Tech Articles

Tech Articles

Found in Street Rodder| May 2010| By Ron Ceridono

In most production cars the centerline of the engine and transmission is higher than the pinion flange on the differential. So keep U-joint angles at a minimum, the transmission’s output shaft usually points down 3-5 degrees, while the pinion points up the same. In other words, the transmission’s output shaft and the pinion shaft are parallel.

Now consider this. Because the engine sits in the chassis at an angle, you’ll find the intake manifold’s carburetor pad is also at an angle to keep the float bowl level. That means when you install the engine in your chassis, the carburetor mounting pad determines the angle of the engine and it should be level front to back (as well as side to side). Now, the next consideration is ride height, which is often overlooked. Simply put, don’t position the engine with the frame level if the finished car will have a 4-degree rake. Put the chassis at ride height, whatever it is, level, nose high or low, then level the carburetor pad and build the motor mounts.

Now in most cases, with the engine in place the driveshaft will run slightly down hill to the rearend and it’s simply a matter of positioning the pinion to be parallel with the transmission’s output shaft and you’re good to go. However, with an extremely low car, the pinion shaft may actually be higher than the transmission’s output shaft and the driveshaft will run uphill to the differential. That’s not a problem as long as the output and pinion shafts are parallel (even though it looks strange) and the angle between them and the driveshaft does not exceed 3-1/2 degrees. If the angle is too severe, the best option is usually to raise the engine slightly.

Now, a couple more points. While we said the input and pinion shafts should be parallel, most U-joint manufacturers actually advise that a small angle (around ½ degree) is preferred over none at all because it causes the cross to move slightly, which distributes the lubricant for longer component life. With solid rear axles there’s enough suspension movement to take care of that. With an independent that has the differential in a fixed position, point the pinion down a ½ degree or so (if there is any movement in the mounting bushings under acceleration the angle will decrease before it gets worse). Finally, if you’re using a fuel-injected engine it can go on level, as there’s no float bowl to be concerned with but all the other angle considerations remain the same.

 


The Crystal Ball | By Pete Chapouris | About 2006

Over the years, we’ve built cars for dozens of people. Each project had its own challenges and personality, and each customer had their own concerns. However, two concerns common to all customers, regardless of how wealthy they may be, is “how much will it cost, and how long will it take?”

Unfortunately, no hot rod builder alive has a crystal ball. This is not production work. A builder may be able to come really close on a “plain-Jane” ’32 Hiboy, or another car that he’s already built (if he’s kept good records of the hours he’s had in it). But when you’re looking to radically customize a ’55 Chevy, or stretch a Model A pickup in a way that has never been done before, you enter the realm of the unknown.

Unknowns come in many forms. For example, it’s unknown what condition the body will be in until you completely strip it down to bare metal. Even the “Hot Rod Gods”, can’t see through layers of paint, primer and Bondo. In fact, the only thing known about unknown is that you’re always going to encounter them.

Because of this fact, many professional builders are reluctant to give estimates, and prefer to work for “time and material”. This is great if the customer and builder trust each other, and share a very clear vision of the final project. But, many customers don’t like to work on a time and material basis for two reasons: 1) they don’t want to be taken advantage of ; and 2) they find it difficult to budget for the work.

There are no easy answers to this dilemma. Hours are hours, and you can’t make them disappear. But, there are guidelines to be aware of when working with a professional builder on a project.

First off, to do a high-quality vehicle with superior fit and finish, you can expect it to require a minimum of 1300 hours plus parts. This is for a fairly stock project with a body in decent condition. To take this same vehicle and make it a show winner, you can expect to nearly double the hours. Anything radical in terms of a chop or stretch, etc., adds numerous hours as well.

Parts price on a project will vary consider ability depending on engine/transmission/suspension choices, but will easily run into the $30,000 range.

These numbers may shock you, but they’re realistic. Consider what it takes to build a modern car. Visit any General Motors dealership, order all the parts to build a new mid-size (base price $18,000), and it would cost you more than $40,000. Then, hire someone to assemble the vehicle for you and paint; you could easily spend another $40,000 to $50,000. This is exactly what must be done when building a hot rod from the ground up, only when you’re building a hot rod, many times the parts don’t exist and you need to fabricate them from scratch. When considered in this light, 1,300 hours plus parts in an incredible bargain.

As for the breakdown on these hours, we’ve found that half of the labor is accounted for in chassis/hookup and assembly work, while the other half is in body work and paint. Obviously, this not an exact formula, but it’s fairly consistent guideline.When people become aware of this breakdown, they often decide to “Skimp” in one area or another. They say to themselves “Gee, maybe I could have my sister’s boyfriend spray the car,” or “I wonder if I could pay my neighbor to finish the hookup on the car.” Inevitably, this leads to disaster. Many times, the car ends up costing more than it should have while the quality suffers.

The best plan when working with a builder is to decide as much as possible before work begins. If you don’t feel comfortable with a “time and material” estimate, don’t start the project. If you have an estimate, don’t start the project. If you have an estimate, be prepared to exceed it if there are significant unforeseen problems in the build. If you want to do some of the work yourself, split the project up into manageable segments. Above all, go into the build with as much information as possible. Your research and planning will pay off in the long run.

As for the time it takes to build a vehicle, that all depends on how much the customer can afford to spend each week, how many projects are under construction in the shop, and the scope of the project itself. If three or four guys can work 40 hours per week each on one car, you can build anything in a few months. But if a customer’s budget calls for a maximum of $1,500 per week, the vehicle could easily take over a year- as is often the case.

When everyone understands these things going into a project, the experience is enjoyable and exciting. Customers hang around the shop, get to know the boys, make new friends and end up with a bitchin’ car. That’s what it’s all about.