Subframes – Part One

Subframe

Getting down the drag strip isn’t just a matter of building power, bolting it in and pointing the car in the right direction.  Certainly, the rear suspension setup is critical (and we’ll get to that down the road), and so is the balance of the power train, but the part of the car that seldom gets respect is the front end.  Sure there are some standard setup procedures, but there are also plenty of things you can do to make the car quicker, faster, and handle and stop better at the strip.  There’s more, too: Today, the marketplace is filled with racing and high performance hardware.  Better still, there’s sufficient technology out there so that you can actually bolt together a pretty trick front end (no fabrication necessary).  Much of it is good quality.  Some isn’t.  And some is actually outstanding in terms of quality.  Now, we’ve personally owned (and flogged) five different first generation Camaros and four ’69-’71 Novas over the decades, so we have a pretty good idea of what’s hot and what’s not!  And we’ll share that knowledge and experience with you.  Follow along and we’ll show you how we set up our own car’s front end for drag duty:

Bare Bones…

You have to start somewhere.  We had the front sheet metal off the car and obviously, the powertrain out of it.  At that point, it was a matter of removing four bolts and the subframe could be rolled away from the body.  Our car was your typical crusty mess.  So what we did was to strip everything out of the subframe – a-arms, motor mounts, steering linkage, sway bar, springs, shocks, steering box, etc.  The truth be known, there was little we’d be using from the stock front end, aside from a few bolts and brackets.  But we’ll get to that later.

With the subframe naked, we dragged it outside and coated the sub frame in degreaser (actually, we used the Super Clean stuff that comes in a purple spray bottle).  We let it sit for a bit and then pressure washed it.  Next up, we scraped off the old dealer-applied undercoating.  Here, a propane torch, a putty scraper, and a brace of wire brushes (in varying sizes) work wonders.  Once the grease, grime, and undercoating were gone, we took the time to grind all of the factory welds and weld splatter.  FYI, this is a dirty job, but the only way to get it done is to grind it with an angle grinder and a die grinder, and then finish it off with a wire wheel.  It works, but it takes time.  In our case, a week’s worth of evenings.  It’s a personal thing, but we also grind down sharp edges on these subframes (there are a lot of them).  Why?  Simple.  There’s way less of a chance of tearing up your skin while working on them when those dozens of sharp corners are gone.  Once that was complete, we hauled it to a sand blaster.  From there, it went to our favorite powder coater.

The reality is, powder coating has a reputation as a pretty remarkable coating.  While accurate for the most part, it’s not enchanted and it’s certainly not without faults.  We’ve all heard the sales pitch where you can smack a coated part with a hammer and it won’t chip.  Fascinating, but not exactly true.  It will chip.  The bottom line here is it’s durable, but not invincible!  Keep that in mind when working with powder coated parts.

Back to the subframe:  We had our example coated in low gloss black.  It’s close to the factory finish (if that matters), but it’s also a pretty low maintenance combination.  The subframe looked absolutely fantastic when we received it.  Honestly, the factory never made them this nice (see the lead photo), but we digress.

At this point, you can reunite the subframe with the body.  There are a lot of ways to accomplish this, but for a drag car, you should use solid mounts.  Solid body mounts provide a simple approach to eliminating the flex that occurs between the body and subframe connection.  This will improve your car’s ET by increasing chassis stiffness.  These mounts should be used when installing subframe connectors for maximum torsional rigidity.  Fair enough, but this is where Classic Industries enters the equation.  Most will think of Classic as a one-stop shop for restoration hardware, but that’s not entirely accurate.  You see, the folks from Classic Industries also sell a wide (and we mean wide) range of high performance parts.  They have another advantage, too (this is a good tip by the way): Let’s just say their pricing is more than competitive and if you get on their mailing list, you can often obtain even better price breaks on parts.

 

Honestly, we picked up a bunch of aftermarket parts from Classic for our project.  And several pieces include a set of billet aluminum Detroit Speed subframe mounts as well as a set of stainless steel ARP body mount fasteners.  The body mounts are CNC machined from billet aluminum.  The mounts are then hard-coated (not bright anodized).  The hard-coating process resists corrosion that can occur between steel and aluminum surfaces.  CNC machined stainless steel bevel washers are included.  Classic Industries also supplied a set of very trick ARP 17-4 stainless steel flanged body bolt kits.  FYI, Classic can set you up with standard height or ½ height mounts.  The ½ height mounts will lower the car (obviously), but they also bring their own issues (dimensions for things like the rag joint stack up). Nova applications have two bolts that are ½-inch longer than a Camaro and they also include a special spacer (which all 1968-72 Novas have) that fits above the first body mount at the cowl.  Finally, the kits are complete with a similar set of solid radiator core support mounts and the bolt kits include stainless steel ARP fasteners for the rad support.  The solid mounts install the same as cushion jobs, but you should use anti-seize on the stainless bolt threads.

Once the mounts are assembled and the subframe is installed, do not torque to specs yet!  You need to square the subframe in the car.  Here’s a quick way to do it at home: At the rear of the body (ahead of the front spring eye) is a body cross member.  You’ll find two trammel alignment holes.  They’re easy to spot – they measure approximately 5/16-inch in diameter and they’re near the rocker panel.  With the car level to the floor, drop a plumb line down from the center of each of these trammel holes.  Mark that point with a piece of tape on the floor.  Beside the forward body mount point on the subframe is an extra hole (see the photos).  Drop a plumb line down from the center of this hole.  Mark that location on the floor with another piece of tape.  Measure front to back on both sides.  Then measure diagonally from the passenger side rear trammel hole to the driver side plumb line mark.  Do the same from the driver’s side rear trammel hole to the passenger side subframe plumb line mark.  What you need to do is to get the two front to back and diagonal measurements as close to the same as possible.  That means the subframe is square in the car.  Keep in mind these are old production line cars and you’ll probably be out a 1/8-inch or so over 6+feet.  When done, you can torque to specs.

With the subframe squared, you can finish the build.  Next issue, we’ll move on to the a-arms and steering box install.  Watch for it.

Other parts of this series:

Subframes Part II

Subframes Part III

Subframe
This is the mess we started with. If you compare it to the lead photo, you’ll see there’s quite a difference. To get there, you’ll have to strip the subframe, detail it, sandblast it, and powder coat it. See the text for more info.

Billet aluminum body mount

Billet aluminum body mount
Here’s the billet aluminum body mount from Classic Industries. The first photo shows the top half on the subframe pad. The second shows the bolt, the upper and lower mount pads and a Nova body spacer.
ARP fasteners
The ARP fasteners should have their threads painted with anti-seize before installation.
solid body mount
This is the installed solid body mount. Note the beveled stainless steel washer. It’s a cool setup.
plumb line in subframe
You’ll need to square the subframe in the car. We dropped a plumb line down from the body trammel points first.
plumb line in subframe
Next, we dropped a plumb line down from the center of this hole in the subframe. From here you can square the subframe to the body. See the text for more info.
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