Boxing frame on 70 GS 455

Discussion in 'Pro-Touring' started by Jpf, Sep 23, 2018.

  1. Jpf

    Jpf Member

    Taking frame for dipping next week an will start the chassis build when I get it back. I've watched videos on boxing the frame but have not seen how the transmission cross member is reattached. Was planing on cutting the pieces and making my own kit. Any pointers on the cross member? 455 with turbo 400. Plan on 2" drop spindles up front with disc conversion and possibly rear discs as well. Suggestions on rear lowering springs or warnings about drop spindles? This is nothing like my past projects and would prefer to not learn everything the hard way like I usually do.
  2. tsgp51

    tsgp51 Well-Known Member

    You might be better off getting box sections from convertible or even a convertible frame. they have mounts for the cross member. You will need the convertible crossmember also because they are shorter (width between rails will be shorter)
  3. cray1801

    cray1801 Too much is just right.

    Coil-overs are nice additions. It also makes minor ride height adjustments and spring installation easy. But keep in mind with coil-over's and tail pipe routing you could have a clearance problem with the tank. My solution was to use a Tank Inc. gas tank with corners cut back (and 1" deeper). Then, why not put a good fuel pump inside the tank?...just things to consider. o_O

    It's a good idea to box the frame where you can, and make sure to inspect in the rear corners where cracking is sometimes found on these frames. Also, make sure to add/include the diagonal support bars in the rear, they connect between UCA front mounting point and the rear cross-member (check for muffler clearance).
  4. hugger

    hugger Well-Known Member

    ABC fabrication has what you need
  5. pbulski

    pbulski Well-Known Member

    I second the motion on ABC. I believe hugger (above) is referring to ABC Performance in Imlay City, MI. Their website is Tony, the owner, and owner/driver of the reddish Chevelle they show on the website told me that boxing in his frame has made a significant improvement in rigidity and handling. I haven't boxed my frame in yet but I will definitely be doing it this winter with the body off.
  6. PGSS

    PGSS Well-Known Member

    A little late but isn't the GS originally optioned with a convertable boxed frame, at least with the 455 option?
    Hemmings Muscle Machine 70 455 and 70 455 Stage1 Buyers Guide issue claims so..For a so called high end magazine, they do make "alot" of mistakes though in their facts. In this one they also claim the bore is 3.90 and stroke is 4.3125..
  7. Duane

    Duane Member

    70-thru 72 GS cars had 3 different frames
    Convertible boxed
    350 Non Boxed
    455 Non Boxed.

    The easiest way to box in a coupe frame is to get a Convertible or El-Camino frame and cut the boxed sections off. It takes a bit of work but works beautifully if you clean them up back to the factory weld lines. They have positive stops built in, so you cannot mount them onto the coupe frame too far. Then you use the Convert or El cross member and you are in business.

    If you use the El-Camino boxed sections you need to cut 4" out of the back half of the boxed section. They are the same from the body mount in the middle of the door to the front of the car..............but are 4" longer from that body mount toward the rear. It's real simple, you make a nice cut then mount it on the frame and mark where it stops. Then take it off mount the rear piece and cut it to the line. I usually tack the 2 pieces together then pull it off, weld it up, grind down the welds and then install the completed piece on the frame. That way you are assured of full penetration with the 2 pieces. I also make sure to weld both ends completely. This was not done at the factory but it will make it a lot stronger.

    I have done a few of these and you can tell the difference in strength/rigidity just by closing the door even before the body is bolted to the frame.

    If you want to make the car more rigid then throw away the rubber body spacers along the outsides of the frame and install regular bolted mounts instead. It's an old racers trick and really does make a difference. Of course all this may make the ride stiffer.
    Julian, PGSS and cray1801 like this.
  8. BrianTrick

    BrianTrick Brian Trick

    Check out my post in Race Car Chassis Tech. I didn’t know where to post it originally,so I put it there. I usually use the inner rails from a convertible frame to box all of mine.
    Also,if you need a pair of 2” rear drop springs,I have a new pair,still in the box.
  9. PGSS

    PGSS Well-Known Member

    Brian, i'm assuming the same for the 70 -72 442?
    I was watching "Garage Squad" when they were helping a guy with a 72 hardtop 442. Had all the W30 442 badges, hood, wing, rear sway bar and boxed control arms. As they kept seeing signs of it not being a true 442 while working on it, i'm screaming at TV "just look for the frame to be boxed:oops:
  10. BrianTrick

    BrianTrick Brian Trick

    The 442 did not offer the boxed frame for the hardtops or post coupes. It only came under convertibles. However,Pontiac did offer it with the GTO as the “heavy duty frame” option. It was simply the boxed frame rails,or convertible frame,under a hardtop.
  11. hugger

    hugger Well-Known Member

    The 64-67 GS,442's,GTO's were boxed that's where some people get confused the 68+ hardtop stuff wasn't

    Wasn't aware of the "heavy duty frame" option for the goats that's good info to know.

    It's safe to say the 64-67 442's were boxed correct?
  12. sailbrd

    sailbrd Well-Known Member

    I used their kit and it sure made things easier. Tony really know his stuff. As far as the crossmember we made an L bracket and welded it to the new surface of the inside of the frame. Mounted the stock bracket on that (the one that holds the rubber cushions. Then sectioned the stock crossmember to fit.
  13. BrianTrick

    BrianTrick Brian Trick

    The mid-60’s Olds and Pontiac’s offered it. 68-72 Olds did not. Pontiac did. There is a local 70 GTO 4-speed hardtop with a boxed frame,and has the paperwork showing the option.
    I know I could easily use the aftermarket stuff,especially for street/strip,or something that isn’t concours,but I use the factory sections most of the time just for the simplicity of it.
    The pic on the trailer is before. The one in the grass is after. Sorry,they are backwards.

    Attached Files:

  14. PGSS

    PGSS Well-Known Member

    Iv'e "read" in Muscle Car Review" that the special ordered 50 or so built 66 W30 L69 didn't use a boxed frame as they didn't think the extra rigidity was worth the extra weight..
    Should really do some more researching before I believe even supposed high end magazine's fact's as i'll bring up again the "Hemmings Muscle Machine" buyer guide which claimed boxed on all 70- 72 GS455's. Could really cause some issues if I were looking at buying 70 GS and claiming "foul" and fake to someone after looking and seeing it's not boxed..
    What is the difference with the frames between a 70-72 GS 350 and GS455?
  15. sailbrd

    sailbrd Well-Known Member

    There is really no such thing as too much stiffness. :)
  16. sailbrd

    sailbrd Well-Known Member

    Do not have a good picture of the crossmember. This is the best I have. Look at the pass side of the frame and you can see where the crossmember was sectioned. IMG_20161111_120546848.jpg
  17. lostGS

    lostGS Well-Known Member

    Don't forget that the Sport wagon frame is also boxed. :p:p

  18. sailbrd

    sailbrd Well-Known Member

    found a picture of the bracket used with the stock crossmember mount.

    Attached Files:

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