Bolting an engine together is easy. It’s much more time-consuming and demanding to custom-build and blueprint an engine. The term blueprinting is an often over-used and misused term that has probably lost much of its meaning in the world of high-performance engines. It was originally intended to mean that you would go further to ensure that the clearances were what you wanted (not just measure how they came out).
Actually, blueprinting is as much art as it is science. It’s about putting effort into the engine rather than just slapping it together. This is more a state of mind than a process. The payoff is with an engine that not only makes great power, but is also one of those engines that seems to run forever. You know you’ve got a good engine when you can buzz the wee out of it for an afternoon at the track, run the valves afterward (assuming you’re running a mechanical cam) and discover that the valve lash has changed perhaps a couple of thousandth’s on one or two cylinders.
This Tech Tip is From the Full Book “HOW TO BUILD BIG-INCH CHEVY SMALL-BLOCKS“. For a comprehensive guide on this entire subject you can visit this link:
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An important rule when assembling an engine for the first time is to not be in a hurry. You have to be willing to preassemble portions of the engine perhaps four or five times in order to get all the clearances correct. The more aftermarket parts and exotic stuff you’ve added to the engine, the more time you can expect to spend on pre-assembly clearancing. For example, a long-stroke crank and a new block will need to go together several times before they are happy. Add in rod clearance to the cam (which means you need to degree the cam first to ensure it’s installed correctly) and you have plenty to do. The last thing you want is for a connecting rod to run into a cam lobe during final assembly. That will ruin your whole day.
The cardinal rule for engine assembly after you’ve learned patience is very simple — trust no one. Even if your mother did the machine work, it’s the engine builder’s responsibility to ensure that the clearances are right. If you slap the engine together and only discover the mistake after the engine begins to eat itself, you will find no sympathy from the machine shop. If a clearance is wrong and you catch it, most machine shops will take the parts back and do the job right, especially if you approach them from the standpoint that you’d like them to re-measure and tell you if they get the same results. If they do, there will be no problem.
However, if you allow the mistake to get past you until after the engine fires, that’s when all bets are off. The machine shop will, and rightfully so, inform you that you probably didn’t assemble the engine correctly, and that’s why the pistons scuffed or the bearings were wiped out. The whole effort of double-checking your work and ensuring all the clearances are correct is designed to protect you as well as the engine. We’ve spent some time on this because failed engines just past startup are a common problem. Sometimes it is the result of a failed component. Much more often, however, an engine that eats the bearings just after break-in either wasn’t machined correctly, was poorly assembled, or both. Either way, it’s the engine builder’s responsibility, and either way, any failure is guaranteed to cost you grief, time, and money.
This may begin to sound like a walk through the Engine Builder’s 10 Commandments, but next in line is the simple concept of cleanliness. The days of building an engine on a dirt floor or rolling the engine around on a wooden bench while you assemble it are long gone. Today, if you don’t have the rudimentary tools like a clean place to assemble the engine, an engine stand, and most of the specialty tools, then you’re better off paying someone else to do it for you. Engine assembly work is not difficult, but it does require a regiment that includes several layers of cleaning before the engine is finally ready for assembly.
The good news is that cleaning doesn’t require a ton of expensive tools, but you will need plenty of hot soapy water and a collection of engine brushes that will allow you to access the entire length of the main oil galleys, as well as all those tiny machine crevices where dirt, sand, and metal shavings like to live. This job may in fact involve several shots at cleaning. The block needs to be machined and hot tanked or cooked before you start the pre-assembly process, and then you will need to thoroughly clean the block at least once more before the engine is finally assembled. The minimum equipment needed will be hot soapy water, brushes, and an air compressor with a blow nozzle.
Besides the knowledge to do the job correctly, it is impossible to assemble an engine without the right tools. This will involve not only the specialty tools used to assemble this cast iron and aluminum puzzle, but also several invaluable specialty measurement tools. We’ll spend a few paragraphs on these instruments because they are so important to doing the job correctly. As dangerous as it may be, we’re going to assume that you are serious about building engines and intend on assembling several, if not dozens over a long period of time. This means you will need the best equipment. We’ll stick with measurement and assembly tools and leave the machine tools for some other time.
Micrometers should be one of your first purchases on the way to becoming a famous engine builder. The best plan, and generally the least expensive one in the end, is to purchase an entire set of micrometers rather than individual units, since you can then get the very handy wooden box that will protect them while they spend time in your tool box. There are several companies that make high-quality tools, and you can expect to pay anywhere from $700 to $1000 for a complete set of five mics. Also, look for micrometers that are accurate down to 0.0001-inch. You will need this kind of accuracy to set bearing clearances. There are two styles of mics. The classic outside mic measures the outside diameters, like a rod or main journal. There are also inside mics that measure, as you might have guessed by now, the inside diameters of bores, like a main or rod bearing.
Inside mics can be somewhat slow and cumbersome to use, which leads us to dial bore gauges. These handy tools combine a dial indicator with a long handle and a three-point foot at the other end. The foot uses an adjustable pointer that can measure between 2 and 6-inch inside diameters. After selecting the proper diameter foot extension, zeroing the dial bore gauge requires a micrometer. Set a micrometer to the diameter you wish to measure. Zero the dial bore gauge to that diameter and then merely slip the foot of the tool in the bore you wish to measure. This tool can also be used to measure bore taper and out-of-round. This tool is most generally used for rod and main bores and cylinder bores.
Snap gauges can also be used to measure the inside dimensions of many components that may not work with a dial bore gauge. For example, we used several sizes of snap gauges to measure the cross-sectional areas of the heads listed in this book. Since this was not an ultra-critical dimension, we measured the length of the snap gauges with a dial caliper rather than with a micrometer. You may think that you could substitute a snap gauge for a dial bore gauge to measure inside diameters and that will work in some cases. But for bearing clearances, these tools are generally not accurate enough to do the job. Of course, a dial caliper is useful for so many things, that it might well be your first purchase just because you’ll use it almost every day.
A good engine builder will own several dial indicators, usually with each one assigned to a specific task. For example, he may have one set up on a magnetic base that can be used to measure valve lift and help with degreeing cams and checking crank and cam end play. He will no doubt have one set up on a deck bridge to quickly establish both piston TDC as well as deck height. He might have a third, small-diameter dial indicator set up for checking bellhousing alignment to crank centerline. As you can see, there are several uses for a dial indicator and a magnetic base that are essential to engine building.
In order to degree a cam, the minimum tools needed are a dial indicator, some type of mount for the indicator, a degree wheel, some type of mount for the degree wheel, a piston stop (usually two different ones — one to be used with the cylinder head on, and one for when the is head off), and a simple pointer that can be made out of a bolt and a length of coat hanger wire. One point worth making here is that the larger the degree wheel, the more accurate your results. A quick test of the accuracy of your degree wheel is to lay it on a large piece of cardboard and mark the paper with the four 90-degree points on the wheel. Then rotate the wheel and see if all four points still agree. For example, rotate the wheel 23 degrees and then do the math to see if each of our four scribed marks still line up 23 degrees from 90. Smaller degree wheels offer less distance between each degree, creating a greater opportunity for error. The large diameter pro wheels offered by Powerhouse or Comp Cams are expensive, but much more accurate.
The other part of this effort is a seemingly simple one, but one that can easily be overlooked. Do the right thing and buy a wheel that works with one of the professional-style wheel mounts. This mount slides over the crank snout which means you’ll have to buy both a small and big-block mount, if you’re building engines with rat snout cranks. This mount is then secured with a locking Allen bolt to the snout. On the front is a large, threaded, male stud that mounts the degree wheel and is locked in place with a large knurled nut. In the center of this mount is a 1/2-inch square drive for a ratchet or breaker bar that will turn the crank without disturbing the position of the degree wheel. This mount design requires a large hole in the degree wheel and not all degree wheels use this larger hole.
If you already have a degree wheel with the smaller mounting hole, you can purchase a crank nut that slips over the crank snout. Then the degree wheel can be bolted directly to the snout, using the crank nut to turn the engine over. This also requires a very large wrench (we use a large, adjustable wrench). You may be tempted to turn the engine with the crank bolt that also mounts the degree wheel. This won’t work because the risk is that you will move the degree wheel after setting TDC, which will add an error into all your subsequent measurements. There are also times when you must turn the engine backwards, which will loosen the bolt, move the degree wheel, and then you will have to start all over. Trust us on this one; it’s not worth the hassle.
You will also need some kind of graduated cylinder for testing combustion chamber volume. The most popular style is a graduated burette with a small valve at the bottom mounted on a metal stand. The original ones were made of glass and very fragile. We bought our first one from a chemistry supply house. But now you can purchase plastic versions that are more durable from several companies like Powerhouse. This tool is also useful for measuring piston volume.
Let’s start with the simplest tool — those little plastic rubber boots that slip over the rod bolts to protect the crank. Never install a piston without these. They’re simple, inexpensive, and necessary. Next is another ingeniously simple tool, the tapered ring compressor. This device forever eliminates the hassle of broken rings when installing pistons in the bore. Yes, you do have to buy a separate compressor for each bore diameter, but these simple tools are worth the money in eliminated aggravation.
Staying with pistons for a moment, you will also need some kind of ring filer to set ring end gaps. The simple handcranked models work fine and are inexpensive, but they are also slow. There are electric models now that are much faster and you might want to consider the investment in time. A rod vise is another useful tool that we can’t imagine doing engine assembly without. It allows you to torque without worrying about twisting the rod and the vise is also an excellent tool for removing stubborn rod caps.
A deck bridge is a simple device that mounts a dial indicator to quickly determine piston-to-deck clearance. This is much easier than using a magnetic base and an indicator. Some of the better bridges also come with magnetic feet to hold the bridge in place. Another useful tool is a cam handle. Yes, you can use a length of 5/16-inch threaded rod, but the cam handles are just so much easier to use.
Finally, you will also need a dampener puller and installer. These tools can be purchased separately as a puller and installer and work well. The latest tool is a heavy-duty universal combination tool that uses Torrington bearings that use the same tool to pull and install the damper. As we said, many of these tools are more money than you care to spend, but once you use them, you’ll realize their value and, if you’re not too hamfisted, they will deliver a lifetime of humble service.
We’ve also included a multitude of photos that deal with specific tasks, blueprinting operations, and ideas that might help you with assembling that street-nasty small block. But the most important tool is the one between your ears, using your head and paying attention to what the engine is telling you. If you work slowly and dedicate your full attention to assembling that engine, it will reward you with outstanding power and reliability. The best part is you’ll have the satisfaction of telling your friends — “I built the engine.”
Written by Graham Hansen and Posted with Permission of CarTechBooks