Engine Rebuilding: The PreparationPlanning and machining
Rebuilding the engine in your restoration project is a big commitment of time, energy and money. It can also be one of the most satisfying parts of the restoration process. Nothing beats knowing that the engine has been put together right and will be dependable for another 100,000 miles.
Once you've made the decision to rebuild there are a number of options. 1.) You can take the car to a shop and have them R&R the engine and rebuild it. The downside is that most shops will not take the same care and attention to detail that you would while removing and installing the engine. 2.) You can save a little money by removing the engine and taking it to a shop to be rebuilt. This is probably the second choice of all the options. 3.) If the engine I.D. number is not important to you (as in a numbers-matching car), you can simply exchange the engine for a rebuilt engine. While most rebuilt engines come with a warranty, many rebuilders take shortcuts such as knurling valve guides instead of replacing them to cut costs. Also, it's virtually impossible to specify specifications from major rebuilders such as camshaft and compression ratio that will produce a "correct" engine for the resto. 4.) If you're restoring a musclecar (and I.D. numbers are not important to you) there are a number of "visually correct" crate motors that are a real bargain. 5.) The best solution is to rebuild the original engine yourself and have a numbers-matching restoration-that has been rebuilt to original or higher standards.
Rebuilding an engine is not rocket science, it does however, require attention to detail and the discipline to stop and get expert advice when you are uncertain if you are doing something correctly. One of the most important steps of engine rebuilding is a thorough "forensic" engine disassembly. First, take photos from every angle of the assembled engine. The engine will be apart for a few weeks; and, upon reassembly, it is very difficult to figure out where all of the accessory brackets, etc belong. Some internal parts such as main bearing caps and connecting rods need to be stamped with a number if they are not already identified. Next, bag all bolts in sealed clear plastic bags and label each bag. Finally, inspect all wear surfaces such as bearings, crankshaft bearing journals, cylinder walls, piston skirts and connecting rod cheeks for scoring, heat discoloration or any unusual wear characteristics. If you don't know what to look for, don't worry because the technicians at the machine shop will also be checking for the same problems with sophisticated measuring instruments and crack-detecting machines.
So far your engine rebuild has required only common hand tools, an engine hoist and a little sweat. The next step is to locate a competent engine machine shop. Check with local car clubs and find out whom their members recommend. Good shops have great word-of-mouth reputations. Take the cylinder block, crankshaft, rods and pistons and cylinder heads to the machine shop. They will measure all critical dimensions with precise measuring instruments such as dial-bore gauges and micrometers and check for cracks by Magnefluxing. This information will determine if your engine just needs "rings, bearings and a valve job" or a more intensive rebuild that includes overboring the cylinders for new pistons and turning down the crankshaft. Typically, an engine with less than 75,000 miles that has been properly serviced can get by with rings, bearings and a valve job. An engine with more miles, or one that has been abused or neglected will probably need the "works."
There are several ways to purchase the parts needed for the rebuild. Most engine machine shops can order the parts for you, or you can probably save some money by purchasing an engine rebuild "kit" through mail order. If this is your first rebuild, it's probably better to have the machine shop order what is needed. Another task best left to the engine machine shop is the cylinder head rebuild and assembly. This part of the operation requires special tools and plenty of experience to do the job right. You want your involvement limited to bolting the finished cylinder heads onto the engine block.
The real fun begins (really!) when you get the freshly machined engine components and new parts back to your garage. What you will need to put the engine together are provisions to clean everything (fresh cleaning solvent and a brush plus compressed air to blow everything dry is recommended). Some special tools such as a torque wrench and piston ring compressor can be rented or borrowed. A list of tightening (torque) specifications and some inexpensive Plastigauge (available from auto parts stores) to measure bearing clearances are also necessary. Now it's time to crank up your favorite radio station and savor bolting your prized engine together.
In the next edition we'll install the crankshaft into the block!