Take a close look at the crankshaft. Its journals should be smooth, without anydiscernable grooves. If this is the case, you should have the machineshop measure the journals for roundness. If they are smooth and not outof round by more than one-half of one-thousandth of an inch, you shouldbe OK. Remember we are building a low-compression, low-rpm engine, not aNextel Cup engine. But again, if you want insurance against failure,then have the crank ground and polished.
Now turn your attention to the cylinder heads. Again, consult your rule book to determine which onesare legal. You might also ask some local racers. The heads you chooseshould be cleaned and checked for cracks at the machine shop. Mostlikely your heads will need a valve job. If the rules and yourpocketbook allow, over-sized valves are nice but not absolutelynecessary. The head-mating surface should be inspected and checked witha good straight edge to see that it is flat. It's always a good idea tomill the surface to get more compression. Also, the machine shop caninstall the valves and springs if you don't have the tools at home.
ASSEMBLY Now you have all the parts in your shop. The next step is toclean all the parts again, even if they were cleaned before. With theblock bolted to an engine stand, turn it upside down so that the mainbearings are up. With the main caps laid to one side, clean the bearingbores with a brand of brake cleaner that does not burn. I use papertowels for cleaning during assembly. Be careful not to leave paperfibers scattered in the engine. Once the bearing bores in the block areclean, install the bearings. For years the standard race bearing hasbeen the Clevite 77 bearing used here. If your set has a groove in onehalf, it should be installed in the block. Do not touch the bearingsurface with anything, including your fingers. Handle the bearing at theedges. To be sure you have the right bearings for the crank and rods,buy a package of Plastigage. It comes with instructions. Plastigage willbe fine for checking. Having a good set of inside and outsidemicrometers handy would be better. What you want to do is verify thebearing clearance. Once the bearings are installed, apply a small amountof assembly lube of your choice. I like Lubriplate white lithium greasein a tube.
The rear seal may need to be installed before the crank,depending on the engine. Now, carefully lower the crank into place. Donot rotate the crank until all the main caps are in place and torqueddown. You must lubricate the main cap bolt threads and under the headwith oil before installation. Get a spec book and follow the torquerecommendations closely. When torquing an assembly, always work inseveral steps and from the center out.
Piston/rod installation requires a bit of work. Turn the block so that one cylinder bank is parallel withthe floor. First it is always wise to check the ring gap. I used PerfectCircle rings that were not file fit, which means they didn't need to befiled to the correct clearance, and the gaps proved to be right. Followthe manufacturer's directions for ring placement.
Remove the rod cap and clean the rod and cap bores with brake cleaner. Install the bearing inboth and lube lightly. Then turn the crank so that one journal is atbottom dead center. Now, from your local hardware store, get a piece ofclear vinyl tubing 36 inches in length that fits snug over the rodbolts. Double up the tubing and place it around the crank journal,sliding it out of the cylinder bore. Each end must slide onto a rodbolt. The tubing prevents the rod bolt from nicking the crank as thepiston is installed.
The head mating surface should be inspected and checked with a good straight edge for flat
The endplay of the crankshaft is checked--a step that is oftenoverlooked.
This is a rod being resized on the big end. It is passed over anexpanding hone to achieve