Since the best gear drive is a two gear unit, this severely limits your camshaft choices because you need a reverse rotation camshaft. Three or four gear, drive units are expensive, but allow for “normal” camshaft rotation. In my opinion you should buy the double roller chain with steel sprockets. The best choice from an engineering point of view is the two gear reverse camshaft rotation setup, but that is not normalcy, because the car makers want your engine to fail. Chains stretch and fail. Remember I said I wrote this article to save people from making big mistakes. Do not use an aluminum sprocket with plastic teeth. The best compromise is a Cloyes double roller chain set, with steel sprockets. On a Chevrolet V8 there is no slack in the chain when it is installed as new, it should be tight. Generally it will stretch before it breaks, so if there is slack it needs replacement. And now we have come to the most important part of our journey into engineering your Hot Rod engine into reality.
Choosing the camshaft.
What the rod bolt is to durability, the camshaft is to performance. The camshaft is the brain that determines whether the same engine will idle smoothly and run out of horse power at four thousand R.P.M., or your engine will idle rough and pull hard past 8000 R.P.M. So here it is, the advise you have all been waiting for. Buy the biggest camshaft you can get, that will fit in the engine without machining the pistons for valve clearance. Read that sentence five times or until you know it by heart. Why? You can buy a new Corvette with five hundred horsepower that idles smooth. That horsepower level is not coming from the camshaft. It is coming from everyone whom has ever taken a die grinder to a cylinder head, and ported the hell out of it. Decades of modification and the factories taking the collective genius and putting it into production. Ditto for Fords five hundred horsepower Mustang and Dodge with their Charger. The point is that cars have become super powerful as delivered and the quest for power alone is shallow. Most people build a Hot Rod as an expression of individuality, to have something unique but safe, fast and fun in a way to suit there purpose. If everyone drove those three cars I am sure the factories would be thrilled, but don’t hold your breath waiting for that to happen. I feel with my 1966 Chevrolet El Camino and the 8500 R.P.M. 355 small block Chevy, I practically started the truck racer craze, with all the other hot rodders that needed something that would be quick, and haul whatever else you could load into the bed, in my case one Fender Hot Rod Deluxe Reverb and three Fender 135 watt Twin Reverb guitar amps, my guitars etc. Back to the camshaft discussion. You don’t want to disappoint yourself. Therefore you should consider factory combinations as a foundation of expectation. This is where I think like Harvey Crane of Crane Cams. Crane has in the past sold Factory High Performance Camshaft profile reproductions. Example: A 425 horsepower street mechanical camshaft for a big block Chevrolet 427 as compared to a 565 horsepower L88 off road mechanical camshaft is the difference between a rough idle and nasty idle. In either case however, these factory camshafts are reliable and quite a joy to own, because they have rather gentle profiles, which do not destroy the valve train too quickly. The six hundred lift two gear driven reverse rotation fuel injection camshaft made about six hundred horsepower, reasonably reliably, and was used to road race. I have seen a lot of people spend a lot of money on a lot of outrageous stuff, that was not as powerful, but they enjoyed their creations as a freedom of expression. Even if that tunnel ram, and two six hundred Holley four barrels on their 283 small
block was slower, they were happy, so each to their own. My suggestion is that each factory has their tried and true high horsepower setups, that you might want to consider. Otherwise you know what to do. Just about everyone else will tell you the opposite and you will have to learn the hard way. So the lesson you should have learned is factory high performance parts combinations are a fairly reliable, fairly sure thing, otherwise “buy the biggest camshaft you can get that will fit in the engine without machining the pistons for valve clearance”. I would patent this copy written protected advise, if I could, and then trademark it too. Remember that, as my original famous automotive Hot Rodding quote, that no one else I have ever heard of, or come across has ever said. You don’t have to do as I say, but I like to do as I say, because I am absolutely right, correct and the truth. Here is why. Gasoline is of a certain quality right now which I call eleven to one. I call it this because eleven to one compression is about as high as you can go on currently available everywhere fuel. Diesel engines have about twenty two to one compression, but they don’t burn gasoline.
There are two very important aspects of compression which effect engine performance and engineering decisions, and that is static compression, which is the volume of the cylinder, and cylinder head at bottom dead center, verses the volume of the cylinder and cylinder head at top dead center. When you buy an eleven to one forged racing piston this is what they are talking about. The other aspect of compression is dynamic and refers to the cylinder pressure in pounds per square inch. This relationship is extremely important and the crux of my advice and high performance engineering and camshaft selection. Now lets talk about motive. I have no motive to advise you in any misleading or other than totally and exactly accurate, honest way. I know what engineers recommend. I worked for General Motors and several racing equipment organizations whom factory and S.E.M.A. trained me. I am not a speed shop, that would like to sell you performance in small increments, with each new engine build experiment you engage in. The reason I experimented with Chevrolets engines primarily, is because of the Chevelle coil sprung, four link suspended, full frame under a unit body from the firewall back chassis. Plus people would give me a 350 Chevy small block if I would just remove it from their back yard and get it out of there. How is that for a good price? I bought 396 big block Chevrolet engines Smokey Yunick made famous, for a whopping fifty dollars each. So I really like other brands and I enjoy them but Chevrolets, in my neighborhood, didn’t grow on trees, but might be sitting in backyards under one. Engineers will always tell you that you are always better off to under cam and be under carbureted. So now back to my famous quote. “Buy the biggest camshaft you can get that will fit in the engine without machining the pistons for valve clearance”. I say this because gas is pretty bad now days. When gasoline was fifty cents a gallon, gasoline was over one hundred octane and you could run a twelve to one compression L88 cam daily anywhere. Now here is another shocker which people will also probably argue against. Detonation from low octane gasoline will destroy an engine very quickly, breaking off the hard ceramic spark plug insulators, breaking piston rings and piston ring lands. With low octane fuel oil companies wipe out engines, like computer software companies make software run slower and slower, to sell faster and faster computers. Lest you be left behind with your abacus and your dead engine, be advised, they want you to buy a new computer and a new car too. Here is something else that just about no one else will tell you. If Diesel engines have twenty two to one compression, and gasoline engines are stuck with less than eleven to one compression, then just mix some diesel fuel with your gasoline and lubricate your valves a little better too. Don’t go crazy with the stuff, just a little. If you add too much diesel fuel, your gasoline engine won’t run because the fuel is too high an octane and your engine does not have enough compression to burn the fuel. Back to my famous quote. “Buy the biggest camshaft you can get that will fit in the engine without machining the pistons for valve clearance”. If you buy too small a camshaft, meaning one with low valve lift and a short duration of time the valves are open, the cylinder pressure will be high, and with ten, eleven, and certainly twelve to one static compression there will be pre-ignition, detonation. Cylinder pressure is a function of valve events. If you stick the same camshaft in three engines whose only difference is the static compression, the dynamic cylinder pressure will exacerbate the situation, making the cylinder pressure on the twelve to one engine probably blow a head gasket. Now if you “buy the biggest camshaft you can get that will fit in the engine without machining the pistons for valve clearance” and install it in three engines, whose only difference is the static compression, the ten to one compression engine will not have as much low end torque and horsepower as the twelve to one static compression engine, which may no longer detonate because the long duration of time the valves stay open reduces cylinder pressure.
