Now that we have sorted out the top part of the engine, let’s turn our attention to the engine block. If you don’t have a dial gauge or other measuring tools, you can bring the block to a reputable machine shop. They can determine the condition of you block and its internal components. Now this is where the proverbial “can of worms” can happen, as well as a never-ending debate. There are some who would just check for the clearances and don’t bother the other details. Take the crankshaft for example… yes, it is standard procedure to check the clearances of the journals, how deep the scratches are… some would max out the allowable size of the journal.
But rarely do I see someone check for crankshaft alignment. Yes, it is possible for the crankshaft to be misaligned. The condition of the main bearings can give you an indication if the crank was moving.
Can a bent crank be saved? Yes, as long as the deflection is within the specs allowed by the manufacturer. And when realignment is done, it should be stress relieved. Not all machine shops are tooled for this kind of work. Then, there’s the Magnafluxing or checking for cracks. If the journals need to be grinded down, it would be a good investment to have the journal surface be treated or surface hardened. This helps prevent wear. And if possible have it dynamically balanced. By doing so, it helps extend bearing life. Added cost? Yes, but it’s added insurance.
For the common engine rebuild, using a single set of bearings would suffice. But there are those who would use three sets of bearings and use the ones that come closest to the factory specs for clearances.
Setting crankshaft end-play is very important. Even for the connecting-rod bearings. If the connecting-rods passes Magnaflux testing, it would be nice to have them tweaked a bit. Have casting marks grinded smooth to minimize cracks, end to end balanced and shot peened for stress relieving. Again, just for added insurance. For the pistons, if you could, have them matched set by weight and checked for cracks. Yes, even if they are bought brand new. If you’re using a replacement brand there’s no problem with that, as long as it’s the exact same piece as the original. Not just on the outside but underneath.
As for the block, make a visual inspection first. If it looks good, have it Magnafluxed for cracks. If it passes then have it hydro-tested. If it’s all good, then you can proceed with the required machining work. Again staying with-in factory specs. If you could ask the machine shop owner how often do they calibrate there machines and their measuring instruments… it may sound like you are questioning the abilities of the shop, but I believe it’s your right to know. Why? If the allowable error for 1.0 millimeter is about 0.3-percent give or take, that’s roughly about .003 millimeter (let me know if I am off) bigger or smaller than 1.0 millimeter… imagine if it was actually 0.4-percent then you may run into fitting problems. Worse is after putting the engine together, during the first start up something goes wrong.
The things being mentioned here are more for engine longevity… the practice of making sure it is within factory specifications, balancing moving parts and stress relieving, and properly assembling your engine is sort of like Blueprinting. Done properly, you can get good performance out of your engine.
Taking an engine apart and putting it back together is easy… making run properly is another thing.