The foundation of a Building is the most important component of construction. Hot Rods are no different.
Difficulty: Moderately Challenging
Building a Hot Rod chassis can be as easy as dialing for dollars. Many companies offer complete chassis packages that you assemble. Companies like Speedway Motors, TCI and SoCal Speed Shop. The focus of this article will be a "Do It Yourself" attitude. From the photo you can see a crusty original chassis. If you can find one of these (this is a Model A Ford)... You are ahead of the game. The truth is, most Auto manufacturers uses Horse buggy technology for cars through the 1930's. The are simple, rugged and easy to work on. Early Ford is the most popular, so we will concentrate on that. Ford Trucks used a version of the "Model A" style through the 50's. First decide what kind of Hot Rod you want to build. Roadster or closed car aren't as important as what the car will be. For example, if you want a Model A, then start with a Model A frame. 1932 Ford? Start with a 1932 Ford Frame. If you want to build a budget Rod and are low on cash, a generic frame and whatever body you can find will work.
Once you have decided on a Hot Rod, acquire a frame or raw steel tubing. Original frames will need work before you can begin to modify them. You must cut off any mounts or brackets that you will not use. If it will be a cut down fender less Rod, you will remove running board brackets, fender mounts, etc. Also Mechanical brake assemblies and linkage. Carefully disassemble the front suspension. (It can come off in one piece if you remove the "U" bolts on the front cross member). Same with the rear axle assembly. Keep everything, in case you need it to re-use or as a reference. The frame should be bare now. It's time to grind, sand or BEST, Sandblast the thing clean. Welds don't stick to grease and rust very well. Now it's time to measure from corner to corner to see if it's "Square". Also, clear your workspace. You will need stands on the floor or BEST, a big solid table to work on the frame. Make sure your surface is LEVEL. Use a LEVEL. When modifying the frame, consider what parts you will use. Plan ahead.
Hot Rods are an individual expression of the builder. No two are exactly alike. How you modify or build your frame depends on YOUR plan. The frame needs to be Square and modified on a level surface. If you can weld and have a good welding set up, you can begin by improving some of the weak points. Specifically, the front and rear cross members. "Boxing" of the frame makes good sense if you are planning to run an Engine that produces over 200 Horsepower. Most builders agree that "Boxing" is required on ANY old frame. It's still up to you, there's no law. If you are running an 80 year old frame it may be brittle or weakened by corrosion... so be smart. "Boxing" is a term that refers to welding a flat steel plate the entire length of the frame on the open inside edge. (Most early frames are "C" channel, or 3 sided). Buying rectangular steel tubing solves the problem. You can weld up a frame from scratch using tubing, by calculating the dimensions you need. This is also the time to pick an engine. An early Hemi will not fit in a Narrow Model "T" frame unless it sits on top, or the frame is widened. Small Block Ford and Chevy will fit into nearly anything and Inline engines are a snap.
The suspension will also depend on what you want and how much money you have. The easiest way to get something that works well is to buy a front suspension "Kit". Of course these are just modified early Ford set ups with new technology. You might find someone turning a restored car into a Hot Rod. If they are going to toss the original stuff, you can get a good deal on suspension that will work on your Hot Rod. I have also mentioned in other articles, that a Pick up truck from the 40's and 50's will have a straight axle (factory dropped) with parallel leaf springs. This can be used as is if you want a Drag Racer/Gasser style Hot Rod. "Batwing" brackets can be fabricated to allow Wish-bone torsion bars or Radius rods for locating the axle. A transverse leaf Spring behind set up will also work with this configuration. Once you have decided on a front suspension, it can be mounted "Suicide" style (on a bracket way out in front of the frame), or under the front cross member like the factory did. Suicide style is used to lower the car more than "Under" the frame. Steering is straight forward. A steering box turns the pitman arm which pushes the tie rod back and forth. (tie rods tie the two spindles and wheels together). Common steering boxes include: Early Ford, Early Mustang, Ford F100 truck (40's and 50's), Corvair and Vega. The box must be mounted properly and at the correct angle. All except the Vega, will mount on their side, with a drag link running to the Drivers side wheel. The drag link should be as level as you can get it. Not running extremely uphill or downhill when viewed from the side. Rear suspension is easy. Just a Rear differential with springs and something to hold it in place. Leaf Springs are the easiest but parallel leaf spring set ups don't work well on small early cars. Semi Elliptical works (leaf springs cut in 1/2). Transverse (like the front) is the way the factory did it. And coils or coil overs will require trailing arms.
Once your chassis is on 4 wheels... you can begin to fit a body and sort out the way it "sits". The attitude is EVERYTHING in a Hot Rod! The engine will need to be mounted. Some factory type mounts will work. The easiest are side pedestals for small block chevy and ford. Front cradle mounts work too, but will require support on the middle. The transmission will need a cross member. Preferably, one that is BOLTED in. Once the engine is mounted and you have an idea how the car will sit, turn your attention to details like Gas, brake and maybe a clutch pedal. Will they be mounted on the firewall like modern cars.. or under the floorboards? If they are mounted under, you will need to weld brackets on the frame. The gas tank can be underneath, in the trunk, etc. In the 70's, people even used Beer Kegs for Gas Tanks, the sky is the limit. Just use your head and be safe!
By now, you should have a chassis that maybe COULD be driven around the yard. You are far from finished.... but the article is over. If you plan to build a finished car, you will continue with the body and details before taking every nut bolt and screw off to paint and chrome the Beast! Good Luck!