Restoring my 1968 Camaro required a certain number of decisions up-front, concerning the intended configuration. Issues such as “authentic suspension, original design” vs “modern suspension, classic skin”, for instance. Or perhaps, “original design but different components/options than my actual car came with”. And if so, which ones? These are issues we all deal with when we own a classic Camaro and elect to perform work that we feel will improve its condition.
Answers for me didn’t always come automatically, but sometimes needed research and thought to decide on my intended use. First and foremost, I needed to decide on a philosophy of intention. Second, I needed to determine what was practical to implement, both in terms of Ricky’s physical reality, and my financial health.
Philosophy of intention was easy. I wanted a 1st Generation Camaro that was a 1st Generation Camaro. I have no desire to have a modern car disguised as a 1968 Camaro. I don’t have a problem with those who do. I just don’t want that for me. I drove this car for around 6 years as my daily driver, back in the early 80's, and I really truly love how crude but powerful it is. I am willing to allow a few improvements, such as the Eaton Detroit Truetrac differential, but in the main, this could have come off the dealer’s floor, been driven to a wheel shop and been equipped with Centerline Mags that same day.
Once I knew what could be done and what I could afford, I had to decide levels of importance assigned to various issues needing resolution. Let’s pick an example to illustrate how decisions were reached, by examining a ‘for instance’ area:
NOISE. I decided that the audio nature of this beast needed to favor a free-breathing engine, balanced against not getting shot by my neighbors. Factors included the nature of the exhaust system chosen, the degree of sound-proofing of the cabin, the quality of the sound system playing the music I happen to love, and the most likely use-case for driving. By use case, I mean: twisty country roads, in-city drives, freeway travel, etc.
Exhaust system decisions for the 396 were fairly easy to make, given my requirement to minimize restriction of exhaust while creating a somewhat harmonious sound. There, I chose high-quality steel-tube tuned headers, 3” tubing, interconnection to minimize bass throb, and Magnaflow “Straight-thru Performance” mufflers.
Sound-proofing the cabin really came down to Lizard Skin versus Dynamat. Lizard Skin is expensive to buy, but inexpensive to apply. Dynamat is pretty much the opposite. I think (without any proof) that they are fairly equivalent in total cost. Just boils down to “different strokes for different folks”, I guess. In any event, I went with Lizard Skin.
Sound system issues were easy for me, due to my personal history with high-end audio sales and use. One item concerning audio that needed some thought concerned sub-woofer bass: speaker location and quantity. The cabin of a 1st gen Camaro is really not very big, and sub-woofers are, especially in a cabinet. So, where to put it (or them)? Another issue to deal with concerned sound-proofing the trunk from the cabin, as a large fraction of road noise comes in through that area. A few entries ago, I made clear how I was solving both of those issues with a common solution.
So, finally we come to the
various use-cases for driving. The reason for that issue being relevant concerns engine RPM at various speeds, and its noise. Freeway driving means relatively constant RPM, while City driving is mostly mellow acceleration between stop lights, or a lot of idling. Back road driving is adrenaline-based at times, where RPM changes are power-induced or dependent on down-shifting into corners. I decided that back road driving times were less relevant to noise, city driving as well, but freeway driving could be “interruptive” regarding the drone of constant RPM, especially if it was relatively high RPM; say in the mid to high 3000’s. In that scenario, hopefully the degree of soundproofing and quality and intensity of audio sound system might enter in, but the other factor I could control would be rear-end gear ratio. One of my givens is the gear ratio of a stock Muncie M20 (i.e. no Gear Vendor overdrive), which at best is 1 to 1 on the freeway. Changing the rear end gear ratio dictated what the engine RPM would be at a sustained speed. However, rear gears also impact the level of performance under acceleration from start to final speed, or varying performance through the gears on back roads. I sought to find a happy medium, then. So, how could I see where shift points occurred with this transmission, while deciding what rear gear ratio to use.
Back when I was a ‘working class hero’, actually doing work that made money for my employer and income for us, I spent some amount of time in Microsoft Excel; the land of spreadsheets. I was aware that there are websites where you can enter your transmission gear ratio, your differential gear ratio, and the diameter of your tires, and be provided an engine RPM. The problem was that I couldn’t see the “big picture” of RPM over a range of speeds, all in one place at one time. My initial solution was to create a very simple spreadsheet that really was just meant to provide that picture, a demonstration of shift points, useful when you knew the torque and horsepower statistics of your engine. I then filled in each cell by shuttling back and forth to the website I chose to use to determine RPM’s. This was a good solution, but very cumbersome if I wanted to see what would happen to RPMs if I changed, say, tire diameter, or rear-end gear, or went with a different tranny, especially if that tranny had a 5th gear overdrive. So, I went researching what the math was that the websites were using to provide the “RPM” answer. And I found it. Once I knew how to compute RPM for a given speed, gear ratio, differential ratio, and tire diameter, I created a spreadsheet that allowed me to change any one of more of those variables and INSTANTLY see RPMs in 5 MPH increments for each gear of the transmission. I added a second worksheet for 5-speeds where the 5th gear was an overdrive (i.e. less than 1 to 1). The result was an area of each worksheet where computations happen, and a separate area of the worksheet that was a print area. In that print area, I left cells where you could specify each gear ratio for the transmission, the gear ratio of the differential, and the diameter of the rear tires. If the end user changes any of these values, you see the RPM’s change for each gear at each speed. Now I had a tool to decide what ring and pinion to use for Ricky Camaro. Since Ricky was going to spend a respectable fraction of his life on freeways, in order to drive to shows or to different back-road areas, and since I was not trying to build a race car, I ultimately went with a 3.42 ratio for the rear gear. Here is what my 4-speed worksheet produces. Note that I have bolded the RPMs in the area I am most likely to find myself, roughly between 2K and 5K RPM.
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Note, the numbers in
bold yellow can be changed, and you immediately see the change in RPM for each gear at each speed. The other worksheet populates the right hand column which in that sheet is labelled “5th Gear”. Ultimately, if freeway sound becomes too irritating, I will entertain the possibility of adding a Gear Vendor overdrive to the Muncie. If I do, the second worksheet looks like this:
So, this discussion illustrates what I meant about reaching decisions in order to provide direction to B&R Auto. Of course many other areas were more consultative as they were in a good position to tell me what my choices were, both financially and realistically.
And a good time was had by all.
