The Machine Shop Lowdown
A big degree wheel like this...
A big degree wheel like this Moroso piece attached to a crankshaft socket helps you degree-in the cam easily and accurately.
There are a number of things that the average enthusiast just can't do himself, not necessarily through lack of want, but because the machinery involved can cost hundreds of thousands of dollars. That is where we come in. As a machinist, I talk to customers every day who are excited about their projects, but don't often have a clue as to what is really involved in making their engine work.
When a customer brings in a disassembled engine, ideally we'd like to bake and shot blast the block and heads (assuming cast iron) to get off all the oil, paint, and goo, and get down to fresh metal. This is followed by magnafluxing or pressure testing for cracks, and if all checks out, then we can start machining.
Using a "bridge" with a dial...
Using a "bridge" with a dial indicator is the best way to figure true top dead center. Starting with the piston a few thousandths of an inch before TDC, check the degree reading on the wheel, at say "10" for example. Rotate the engine so the piston is the same depth after TDC and record the degree reading there, say at "5." Subtract the smaller number from the larger (giving us 5) and divide that in half (2.5 degrees). That is how many degrees you need to move the pointer over from "zero" toward the "larger number" side and land it on true TDC.
A quick check with the dial-bore gauge will tell us what the engine needs to be bored to. Then we can punch it out and finish-hone it with the appropriate grit stones for the rings used. The block can be decked true at this point, then washed in the hot tank. The crank would be mic'd and polished if all is good, otherwise it would be ground for undersized bearings.
Old pistons are pressed off the rods and the rods checked for size and straightness. A lot of shops claim they will shot-peen your rods to reduce stress risers, but be aware that true shot peening is done within specified parameters and with a specific type of shot. If your shop can't provide you with the specs for their shot-peen process, then they are just making your parts look nice by shot blasting them.
With the heads disassembled and the valves and guides measuring up to spec, a valve job can be done. A stock valve job with stones is good for most applications, but a multi-angle valve job done with cutters can be had for a premium. (For more on the benefits of a multi-angle valve job, check out Christopher Campbell's informative story, "Flow Job," in the October issue of PHR.) Surfacing the heads is also a good idea to give the gaskets a head start on life.
Assuming you're building something worthwhile, balancing the rotating assembly is recommended for any engine destined for engine speed above 5,000 rpm. If this is some super-secret build that you don't want the local competition knowing about, just tell the shop owner not to say anything about who's stuff he's working on. Machinists gossip amongst themselves but not a whole bunch to the rest of the world, so don't worry about your "secret" engine build being blasted around the Internet.
The basics of a complete engine build with the above work done will probably set you back anywhere from $600 to $800. The benefits are that you now know the guy who did the machine work, and if you have a question you can talk with him face to face. You get to pick what does or doesn't get done to your engine. You know the history of the engine core that you started with. And one of the more important factors in this Wal-Mart age: You actually help keep a small, old-fashioned machine shop in business. -Daryl White