setup the puller and removed it. The HD has a hald a mm indent from the key and the key was pushed half way down the keyway. So this is were you have to be very careful because you can ruin your parts. On my second attempt things worked pretty good. I've rotated the crannkshaft so the keyway was at 12 o'clock, placed the key after testing the fitment with the keyways, You need to have good visibility. I recomment a flashlight. You need to alingn it very carefully. You push it by hand, may tap it with a very small hammer I think. After you think it is in place watch what happens to the key and the snout of the damper as you tighten it. The key is D shaped and can rotate so make sure it stays almost parallel to the axle. If it gets pushed realign it using a round rod so you don't scratch the seal. The force required was similar to when I removed the old shaft. You should see how the HD is pushed. If the force is high you can risk breaking the crank bolt adapter so even if it takes some more time it is better to just stop, remove it and retry. When it was originally installed. The builder used silicone to glue it to the shaft, which should help, But I've just used engine oil, and shoud be ok "afaik".
from there just follow instructions, should be easy. PS. just realized the pulley needed to be installed before the main bolt. smh. for now I've only torqued the main bolt on the crank. I've did this incremently to have more control. I've set it to 50Nm initially to have a sense of how much force is required tthen 60, the added 5Nm each try until 95Nm/70lb ft.
This is beter "imo" because in case something is wrong with the torque wrench you know you only needed a bit more force to produce a click and if it doesn't happen the something could be wrong with the wrench. I've already went through this when tightening some spark plugs that is how I thought of this.
Be careful that I've only discussed some of the steps, this is not a full tutorial
The idea of this is maybe I can help other members avoid problems when installing a damper or someone may spot something I actually did wrong so feel free to comment.
Thank you.
Last edited by Nilak; Nov 2, 2024 at 10:12 PM.
