Views : 991,905
Genre: Autos & Vehicles
Date of upload: Apr 19, 2020 ^^
Rating : 4.894 (689/25,399 LTDR)
RYD date created : 2022-04-09T02:07:18.122256Z
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Top Comments of this video!! :3
SUMMARY:
aluminum block pros:
-much less weight
-slightly better cooling
-slightly higher compression
-much easier to fix cracks
-more fuel efficient
iron block pros:
-better bang for your buck (much cheaper)
-can generally handle more power
-slightly less prone to warping
-much easier and faster to manufacture
-much easier to rebuild/resurface
-less noise
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Very informative, as always.
As a sidenote: there is one advantage iron blocks have over aluminum blocks: seasoning. With various heat cycles, the microscopic porosity of iron blocks can help it absorb oil into the block. When building performance engines, many will go for a well-maintained high mileage iron block with as little wear as possible. Many aftermarket iron blocks even come seasoned from the supplier.
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I appreciate your channel and also this content, but let me add some points:
-thermal expansion matters! The bearing clearance in aluminum engines increases when the engine warms up, this leads to higher oil flow through the bearings, so that the oil pump must be bigger in aluminum engines (=> higher friction losses => less efficiency). Keep in mind, that the crank shaft and (for OHV engines) will not expand as much as the surrounding material. The use of iron bearing caps is one way to reduce the thermal expansion in the bearings. The larger bearing clearance also contributes to higher engine noise.
-wall thickness: in sand casting (like all gray iron cran cases) you canāt reduce the wall thickness as much as you need for strength. Below 4 mm it will become very difficult, although some serial applications succeeded with only 2.5 mm. So bigger the engine, so easier it becomes to reduce the relative wall thickness and so more use can be made of the higher strength of the cast Iron.
-GJS 450: This material is replacing the old standard GG250 (donāt know what you call it in the US) and offers much higher strength (1,8 times as much) than the old gray iron materials. For Diesel engines it is the best choise for low weights.
-cylinder distance: For a given engine length, iron crank cases enable more capacity than aluminum crank cases, simply because the wall between the cylinders can be as low as 5,5 mm in an iron crank case.
-engine overhaul: this can be very simple in classic aluminum engines with wet iron liners by simply replacing them (like.g. in old Alfa Romeos). You can replace them almost indefinitely, unfourtunally this design is no longer used in modern engines (due to increased cylinder spacing).
-Tooling: Aluminum is easier to machine an when using dye castings, very little material has to be removed, thatās why aluminum crank cases for small gasoline engines can be cheaper than gray iron crank cases.
-threads: with aluminum crank cases you can only apply bolt with low strength (up to 8.8 strength) whereas GJS 450 can handle up to 12.9. With all the threading for the head, bearing caps, auxiliaries etc. this can be a real weight disadvantage. Due to the difference in thermal expansion, the threads in aluminium engines are suffering each time, the engines changes its temperature, which can shorten engine life. To compensate that, the threads for the main bearings are often very long because the thread damage is moving slowly upwards, so that there is a āreserveā of thread length.
Aluminum can give a weight advantage for small gasoline engines, but not for bigger Diesel engines which can make better use of the high material strength of GJS 450 due to relative thin walls.
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Thank you so much for sharing all that knowledge, my friend! You're a natural born lecturer and your friendly manner of speaking adds so much charm to your videos and make them amazingly watchable - I didn't even notice how an over 20 minute clip came to an end. So exciting and dynamic! When I'm finished watching this whole playlist "Engine Bootcamp" I guess I'll be knowing more about engines than some of the workers at the local shops LOL
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