Second gen subframe to firewall Y brace

[yody]

On nastyz28.com there is a guy there from pro-touringf-body.com that sells a Y bar that goes to the upper control arm bolt and then Y's out the the cowl area and the hood hinge bolt on the firewall. I am thinking of buying this "bolt-on" part but am having a hard time understanding how this helps subframe flex much. THe cowl area has a lip on it, that i suppose you drill a hole through to mount the brace, that cowl area is really flimsy. Also hte hood hing mount isn't the strongest thing in the world. And then the brace only bolts to one bolt on the upper control arm. Just wondeing if anyone sharper than me could point out how they work?
https://www.pro-touring.com/featured_cars/Camaro/1969_Camaro/dale_buerger_79_z28/dale_no_front_clip_001.jpg
https://static1.pt-content.com/images/pt/2005/02/Picture012223x149-1.jpg
https://static1.pt-content.com/images/pt/2005/02/DSC00127180x129-1.jpg

[JMarsa]

Yody,

I would think it would help a little in keeping the subframe parallel
to the car. If the body mounts are soft and you jack a F/X body up from the front crossmember you usually get several strokes of lifting on the jack until the front end "pinches" itself tight to lift the car. I'm using a bar from the frame rail to the firewall to eliminate this flex. The inner/outer fenders, core support and hood are all integral to providing support to the subframe in this area.

--JMarsa

[David Pozzi]

Herb Adams came up with a kit like that. I think it bolted to the rear bolt though, maybe not. It helps stiffen the sub but you are correct that the inboard legs of the braces bolt to a weak area that is likely to bend or deform. You can put a reinforcing doubler inside to stiffen the area. The outer end bolts to the hinge and fender mount area, It is stronger but how much I don't know.

If I were building one for my car, I'd weld a bracket to the sub just behind the A arm, and bolt to it, that way it's out of your way when adjusting Caster and Camber.

[Tom Welch]

having purchased and used Herb Adams' products, in particular the second gen f-body parts I can tell you from my experience that the concept shown works very well.

[Marcus SC&C]

I haven`t used these particular braces but I can tell you that a suprisingly small amount of bracing,properly placed and make a big difference. Since the subframe is basically cantilevered,the brace just needs to reduce body mount bushing deflection. Herb actually recomended this type of brace (and aluminum upper subframe bushings) instead of subframe connectors. I dunno if I`d go that far... Marcus SC&C

[79T/Aman]

yody they do not bolt to the hinge but to the re-enforced bolt bulk head the fender mounts to.

[yody]

in the picture it looks like they bolt to the part on the firewall that your hood hinge and fender bolt to, is this not correct? that piece is just tack welded in.

[79T/Aman]

ok I see what you are saying, yes it bolts to where the fender bolts to the firewall, thanks DJ

[DB Z28]

Yody in the Picture it bolts to the upper fender mounting ,two holes to the top lip of your firewall, and to your upper control arm I bought that kit in the picture about 15 years ago from herb adams If you want more pictures I,ll send them to you when i get home. [email protected]

[DB Z28]

Their is a better close up Of the bars on Pauls site Hydroboost under pictures Dale

[Mean 69]

This is a great idea, I have been pndering the same thing for the first gen's too. Even though you'd be suspect of the loads going into the firewall, which is pretty thin (and can be further braced ala David's suggestion), the main load path here is not longitudianl (i.e. fore and aft, which would be nasty for the thin metal), but rather torsional. If you tried to twist the subframe, think about how this would strain these arms, basically the majority of the load would be trying to shear the sheet metal (firewall), and while the firewall isn't a great place to handle other types of loads, it can do quite a lot to offer shear resistance without being damaged.

Now, the execution, due to packaging obviously, might be improved a bit, but may not yield any gains in practice worth the trouble. The outer arms, that bolt near the hood hinges, by the way, do little to nothing to resist torsion (twist), their main load path is to prevent upward and downward bending. I "hope" you don't have a problem with that!

I'd say they are money well spent.
Mark