FRAME MODS

Frame Construction and Mods - 1970 Chevelle Wagon
The Chevelle wagon frame is unique for '68 to '72. It is the same as the '68-'72 El Camino (116” wheel base) with one difference; the Elky has boxed frame rails, that’s the long section of the frame between the front and rear wheel areas of the frame. A wagon frame just has c-channel frame rails because it achieves its strength with the help or the full body and roof, which is not present on Elkys. Just for informational purposes this same difference is parallel with Chevelles. Chevelle 112” wheel base cars, which are the 2-door coupe and the convertible, are 4” shorter in the frame rails and several inches shorter in the rear frame section than the wagon and Elky. The convertible has boxed frame rails and the coupe does not. 4-door Chevelles are a hybrid. They are the same wheel base 116” as the wagon, but have the rear section like the 2-door, which makes them unique. All the frames front sections are the same. FYI, in '68-'72 there were not any SS or 2-door wagons. If you see one it is not original. So don’t fall for it. I am choosing the El Camino frame to put under this wagon because it is boxed, providing more rigidity and it is a direct swap with exception to the way the fuel and brake lines run, and the transmission cross member. Also I am making this wagon a 4-door hardtop as opposed to the 4-door sedan, which has posts between the door windows. The added strength of the boxed frame rails is necessary for this mod. I have a computer-altered picture of a wagon to show the difference.
It is subtle but when all 4 power windows are down it will create one big open space like a 2-door coupe does and when the windows are up, the door windows appear as one big section like the big rear side windows, which are separated by body color. I think it is much more astatically pleasing, functionally more practical for interior wind flow and just all out pretty darn sporty in my opinion. I found an El Camino parts car and removed the frame after a preliminary inspection. The first thing on a frame to check is cracks behind the front lower control arms. Next take a screwdriver and hammer, hit any questionable rusty areas to see if it has rusted thru. People for some reason like to tow, push or pull cars by the frame and bend the rear cross bar or the front frame ends. Normally if it is bent slightly, that can be bent back into place with no problems.
Next, it is very important before putting too much work into the frame to check it for “frame sag”. Frame sag occurs with age and use of a vehicle. It effects the front-end alignment. If a frame is sagged too much, you can tell if the front-end alignment cannot be achieved and all the shims under the front upper control arms are out from between the c-arm shafts and the frame. By measuring the distance between the c-arm mounts you can see how much your frame has sagged. A new frame measures 32”. A frame that measures 31-3/8” is too close. You should have at least 31-3/4” to start with. You can get away with offset shafts if it is not closer then 31-3/8” but the best fix is to take it to a frame shop and have them pull it back out to 32” while you have it apart. If you are using stock c-arms thee is a concern with the clearance as frames sag, between the c-arm shaft bolts and steering shaft and the exhaust manifolds or headers on big blocks.
However, I am using polepossitionrp.com adjustable upper front control arms. These allow more clearance to concerned areas and because of the full adjustment range shims are never needed and a large range of wheel alignment can be achieved. Frame sag should be checked and dealt with properly before finishing the frame and adding suspension parts. My frame measured 31-3/4”. Check frame for "squareness" by measuring from the front right body mount to the rear left. It should be with in 1/4” of the measurement from the front left back to the rear right. If it is not a frame shop can true it up.
My frame was square but someone welded exhaust side pipe hangers to it. Rust formed holes were evident between the layers of steel when I cut the hangers off. I cut out the rusted material and welded new steel in.
Several of the places where the body bushing fit into the frame were rusted. I bought washers, McMaster-carr p/n:97063A520, (1-1/2” ID, 3” OD).
I made a circle template from ¼” plywood that was offset larger by half the nozzle thickness of my plasma cutter to achieve a 2-1/8” hole in the frame centered where the body bushings are supposed to sit. If you just add the washers without cutting the holes larger the bushing cannot accommodate the additional material thickness and can shift location. Also opening the hole allows the bushing to have a nice face to seat itself on the underside of the washer with out being chewed up or cocked by the irregular shape of the rusted frame. The washers are .134” thick and I was concerned that if I did not do all the body mounts that I would cause the body to twist on the differently elevated mounts, so I did all the body bushing locations the same way. Measuring and cross measuring was critical in achieving perfect location of these hole locations to insure the match-up with the body.
After Galvanizing
Right behind the front sway bar mounts there is a 1/8” drain hole in the frame. It does not take mush to clog this hole and cause the front frame sections to collect water and rust out. Good frames are getting harder to find and with the cost of shipping one, the costs of fixing them is getting worth considering. Fortunately the passenger side was fine so I just enlarged the drain hole to 1/2 “ to allow proper drainage. The drivers side however, was not as lucky. The 3 spacer tubes welded inside the frame for the steering box were disintegrated and the sway bar mount was eaten away a little. So I cut a clean donor frame piece off of a cut I frame I have. I matched up the effected area to be replaced and welded the newer rust free section, using the steering box to accurately locate the new section. While I was at it I opened up the drain hole on that side too.
In addition to that, I welded 3/8” thick steel blocks with taped holes to give a much stronger front sway bar mount. I am using a 1-3/8” front sway bar and a hard corner with this heavy vehicle, there is no doubt in my mind that the mount bolts would just rip right out of the factory tapped holes in the thin frame material. I also put a hole in the middle of the block to allow area for paint etc. I did not want to trap any areas for rust to create holes, like what happened under the side pipe hangers. The 3/8” blocks also give the sway bar additional clearance from the idler arm.
My experience is that the cupped shape steel that is the rear mount for the lower front control arm is prone to braking off due to fatigue caused by harsh braking or potholes. Additionally, the curved portion of the frame between the body mount furthest forward, under the firewall, and the front lower control arm mount is taking a real punishment. It is often prone to cracking propagating from the senseless placement of the factory transportation tie down slots. I supported this region 2 ways, first I put a triangular gusset behind the c-arm mount and welded it to the frame, and secondly I welded a plug over the tie down slots to hopefully prevent cracking from ever starting.
Next, I welded Steel plate to box the rear section leaving clearance to access the bumper bolts. Then welded steel plates in the remaining rear c-channels of the frame, being sure to leave access holes for the bumper bracket bolts and the fuel line paths.
After the frame was finished to my satisfaction, I had a major concern how I was going to get the surface rust off, especially inside all the boxed sections. I did some research. A hydrochloric acid dipping place in PA wanted $400 just to dip a frame. Then I would be faced with how to effectively apply paint inside where I could not reach. I bought long spray rods sold for applying undercoating and considered that approach. I also looked into sand blasting. That was about $400 for just that and it does not solve any of my concerns. Powder coating was around $500 locally, they sand blast it first the electrically charge the frame and spray power all over it. The heat it up until the powder melts. Great product but it does not get up inside the boxed sections and sand blasting does not remove the tiny rust deep in the rusty pits. Upon further investigation, I found a place that could and would galvanize the frame.
Virginia Galvanizing804-798-3257
Galvanizing is the process of dipping steel in a vat of molten zinc and coating the surface. It was done in production of some auto frames and many boat trailers where there is constant exposure to salt water. If you not worried about originality, this is the way to go. It is about $200 for the frame and the acid dip it to remove all the microscopic rust crevices. First they dip it in a tank to clean it, then the hydrochloric acid dip it then they rinse it off then the dip it in a flux to get the zinc to adhere, then they dip it in the zinc. Each time they dip it, it is held at an angle to allow good flow of air out of the channels and fluid in to insure full coverage inside and out. The zinc is at 850 degrees, which is not hot enough to alter the properties of the steel frame. Warping can occur with some shapes due to the heat difference between the part of the object submersed in the zinc and the part out of the zinc, but I have done 3 frames and no warping has occurred. The newly galvanized frame comes out very shinny. There is lots of information on hot galvanizing but the best thing about this process is that zinc is lower down on the noble element list than steel. What this means is, as galvanic corrosion occurs and it is unavoidable, electrons flow from the less noble material first, this is considered sacrificial, which means the steel can not rust until all the zinc is consumed. So the steel frame is surrounded by a protection. Which will not allow the steel to rust even if it were chipped.
After galvanizing, chase a tap through all the fuel and brake line clip mounting holes and the sway bar mount holes to remove the zinc. It is recommended to cover the bare zinc with something to prevent it from oxidizing. It will quickly turn to a dull luster. It is critical to spray or wipe down the galvanized parts with vinegar prior to priming. The acid in the vinegar neutralizes the oxidization. Then hose everything down with water. As soon as it is dry apply the primer. You cannot skip this step if you want the paint to stick. A revolutionary industrial water bourn primer specifically made for galvanized metal is available for $14 per gallon. Do not use any oil-based products on galvanized parts. The primer is the 2700 series by Anchor Paint.com . Just brush or cut with water and spray on 2 or 3 coats. After that you can top coat with anything. I used Rustolium’s outdoor lawn furniture latex paint, satin black. All this was really for cosmetic reasons and extra protection from zinc oxidization, but if you don’t mind the dull galvanized look, like a road guardrail, then you can leave it alone. Independent published sources say that the duplex system of hot dipped galvanizing combined with painting offers approximately 1.2 to 1.5 times that of the durability of either the painted bare steel or the zinc coating alone. Your frame will have enough protection to out survive you and your children.
Now that the frame is repaired, enhanced and looking good, next I will discuss the rear differential, rear brakes and rear suspension rebuild, enhancements and upgrades.
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