Fix for Cowl Shake and Body ?

[GaryS]

It's not bad on my restored and modified daily driver '64 200, but it is noticeable at in-town street speeds.

I've been told that brand Cs use some kind of counter balance weights in their convertible fenders to dampen movement, but that sounds like something that needs calculated engineering with extensive testing and doesn't sound feasible for retrofitting our convertibles.

Despite all new seals and weather stripping, adding expensive sound deadening materials throughout and upgrading under-carpet padding, closing the doors makes the posts shake and the doors reverb until it sounds almost "tinny". I've seen braces to help control frame twisting for racing and handling, but I've never seen anything designed to stiffen or dampen vibration in other parts of the body to improve overall rigidity and reduce noise.

Anyone else thought about doing this?

 

[Dana67Dart]

Na... It's a convertible, I can't hear anything after driving for an hour on the interstate. When I drive with the top up, I hear all kinds of noises, but it is a 54 year old car not a modern plastic disposable car.

Just my 2 cents.

Many cars have spray on panel stiffener like that in our trunks on the quarters.

Anything to thicken the sheet metal will reduce the tinny sound you talk of.

 

[Jim Lusk]

Subframe connectors will help some, not just for drag racing and road racing. We never put them on the GTS convertible and likely never will, but you can tell a VERY noticeable difference in total stiffness between it and my son's '67 Dart convertible, even though the '67 has a 440 to add more weight.

 

[jbc426]

I have a '68 Barracuda convertible that I welded in the full US Cartool Chassis Stiffening Kit. I made a huge difference, but I still had a bit of the cowl shake left. It was most noticeable around town.

When I still had the Slant 6 under the hood, I made a Monte Carlo bar that tied the cowl and fenders together. It consisted of 3 tubes that formed a triangle and attached to several of the inner fender bolts and the pinch weld above the wiper motor.

This Monte Carlo bar stopped the remaining cowl shake.

It no longer fits with the 5.9 Magnum & A/C I installed, and I haven't bothered modifying it for the V8.

 

[GaryS]

Thanks for the replies. I already have a lot of "Road Kill" sound deadener material installed, but next spring I'll do a better job by installing more, especially in the trunk and quarters.
I'm also going to find out about the US Car Tool stiffening kits and see if there is a way to reinforce the door post latch pin area. I don't think the bar idea would fit with my A/C setup.

 

[sccachallenger]

A fiends '73 Swinger 383 always felt kind of flimsy when closing the doors. Might be why many suffer cracks around the door strikers. Even a basic homemade set of sub connectors will help. I mean compared to a sedan, no pillar, and no roof! What do we expect from 50+ year old metal?

 

[A56]

These are in production from USCT (inner rocker sill brace) and they are for A bodies. Very similar to what was used in E body convertibles from what I've read. The only down side is the lower outer rocker panel on each side has to be removed. I'm presently waiting for them to be released.

 

[burdar]

Starting in 74, the factory added bracing from the firewall to the fender tops. They were getting complaints of cowl shake and this was their fix. I'm adding them to my 68. Since the pinch weld on the firewall isn't wide enough for the braces(the factory widened the pinch weld in 74) I made up some aluminum extensions to give me a place to mount them. I think they will look fine on the 68. The main thing is that I'm not going to try and color match them to the car. They will just be matte black. Anything else and I think they would stick out like a soar thumb.

 

[4spdragtop]

Starting in 74, the factory added bracing from the firewall to the fender tops. They were getting complaints of cowl shake and this was their fix. I'm adding them to my 68. Since the pinch weld on the firewall isn't wide enough for the braces(the factory widened the pinch weld in 74) I made up some aluminum extensions to give me a place to mount them. I think they will look fine on the 68. The main thing is that I'm not going to try and color match them to the car. They will just be matte black. Anything else and I think they would stick out like a soar thumb.
View attachment 1715788839
View attachment 1715788840

 

[sccachallenger]

Like your idea!
Hope your "soar" thumb feels better soon