Thanks for all of the replies guys. I appreciate all input...makes the old brain work.
The frame rails on the late b are essentially flapping in the breeze. I think your boxing the radiator support is a good idea. I'd also suggest doing a pipe from the firewall down to the end of the frame rails to triangulate them and to stiffen them up. I wouldn't make them straight. Not only would it interfere with the bolt on inner fenders, but a kink would also give it a crush zone in case, God forbid, a front end collision. Solid iso biscuits are best, but because of their thickness, the K-frame's loads will have a larger torque vector on the frame rail rather than a non-iso mopar, so it won't be doing as good a job as the other Mopars. A late B K frame is mondo heavy compared to the earlier ones, too. There's ways to lighten that up without sacrificing stiffness (think installing windows, but welding up the trim) but now we're in mission creep regarding not going max-effort. A Monte Carlo bar from the firewall to the top of the fenders is almost worthless as there is no strength up there on a late B.
Thanks cudazappa. I was hoping you were still around to chime in. You had a '79 300 did you not? If I'm thinking of the right forum member and car, I have pictures of you auto-crossing it at Carlisle among my rotating desktop backgrounds.
Flapping in the breeze...that was sort of my thought. Not in a literal sense, as there's a 100lbs. of steel on the froont in the form of bumper and impact bar that tie that all together. But I'm not sure a "whole lot" that goes on out there impacts the frame where the K is bolted in, this probably has minimal impact on suspension movement (all a guess on my part).
I guess I was thinking of something different when I pictured a Monte Carlo bar. I wasn't thinking of the std. Mustang V from cowl to shock towers, but the addiiton of triangulation with the cross-compartment bar, like a strut tower brace in a newer car. Just about impossible to fit with a big block and low hood I would think.
To clarify, that crude little drawing that shows the lower core support boxed...that's my drawing in section of what is already there. Ma already did that work for me. And it's pretty stout steel too. I'm planning on leaving that alone.
FWIW, when the 3rd-Gen GM F-bodies were designed, they found that a rad support reinforcement helped handling.
IIRC, Z28s & TransAms got that. Those were the first truly unibody F cars.
I think the point was to help fight flexing frame rails.
If you want that structure stiff, so the suspension action isn't masked by structure flex, look at triangulating the rails into surrounding structure.
Doesn't have to be in the engine compartment either, look at the wheelhouse area.
By a strange coincidence, I have an '88 Trans Am. I bought it as a turn-key driver to take the kids to shows and cruises while they were still young enough to go, knowing the MOPARs would have to wait some years for me to get to them.
![[Linked Image]](https://live.staticflickr.com/65535/49905240411_25f6a57ab9_b.jpg)
Are you referring to the "wonder bar" that braces the front rails, particularly in the area of the fast ratio steering box? I had thought of something like that as a plan B for reinforcing that core support area.
A Monte Carlo bar from the firewall to the top of the fenders is almost worthless as there is no strength up there on a late B.
I would say there are more for cowl shake than anything. Not that reducing cowl shake is not a worthy purpose, but it probably not adding the kind of torsional stiffness I was thinking of here.
My '70 Duster did not have them, but my brothers Hang 10 did. So I added a pair to it. Then again, as a teen, I did a LOT of bad things to that poor old car.
Moving the upper control arms from the unibody structure to the K-frame was more about ride quality than anything else. General idea being that any road vibration that gets picked up by the upper control arm has to travel through the rubber k-frame iso mounts before being picked up by the front stub frame. A secondary benefit might have to do with production cost by eliminating welded in inner fenders.
No clue what, if any, value is added by the diagonal braces from the cowl to mid fender. For starters they are thin wall tubes and ya can pretty much bend them with your hand. The fenders are thicker and it's not like they rattle around with those bars. The metal inner fender which is mostly a splash shield likely adds more stiffness to the fenders than that brace does.
The k-frames in these things are massive, boxed and plenty stiff but they do have weak spots. The worst being where the rear mounts attach and if yer gonna crack one, that's where it's gonna happen. Adding a plate there couldn't hurt. I would tend to agree with statement that the front bumper reinforcement adds more structure to the front of the frame rails than the rad core support does. It's one seriously solid hunk of steel. As you intend to delete that, adding something to core couldn't hurt. As for the idea of running some tubing from the front of the frame to the firewall, the weak link in that is the firewall. Only way I see that having any real value is if it goes through the firewall and ties in to a full roll cage.
If you've been around these things for a while you've probably seen than full tilt road race Doba that occasionally pops up for sale. Owner strikes me as more than willing to discuss the mods he's made. There's a couple hints about front frame mods in the first vid here:
https://bringatrailer.com/listing/1977-chrysler-cordoba-3/ I have seen that car. I wrote to him once many years ago when there was a Cordoba forum, and I was writing a quarterly newsletter. It was called Miss DD back then. It was a cool effort to see.
And I agree about the bulk of this K. It's a beefy piece for sure.
