surensm Second gear

Join Date: Dec 2014 Location: California Posts: 196

How To: Gut the hood on your NA Miata



Benefits:

~Save what felt like 2.5 lbs

~Allow for installation of Aerocatch latches.



Drawbacks:

~Possible damage to your paint.

~90% likely to dent the hood from the inside.

~Relatively likely to cut/drill through the hood.

~Possible damage to engine/turbo (if applicable) may occur if metal shavings are allowed to go everywhere.

~Possible skin/bone damage or death may occur if using cutting tools improperly.



Tools Used:

~8 mm. spot-weld drill bit.

(this is what a spot-weld drill bit looks like:



)

~A powerful 18V drill (at least).

~Angle grinder with extra metal cut-off wheels.

~A long screwdriver/pry-bar.

~A hammer, 5-pound preferred.



Gear suggested:

~Safety goggles.

~Face mask.

~Tough gloves when cutting.



Recommended Number of People: 1 will do.

Difficulty: 7/10 (4-5/10 if you don't care about the hood)

Time to Complete:

2-4 hours, depending on how fast you work and if you have all the batteries charged and all the bits needed.



Dangers: 7/10

Serious injury or death may occur when using cutting tools. It is highly suggested that you know what you are doing. No beers for this one, ladies and gents.



Figure 0:



Step 0: Cover the engine bay with something- multiple newspapers, cardboard- whatever works.





Figure 1:



Red- spot welds

Yellow-glue for the main skeleton

Green- areas with tons of glue for the second level of reinforcement.



Figure 2:





Step 1:

Drill out all the spot welds highlighted in red in figure 1. This will allow you to separate the primary skeleton from the secondary reinforcement. When drilling, you will hear a "pop" noise every time you break a weld. The closer you nail the drill to the center of the weld, the easier it will be to drill through it. Be careful as to not drill through the hood itself. Shown in figure 2 is what your spot welds should look like after you've drilled them.



Figure 3:





Step 2:

Try and separate as much of the glue as you can from the primary skeleton (highlighted in yellow in figure 1). This will allow you to separate the skeleton from the hood faster, leaving very little chance to seriously bend the hood.



Use a screwdriver/prybar, and a 5 pound hammer. For even more damage control, place the screwdriver between the glue and the skeleton, as shown in figure 3.



Figure 4: Before the cut.





Figure 5: After the cut



.

Step 3:

Start cutting the hood. Follow the lines shown in the comparison photos in figures 4 and 5. Use maybe 1cm of the cutting wheel in the deepest sections, and don't even cut through completely the first time around in the shallow areas. You don't want to see the cutting wheel stick out the top. Needless to say, keep both hands and the guard on the angle grinder.



Figure 6:





Step: 4

Remove the secondary reinforcement shown in figures 5 and 6. Take your time with this one, because with the skeleton off, you no longer have the rigid hood you once did. It will bend all over, and using the screwdriver will leave worse marks than before. Not sure if heat will work better on the glue, but I used the screwdriver. It didn't come out too bad, but I could've been a lot more careful.



When finished, your hood should looks like this (or better):





Best if you have 4 aerocatch latches, but I'll start with 2 for now. Aerocatch sends templates with their latches, so that's pretty self-explanatory. I figured I'd set the latches in the very front, but note that you'll have to cut pretty deep into the front section of the hood to allow for the latches to be installed properly.



Again, my car is a racecar project, and I do want to save every pound possible.





Hopefully someone finds this useful. It's been some time since I made a how-to, and I think this is my second one this year (I usually try to crank out more, but haven't had the time). This is for those of you seeking to save every pound on your race-car, or if you want to do another project. Note that this will make your hood flimsy, noisy, and will require the use of external latches (Aerocatch in my case). 2 at the very least, 4 recommended. Please don't turn this into a battle of "why this is cool vs why this is stupid". Different strokes for different folks.~Save what felt like 2.5 lbs~Allow for installation of Aerocatch latches.~Possible damage to your paint.~90% likely to dent the hood from the inside.~Relatively likely to cut/drill through the hood.~Possible damage to engine/turbo (if applicable) may occur if metal shavings are allowed to go everywhere.~Possible skin/bone damage or death may occur if using cutting tools improperly.~8 mm. spot-weld drill bit.(this is what a spot-weld drill bit looks like:~A powerful 18V drill (at least).~Angle grinder with extra metal cut-off wheels.~A long screwdriver/pry-bar.~A hammer, 5-pound preferred.~Safety goggles.~Face mask.~Tough gloves when cutting.Recommended Number of People: 1 will do.2-4 hours, depending on how fast you work and if you have all the batteries charged and all the bits needed.7/10Serious injury or death may occur when using cutting tools. It is highly suggested that you know what you are doing. No beers for this one, ladies and gents.Cover the engine bay with something- multiple newspapers, cardboard- whatever works.Red- spot weldsYellow-glue for the main skeletonGreen- areas with tons of glue for the second level of reinforcement.Drill out all the spot welds highlighted in red in figure 1. This will allow you to separate the primary skeleton from the secondary reinforcement. When drilling, you will hear a "pop" noise every time you break a weld. The closer you nail the drill to the center of the weld, the easier it will be to drill through it. Be careful as to not drill through the hood itself. Shown in figure 2 is what your spot welds should look like after you've drilled them.Try and separate as much of the glue as you can from the primary skeleton (highlighted in yellow in figure 1). This will allow you to separate the skeleton from the hood faster, leaving very little chance to seriously bend the hood.Use a screwdriver/prybar, and a 5 pound hammer. For even more damage control, place the screwdriver between the glue and the skeleton, as shown in figure 3.Before the cut.After the cutStart cutting the hood. Follow the lines shown in the comparison photos in figures 4 and 5. Use maybe 1cm of the cutting wheel in the deepest sections, and don't even cut through completely the first time around in the shallow areas. You don't want to see the cutting wheel stick out the top. Needless to say, keep both hands and the guard on the angle grinder.Remove the secondary reinforcement shown in figures 5 and 6. Take your time with this one, because with the skeleton off, you no longer have the rigid hood you once did. It will bend all over, and using the screwdriver will leave worse marks than before. Not sure if heat will work better on the glue, but I used the screwdriver. It didn't come out too bad, but I could've been a lot more careful.When finished, your hood should looks like this (or better):Best if you have 4 aerocatch latches, but I'll start with 2 for now. Aerocatch sends templates with their latches, so that's pretty self-explanatory. I figured I'd set the latches in the very front, but note that you'll have to cut pretty deep into the front section of the hood to allow for the latches to be installed properly.Again, my car is a racecar project, and I do want to save every pound possible.Hopefully someone finds this useful.

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