The machine shop should automatically clean and inspect the block and tell you what it nee
If you've been into cars for a while, you've probably swung a few engines over the fender that were assembled by someone else. That's cool, but it's probably about time to build one yourself. Overall, it's really not that complicated, but there are a few things to watch out for if you want to get it right. Even something as simple as pulling a block from a yard has tricks. You've got to know the math before you start to order parts, and it's also important to communicate with the machine shop if you want to get what you paid for.
We gave you the theory on complete engine blueprinting in the Sept. '05, issue so we decided to put that stuff to the test on a real engine. There are a couple of differences between a standard rebuild and a performance engine, so we are going to include the research techniques and tools available to get exactly what you want. You should be able to read right through this series of stories and get the job done.
We are eventually going to use the engine we build as a test mule for heads and cams, so it's going to need to last a long time and take plenty of beatings. That also means the engine should take anything we can throw at it once it's in a car. The goal here is an engine that anyone can assemble and that makes good power for money well spent.
Just Pull the Thing
It's still better to pull an engine from a car than to buy one anywhere else. The simple reason is cost. Every part that's included with a complete engine is a part you don't have to buy, and cars that have been wrecked were running and driving right before they ended up in the yard. During our search, we stumbled across two identical, smashed '74 Chevy Caprices and scored two complete 400-cid engines. We figured that was a sign.
Dry Magnaflux is still the way machine shops look for cracks. A large U-shaped magnet is p
So how do you know if the block is good? We always bring a crank socket and barring tool, a compression gauge, and a dial indicator when we are checking out an engine. Most yards will have a stack of batteries up front for some cranking power. Crank the engine five or six times and take the highest reading with the compression gauge. The cylinders should be within 10 percent of one another. Chances are the heads aren't great castings, so we pop them off and check the cylinder bore for wear and taper. The math for displacement is: displacement = pi / 4 x bore2 x stroke x number of cylinders. From there you can solve for bore (bore = displacement / (pi / 4 x stroke x number of cylinders). In our case it was 4.125 inches. We were lucky that both engines had stock or close-to-stock bores. The machine shop will measure final cylinder runout with an inside micrometer, but in the yard, it's OK to just run your finger down to the top of the piston and feel for a ridge. If there is a slight ridge and a stock bore, there is room to work.
The biggest buzz kills at the machine shop are cracks in the block, especially on 400s with steam holes and siamesed (thin) cylinder walls. Little cracks are worth the gamble, but the big ones are death and are evident by a trail of rust down the center of the bore or between the head bolt and the cylinder wall. Rust means water entered the bore somehow. Look for cracks in the lifter valley as well.
We tossed the heads and trundled one of the engines down to JMS Racing to be cleaned and inspected. The machine shop is going to tell you if the block needs to be overbored and whether the crankshaft can be saved. Seems obvious, but this is going to predict the parts you'll need to get the correct compression ratio, piston bore, and deck height. We try to order the bearings, rings, and gaskets from the machine shop and pick them up when the machine work is done. Saves a lot of time.
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