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11-19-2007, 11:40 AM #1Registered User
- Join Date
- Sep 2006
First generation unibody strengthening
Howdy. I’m trying to figure out the best way to stiffen up the zero-generation unibody on my 1966 Ford Fairlane GT with a 390 FE. It’s mostly for street with some light strip, and my main goal is to make it handle decently. I’ve done pretty well so far, it’s got Global West upper a-arms, Edelbrock tubular tie rod sleeves, 1-1/8” front anti-roll bar and ¾” rear, QA1 adjustable shocks front and Bilstein Heavy Duty rear, new stock springs, and mix of new poly and rubber new bushings, as well as a shock tower brace and subframe connectors.
I’m not asking about suspension setup stuff, though: what I am trying to do is get information on general unibody strengthening tips that would be applicable not just to me but to others with older nose heavy muscle type cars. I’ve looked through this board as well as other web resources and parts that are available for my specific car. The parts and techniques I’ve found, in order from front to back are listed below. I’ve also listed what I think are the key attributes of each:
- Vertical Radiator V brace: reduced front end parallelogramming (from Evolution Motorsports)
- Shock tower brace (Mustang Monte Carlo Bar): torsional and beam stiffness via triangulation
- Firewall to shock tower braces (Mustang Export Brace): torsional and local beam stiffness by providing a load path between the two individual strut towers and between each strut tower and the firewall. A post here said that bolting an export brace on a classic Mustang brought deflection from 1.062" down to 0.319", a 70% improvement over stock. This clearly seems to be the single best improvement to make based on multiple sources.
- Subframes: A post here said that Maximum Motorsports said that testing on Fox body sub-frame connectors revealed that they help improve beam deflection of the frame rails, but have little to no effect on reducing torsional deflection.
- Driveshaft loop tied into subframes: some torsional stiffness if done right?
- Driveshaft tunnel brace (used on convertibles): reduces overall parallelogramming by closing the bottom of the driveshaft tunnel thereby reinforcing that portion of the floorpan
- Vertical sheet metal panel closing open area behind rear seat: improved torsional resistance? A post here stated that the structure to the rear of the driver’s seat is much more stable than the area in front of it.
- Seam welding: Probably too pricey for me, but many benefits.
- Doublers: Any ideas where in general would be good places? From the drifter community.
- Structural Foam: Best places seem to be A-pillars and runners under door sills
David on this board said that he thought a stock 73 Camaro he had tested measured at about 4,000 ft lbs/deg of torsional rigidity. With Herb Adams style braces from firewall to upper A arms bolted to each side torsional rigidity was raised to about 6,000 ft lbs/deg, and that about 10,000 ft lbs/deg is a good goal for a tube chassis race car. So I guess my goal would be somewhere in the 7,000-8,000 ft lbs/deg range, and my question is if I finish doing steps 1 through 7 above will I get close? If not, what kind of additional steps would make sense?
For reference David also noted that the major torsional members in order of sensitivity to torsional loads translated from NASCAR to a unibody are:
- The roof structure that runs from the "A" pillars at the windshield to the "B" pillars behind the drivers door.
- The strut towers and any reinforcement that runs from the tower to the firewall at the "A" pillar.
- The "A" pillars themselves.
- The front frame rails from the firewall to the core support.
- The rockers and the torque box structure.
- The structure at the top of the windshield.
- The structure at the bottom of the windshield or cowl area.
- The frame rail extension that runs from the firewall to the seat pan structure.
Some of the references I found:
Thanks for any help, Scott
11-19-2007, 12:24 PM #2