Grand Prix Koni Upgrade

Written by Mike Napurano, Member 1
Applies to the following vehicles: 1997-2003 Grand Prix
Created 5/19/1999, Updated 3/25/2003

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Rated by 11 members

Well, here you go! You've been wanting some nice replacement struts for your Grand Prix? Well, here is an upgrade you can do. If you have all the tools, do it yourself, cheap! Otherwise, pay a friend/shop/etc to do the mods for you. It took about 2 hours to do the modifications and alignment. I expect a person/shop doing it for the first time will take more like 3 hours or so if you have all the needed tools in one place.
FYI: This is currently a front strut upgrade only.

Special thanks to John Paul Hudson for the method, idea, and doing it on my car! JP has been competing with this setup in SCCA Solo II competitions for a while, and really annoying the Porsche 968's and BMW M3's (grin)!

One obvious recommendation, if you don't already have them, is to put on Eibach or other performance springs with this upgrade.

Okay, so what do you need? Well, below is a list of most of the parts and tools.

Click on any of the pictures below for a close up.

Preparing the car for the operation.
I'm assuming you know how to get the struts out, since this is a pretty straight forward process. This is a shot of the stock struts out of the car.
Remove the top of the strut and springs (as if you were going to replace the springs). The strut is then put into a vise. JP is pointing to the area that will be cut by the pipe cutter in his hand. You will cut about 3/4" below the lip of the strut.
You can see that the strut is now cut. You can now remove the old strut "guts" from the strut assembly and dump out the oil.
With the "guts" removed and out of the way, you now want to take your air saw and cut out a notch on each side of the strut, approximately 1 1/4" long, and about 1/8" wide.
Here is the opposite side getting cut.
Finished with the cuts.
Invert the strut and put it back in your vise. You can now see the bottom of the strut housing.
Take one of the new strut assemblies and use your air grinder to grind off the paint around the lower nipple of the strut.
Here you can see the strut after sanding off the paint. You want to do this to give yourself clean metal for your welding later.
Use your drill and/or air saw to cut out the bottom of the stock strut assembly. You want to cut a hole that is just big enough for you to be able to drop the Koni into (the area you sanded the paint off of). After it's drilled out, rinse out the housing (oil works well) and dry it off.
Put the strut assembly right-side-up into your vise. Drop the Koni insert down into the strut assembly. Then take your exhaust clamp and put it over the strut assembly as shown. Use an air wrench to tighten down the clamps. This will pinch the stock strut assembly (from those cuts you made) down around the new strut insert.
Go to your welder and weld the bottom of the strut to the strut housing.
This shows you how/what you should be welding (grin). This is obviously a post weld shot.
Put your spring and the rest of the strut assembly back together.
Here's a shot of JP's little tool bench. If you have one of these, you should have all the tools neccessary to do the job (grin).
Re-install the strut assembly back into the car. In this picture you can see the little bit of evidence that the car now has Koni's (the school bus orange strut housing).

That's basically it! It's actually a pretty simple and straight forward process (for those mechanically inclined of course). After this, go for a test drive (I recommend using the firm setting for your first ride!).

After your test drive, the next step is to have an alignment done. My car wasn't out much at all, but better to be safe!

Below is a few shots of me and JP's car after we finished up in the shop.

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