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Old 01-18-2022, 11:25 PM   #1
Drives: Chevrolet Camaro 1SS
Join Date: May 2020
Location: Houston
Posts: 20
ZL1 Valance/Diffuser install on lower Trims

This is for those whoíd like to install an OEM ZL1 valance on lower trim Camaros. Itís probably a very niche cosmetic change as attaining a ZL1 valance can be difficult or pricey if bought new. Iíve seen a couple people do it (or wanting to) so I figured Iíd give a few pointers. I was interested in installing this particular one as i hated the aftermarket sideskirts that i installed. They donít line up with the front splitter and just donít look right. So i looked at the OEM ZL1 skirts and found that those are actually built into the rockers of the car (pretty much one piece). They also line up w the front splitter and look great as they go right up under the door. So once I installed those i had to install the valance as well for the ground effects to line up and tie in together. Thereís quite a few threads on ZL1 skirt installs but none for the valance so hereís my attempt.

First off why didnít I choose the GM Ground effects package as opposed to the ZL1 ones? They look just as good but have a different style. Well honestly at the time I didnít even know about the ground effects accessory from GM. However once I did learn about them they were really expensive over $2000 and they include the front splitter which i already had. So I looked at alternatives as I was unsatisfied with the aftermarket skirts I initially got. I was lucky enough to find a ZL1 that was being parted out and so i claimed the rockers and valance for a great deal.

Besides the obvious exhaust cutout, the ZL1 valance is a quite similar to the OEM Ground Effects Package valance. The ZL1 one is wider on the bottom and rides up the sides a bit higher than the GE Package. It is also installed differently. It comes with a separate template that you lay on top of the bumper and shows you exactly where to drill holes (which is weird bc the bumper itself has a template already built into it. Iíll get into that later). The valance then has bolt-like clips that go into the holes. Also, all the Camaros Iíve seen w the GE Package the valance does not have a tight fit on the sides of the bumper. As in thereís a bit of a gap on the sides. I believe this is bc the bumper is curved inwards where as the valance is straight. The ZL1 valance is a tight fit and curves inwards leaving no gap and looks much better IMO without the exhaust holes.

The install does require one vital part (10 of them). It is called a Ďretainerí GM part 11547341. There are cheaper versions of them on ebay as an OEM set was gonna set me back $50 (yikes!). These are the same retainers that hold the dive planes in the ZL1 1LEís front bumper. Luckily i found an OEM set on ebay for about $10. These will hold the sides tightly in place.

As for the install, it will require the removal of the rear bumper. I was able to install it without removing it but it was a massive PITA. I also did not know that the slits that will need to be cut out are actually templated into the bumper itself (referenced above). Just like non-1LE ZL1 bumpers have the template to cut out slits for the diveplanes on the inside. Had I known that I wouldíve definitely removed my bumper bc i spent way too long trying to figure out where to cut from the outside and still did not manage to cut them out perfectly. I did get really close however. Anyways take my advice and just remove the bumper. Hereís a link to LethalGarageís youtube channel as he explains how to remove everything much better than i will be able to in text [url]https://youtu.be/waahi8vu_Cc][/url
Once the old valance is removed you now have to cut out the slits in the bumper. They are kind of hard to see as theyíre only outlined but once you identify them, they are easily spotted. They are on the sides of the bumper, theyíre thin, rectangular and thereís 10 of them. 5 on each side, and they also vary in length. I used a dremel but a drill with a 1/8Ē or maybe 3/16Ē drill-bit will also work. Just cut out each slit and this is where the tabs on the sides will go onto. Once the slits are cutout, the new valance can be installed. First start clipping it on from the middle and leave the sides for last. To hold the sides in place you will need those retainers i mentioned earlier. They clip right into the rectangular hole of the tabs once they are inside the slit. It goes in from the top and should be a really tight fit. Once that is done you can begin to retrace your steps to reinstall the bumper.

Thatís pretty much it. I will provide a few pictures of the slit template and where i cut (badly from the outside) as well as a picture i found online of the retainers in place. Also a picture of the finished look. Finding out that the slits were actually templated onto the bumper is was prompted me to write this out as i wanted to inform everyone about it. Also i know of one guy who installed it and ended up cutting the tabs out and installed it with double sided tape instead of using the retainers. Thatís not going to hold for long nor be a tight fit. Good luck to anyone doing the install.
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Old 01-20-2022, 09:06 AM   #2

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Drives: 2017 SS 1LE, 2016 1SS (previous)
Join Date: Apr 2016
Location: Metro-Detroit
Posts: 1,809
Interesting. I found a deal on a used ZL1 rear fascia from a wrecked car and just had it repainted. Had I known that the marking points for the diffuser attachment were there, I'd just bought the rear diffuser...

I'm surprised that no one seems to point out the particular part of the ZL1 diffuser that is the PITA: inserting the diffuser onto the tab, on either end, last before you engage the side portion of the diffuser at each side. There is some real gymnastics going on there, even with the entire rear fascia off the car. You end up essentially bending those last tabs (these are a very long side tabs) considerably; I'm sure if one were careless, they would snap them off.
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