{"id":27583,"date":"2016-05-31T10:15:14","date_gmt":"2016-05-31T17:15:14","guid":{"rendered":"http:\/\/www.racingjunk.com\/news\/?p=27583"},"modified":"2016-11-30T11:47:00","modified_gmt":"2016-11-30T19:47:00","slug":"using-subframe-connectors-to-stiffen-your-gm-f-body","status":"publish","type":"post","link":"https:\/\/www.racingjunk.com\/news\/using-subframe-connectors-to-stiffen-your-gm-f-body\/","title":{"rendered":"Using Subframe Connectors to Stiffen Your GM F-Body"},"content":{"rendered":"

Stiffening Your GM F-Body with Subframe Connectors<\/strong><\/p>\n

\"Convertibles<\/a>
Convertibles are especially susceptible to body and chassis flex when they utilize unibody construction. Let\u2019s take a walk through correcting it by the installation of subframe connectors. Image courtesy GM Media Center.<\/figcaption><\/figure>\n

Automotive engineers came up with a winner when they invented the unibody construction method of building cars. It made them lighter. It made them less expensive. But it also introduced problems that were known even when they started building the cars. We\u2019re going to do a three-part series on installing subframe connectors to correct the problems inherent with unibody construction. This article will touch on GM bolt-in kits. Part 2 will cover Mopars, and Part 3 will cover Fords.<\/p>\n

What Defines a Unibody Car and What\u2019s Wrong With It?<\/strong><\/p>\n

Unibody cars are those designed and built with front and rear frame sections. These front and rear frame sections are either bolted or welded to the bottom of the body of the car-the floorpan and rocker panels.<\/p>\n

Some cars-mostly GM products, are built in such a way that the rear frame rails are welded to the car\u2019s body, while the front frame rails are bolted, making for easy front clip removal. If you\u2019ve ever watched a show such as TLC\u2019s Overhaulin\u2019, you\u2019ve seen examples of these when they do the teardown portion of the restoration\/modification that is performed on the show.<\/p>\n

The problem with unibody construction is that it\u2019s not as rigid as the body on frame type of construction. This is the automotive construction method where the frame rails run from just behind the front bumper to just in front of the rear bumper on both sides of the car.<\/p>\n

Metal fatigues over time. Time also causes cars that aren\u2019t perfectly cared for to rust, often in the floorpan and rocker panels. Again, in unibody construction, these are supposed to be load-bearing portions of the car. However, when rust begins to take hold, they lose their strength characteristics.<\/p>\n

This allows the car\u2019s body to flex, especially when we add engines with more horsepower and torque. One guy I know that rebuilds cars says \u201cIf you don\u2019t want your older high performance car to twist into pretzel the first time you romp on it, you need me to rehabilitate the unibody construction method. We do that by installing subframe connectors.<\/p>\n

What Are Subframe Connectors?<\/strong><\/p>\n

\"Hotchkiss,Subframe<\/a>
These are the Hotchkiss subframe connectors we\u2019ll be walking through the installation of. Image courtesy Hotchkiss<\/figcaption><\/figure>\n

The subframe of a unibody car consists of the front and rear frame sections. Subframe connectors are the same width as these frame rails. Most of them slide over the rear rails and, depending on what kind of car you\u2019ve got, they either bolt or weld (or both) to the front frame rails.<\/p>\n

Since these subframe connectors are made out of steel that is thicker than the steel used in the floorpan and rocker panels, they give the chassis almost the same stiffness as a body on frame car would have. It\u2019s well-known in the automotive performance aftermarket that a car with a stiff chassis is one whose suspension functions properly. Since the chassis isn\u2019t flexing on launch, the shocks and coils are able to function as they\u2019re designed to.<\/p>\n

Welded or Bolt-In, Installation Is Easy<\/strong><\/p>\n

Most of the available instructions for the weld-in subframe connectors say that you should allow someone else to do the installation if you\u2019re not a good welder. That\u2019s not necessarily true. If you\u2019re building your own hot rod, you\u2019re going to need to do some welding at some point in time. Getting yourself a low-cost welder and learning how to do it will save you quite a bit of money over the long run-money you can put into go-fast or be-safe goodies.<\/p>\n

You don\u2019t need a professional welder to work on your car at home. You just need one that will get the job done. There are numerous 110 volt models available for sale on ebay for less than a hundred bucks. Learning how to weld is the same as learning to ride a bike or drive a car: Practice.<\/p>\n

Pick up some scrap metal, prep it by wire brushing, sanding, or grinding the edges, and learn how to run a bead. Remember, they\u2019ll be underneath your car, and unless you\u2019ll be entering your car in shows, your welds don\u2019t have to look perfect; they don\u2019t have to be pretty. They just have to join the two pieces of metal. The welds just have to be functional.<\/p>\n

The main key, after getting a little practice, to getting a good weld seam is properly prepping the metal. Any contamination of the metal has to be removed. Stick a stick wire wheel on your drill, slap on a pair of safety glasses, and wire brush the metal until it shines it\u2019s so clean. Even better, get a fine grinding wheel with a 3\/8 inch mandrel and use that. You need to clean an area larger than the area you plan on welding.<\/p>\n

\"Hotchkiss-Early-Model-F-Body-Bolting-Front-of-Connector-in-Place,Hotchkiss,Subframe<\/a>
This is what the driver side looks like after the installation of the Hotchkiss subframe connectors. Image from Hotchkiss video.<\/figcaption><\/figure>\n

What You\u2019ll Need to Install Subframe Connectors<\/strong><\/p>\n

This article will address the installation of the subframe connector kit from Hotchkiss for GM F-body cars as they\u2019re my favorite and fairly representative of what\u2019s available for GM F-Body cars. You\u2019ll need:
\n\u2022 A jack
\n\u2022 Four jack stands
\n\u2022 Ratchet and socket-usually \u00be inch
\n\u2022 Wire wheel adapter, grinder, or 80-grit sandpaper to weld prep the parts and the car
\n\u2022 Prybar
\n\u2022 Welder-With all personal protective equipment-Helmet or goggles and gloves
\n\u2022 Deadblow hammer
\n\u2022 Spray metal primer
\n\u2022 Spray paint
\n\u2022 Safety glasses
\n\u2022 A set of subframe connectors<\/p>\n

Get the Car in the Air<\/strong><\/p>\n

Due to the power requirements of most MIG (or arc) welders, you really should do this work in your garage. Welders draw so much current that you\u2019re likely to burn up a regular extension cord. Put the car in park, or, if you\u2019ve got a standard transmission, put it in gear, and firmly set the parking brake. Raise the front end enough to slide the jack stands under the lower control arms\/ball joints and keep the car high enough for you to slide under easily. Slide the jack stands under the control arms\/ball joints and slowly lower the jack. If you\u2019ve got ramps, drive the car up onto them.<\/p>\n

Move the jack back to the differential and raise the car enough that when you lower it back onto the jack stands it remains level. Slide the jack stands under the ends of the axle housing near the wheels. Slowly lower the car onto the jack stands. Adjust the front or rear so the car is level. You want to make sure the doors and trunk open and close smoothly and easily. If you don\u2019t do this, you could end up with serious problems that will require you to remove the connectors and start over. It could also cause problems with the paint and body when you put the car back on the ground.<\/p>\n

Gain Access to the Frame Rails and Floorpan<\/strong><\/p>\n

You may need to completely disconnect the parking brake cable so the subframe connector is able to rest flush against the frame rail and floorpan. You could also use a die grinder to cut notches in the connectors for the brake hard lines and cables. Most subframe connectors for the GM F-Body product line won\u2019t require any special treatment here except maybe the brake lines and\/or cables at the rear.<\/p>\n

However, fuel lines will need to be unbolted from their clamps and carefully moved out of the way, especially if you\u2019ve got an aftermarket fuel system installed. I also like to wrap them with a welding glove just for added security against the sparks given off by welding.<\/p>\n

The most important thing to remember here is that if you\u2019re installing welded-in subframe connectors that have to weld to the floorpan, they\u2019ve got to sit flush against the floorpan their whole length between the frame rails. Most will have small break-out tabs for the dimples most floorpans have for rigidity.to help you accomplish this. Again, most kits for GM cars don\u2019t have this worry.<\/p>\n

Prepping for the Subframe Connector Installation\\<\/strong><\/p>\n

\"Hotchkiss,Subframe<\/a>
Just like paint, prepping the car and parts properly prior to welding helps to ensure a good weld. Image from Hotchkiss video.<\/figcaption><\/figure>\n

Once you\u2019ve got the car in the air, leveled, and have made sure the doors open and close properly, remove the bolt that secures the front frame rail\/unibody member to the car. Next, insert the prybar between the frame rail and the floorpan and slide the front end of the connector into place. You may need to use a deadblow hammer at the back end to get it fully seated. Wear safety glasses.<\/p>\n

\"Hotchkiss,Subframe<\/a>
The outline drawn to show where to grind is shown clearly here. Image from Hotchkiss video.<\/figcaption><\/figure>\n

 <\/p>\n

Next, use your marker (I prefer a fat silver or white Sharpie or White-Out) to mark where you need to weld. On the Hotchkiss product, this means marking around the whole rear saddle. Next, use the prybar to remove the connectors.<\/p>\n

\"Hotchkiss,Subframe<\/a>
With the connector in place, use a handheld wire brush to clean off any grime that was scraped up when you pushed the connector into place. Check out the welding glove wrapped around the brake and fuel lines for safety. Image from Hotchkiss video.<\/figcaption><\/figure>\n

Now, clean the areas you marked. You need to remove every trace of road debris, grime, undercoat, paint, clearcoat, and powder coat from the frame rails, the connectors, and, if necessary, the floorpan. You need to take these areas completely down to bare metal. Wear safety glasses, especially if you\u2019re using a grinder or wire wheel attachment on your drill.<\/p>\n

Install and Secure the Front of the Subframe Connector<\/strong><\/p>\n

\"Hotchkiss,Subframe<\/a>
The Hotchkiss GM kit comes with new subframe bushings. Image from Hotchkiss video.<\/figcaption><\/figure>\n

Next, pry the front frame rail down and remove the old subframe bushing. Install the upper piece of the two-piece bushing above the frame rail and place the large washer on top of this. Remove the prybar. Insert the bushing and slide the lower bushing half over this.<\/p>\n

\"Hotchkiss,Subframe<\/a>
Once the new bushing is installed, install and tighten the supplied subframe bolt. If you don\u2019t have an impact, use a ratchet and make sure the bolt it tight. Image from Hotchkiss video.<\/figcaption><\/figure>\n

Next, slide the front of the subframe connector into place and put the smaller washer on top of it, between the bushing and the connector. Use the jack to keep the connector in place and thread the supplied subframe bolt in and tighten it down. For extra security, you can also weld the connection between the frame rail and the connector, but you\u2019ll lose the ability to pull the front clip at a later date if the need arises.<\/p>\n

Install and Weld the Rear<\/strong><\/p>\n

\"Hotchkiss,Subframe<\/a>
Pros have access to more tools than the rest of us. You can use your jack and a block of wood (to protect the finish) to support the connector in place. Image from Hotchkiss video.<\/figcaption><\/figure>\n

Finally, slap the rear of the connector into place using a deadblow hammer and make sure you\u2019ve got clean metal to clean metal joints where you need to weld. If not, loosen the bolt up front and pry the back out and do you weld prep again.<\/p>\n

\"Hotchkiss,Subframe<\/a>
Your first welding step should be to tack the rear of the connector into place so you can ensure that it is properly located. Image from Hotchkiss video.<\/figcaption><\/figure>\n

Ready the welder according to the instructions that came with it. Clamp the negative cable to a good ground-I like to use the exhaust or the leaf springs. Put your welding gloves on. You should also be wearing at least a long-sleeve shirt while welding-gauntlets are better. Put your welding glasses or helmet on, but hold off on putting them over your face just yet.<\/p>\n

Get yourself comfortable and positioned so the sparks aren\u2019t all going to fall on you while you\u2019re welding. Some will; that\u2019s unavoidable. Place the tip of the welder about a \u00bc-inch from where you will be welding and pull the trigger. Walk your bead along the joint between frame and connector at a steady pace of about an inch per second. Rinse and repeat on the other side.<\/p>\n

Finish the Job<\/strong><\/p>\n

\"Hotchkiss,Subframe<\/a>
After the welds have cooled down, paint them to protect them from rust. Image from Hotchkiss video.<\/figcaption><\/figure>\n

Apply a good coat of metal primer paint everywhere you cleaned the metal and welded. Let it dry for ten to 15 minutes and apply another coat. Now apply a good coat of your chosen color. Again, let it dry a bit and apply another coat. Just for grins and giggles, let it dry and apply a third coat. Raise the car off the jack stands in the rear and lower it then lower the front. Take it out and drive it like ya stole it!<\/p>\n","protected":false},"excerpt":{"rendered":"

We\u2019re going to do a three-part series on installing subframe connectors to correct the problems inherent with unibody construction. <\/p>\n<\/div>","protected":false},"author":28,"featured_media":27663,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[5011,3448,11,9],"tags":[4540,4542,1074,4541,4543],"class_list":["post-27583","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-chassis-suspension","category-drag-race-101","category-how-tos","category-tech-tips","tag-hotchkiss","tag-how-to-tips","tag-mike-aguilar","tag-subframe-connectors","tag-using-subframe-connectors-to-stiffen-your-gm-f-body"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/www.racingjunk.com\/news\/wp-content\/uploads\/2016\/05\/1967-Chevrolet-CamaroZ28-001.jpg","jetpack_shortlink":"https:\/\/wp.me\/p42YSK-7aT","jetpack_sharing_enabled":true,"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts\/27583","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/users\/28"}],"replies":[{"embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/comments?post=27583"}],"version-history":[{"count":2,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts\/27583\/revisions"}],"predecessor-version":[{"id":27665,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts\/27583\/revisions\/27665"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/media\/27663"}],"wp:attachment":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/media?parent=27583"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/categories?post=27583"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/tags?post=27583"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}