Anyone install coil overs instead of using torsion bars?

Hi Clive…no mention of removeing the reaction plate as mentioned in the original post…Steve

Why not fabricate a channel shaped piece of sheet metal that mimics the profile of the top section of the picture frame. I imagine any decent sheet metal shop could fabricate it out of 18 ga. stock. Drill the holes as appropriate and spot weld it in place.

Crude drawing below:

I haven’t read every word in every post so I may have missed the answer to the following question: What do you gain by replacing the torsion bars with coil over shocks, other than the elimination of the bars themselves?

For me, it’s simple, with an adjustable shock/spring combination, easy and quick to adjust height and removal/replacement/adjustment if the bars……PITB……no longer required, so getting engine/bix assy easier too.

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The original poster wants to remove the torsion bars so that they can remove the reaction plate to make room for a different drivetrain. As discussed much earlier in the thread, the reaction plate also serves the purpose of stopping the car splitting into two down the center line, so removing it without something that serves this purpose is likely to be problematic. The thread has almost entirely focussed on the coilover issue, which has made for an interesting and educational discussion but begs the question you have asked - “why bother?”

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There’s no likely: it will be problematic.

Even if one removes the torsion bars, one still needs to put the reaction plate back in place, otherwise you are losing a major structural member. I brought this up nearly 20 years ago and was laughed at: well, laughing or not, the fact still remains.

On reinforcement. Be aware of a problem - you cannot overlay the picture frames where the front and rear frame bolts to it as that would push the picture frame and the bonnet hanging frame forward.

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Hi Terry, howcome?
Do you have a pie chart or graph or similar to explain? :smile_cat::smile_cat:
Thanks to everyone chiming in. It’s been an interesting rabbit hole.
I decided ultimately decided to keep some sort of reactor plate, although I will redesign it to accommodate the new drivetrain.
And even though the E body is quite rigid for unibody, I’m still going to reinforce structurally with chromoly framing front to back.

Could one add same thickness shims at the bottom mounting points to compensate?

Remove some shims at the front mounting points, if you have enough there?

Forget I said that, side plates better :roll_eyes:

I’m not qualified to discuss the reaction plate, the recent flood of posts makes it clear that others are. My comments are limited to coil springs, of which I have some experience - nothing from me on torsion bars except…why?! :fearful:!?

Seems like a worthy goal in itself. Fleets have set sail for less

Two areas you might look at for increased stiffness:

  • the upper, outboard diagonals of the front frames attach to the firewall but there’s very liitle structure behind there to carry the loads on. With the project car I’m working on we concentrated on a new tubular tunnel structure and left the outboard tube as mainly symbolic.

  • linking the left and right front frame “pylons” to each other in the horizontal plane. As we were switching to an AJ6 engine we were able to run a diagonal under the engine,

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You may want to explore the body stiffener system offers by Chuck at Moncoque Metalworks.

The system includes stronger gussets that go inside the sills along with a length of rectangular steel welded into the inner sill between the gussets. Also - two HD 16-gauge stiffeners for the rear lower bulkhead behind the seat dish.

From his website:


Body shell flex, chips along the edge of the rear doors, and eventually the inability to close or open the doors are all distant memories for this 1968 Roadster. There have been many different attempts to stiffen the sills of these cars – extra gussets, sheetmetal tie-ins with fancy little holes in them – you’ve probably seen them on other forums. They are all TINFOIL compared to our 12-gauge tubing and thick 16-gauge gussets. On our shells, the passenger cockpit is essentially boxed-in with a “flat roll-cage.” AND – it’s an inexpensive addition that only adds 32 pounds – a small price to pay for the added stiffness – and safety! More details and MANY more photos in “1968 Open Two-Seater – GP.”

Several photos i this link

Talk to Chuck about your plans - he may have others thoughts

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Hi Les, I think your L-shaped addition would be good, especially if you can increase the radius in the corner as shown in the sketch below.
I’m speculating that cracks initiate in the corner (where the red dashed line is) because that’s where the highest bending moment from the damper loads occurs. Also, much of the surrounding area is stiffened by bolted parts and attachments, so the stress will concentrate in that corner.
If you could increase the section depth by 6mm without intruding on the wishbone you would add 20% to the strength in that critical area. That matches the amount I estimate loads increase with current dampers and a coil spring, so could be a simple solution.

Additionally - the L-plates will help stabilise the frame against the compression (buckling) loads applied by the high rebound forces of current Girling and Gaz dampers, not present in the original car.
All the above assumes there is a solution to the point Terry raised re the picture frame location. Perhaps the L-plate could go inside the frame, with adjustment to existing parts?

Clive,
What guage material would be required and what type? Stainless would look the part!:slightly_smiling_face:

Anyone?
I’m thinking it wouldn’t need to be very thick to reduce the direct stress in the corner, because it’s the vertical height and radius that’s important. Maybe 1/16" or 2mm would make a useful gain?
Thickness would be more important to reduce buckling tendency but I think that’s more theoretical / lower risk, so I’d still aim around 2mm. A good connection most important - welded, riveted, bolted?
Anyone with more direct practical thoughts?

I would consider a tent-shaped addition to the top of the picture frame, and just use mild steel double plates, welded on the sides.

I would still suggest increasing the corner radius, as stiffening other areas will tend to focus the stress in that corner. Does any of the replacement builders do anything like that? Including it in frame build would be zero cost insurance - would it raise concern on originality?

Hi Clive…is this all that you suggest needs doing to use coil overs in place of torsion bars… Steve