Herb Adams Mod???

Discussion in 'Suspension, Steering, Brake & Wheel Topics' started by nitrobully, Oct 15, 2008.

  1. nitrobully

    nitrobully Member

    Oct 6, 2008
    Kansas City
    Just wanted to ask about the theory behind this spring perch mod.
    What are the benefits and how is it done? Any help is much appreciated as I'm going to throw around 900hp through these split monos and will need all the help I can get!

    Also, is there any upgrades to those little J-clips or is there none really needed?
  2. 79Zed28

    79Zed28 Veteran Member Gold Member

    Sep 27, 2006
    Phoenix, AZ
    the search button is ur friend, many other posts on the topic
  3. aero80

    aero80 Veteran Member

    Jul 8, 2003
    If you mean raising the spring mount by .750" by drilling the eye-bolt holes higher up, then the main benefit is anti-squat increase, with the secondary benefit of lowering the car slightly.

    Whether it works or not, depends upon a few other variables, including the length of the rear shackles, and the durometer of the front spring-eye bushings if you are running rubber.

    Sounds like you're into straight-line? Not a lot of worthwhile result on the strip, when other solutions are much more modern and scienced-out.

    I wondered about those J-clips too...
    ... but, I ran a stock-chassis'd (with respect to spring-eye mods anyway) '77-1/2 Z28 with an aluminum 427 (a 1971 ZL-1 engine) and a 4-gear, and I never had any problems with the rear spring eye mounts.
    ... same with my '80 canyon car, 496/540 motors, 4-gear, never a problem with the eye mounts.

    EXCEPT: the strange moving wheelbase phenomenon... under extreme conditions, a rear wheel might move back in the wheelwell, leaving no marks on the spring where the perch might have sheared off the locating pin, or movement detectable in the front spring-eye perch area, nowhere else to check... very strange.
    By exteme conditions, I do mean extreme. Leaving the track backwards at 140 mph over rough ground, or hitting a bump at high speed, stuff like that.

    The best Adams mod, in my opinion, was always the front structure bars, bolt on and stiffened the car considerably.

    The best I did it myself 'cause nobody makes a kit for it mod was always the doubling of the inner rocker panel. Take a rocker cut from a car in the yards, separate the inner floor panel along the entire length, then weld solidly to the floor and inner rocker, and cover back up with carpet. Nobody can see it, but oh man is the car ever stiffer.

    2nd best mod in the same area (rear of car) was to reinforce the structure around the back window, and make sure that the window itself is well-sealed and attached. You'd be surprised how much our cars move around in this area.

    For under a hundred bux you can increase the stiffness of your car by a huge amount.

    I made my own subframe connectors which went from subframe rail to rear rail rather than to the spring-eye pocket.
    Major improvement over the commercial traditional type offered for our cars.
    Now Global West and maybe a few other companies offer this type of connection, but they are always weld-on at least on one end.
    Mine were fully removable, great for frame alignment work on very high performance and often used at 100% cars.
    The key is to place the bolts in all 3 axis locations... X, Y, Z.

    With the above mods, my '80 T-top car could jack under the front subframe and lift both wheels on the side with no bending... that means even on the single support of the jack pad, the doors would open and close no prob, the T-tops could go on and off no prob, etc etc.

    All this stuff makes for a HUGE improvement in road manners, and of course safety.

    *** THE PROOF ***

    In my fully stiffened '80 big-block T-top canyon car, I hit a coyote full-on at 125 MPH and suffered no damage to the car and the vehicle remained completely stable during the impact.
    Well, there was a little biff mark on the corner of the rubber nose...

    This is the car.
  4. K5JMP

    K5JMP Veteran Member Lifetime Gold Member

  5. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

    Nov 4, 2004
    Ringgold, GA
    No crapksi... Just looks mean to the bone. :)
  6. nitrobully

    nitrobully Member

    Oct 6, 2008
    Kansas City
    Exactly what I wanted to know and I appreciate it a lot. That car just flat bad-ass too.
  7. 70Camaro406

    70Camaro406 Veteran Member

    May 4, 2006
    Cadillac, MI
    Oh yes, that car looks tough. That's the stance and attitude that I want to do to my '70.

    Give us more specs!!
  8. muenk79z28

    muenk79z28 Veteran Member

    Apr 12, 2007
    Franklinville, NJ
    you mean like this....? :crazy:

  9. ErikNORCAL

    ErikNORCAL Veteran Member

    Aug 6, 2003
    now in VA
    any pictures of those chassis stiffening mods? I'd sure like to try them.

    oh yeah - baaaaaaaaaaaad ass car
  10. aero80

    aero80 Veteran Member

    Jul 8, 2003

    My canyon car pictured above was a genuine 180+ mph American fighter.
    It was completely modified in just about every area. The point of the car was to be a serious long-range bullet and I did routinely take in on 5,000+ mile cross-country cruises. The car also went to Germany on a Lufthansa 747 air freighter, and toured Europe, gaining plenty of attention wherever we went.
    The exhaust used to make a kind of howling sound, and in France and Italy it would draw crowds when we would pull into a village, downshifting the big rat with the car covered with rain streaks and filth and road grime on the NASCAR wheels. It looked like a LeMans pit stop in the 20th hour.

    It was gutted under the hood and dash, carrying only essential wiring and controls and gauges. There was no heater, fan, defrost, etc. The doors were usually the fiberglass versions I had, with pop-in windows similar to what you see on older 50s-60s sports cars without windows in the doors. The hood was glass, as was the nose and tail. The T-tops served as molds for carbon fiber copies, but the carbon versions were never finished before I had to sell the car. There were no sliders in the seats, which were bolted directly to the floor.
    Naturally, it was often impossible to continue driving on a trip in bad weather, and we often spent several nights and days in a single location waiting out the weather. There were no windshield wipers. In Europe however the car carried full doors and weather equipment.

    There was a rack of communications equipment which was removable along with various camera mounts for 16mm, 35mm, and digital motion picture equipment along with computers and other electronics. Much of the mounting structure would bolt directly to the passenger seat mounting locations and brace forward and to the rear. At the time, and still today, I own a motion picture production studio and the car was often used in filmwork as a camera car for motorsports productions.

    The body was re-welded everywhere, paying attention to places like the pinch-weld running along the top of the rocker under the sill plate, lots of improvement to be had there in stiffness for free. The rockers were doubled as I explained above, and also the subframe connects were as I described already.
    All of the hinges,etc were new. The door latching mechanisms were factory and bolted to reinforcing plates made of aluminum in the 'glass doors, or when running roll-up window steel doors, then all was as usual.

    The suspension and running gear are probably of more interest here in this thread.
    The front started out by tossing all of the GM stuff and running a complete Vette Brakes carbon fiber leaf spring front suspension. This was fully adjustable for ride height, spring rate, and dampening. I always run Konis. This suspension included (of course) custom-designed geometry using square tubing for the upper and lower a-arms. This stuff is now available for general purchase at Vette Brakes.

    The rear was a modified leaf-spring live axle like all our cars have. I paid extra attention to the leaf spring bushings... when a car negotiates a corner with leafs, the springs themselves become torsion bars- this is not very well known, but it is critically important- by allowing the spring to "rock" the suspension takes on a whole new feeling of controllability.
    We dialed out the built-in roll understeer to gain a much more neutral steering chassis. This is not hard to do, but requires fabrication skills and a good plan. Without the GM-designed roll characteristics, the car became a completely different handler, especially responsive to throttle changes in mid-curve application, and in this condition I took out a Kawasaki KZ1000 Turbo motorcycle on a tight mountain road. He was sparking the pegs, and the Camaro was totally confident, controllable, and comfortable, even at 10/10ths (100% effort).

    The brakes were 12" inside 15" NASCAR steelies. I always try to run a 60-series tire on my road cars, since the other mods respond really well to the extra cushioning effect of the slightly taller sidewall. This usually dictates a 15" wheel size.
    The front calipers were Wilwood GM-III, used for the comparatively larger swept area of the D-52 pads or the even larger D-something police pads which fit the same calipers. This is a triple-bridge aluminum caliper, very light, very stiff, very good.

    The rear brakes were standard Wilwood 12.19" rotors with aluminum hats, no park brake, and 4-piston calipers.

    Various engines, all rat motors, were used at times. Same with transmissions, and always clutch 'boxes, never mommy-shifters. Always a 3-pedal car.

    This post looks like it is getting too long and maybe a little boring so I'll cut it here. There is a ton of other stuff which I'm forgetting right now, I'm sure.

    Thanks guys for the compliments ! They mean a lot to me. I did 100% of the work myself.


    Scene 2, STORYBOARD 1940
    Last edited: Oct 17, 2008

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