Any (convert) structural damage with increased performance?

[droptail]

Particularly relating to convertibles, has there been a discussion on structural/body damage/warp with increased engine (and even perhaps suspension) mods?
I've done about all that I am comfortable with on this convertible, prevented me from adding some aluminum heads that I've always wanted.
I've always been concerned about getting any more engine with my structurally compromised convertible.  I have seen evidence of some (minor) flex when jacking the car up at times.

[HP2]

Lots of topics on here about how weak the uni-body chassis  is, even if it hasn't been tweaked. However, even if your car has been wracked and straightened, it doesn't eliminate it from being able to be improved.

IMO, anything with  a slant six or better should be installing sub-frame connectors at a minimum. If your serious about stepping up the performance of you engine at all, then it should also include a comparable number of chassis mods to support the increased output.

If you car is already structurally compromised, then you really need to get it back to a good starting point, then improve it from there.

[GoodysGotaCuda]

In my opinion, these cars were mediocre in terms of chassis rigidity the day they rolled out of the factory. Time has not helped either, nor does it being a convertible help as well.


I agree that subframe connectors should at least be on all of these cars, if you can swing it, go for the weld-in. I'm not a fan of bolting in something like that personally.

[droptail]

The only evidence I have seen is perhaps a minor misalignment of the door when jacked up on 1 corner (not great practice), but re-aligning when back on the ground.  I will verify.
I should check for any cracking at the spring mount locations.

I won't be welding or drilling anything on the car.

I searched for structural damage but got nothing.

Thanks

[CudamanTom]

I won't be welding or drilling anything on the car.

Thanks

Then you are limiting yourself for any structural improvement. I too own a cuda convertible with a 440 and you have to be careful as to where to even place the jack, as you mentioned, so not to tweak the body.
But if no welding or drilling, then don't look for more power under the hood.

[71gogreen]

On one of Graveyard cars episode Mark Worman said to Darwin that subconnectors are not necessary.He also stated that behind the rocker panels were 1/4 plate steel to stabilize the frame. Mark said with the torque boxes it was not needed.      

[HP2]

Bzzzzt. Incorrect.  There are no quarter inch thick steel plates behind the rockers in convertibles. There is a fairly large 3/16" thick bolt in panel behind the rear set quarter trim panel and under the window, but I think this was limited to '73 and'74 models. Additionally,  not all 'verts got torque boxes, although they should have.

The lack of a roof makes convertibles highly susceptible to beam bending under load. This is exactly the type of resistance that a subframe connector is designed to prevent. While I am a big fan of welding in structural improvement for the best result, a bolt in SFC will help considerably over nothing at all. Especially in a 'vert. I'd also highly encourage adding torque boxes, welded in, if your 'vert does not already have them. These can be purchased as reproduction items if maintaining originality is a huge concern.

[dfrazz]

Bzzzzt. Incorrect.  There are no quarter inch thick steel plates behind the rockers in convertibles. There is a fairly large 3/16" thick bolt in panel behind the rear set quarter trim panel and under the window, but I think this was limited to '73 and'74 models. Additionally,  not all 'verts got torque boxes, although they should have.

The lack of a roof makes convertibles highly susceptible to beam bending under load.

Curious, beyond the panel was there any other additional structure support on verts?

[1 Wild R/T]

Bzzzzt. Incorrect.  There are no quarter inch thick steel plates behind the rockers in convertibles. There is a fairly large 3/16" thick bolt in panel behind the rear set quarter trim panel and under the window, but I think this was limited to '73 and'74 models. Additionally,  not all 'verts got torque boxes, although they should have.

The lack of a roof makes convertibles highly susceptible to beam bending under load. This is exactly the type of resistance that a subframe connector is designed to prevent. While I am a big fan of welding in structural improvement for the best result, a bolt in SFC will help considerably over nothing at all. Especially in a 'vert. I'd also highly encourage adding torque boxes, welded in, if your 'vert does not already have them. These can be purchased as reproduction items if maintaining originality is a huge concern.

Bzzzzt. Incorrect.

[71gogreen]

Thank you for clarifying the plated steel reinforcement in the rocker panels! So Mark Worman does know alot about Mopars! I under by trying to reinforce the mid section might help out in the "Torque factor" ,but I don't see how welding a piece between the front and rear box frames will make a difference? Plus your changing the value of originality .I'm just not completely sold on this concept!

[HP2]

Bzzzzt. Incorrect.

Thank you for clarifying the plated steel reinforcement in the rocker panels! So Mark Worman does know alot about Mopars!

Okay, I was wrong. Worman is still a boob.

I under by trying to reinforce the mid section might help out in the "Torque factor" ,but I don't see how welding a piece between the front and rear box frames will make a difference? Plus your changing the value of originality .I'm just not completely sold on this concept!

I'm confused. You say it helps the "torque factor" but don't see how that makes a difference?  If you do not use the floor contoured type and weld these only to the front and rear subframes, then they are effective and can be easily reversed if you decide to sell and have a buyer who wants flexi-flyer originality.

[71gogreen]

I would think the faster an engine is given power the more torque is applied through out the body before its transferred to the rear axle. Mopar engineers compensated for torque values by offsetting the engine mounts and offsetting the rear springs. I believe the only way to reinforce the center section is to extend the sub connectors past the welded points that are being sold currently. I'm just not convinced that it makes a Real difference unless you hammer the crap out your car.

[HP2]

Engines are offset to allow steering box clearance. I'm not sure what you mean by offset leaf springs. Some earlier body styles use parallel springs, some later ones use splayed mounting. This wasn't designed for torque resistance so much as handling improvements. If you mean biased leaf counts in spring packs, then yes, this is for torque resistance, but it only came on high powered cars.

The simplest test, as pointed out earlier, is to put a bumper jack on the corner of the car, crank away, then try to open the door. In some cases the door won't open at all, in some cases it will, but you won't get it shut. Now put the rinky dinkiest, thin wall, 2x1 bolt in frame connectors out there and repeat the test. You will now be able to open and close the door with ease. This is because the sub-frame connectors tie the front and rear frame structures together creating that extension out past the actual pieces you are installing to shore of flex along the entire length of the car.

This additional rigidity not only helps in high power applications but in mundane under-powered cruisers as well. By reducing the deflection of the body, you also eliminate body shake, squeaks, rattles, and wind whistles. It keeps body gaps more consistent and allows seal to maintain their seal consistently. it makes the overall driving experience more predictable and even if it is an underpowered car, allows the suspension to work more effectively at doing the job its designed for.

Ever watch XV Motorsports video on chassis flex? It was pretty revealing. Its too bad the new XV doesn't repost it.