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Practical Engine Building: Step 3: Engine Machining

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Step 3: Engine Machining

05.59

00:00 - Now that we have the engine stripped and inspected it's time to have the machine work completed in preparation for reassembly.
00:07 Before heading to the machine shop however, we want to take some time to check on the clearances and tolerances with the components that we're going to be fitting to the engine.
00:17 What I mean by this is we want to check aspects such as the oil clearances for the main bearings and big end bearings, as well as aspects such as the side clearances for the big end of the connecting rods.
00:29 What we need to do here will depend on what we're doing with the engine and for example if you're just performing a basic freshen up with a stock engine, it's unlikely there'll be any need to adjust any of these clearances.
00:42 If on the other hand you're using aftermarket conrods and crankshafts, or you're building an engine designed for much more power or higher RPM than stock, then it's important to know what you have to deal with here as you may need your machinist to make adjustments to these components, and we'll discuss how this can be done shortly.
01:03 As discussed earlier in this course, we're not expecting that the engine machining is a task that you're going to complete yourself, and it will require selecting a competent machinist who's able to work to exacting standards.
01:16 It would also be helpful if the machinist is knowledgeable with the sort of engines you're dealing with, as well as the sort of applications you're going to be using them for.
01:26 While a workshop full of brand new, high quality CNC machinery might give you confidence that the machine shop know what they're doing, it's really the skill of the machinist that's often more important than how modern their equipment is.
01:41 In the engine machining world we're dealing with very expensive precision equipment, and if it's well looked after and maintained, it can produce excellent results for decades, so it's unfair to disregard a machine shop entirely just because their equipment isn't brand new.
01:59 When looking for an engine machinist, it's important to develop a relationship with the machinist.
02:06 This can take time but if you're just starting out, it's always a good idea to introduce yourself, and explain that you're just getting started assembling your own engines.
02:16 Trying to prove to the machinist how much you know at this point is not a smart way of developing the relationship, and you're far better to be open and honest and explain the you're still learning and would appreciate their guidance.
02:29 When there are a number of local machine shops to choose from it can be hard to decide where to lay your trust.
02:36 My advice here would be to get in touch with your local car clubs and find out who the members are using for their engine machine work.
02:44 This will give you the benefit of some of their first hand results and experiences that will help you make a more informed decision and potentially avoid expensive mistakes.
02:54 Sadly even after doing your research you may still find that you're not happy with the results you're receiving.
03:01 Many machine shops spend their days working on low end passenger car engines that don't require the care, attention to detail, and accuracy that we would demand for a high performance engine build.
03:13 If you're not happy with the machinist you've chosen, don't be afraid to fire them and continue your search.
03:20 I personally went through three machine shops local to me before finding one that was able to work to my own standards.
03:28 When it comes time to deliver the engine components to the machinist, it's important to make sure that you have a clear list of all of the required work, as well as ensuring all of the components they require are supplied.
03:42 It's easy to overlook something minor such as a cam drive sprocket or a harmonic dampner that will be required when it comes to the balancing work on the crankshaft.
03:53 The required engine machine work that you'll need completed will depend on exactly what you're doing and how extensive the modifications to the engine will be.
04:02 We've covered the common machining tasks in some detail already in the Engine Building Fundamentals course, but in brief the tasks you may need completed would likely include boring and honing the block, decking the engine block and cylinder head, crack testing your internal components, as well as checking them for size, and ensuring they're straight, balancing the rotating assembly, and perhaps cutting new valve seats in the cylinder head.
04:31 Of course there are a variety of other tasks that may be required depending on the specifics of your engine and this is where a conversation with your machinist can be helpful, where you can draw on their extensive experience.
04:44 When it comes to aspects such as the piston to bore clearance or any clearance in the engine for that matter, it's very important to give clear instructions to the machinist covering what you require.
04:56 I normally provide this in the form of an email, so that we can both reference back to this at a later date if required.
05:04 The more information you can provide to the machinist, the more likely they'll be able to complete the task to your exact requirements.
05:12 If you have any specific requirements for bearing clearances that will stray from the manufacturer's specifications, it's also worth discussing this with your machinist at this time.
05:24 There are a variety of options when it comes to altering clearances including using different grades of factory bearing shell, or specially manufactured bearing shells with the purpose of adjusting oil clearances.
05:36 On other cases though, we may require the crankshaft to be polished or ground, depending on the amount of adjustment necessary.