70-74 early 2nd gen F body 9/16" Lower control arm mount reinforcement kit click for more pics and product details
The Lower Control Arm mounting points on the 2nd gen F bodies weren't a very good design. Side forces from cornering etc. are transferred to the thin edge of the sheet metal the sub frame is stamped out of through the LCA mounting bolts. To make things worse the stock bolts contact the frame through the threaded section of the bolt on one side of each bolt. The lateral forces can oval the mounting bolt hole over time allowing the lower control arm to move causing noises as well as constantly changing alignment settings.
The 70-72 models and many 73's used 1/2" diameter LCA mounting bolts from the factory which didn't provide enough area for the forces transmitted so the holes may become oval. GM started using larger 9/16" bolts sometime during the 73 model year presumably to help reduce the problem, although it didn't make the original poor design any better. The larger diameter bolts may have made enough of a difference in slowing wear (with original equipment and tires etc.) to get the daily driven cars through the warranty period before the LCA's started making knocking noises in oval holes as they moved.
Aftermarket suspensions and/or tires available now allow us to far exceed the cornering and braking forces the GM engineers originally designed for. The designs were done before radial tires were even available and most were less than 7 inches wide made of a hard rubber compound. The additional force todays aftermarket performance equipment and tires can produce can/will overload the factory mounting holes in the sheet metal the stock sub frame is made of and the holes start stretching getting bigger which allows the control arm to wiggle and move at the bushing pivot point. You can see in one of the pics how the frame bracket holes get damaged.
If you are using the car for auto sports (other than straight line) and have modern aftermarket suspension components with sticky tires. You can easily exceed the factory pivot point capabilities and it will probably only be a matter of time before you realize there's a problem. It doesn't really matter what brand of springs, control arms, coil overs, tires, or steering components you're using. If they're better than stock you need better mounting points than stock. Those products need a solid mounting point that isn't going to fail like the factory one will over time.
This Lab-14 kit is designed to spread the shear force exerted by the lower control arms over wider surface areas (more than 3X original) to eliminate stretching of the mounting holes in the frame. The kit also reduces frame flex by stiffening the LCA mounting points on both sides of the frame at each mounting bolt. The hardened grade 8 bolts and grade 8 pieces welded to the frame can handle much more shear force than the original factory set up and the shoulder of the bolts in our kit contact both sides of each mounting point where the stock set up actually had the tips of the threads as a contact point as seen in the pics.
This kit can be used on all high performance aftermarket lower control arms using 9/16" bolts. It can also be used to repair damaged LCA mounts for applications where late 73 and up stock 9/16" LCAs will be used instead of the original 1/2" as well as all 73's and 74's that used 9/16" factory bolts. This 70-74 kit for the early frames has plates that weld to the engine cross member which are different than ones for the later style frame. If upgrading to 9/16" diameter bolts on a 70-73 that came with 1/2" factory hardware the frame will need to be drilled out before installing this 9/16" kit. Any questions contact us before ordering.
Standard kit comes with a combination of custom fitted pieces and grade 8 washers that get welded to the sub frame along with grade 8 bolts and correct distorted thread (one time use) locking nuts. We use the grade 8 stuff for shear strength, load dispersion, and very low wear characteristics. The distorted thread nuts similar to what the factory installed are used because they're not affected by exhaust heat like Nylocks. The 9/16 hole through the plates and grade 8 pieces that weld to the frame are all a snug fit on the bolt to prevent the bolt from moving at all after tightening (and no, you can't just weld on 9/16" washers and have it work). Our 9/16" LCA tool (available separately) is highly recommended for use with this kit.
So who should buy this kit? Anyone who is installing high performance suspension equipment and tires on a factory sub frame who will be doing any kind of spirited driving or racing as well as anyone repairing a damaged factory sub frame.
Why buy this instead of making up your own kit? It's easier, quicker, aaand cheaper....So in this case you can have all three.
Easier, because I've already spent the time to make patterns, test fit, done the cutting, grinding, and drilling necessary to modify pieces, then determined the hardware necessary and put it all together so you can buy everything from one place and receive it knowing everything works together.
Quicker, because if you try to put this together you'll spend some time driving around to your favorite local hardware places, then probably find out some things aren't available or won't work as you thought. Then order the things you can't buy off the shelf locally and wait. Then make patterns, modify and mock things up. I know because this is how I started on the first kit for my own car and I have Fastenal, Ace hardware, Lowes, Home depot, and a half dozen auto parts stores within short distances.
Cheaper because of the expense of driving around, then the shipping expenses for various orders, then having to buy packages of quantities larger than what you need to get enough for the job and having left over hardware you'll never need for anything. If you have a shop do it you'll also pay them labor time for pattern making, cutting, grinding, drilling, and mocking up a small number of custom pieces.
Before Lab-14 evolved I did all the driving around, ordering, and buying packages of extra I items I didn't really need and would never use for each different kind of car and wished someone just offered kits like this I could just buy, weld in, and move on with building the car, so now I do, and you can just click and buy here. I buy the steel and hardware for Lab-14 products in bulk from various companies so shipping costs per item to me are much lower, I make and/or modify the parts for an accurate close tolerance fit in large quantities so less time per item spent cutting, grinding, drilling etc.. You can order this kit along with a combination of all the other Lab-14 parts available for one car with only one shipping charge of $15.00 max. So, easier, quicker, and cheaper for you.