Sparco latch springs are a simple, lightweight solution for holding trunks closed. The BMW E46 has an electromechanical latch that normally requires the key or the driver to push a button under the dash to release the trunk. The Sparco kit eliminates the hassle and a bit of weight.

So many videos and pictorials involving the modification or building of a race/track car are available out there to educate people on how to do certain tasks. One task I looked for wasn’t available online. That’s about to change.

The task is the installation of a Sparco Spring Kit. There are similar kits out there and they all do roughly the same job. This is an old-school latch system that applies tension, via a pair of springs, to hold a trunk or hood closed. A simple lifting of the latch quickly releases the hold downs and you can easily open the trunk. It allows you to remove the factory latch system, trunk lift shocks, and related hardware. It’s a way to remove some weight from the car and depending on the car, simplify the ability to open the hood or trunk.

For a Spec E46, it fits the bill perfectly because the factory trunk latch is electric and it requires the use of the ignition key. The stock hinges articulate the trunk lid in a way that it opens fully and will stay open all by itself. So really, you just need a way to keep it closed and not flopping around while charging over curbs and other rigors of racing.

Using the Sparco kit allows complete removal of the factory latch and lock cylinder lifting struts and assorted hardware, and pulls a few pounds out of the car.

Examining the Kit

I examined the see-through packaging and noticed that Sparco supplied all the hardware you would need. Well, not exactly. It suppled everything for the kit to work once installed. Mounting hardware for the top hook is up to you. I find this is best, because the hardware options manufacturers could supply don’t always fit the job. Leaving the mounting hardware options up to me allows me to be creative.

The Sparco kit comes with most of the hardware, but not everything you’ll need to make it work. I used pop rivets to attach the spring catch to the deck lid.

For some fasteners, I like pop rivets. Their ability to clamp and hold parts in place, quickly, with lightweight materials, appeal to my inner racecar engineer. One thing you should know is the material you are going to attach it to, and what material you will attach it with. In this case, the trunk and the bracket materials are steel. You might think to use an aluminum pop rivet because it’s lighter, there is a little thing called “dissimilar metal corrosion.” To get really fancy, it’s also known as “bimetallic corrosion.” Here’s how it works.

When there are two different types of metals, one or the other will corrode more rapidly than if they were of like materials. So, when choosing a fastener, always use one that is of the same material as what you are using. If, by chance, you are forced to use two different materials, you can treat the surfaces to help reduce the corrosion. Naturally, I chose a steel pop rivet. The weight savings versus an aluminum pop rivet is negligible since I’m only using four rivets total for the installation.

There are many sizes and thicknesses of pop rivets to choose from. You will want one long enough to go through the bracket completely and sheet metal or material that you will be attaching it to. Additionally, most pop rivet packaging will tell you what size drill bit you will need for the rivet to fit properly. If what you have is a little bigger than the bracket you need to attach, you always have the option to drill out the bracket to the size you need. Just be realistic about how much bigger the holes will be in relation to how much bracket is left after drilling.

The Installation

I like to lay the parts out and visually get a good understanding of how it all will fit together once installed. Looking around online, I saw images of the brackets installed in two different ways. One method looks better than the other. Both are viable and both will work. I prefer the handle of the latch to be securely attached to the hook bracket, and not the stub. To each his own. I made my own decision and went with it.

There are two ways to install the spring latch kit. The method on the right is the one shown on the Sparco website.

Then I found a location I thought would work the best in terms of ergonomics and physical fitment. Then I added a quarter-inch of length to create some some spring tension to hold the deck lid down. I found the best place on the E46 trunk was the flat sheet metal of the trunk lid for the hook portion. And the single bolt with the bushing for the spring to attach at the bottom.

I found this was the best location on an E46 to mount the spring latches.

The bottom bolt hole location won’t exactly work as the kit supplied the bolt, washers and nuts. The area behind the body work where the bolt would go is a blind hole. There is no way to put the nut behind it. I could have gotten a longer bolt and made that work. A large pop rivet could work there using all the supplied hardware, but I wouldn’t trust it. I decided to go with a 6 mm Rivnut, also called a Nutsert. This is like a pop rivet, but it has a threaded section so you can thread in a bolt. They aren’t expensive, and you can make your own installation tool if needed, or you can buy a tool.

The panel beneath the deck lid and above the bumper is a blind hole, so a bolt wouldn’t work there. I opted for a Rivnut, which does not require access to the back of the panel.

I already had one so it worked out great. I marked the two holes for the pop rivets with a felt-tip pen, then marked the bottom hole location with the same pen. Then I used a center punch to make the drilling more accurate. Without a center punch, the drill bit can wander away from the location where you want the holes to be. Once punched, I drilled all six holes with the same drill bit.

Then I loaded the top bracket with two pop rivets and installed them both. All that was left was to install the Rivnut. I also bent the tab around the bushing for the bottom bolt to help keep the spring from falling off the car when the latch is unhooked. The spring is hardened and not easy to bend. I had to put it in a vice to get it to take the shape I wanted.

Done right, the bottom bolt and top hook must be spaced properly to create spring tension to hold the deck lid down.

In all, it took less than 30 minutes to install both latches. It took longer to take the pictures and video along the way than the job itself.

The Sparco spring kit is a lightweight simple solution for retaining a deck lid or hood that can be operated from the outside of the car without a key.

Tools Required
Various sized drill bits
Screw driver
Allen Wrench
6 mm Rivnut
Rivnut installation tool
Center punch
Felt tip pen
Pop Rivets
Pop Rivet Gun

I crimped the spring at the bottom so it wouldn’t fall off when it was detached from the deck lid.
Image courtesy of Shawn Meze

Join the Discussion