Ask Joe Special- This month and next month we are going to address a question that is often asked. The question is “What is blueprinting?” we will go into detail the major and minor aspects of engine blueprinting. Blueprinting is basically rebuilding an engine and looking to reassemble each part to gain the maximum performance without necessarily compromising the durability out of the assembly.
Starting with the block, there are key aspects of an engine block which should be addressed before beginning a blueprinted engine assembly. After a thorough cleaning, the block should be professionally checked for cracks. Sonic testing is one method of accomplishing this. The block should be checked for previous over bores, as this would not be recommended due to thin wall casting designs of many late model blocks. Line boring and honing of the crankshaft main bearing caps and saddles is another operation included in blueprinting operations and is not necessarily done during a standard rebuild. This ensures that the crankshaft is rotating on an absolutely perfect block and main cap surface. This procedure will check to see if the main caps have walked or distorted. This is crucial for race engines that see higher rpm and the added stresses of racing and severe street duty. Bearing longevity and an even bearing wear pattern is an absolute requisite for a race engine.
Cylinder bore preparation is another area of blueprinting that can really make the difference between a standard rebuild or a stand out race engine. Within a given set of pistons there are variations in the actual size of each piston. In any blueprinting operation each piston must be fitted to an individually tailored bore. A standard rebuild will usually do a bore and hone and fit the pistons in random bores, by fitting each piston to its own bore, more precise tolerances and clearances can be adhered to. In a race or high performance engine, these are the details that will separate the winners. This is why choosing the piston will be one of the first steps in putting together a short block assembly. At this juncture it is critical if you are going to be using a power adder as this will dictate the compression ratio and dome/dish configuration of the piston. There is also some blueprinting to be done when it comes to the piston itself. Most quality pistons today do not need any modifications, but small amounts of de-burring and combustion chamber contouring of the piston can aid in flame travel. Dome height can be reduced and dishes or valve notches opened up to dial in compression ratios. Coatings are another 21st century innovation that has proven to be beneficial in all forms of motorsports. Coated piston skirts as well as other engine components are now available from many manufacturers.
Pushrod style blocks can also use a little help in the oil galley plug areas. The factory uses caps instead of NPT pipe threads, and can be easily converted by any competent machine shop. The factory caps are not foolproof and loss of one can lead to catastrophic engine failure due to loss of oil pressure. Chamfering of oil passages in the pump area can aid in better oil distribution to the motor. A standard rebuild will almost never take something like this into consideration, where the blueprinting operation will pay attention to all aspects of severe use. Stroker motors will also require some notching of the bottom of the cylinder bores to accommodate the longer throws of the crankshaft.
Crankshaft blueprinting options include polishing, chamfering, cross drilling, internal balancing, and lightening, all involved in the process of building a durable and horsepower producing engine assembly. Each individual motor and its use will dictate how much crankshaft preparation will be necessary for a given application. High winding small blocks will generally need to be given the highest attention to detail. Once again, modern technology has caught up with aftermarket crankshafts and improved bearings to eliminate many of yesteryears problems that were encountered due to a lack of aftermarket choices and the limitations of the factory pieces.
There is no part of an engine assembly that should not be looked at to gain an edge or improve upon an existing setup. This is basically what blueprinting entails. This month we have looked at just some of the blueprinting details of a short block. Next month, we will go into detail some of the aspects of blueprinting the cylinder heads and valve train as well as outline some of the final assembly of the engine.
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