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Engine Building Fundamentals: Engine Block Preparation

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Engine Block Preparation

05.02

00:00 - One of the first steps before we begin the assembly of our freshly machined engine components, is to prepare the engine block.
00:07 Since engine blocks are produced via our casting process, this can result in what's referred to as casting flash along the parting lines of the mould used for the casting.
00:18 Casting flash is essentially excess material that needs to be removed.
00:23 And while some of this casting flash will be removed by the OE manufacturer, often there will still be casting flash left in some areas of the block and also the cylinder head too.
00:34 Under normal operating conditions this casting flash is unlikely to cause any real concern.
00:40 However, if we're developing an engine, for a high power, high RPM application, then the stress and vibration that the engine components will be subjected to, may be enough to break loose some of this casting flash.
00:54 The results of casting flash breaking loose and making its way through the engine could very well be catastrophic engine failure.
01:02 So we need to deal with this early in the block preparation stage.
01:06 Aside from the casting flash, a raw engine block will also have a lot of sharp edges.
01:11 Where for example a machine surface such as the sump rail or decks surface, meets the raw cast finish on the outside of the block.
01:20 As part of the block preparation process we also want to smooth out these sharp edges.
01:26 This is a good practise anytime you are preparing a block as it really takes a minimal amount of time to achieve.
01:32 Removing these sharp edges can help reduce stress raises in the block.
01:37 As well as reducing the chances of you cutting yourself on the sharp edges while handling the engine block.
01:43 The process of removing the casting flash and sharp edges on the block is called deburring and it requires nothing more than a die grinder and a little time.
01:54 Using a relatively course carbide cutter on an air die grinder, we can simply remove any thin sections of casting flash around the parting lines in the engine block.
02:04 Deburring the sharp edges just requires the die grinder to be ran lightly across the edges to break down the sharp edge and leave a slight chamfer in its place.
02:16 It can be tempting once you get started to polish the entire cast surface.
02:22 However, that's really not necessary.
02:24 All we're looking to do is remove any thin sections of casting flash and any debris that could potentially break free when the engine's in operation.
02:34 It's simple enough to inspect the part you are going to be working on and you'll be able to see where the parting line is on the casting.
02:42 If you follow this parting line through the casting you will then be able to see any areas requiring attention.
02:49 An alternative to the die grinder that can be used on more accessible areas is a power file.
02:56 Which uses a thin abrasive belt.
02:59 These tend to produce a smoother finish on the surface of the part.
03:02 However, they aren't suitable in tight spaces.
03:06 Some engine builders will go to the trouble of smoothing all of the rough cast finish off on the inside of the engine block using a die grinder or power file.
03:16 The theory, is that this can promote improved oil drain back from the engine crank case into the sump.
03:22 And hence reduce windage loses that come about because of the suspended oil missed in the crank case.
03:29 I haven't ever been in a position to test this theory back to back, and it's a very time consuming process to do a good job of this.
03:37 So it's up to the individual as to whether this amount of time is justifiable.
03:42 While we have the die grinder out it's also a good idea to spend some time smoothing and deburring the oil galleries.
03:49 Removing sharp edges here and adding radiuses to any sharp directional transitions will promote improved oil flow through the galleries.
03:59 Particularly, where oil galleries are cast as opposed to being drilled.
04:03 This will result in a rough surface finish that can reduce oil flow.
04:08 While we're discussing oil flow, it's also worth spending some time deburring and smoothing the oil return galleries from the deck surface into the engine block.
04:18 Doing this will promote faster oil return into the sump and reduce the chance of oil collecting in the cylinder heads.
04:26 Lastly, I also deburr or chamfer any holes on the deck surface of the block such as the head bolt holes.
04:33 As well as the water jacket and oil galleries.
04:37 This sort of work can still be accomplished with a die grinder.
04:40 However for circular holes you can also use a handheld deburring tool, or alternatively a countersink drill bit.