OK, gas struts are all installed for the trunk and I'm pretty happy with it. Just to recap so it's all in one post. This is in a '67 Dart Convertible so there are some special considerations for where the top rests in the down position.
The basics are:
- 15", 100lbs each gas struts. 14.96" expanded, 9.06" compressed. Amazon link.
- Pivot point on the hinge is about 3/4" off the bottom edge and just a little off the bracket that the original torsion bar pushes against. Original torsion bars still can be installed.
- Pivot point at the base is 3.5" from the flat of the L bracket to allow for clearance of the top and the original torsion bar mount base.
The action on the trunk is pretty lazy. It's easily movable but doesn't fly up after opening it. As it approaches the top it starts to move on it's own and is obviously not going to come down. Maybe a different position on the pivot points would help but with this setup I only have about 1/2" left of travel on the 15" struts. So, if you wanted the trunk to pop up from the key open then you'd probably want a longer strut and to take the hinge pivot point further off the hinge. Or, maybe just a stronger strut. I might try some 120lbs if I can find them in 15". At $20 a pair we're not going broke on this one.
I'm super happy with how this turned out overall.
- I like that it's completely hidden and out of the way.
- I actually like the way the trunk just stays where you put it. I drive this car daily in San Francisco and there are times I just don't want it hanging open for the world to see what's in there.
- I feel good about it being sturdy especially after adding the straight bar from the L bracket to the original torsion bar mount bracket. That was a gimme since there is already a 3/8" hole right there. Could have just punched a single hole through the wheel tub but just didn't feel like there was a lot of strength there.
- I like that there are no holes drilled in the hinge and that the clamp on bracket is movable.
- I like that this setup allows the original torsion bars to be installed although I think I'll just leave them out for now.
- Clearances are all good and there are a few places I was a little worried about including the travel distance of the strut rod.
Some things I might do differently if I did it again:
- Maybe use a longer strut that offers a higher weight rating. Haven't yet seen a 120lbs strut in 15" but I think 100lbs should be considered the low end with the pivot points used here. A longer strut would also bring the pivot point down on the L bracket meaning less stress on the body panels. Longer struts would mean you get to play more with the pivot point on the hinge which should mean more pop when the trunk opens - if you want that.
- Drill more holes in the L bracket to allow for at least an inch longer strut and possibly an add-on plate to kick it back even further to allow for even longer struts. I did leave some options in the design since this was the first time by using a bolt on setup on the hinge side since I've ever used gas struts but it'd be nice to have some options on the base mount point.
These are the parts I ended up making/using minus the straight bars I added when switching to 100lbs struts.
View attachment 1715648121
- L brackets are 3/16" steel drilled 7/16" at the bottom and 8mm for the strut.
- Hinge brackets are 1/8" thick steel drilled 1/4" for hardware and 8mm for the strut.
- Hinge bracket hardware are (8x) 1 1/2" 1/4-20 with nylock nuts.
- L bracket mount hardware is (6x) 1" 7/16" stainless with stainless nylock nuts and washers.
- Strut rod hardware (4x) 8mm nylock nuts (hardware store by me only had 3 left so you can see in the photo above that I'm one short for now.)
First thing I did after figuring out where the hinge pivot point would be was to make some plastic template plates. Note that with the 15" struts the mount point has to be pretty close to the hinge or else the travel distance is used up pretty fast.
View attachment 1715648122
Then I redid the test with a coat hanger to see if the travel on the strut would be enough and to make the final decision on the height of the base pivot point. I was liking the 1/2" clearance it looks like I'd have since the original tests weren't showing quite that much.
View attachment 1715648123
Then make and install the plates based on the templates.
View attachment 1715648124
Make the L brackets. Be very careful with the hole placement since you need to straddle the frame and there isn't much space on the one side. That dimple in the floor snookers you just a bit but it's good to be just about that far off the wheel tub so the struts can be removed without meeting with the L bracket bolts. That's why the holes are so close to the bend. This plate is straddling the frame below. Install the struts and bolt them to the L bracket position it in the car and mark off the hole positioning on the car. Double-check placement and drill those holes at 7/16".
View attachment 1715648125
L bracket mounting hardware as seen from below. It's not quite as close as it looks in this photo but it's close so definitely pay attention to this part.
View attachment 1715648127
The other side had a slight obstruction that required a slight modification.
View attachment 1715648126
Throw a little paint on the brackets then install them for real. Hinge first then L brackets. I first installed this with 67lbs each side struts and the bracket seemed plenty strong with no flex going on but the struts were not strong enough. When I went with 100lbs struts I decided there was an easy opportunity to add a 1/8" x 1" support which should keep a lot of stress of the body panel.
This how it ended up looking. I'll take them off and paint them too.
View attachment 1715648128 View attachment 1715648129
I didn't fully install the original torsion bars but you can see they just fit under the struts. This space opens up as the trunk closes.
View attachment 1715648130
And there you have it. Hope this helps someone else in the future. I've had a floppy trunk for quite a while and have yet to see any new torsion bars made for the convertible and could not find anyone to recondition mine. So after all that hassle I'm really happy with this mod. Hopefully get a few years out of a pair of strut rods on the daily driver. Gotta get those groceries!
