Shortblock Assembly:
Above I went through everything to look for during tear down or parts selection. Now we can put it all together.
Again, I can not stress how important it is for ALL the parts to be spotless and clean. Not only clean to your sight, but clean enough when you wipe them with a cleaner on a white rag, the rag stays clean. If you are not sure, clean it again!!
First off, I'll tell you what I use for assembly oil. And nearly every builder has their own mix they use or off the shelf brand they prefer. It's really hard to say anyone does it wrong if it works for them and I'm not here to tell you the way I do it is the ONLY way, just what works for me. I use 16 ounce squeeze bottles (like a restaurant squeeze ketchup or sauce bottle). I get the bottles from my local restaurant supply house, they are cheap. I put 2 ounces of STP Oil Additive in the bottle then fill the rest with Wal-Mart Supertech 5w-30 cheap petroleum oil and shake vigorously for several seconds to make sure it is all shaken up. The reason I use this mix is, the STP additive is loaded with zinc (zddp) which prevents scuffing of the piston, rings, and bore which the Animal is prone to during assembly. My theory on assembly lube is you can NOT use enough. I typically use 4 to 8 ounces of assembly lube putting the motor together. Sure, you have to drain a little out when you are done, but I know it's in there and I know it's got it where it needs it.
If it is not already in the block, first install the flywheel side oil seal. Take care and pay close attention to not hit the seal surface (rubber part) during installation. Install the seal just past flush with the outside of the block. In the block you will see a small chamfer; just past this chamfer is what you are looking for. If you don't have a seal driver of the right size, a large socket will work. Just make sure it's driven in straight.
Next the crankshaft goes in. Unless you have removed the flywheel side bearing it is pressed on the crankshaft. If you did remove it, the bearing must be installed before putting the crankshaft into the block (unless you slip-fit the crank & bearing). For whatever reason, the bearing to block fit on the flywheel side is terrible from Briggs. I believe this helped start a lot of the block cracking problems in the early Animal blocks. To try and reduce some of the slop in the fit and I'm sure induced harmonics and vibration from this fit, I put a thin coat of Loctite 620 bearing retaining and gap filling compound on the outside of the bearing surface where it mates with the block. Just be sure to not use too much so that you get some dripping into the bearing, you don't want that. On the crankshaft end that slips through the seal, put a good coat of oil on it and put a good coat of oil into the bearing. The oil on the crank will ensure as you slip the crank into the seal it does not damage it and there is no dry start on the seal when you fire the motor up.
No you have the block sitting there with the crankshaft installed.
Next we assemble the rod, piston pin, and rings. The easiest way to make sure you get it together right is to lay the piston on it's side so that you are looking at the bottom of the piston and the arrow on the piston is pointing to your right side. Next put the piston pin lying right behind it (it can go in either direction, it is not directional sensitive). Next lay the rod below the piston pin so that the Mag Side is to your right. If the rod cap is on, take it off. Use your assembly lube and coat the piston pin bores, the piston pin, and the piston pin bore in the rod. Take the piston pin and slide it into one side of the piston, push the rod up into the piston to where it lines up with the piston pin, and slip the pin through the rod into the other side of the piston. Install your piston pin(s). A set of needle nose pliers works great for installing the clip(s). Grab the clip by the straight portion of the clip, put the end of the rounded section into the clip bore and roll the clip into the hole. Just personal preference, but I like to install the clip where the straight portion is in the vertical position when done.
The rings go on next. I install all the rings and expander over the top of the piston down into the grooves. I also use just my hands to install the rings, but I have also been doing this a long time and have a knack for it. If you have not installed rings before, a ring expander might make the job a little easier, but you must also pay close attention to not OVER stretch the rings as you can add additional drag into the ring or worse yet, break the rings as they are very brittle. I slip the expander over first and put the gap in the expander to the PTO side of the engine (away from the arrow). Next I slide the oil ring over. The second ring gets installed so the o dot on the ring is up and the inside chamfer is DOWN. The top ring gets installed so the o dot on the ring is up and the inside chamfer is UP. Make sure you get these installed correctly. As for ring gap placement, I put the ring expander to the PTO side, the oil ring to the flywheel side more toward the pushrod side of the bore, the middle ring pointed directly to the clutch/PTO side of the engine, and the top ring pointing toward the flywheel favoring the top of the bore (just make sure the top and bottom ring do not overlap and have approximately between the gap ends. Roughly each gap will be on opposite sides of the piston pin bore.
To install the rod & piston into the bore you will need some type of ring compressor. I have seen everything used from fingers, to hose clamps, to professional compressors. Again, I'm not here to tell you there is a wrong way to do it, but you want to ensure however you get the piston in the bore that you do NOT scuff or scratch the piston, rings, or the bore. I like the stainless steel tapered compressor from Goodson. Make sure the crankshaft is turned DOWN before installing the piston so you don't gouge the crankshaft main journal when pushing the piston in the hole. Prior to pushing the piston in the hole, give the cylinder bore, the piston skirt, and rod and crankshaft main journals a good heavy coat of oil. Make sure you do NOT get oil into the rod bolt holes.
You now have the rod installed into the bore and should be right at the top of the bore. Take the crankshaft and rotate it around slowly counter-clockwise until the crankshaft main journal comes up to the rod bore. Make sure the rod is turned right so that the crankshaft slips right into the rod bore. You can now push the piston down into the bore about ways down the bore. This will bring the crank and rod into position so you can install the rod cap. First, put a good dose of oil on the rod cap making sure to keep oil out of the rod bolt holes. The rod cap will snap into place and should hold it's self. The rod cap dipper should be pointed toward the cam/lifter portion of the block. Grab the rod bolts and put 3-4 drops of BLUE Loctite on the end of the threads (some people use Red, but I have not seen the need). Install the rod bolts to 115inch/lbs of torque with your torque wrench. I torque my bolts at 55, 85, and 115in/lbs.
Take your lifters and coat them good on the stems and face and place them in the lifter bores. I always engrave an X on the top of my exhaust lifter so if they fall out when tearing the engine down, I know which the exhaust is and which the intake is. Put a good dose of oil in the blocks camshaft bore, coat the camshaft lobes down with oil good and install the camshaft into the block. When you install the camshaft, make sure the o dot on the camshaft and crankshaft gears mate/line up. Being even 1 tooth off can throw the cam profile well out of alignment.
You are now ready to put the side cover gasket on the block, slip it over the dowels to hold it. The crankshaft shims go between the crankshaft gear and the bearing in the side cover. I like about .010 -015 crankshaft endplay. Some guys like more, some less, but that is what works for me. You will have to slip the Sidecover on with the gasket and tighten down a few bolts to check your end play. Most of the time, you will end up with the one thick spacer and possibly a single thin spacer. Just have to check it to make sure.