Short Block

The short block is the main part of the engine (like a computer's mother board). Everything is connected to it. Engine blocks are made of cast iron or aluminium (in high performance engines). The cylinders and bearing saddles are machined with precision, to create the correct fit for the main bearings and the pistons, which increases the engines efficiency and it reduces wear. The block contains the crankshaft and pistons, in some cases it also contains the camshaft, lifters, valves and push rods depending on what type of engine it is. In the block the pistons' reciprocating motion is converted to rotational motion by the crankshaft. The block has channels and cavities like pipe lines to allow water to pass through to cool it down and for oil to be directed to engine parts that need lubrication.

Experiment


Block


I measured the cylinders in three places and then in another three places in another direction (at a right angle to the first three measurements) I did this to find out if the cylinders were worn, if they have taper or ovality. I then checked to see if the block's surface was warp by placing a straight edge on it at different places and measuring the gaps with a feeler gauge.

Pistons

I measured the piston diameters with a micrometer to check if they are worn. Then I removed the rings and cleaned the groves. When the "new" rings were fitted i checked the gap between the ring and the grove. Before I replaced the rings I check the ring end gaps by placing the ring in the cylinder and measuring the gap with a feeler gauge. If the gap is to small the rings could break when the engine heats up.

Crankshaft

 With the crankshaft out I measured the main bearing journals and the big end journals in two places and then again in two places at right angles to the first measurements. This it to check for taper or ovality. I then put the crankshaft back in its place and put one piston in. I placed a piece of plastic gauge on one of the main bearing journals and one on the big end journal and put the caps on and torqued them to the manufacturer specifications. Then took them off again and measure the plastic gauge. This was to check the gap between the journals and the bearing shells where the oil moves through. To measure the crankshaft end play I placed the DTI gauge on front of the block with the gauge on the crankshaft and move the crankshaft back and forth with a screwdriver. I then measured the big end play with a feeler gauge.


Reflection


The measurements that I did was to check the clearances and gaps in the engine. It will indicate weather or not the the parts are worn. If the parts are worn it means they need to be repaired or replaced. The clearances are also to compensate for the metal expanding when the engine heats up.