Before the rebuilding process can begin, you need something to rebuild. This might simply be the engine that came in your car, though if it experienced some sort of catastrophic failure, all its critical parts and pieces should be checked by a competent machine shop before you proceed (more on that later). Damage isn't always detectable with the naked eye, so these determinations should ultimately be made by the machine shop.
If you find any faulty core parts, what to do about them depends on the extent of the damage and the rarity of your engine. Many major maladies can be repaired-for a price. Damaged cylinder bores can be sleeved, casting cracks can be welded or drilled and pinned, stripped threads can be re-tapped or repaired with inserts, main saddles can be resized, cam bores can be sleeved, and so on. The important point here is that although each of these conditions can be cured, the cost of repair might outweigh that of replacement, depending on the type of engine in question.
If a new core is needed, you'll once again need to arm yourself with knowledge. Interchangeability is obviously crucial, but not always apparent. Know what fits and what doesn't, and how to identify the good stuff on the fly (i.e., at the junkyard or swap meet). Also, familiarize yourself with your particular engine's critical dimensions and consider investing in a basic measuring caliper that can determine the diameters of cylinder bores and crank journals. Knowing what oversize pistons and bearings are available for your engine and how far the block can safely be overbored will be very helpful. A Chevy 400 small-block that's already 0.030-over might be worthless, as 0.060-over is generally considered too far, but if you know that 0.040-over slugs are available, you could save it. It's best to know this before investing.
Our core is a '90 Chevy 350 block and crank from a pickup truck. The engine was a low-mileage unit that displayed very little wear in the cylinder bores and bearings. We were about to reassemble it with the original dished pistons and stock rods when we came across a set of barely used GM Performance Parts ZZ4 pistons and rods that had been swapped for aftermarket pieces after a few dyno runs. The ZZ4 pistons are hypereutectic cast-aluminum flattops with a short skirt, nearly identical to mid-'90s LT1 production slugs, as are the powdered metal connecting rods. We figured we could get away with our block's standard bore, allowing us to use these virtually new standard-size pistons.
Picking a Machine Shop
Many rodders seem to place more emphasis on engine assembly than the machining process, though the opposite should probably be true. The process of bolting an engine together-provided you use the proper specs and techniques-is fairly straightforward; it's the machining stage that can make or break a rebuild. Deal with a shop that's on the ball and your role in this stage of the project will be nearly a no-brainer. However, handing your parts off to a hack could create enduring nightmares.
All machine shops are not created equal, though the true measure of any such establishment lies with the skill and experience of those operating the equipment rather than the machines themselves. For your first project, deal with someone who will understand your situation and goals for the final product, particularly if it involves nonstandard equipment (read: speed parts). A lot of "production" shops are geared mainly toward refurbishing engines to get them back in service. Often, places like this won't understand the deviations that are frequently required for performance-engine building, nor are they very tolerant of such things. High-volume re-man shops have also been known to operate under the "good enough" standard, so your money is probably better spent elsewhere. The shop you select should also communicate with you thoroughly, from the time you drop off your parts and discuss the job until the time you pick them up again. Again, the shop should understand what you want, explain what you need, alert you to any trouble areas that may arise, and detail any particulars you'll need to pay attention to during assembly.
Your best bet is to approach a shop known locally for high-performance street and racing engines. Most areas have at least one machine shop that deals with regional circle track or drag racers, and this is typically where you'll find the most knowledge and willingness to deviate from stock. If you're intimidated by approaching experienced race-engine builders for your first project, keep in mind that most of these shops still have to rebuild truck engines and the like to keep the workflow steady and the cash drawer full-your project is not beneath them. Be honest about the objectives of your engine (don't pretend to be chasing down Warren Johnson the following weekend) and don't be afraid to ask questions, though you should attempt to make them as informed as possible; again, preparation is the key.
We've worked with a number of machine shops over the years, but one of our recent regulars is Dougan's Engine & Machine in Riverside, California. We've established a good working relationship with co-owner Ray Field, and we trust his recommendations on machining procedures. Dougan's rebuilds plenty of standard-duty engines, but has also become known among local racers for quality work. We figure if its rebuilds can endure the rigors of circle track racing, it's good enough for our junk.