Calling the rigidity experts....

I've got a solid '75, converted to SBC and I've already got the inner long kit and steel GT flares ready to be installed. This is a daily driver, pressed hard (track and mountain roads) occasionally. I don't want a cage or roll bar, but I'd like the car to stay together over time.

I've heard that the standard GT chassis kit doesn't really address the proper issues in the engine compartment area, and that the box arm stiffners aren't worth the weight.

What alternatives are available for the GT chassis kit that will get the job done right?

With a V8, 200# rears and 9x16 fuchs on 1 inch spacers, is the box arm kit justified?

Thanks in advance...

Eric

I'll mimic what other people say. it adds unsprung weight, you can easily bend the arms when welding it from the heat. If all goes well and you have it installed - then hit a curb or something, if the trailing arm doesn't bend, where does that force go? Suspension pickup points, trailing arms are easier to find and install than broken suspension ears.

QUOTE (Travis Neff @ Apr 21 2005, 12:35 PM)

I'll mimic what other people say. it adds unsprung weight, you can easily bend the arms when welding it from the heat. If all goes well and you have it installed - then hit a curb or something, if the trailing arm doesn't bend, where does that force go? Suspension pickup points, trailing arms are easier to find and install than broken suspension ears.

Concentrate on the chassis first, not the arms.

Would the shock tower mod, like the one gint did help him any? I think you could do some kind of brace from the firewall to the shock towers too. BTW I have no idea what I'm talking about, just trying to brainstorm

Check out one of "Z's" avatars? Usually does it for me.

I disagree with most of what's been said about GT chassis stiffening kits. The large piece ties in the outer longitudinals from the tranny mounts forward to the rear shock mount area (that area of the body "is" the outer longitudinal). I've visited many a bare tub and had a retired Boeing airframe engineer there on one occasion. The GT chassis kit is very viable IMHO. Porsche racing engineers were and are some of the best in the business.

with most of what's been said about the trailing arm kits. I think the kits would help. I, in no way, think welding on them can warp them but: I think they should bend before your suspension pickup points do and I think then the weight is unnecessary.

Gint didn't do any shock tower mods other than a few well-placed stitch welds inside the tower itself.

On that note: I think Gint's tub is one of the best examples of a stiffened tub w/o a bar or cage. I think he did it right. Here's what was done:

Windshield base reinforcements
Engman Inner kit
GT Kit and,
The aforementioned stitch welds in the shock towers.

Hope that helps...

I think the inner long kit will do wonders for your stiff ride. maybe add a pillow for your arse to soften the daily stiff ride

Look at the pictures of Robert Gagnon's car. Don Araki built this cage and his approach to cage design is much different than everything else out there.

Notice the bar that ties the rear shock towers and frame rails together no one else does that.
http://www.pbase.com/9146gt/image/22288844

Notice the rear trailing arms. Reinforced and setup to run custom monoball set up.
http://www.pbase.com/9146gt/image/22288851

If you have never cut a rear trailing arm apart, you should it is a great learning experience. THe whole trailing arm is made of .095 thick steel plate.

I'm planning on Engman's kit. That design is undoubtedly the strongest/best reinforcement for that section of the car. Then bars from shock towers to firewall, and that point other side of firewall down to longs (the red lines in the picture below). This will cause the longs in front of the red bar to get more stress, but if the longs are strong enough then it's ok (and the reinforcement kit should be sufficient for that).

The bar in the cab is steep enough to not interfere with getting in and out, but has enough angle to support the bar from the shock tower.

I trust Brad's opinions more than anyone's on this stuff and he said he liked those bar positions. He also added that a crossbar should run horizontal across the top of the firewall - can go on rear side just under engine lid.

The one question I have never been able to get an answer to though (someone please?)... Is the green bar in this picture necessary? Yeah, it's at a great angle for strength, BUT the firewall should provide plenty of strength to cover that angle of stress. Unless the firewall isn't tied into the frame rails strongly enough. Is that the case?



My goal is stiffer for handling improvements, strong enough for a V8 conversion and agressive driving, but more subtle than a full cage.

QUOTE (Brett W @ Apr 21 2005, 01:59 PM)

If you have never cut a rear trailing arm apart, you should it is a great learning experience. THe whole trailing arm is made of .095 thick steel plate.

Brett,

I believe the trailing arms are made of 2mm (.079") thick material. The welded tube that encircles the CV has the same wall thickness as well.

Andy

QUOTE (Sammy @ Apr 21 2005, 07:30 PM)

What, no viagra jokes? you guys are slipping ....

Naaa.. this one is too easy.


But it DOES sound like a personal problem to me.......

Kind of shocked that there's no mention of Brad Mayeur's outer long reinforcement kit. I've got one on my '73 (PO was going to go V8), and it's stiffer than wedding day dic....uh..it's pretty rigid! It's not light, but if you're going V8 what's 15 - 20 lbs? I think the combo of Brad's and Marks (Engman) would make the car as stiff as possibly be without going "cage".

Couldn't resist.