Gas Struts on The trunk lid? Here you go.

I'm using Guden gas springs on my hood and in the trunk. I used 150 pound, 15 inch gas springs for the hood, I'm planning on using 120 pound 15 inch springs in the trunk. The Guden webpage lists various struts, with length and load ratings. I called Guden and spoke with Karen Kavanagh, a customer service rep. She was outstanding in helping me get the struts I needed. If you need help give her a call. Tell her I said hi. If I can help with information let me know.

Karen Kavanagh
Customer Service Representative
H. A. Guden Co., Inc.
Industrial Hardware Made Easy
www.guden.com ** kak@guden.com
1-800-344-6437 x108 Fax: 1-631-737-2933

About to embark on a gas strut conversion on my 67 Dart convertible. Been a long time coming. Had been hoping to find someone that can recondition the torsion rods but no luck there. The last straw was buying a set of used rods that also turned out to be mushy then finding I had some torn metal on the mounts as well. I'm kind of over torsion rods at this point!

So here we go. Maybe you guys can check me for sanity on this. I haven't done it yet but I just put in the order for the struts - 15"/67lbs each side so 134lbs total. Came to this by doing a little math. Trunk weight at the outer edge where the key is comes in at about 35 pounds which is about 38" from the pivot point. Looks like I'll have the rod mount at about 8" off the pivot point so it looks like that's about 160lbs. The plan is to have the strut rods assisted by the mushy torsion bars so I'm going to try this out. Worst case weight-wise is that I'll waste the $14 on the set of struts I just ordered.

The rods I ordered:
https://www.amazon.com/gp/product/B01M9FWIV6/?tag=fabo03-20



So with the top folded down and some obstructions the first this I was concerned about is the routing and extension needed to have the rods as out of the way as possible. So I made a little jig with some magnets and a coat hanger. Marked the coat hanger off at the 14.96" extended and 9.06 compressed points then put the one magnet on the hopeful hinge mount point and set the other one down by the wheel tub right at the extended point on the rod. Then close the trunk and see if the hanger pushes past the compressed point. It didn't. Maybe an eighth of an inch to spare!


Not a lot of room with the top lowered, the gas fill tube and there is a triangle of space cause by the support bracket.

Anchor point on the hing just under the original rod.

Man that is close. The white marks are extended and compressed lengths in relation to the hinge mount point. This is the trunk in the closed position as seen from the seat area with seats removed.

Had also considered going from the trunk lid to the hinge bracket. Would have been a no-brainer extension-wise and could have used lighter struts but this is a daily driver and I do put my bicycle in trunk hidden away fairly often so I thought I'd try the more hidden method.

So the plan is to have the hinge mount point just under where the original rod and slider meet. Want to make sure that they don't interfere with each other but can't afford to come too far off the hinge without getting a rod with more extension. So far it looks like it will work.

Going to make some 1/8" flat bar steel brackets that bolt on to the hinge with a hole for the strut. Make one, re-test the extension then make another bracket for the lower end that will mount to the floor just next to the wheel tub with holes drilled in the floor and stainless steel hardware. Floor seems like much thicker gauge steel than the wheel tub so I'm going to trust that to the 67 pounds of force that's coming. Will connect the rod to that bracket, mark off the hole positioning on the floor, drill that and attach bracket to the floor. Going to make the floor bracket a little long in case I need to get a longer strut and drill a new hole in it rather than a whole new bracket. Next do a little trunk close and open test to make sure nothing unexpected is happening then do the other side. Once they are in and working I'll maybe add the original torsion rods back to help, leave it as-is or buy some different weight shocks depending on how it goes weight-wise. Seems like there are several weights available in the 15" struts that have the same extended and compressed lengths.

Am I missing anything?

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.

• 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.


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.


Then make and install the plates based on the templates.

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".


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.


The other side had a slight obstruction that required a slight modification.

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.


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.

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!

maurice_meyer said:

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!

Click to expand...

Thank you, Maurice! Lots of great info! So am I reading correctly that you currently have just the struts hooked up? And not the torsion bars to assist in lifting?

This is one of the cleanest trunk strut installations I've seen.
Impressed!

75slant6 said:

Thank you, Maurice! Lots of great info! So am I reading correctly that you currently have just the struts hooked up? And not the torsion bars to assist in lifting?

Click to expand...

Yes, that's right. Fully working on struts alone. Doesn't pop up from unlock but holds tight at every point along the way and self-raises from the higher position. I kind of like that.

I should say: I haven't installed the torsion bars and actually verified that the whole thing works together with strut rods and torsion bars together - just that there is clearance in the open position that should work as long as the torsion spring doesn't travel any further up the hinge.

ocdart said:

This is one of the cleanest trunk strut installations I've seen.
Impressed!

Click to expand...

Thanks! Hope it helps someone else. The recommendation on rear 10x2" drums on this site saved me just a little while back. This floppy trunk has been my car nemesis for a long time and I really didn't want to break from originality but it had to happen after I finally found another set of torsion bars that also didn't have any spring left.

Here's a quick video on the strut rod setup. You can see how even though it doesn't raise from the low point it's nowhere near falling. This is with 100lbs per side 15" rods. I'd like to try 120lbs rods but the smallest I see so far are 17" which means making an add-on to the L bracket on the floor. considering it.

maurice_meyer said:

Here's a quick video on the strut rod setup. You can see how even though it doesn't raise from the low point it's nowhere near falling. This is with 120lbs per side 15" rods. I'd like to try 120lbs rods but the smallest I see so far are 17" which means making an add-on to the L bracket on the floor. considering it.

Click to expand...

That’s awesome! One thing that just dawned on me, I have a Duster and my trunk lid is quite a bit smaller and probably a fair amount lighter than a 67 Dart’s. So the 100 pounders might actually work well for me.

Thanks Maurice! Found this while searxhing for info on 69 cuda vert trunk hinges.
excellent work and detailed write up!

maurice_meyer said:

Here's a quick video on the strut rod setup. You can see how even though it doesn't raise from the low point it's nowhere near falling. This is with 100lbs per side 15" rods. I'd like to try 120lbs rods but the smallest I see so far are 17" which means making an add-on to the L bracket on the floor. considering it.

Click to expand...