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Engine Building Fundamentals: Engine Building And Engine Blueprinting

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Engine Building And Engine Blueprinting

07.19

00:00 - One of the terms that's often thrown around by those assembling engines with little understanding of its actual meaning is the term blueprinting.
00:09 This would easily be one of the most misused terms in the engine building industry.
00:15 And simply selecting off the shelf parts and assembling them into your engine does not constitute blueprinting.
00:22 Engine blueprinting is, in fact, a much more involved task and a lot more specialised than just assembling the engine.
00:30 I think it's important to start by clearing up the confusion surrounding this term right here at the start of this course.
00:38 When a manufacturer produces an engine component it will always be produced with specific tolerances.
00:45 For example, a crank shaft journal may be specified as having a diameter of 56.994 millimetres through to 57.0 millimetres.
00:57 This means that the journal can measure anywhere from 56.994 millimetres through to 57.0 millimetres and it will be accepted as being the correct size.
01:09 In this case, the journal has a tolerance of 0.006 millimetres, which, in itself, might not sound like much.
01:19 We need to consider, though, that every component in the engine will be produced with a respective tolerance and we can get into a situation where these tolerances stack up to result in a final clearance that may not be desirable.
01:35 This is referred to as tolerance stacking.
01:38 Notice that I've said the result may be undesirable, however, that's not necessarily saying the result may be dangerous and it might still be completely acceptable for a normal production engine.
01:52 Let's look at an example where we have a crank shaft journal that is on the low limit of the tolerance, which means that it measures on the smallest size of the allowable tolerance range.
02:03 The bearing journal in the block will also have a tolerance range, and let's assume this time the measured journal is on the high limit, which means its at the large limit of the allowable tolerance range.
02:16 While each component is within its tolerance, in this particular case we're likely to end up with an oil clearance that may be larger than we, ideally, want.
02:28 These component tolerances are an essential aspect of manufacturing, as it's not possible to produce commercial parts with infinite precision.
02:39 While in a typical production engine the factory tolerances are going to be just fine, when we're talking about building a high-performance engine that's going to produce considerably more power than the OE manufacturer intended we need to be more careful about the component choice, as well as the final clearances.
03:00 Unlike simply assembling an engine and accepting whatever final tolerances we end up with blueprinting goes further by adjusting key measurements in the engine components to ensure that every clearance in the engine is exactly what we require.
03:18 When we're blueprinting an engine the specifications may also differ from what the manufacturer of the engine suggests, too.
03:26 For example, it's quite common to specify bearing clearances that may be slightly looser or, perhaps, in some instances, tighter than what the manufacturer recommended for the stock engine.
03:39 An example of a common minor blueprinting operation would be selecting different grades of bearing shelf from the manufacturer to achieve exact and repeatable oil clearances across every journal on the crank shaft.
03:55 Let's take, for example, the bare engine block as the starting point for an engine blueprinting project.
04:02 Blueprinting would begin by inspecting the block and every critical measurement would be checked.
04:09 Any variations in the block measurements from those that are ideal would then be corrected.
04:16 This may entail, for example, machining the deck surface of the block to ensure it's exactly parallel to the main crank shaft journal centre line.
04:25 Another common process would be ensuring that the cylinder bores are all correctly spaced and aligned as well as being perpendicular to the crank shaft.
04:35 Now, this is only touching on what may be covered by a thorough engine blueprinting operation, though.
04:42 In addition, we might also need to adjust the combustion chamber CC, dynamically balance the rotating components in the engine, ensure an equal valve seat depth across all the valves, adjust valve seat pressure and valve stem length, and the list goes on.
05:01 Admittedly, the quality and production tolerances of a lot of the modern engines we see these days are far superior to what we may have seen 40 to 50 years ago, but the underlying principle of engine blueprinting is to never assume that a part or a measurement is correct.
05:21 Instead, we need to understand what is required from a specific component and ensure that its specification and clearance is correct for that application.
05:32 Instead of assuming that our engine components, either OE or after market, are supplied in a ready to fit state, we would simply treat them as little more than a raw starting point and begin the process of checking and correcting their dimensions as required.
05:52 In reality, engine blueprinting, taken to the fullest extent of its definition, where every single dimension, nut, gasket and fastener is checked and corrected is most often only applied by those building engines at the highest levels of professional motor sport.
06:11 Understandably, it's an immensely time-consuming process, and correcting dimensions is also expensive, requiring skilled machining and specialised fixtures and machinery.
06:24 The end result will be a dimensionally perfect engine that is optimised for a specific use and will typically offer improved power and reliability over a production engine, but it's definitely not for those that are financially limited.
06:41 A slightly more relaxed application of blueprinting is more often applied at the hobbyist and semi-professional motor sport level, where we'd focus our time and money on measuring and correcting the critical dimensions in the engine block and cylinder head, ensuring that our componentry is dimensionally accurate, our clearances are within specification, and that the engine components are dynamically balanced.