Hey guys,
Page 11 shows the subframe connectors being installed. I also welded the K member solid and added a flaming river close ratio steering gear for handling. I have tubular A's also, and a 1.250" sway bar.
My '68 'vert had significant cowl shake after installing the sub-frame connectors and under radiator brace. The under fender bracing and welding the shock towers to the inner fenderwells made a huge improvement. Before I welded them in, I noticed there were already cracks forming on the inner fenderwells where the shock towers were spot welded to the inner fenders. This was with a rust-free chassis and a stock Slant 6.
Subframe connectors are a great place to start with to stiffen the chassis. Next best and easiest thing to add is a bar to tie the front frame rails together under and just behind the radiator(between the K-frame and lower radiator tank). The US Cartool one hangs down out of the way and is a nice point to jack the car up with a floor jack.
Then the under fender braces and welding the shock towers solidly to the inner fenders and finally fab up a triangulated Monty Carlo bar that bolts on in the engine compartment and ties together the cowl to both front fenders. It looked cool too. I used a few of the factory fender attaching bolts to mount it and added a few bolts to the rear attaching point above the wiper motor. It did require me to drill 3 small holes in the sheetmetal spot welded in above the wiper motor. Once all the other chassis improvements were welded in and the Monte Carlo bar was bolted in, the remaining cowl shake was not detectable. I had to remove the when I swapped engines from a Slant 6 to a Magnum, as the A/C compressor was in the way. I'm going to make another one when I get back from Spring Fling.
The biggest improvement from adding all these improvements was the way it made the chassis feel so much solid and composed when driving over rougher wash-board type roads. The car also felt like a solid platform for the suspension to work under harder braking, cornering and accelerating. It's hard to explain. The car just felt way better at all times when just cruising along and especially when enjoying a more spirited drive. Chassis stiffening is worth the effort if you really get into fine tuning your cars overall performance.
If you look closely, you can see barely see part of the lower frame tying bar.
