HOW TO BUILD A HOT ROD ENGINE (BLOCK TO DYNO)

The first engine I ever watched come together belonged to my uncle, and it took him about four years. Not because the build was complicated. Because he kept getting distracted by other projects, and because the machine shop he liked was an hour away, and because parts kept showing up in the wrong sizes. By the time it fired for the first time in his garage, I was old enough to drive and he was old enough to have completely forgotten where he put the timing light.

I bring that up because the romanticized version of engine building skips most of what an engine build actually is. The cool parts, the assembly montage and the dyno pull at the end, are maybe ten percent of the work. The rest is measuring things, waiting for parts, measuring them again, and sweeping aluminum shavings off your workbench. I love it. I want to talk about how it actually goes, start to finish, using a small block Chevy 350 because that's the engine almost everyone uses to learn this stuff.

I also want to talk about how a hot rod shop simulator could turn this whole process into a game, because I keep thinking about it and I cannot stop. There's a real game in here. Someone please make it.

Picking the Block

The whole thing starts with a hunk of iron sitting on a pallet. Maybe you pulled it out of a truck in a field. Maybe you bought a brand new GM Performance crate block. Maybe a guy at the swap meet sold you one for two hundred bucks because his wife was making him clean out the garage.

The small block Chevy 350 became the default hot rod engine for a reason. GM made something like ninety million of them. They are everywhere. Parts are cheap. Knowledge is plentiful. You can walk into any speed shop in America and someone will know what you're doing. If you want a different starting point you've got the Ford 302, the Mopar 360, or if you're feeling fancy and have a lot of money, an LS swap. But for learning, for fun, for the classic experience, the 350 is the move.

The first thing you do with any used block is clean it and inspect it. You're looking for cracks, especially around the cylinder walls and the main webbing. You check the deck for warping. You measure the cylinder bores to see how much life is left in them. A standard bore on a 350 is 4.000 inches. If the previous owner already bored it out 0.030 over, you've got 4.030 cylinders and only so much meat left before you're sleeving it. If somebody bored it 0.060 over and ran it hot, you might have a paperweight.

In a hot rod shop sim, this is where the strategic decisions start. You're at the swap meet, you've got a budget, and there's a row of blocks with different histories. Do you take the cheap one that needs machining? The crate block that costs three times as much but saves you a week? The mystery block from the guy who won't make eye contact? Each choice cascades into the rest of the build. That's the kind of decision that makes a building game actually interesting.

If you want to read more about why this whole genre keeps grabbing me, I wrote about it over here in what is an engine building game.

Off to the Machine Shop

This is the part that nobody who hasn't built an engine really understands. You don't just buy parts and bolt them together. The block has to be machined to actual specifications, and unless you own a Bridgeport mill and a line bore setup, you're paying somebody else to do it.

The first operation is usually hot tanking or thermal cleaning. The block goes into a giant oven or a chemical bath that strips off thirty years of oil, paint, and baked carbon. It comes out looking like a fresh casting. Then it gets magnafluxed, which is a fancy way of finding cracks you couldn't see by eye.

Then comes boring. The cylinder walls get cut oversize on a boring bar so they're perfectly round, perfectly straight, and perfectly sized for the new pistons. After boring you usually do a torque plate hone, which is when the shop bolts a thick steel plate to the deck to simulate the stress of the cylinder heads being torqued down. This matters because cylinders distort under that pressure, and you want them round when the engine is assembled, not when it's sitting empty.

The deck gets cut next. Decking the block means milling the top surface flat and parallel to the crankshaft centerline, usually shaving off a few thousandths to clean up any warping. This affects compression ratio, so it matters. A few thousandths off the deck can bump compression by a tenth of a point, which can be the difference between pump gas and race gas.

Line honing is the last big one. The main bearing bores all need to be in a perfectly straight line. If they aren't, your crankshaft binds and your bearings wear out fast. The shop runs a long honing tool through all the main saddles at once and trues them up.

Now picture this in a sim. You drop the block off at the machine shop and there's a queue. Three other customers are ahead of you. You can pay extra to skip the line, or you can wait three in-game days and use that time to source other parts. The shop has reputation stats. The cheap shop on the other side of town gets it done fast but their tolerances are looser, and your engine will run but make less power. The expensive shop with the old guy who's been doing this since 1972 charges double but every measurement comes back perfect. That's the kind of choice that turns a sim into a game.

The Rotating Assembly

Once the block is back, you start collecting the parts that make it actually go. The rotating assembly means everything that spins inside the block. Crankshaft, connecting rods, pistons, bearings, rings, harmonic balancer, flywheel.

You can build a 350 a thousand different ways. You can leave it at 350 cubic inches, or you can stroke it out to a 383 by using a longer stroke crank from a 400. You can run cast pistons for a daily driver. Forged pistons for anything that's going to see boost or nitrous. Rods come in stock, H-beam, I-beam, with cap screws or bolts, in steel or aluminum if you really hate yourself.

This is where the parts shopping turns into a puzzle. Every component has to match every other component. The pistons have to match the bore size after machining. The rods have to be balanced against the crank. The compression ratio is determined by piston dome volume, head chamber volume, head gasket thickness, and deck height all together. Get one wrong and you've built a paperweight or a bomb.

Assembly itself is patience work. You install the main bearings dry, set the crank in, torque the main caps to spec, and check crankshaft endplay with a dial indicator. Then you measure bearing clearance with Plastigage, which is a strip of green wax that squishes out under torque. The width tells you the gap. Too tight and the bearing will weld itself to the crank. Too loose and the engine will knock and lose oil pressure.

Then pistons. Each one gets ring gaps measured and filed if needed. Each one gets installed in its specific cylinder with the dot facing forward and the rod cap torqued to the right value. Most builders use ARP fasteners, which involve stretching the bolts to a measured length rather than just torquing them. It is fussy and slow and absolutely worth it.

A sim that mechanizes this part has to do something clever. You don't want it to be a torque wrench minigame for forty minutes. But you do want the player to feel the difference between a hasty build and a careful one. Maybe a dice roll system where each rushed step adds a small chance of failure later. Maybe an oil pressure stat that drops permanently if your bearing clearances were too loose. Something that rewards the player for the boring, careful parts of the work without making them act out every step.

Heads, Cam, and Valvetrain

The bottom end is the foundation. The top end is where the power comes from. Cylinder heads matter more than almost anything else on a small block. The factory heads on most 350s are mediocre. They flow okay at low lift but choke off at higher rpm. Swap on a set of aluminum aftermarket heads, port matched and bowl blended, and you can pick up sixty horsepower without changing anything else.

The camshaft is the brain of the engine. It controls when the valves open, how far they open, and how long they stay open. A mild hydraulic cam will idle smooth and make great low end torque for a street car. A big solid roller will sound like death itself, run hot, eat lifters every season, and make six hundred horsepower at eight thousand rpm. The choice depends entirely on what you want the car to do.

You install the cam first, before the heads, because it goes in through the front of the block. Then the lifters drop in, the timing chain or gear drive sets your cam timing, and the timing cover closes everything up. After the heads are torqued down with new gaskets, you install pushrods of the correct length. Pushrod length matters because it sets the rocker arm geometry, which affects valve lift and valve seat wear. Most builders use a checking pushrod, which is adjustable, to find the right length before ordering the real ones.

Valve lash gets set last. Hydraulic lifters self adjust, so you just snug them down. Solid lifters need a feeler gauge and the patience of a saint. You set lash on each valve at a specific point in the rotation, write it down, double check it, and then come back and check it again after the engine has been run because it always changes a little.

For a sim, the cam choice is one of the most expressive decisions a player can make. It determines the personality of the entire car. A radical cam should make the engine sound mean in the game audio, idle rough on the test stand, and lose money on emissions tests. A mild cam should be reliable and forgettable. The choice should feel like it matters.

Break In

The first time an engine fires up after a build is terrifying. You've spent weeks or months on it, you've spent thousands of dollars, and now you're going to find out if it works.

Before you crank it, you prime the oil system. There's a tool that goes into the distributor hole and spins the oil pump with a drill, pushing oil through every passage so nothing is dry on first start. You crank the engine over without spark plugs first to build oil pressure. You watch the gauge. If it doesn't come up, you stop, figure out why, and fix it before going further.

Then plugs in, fuel on, ignition timing roughly set, and you turn the key. The engine fires, and immediately you have to bring it to two thousand rpm and hold it there for twenty minutes. This is the cam break in. The lifters and lobes are mating to each other for the first time, and they need oil splash and rpm to survive. If you let it idle during break in, you'll wipe a cam lobe and the whole top end has to come back apart.

After break in you change the oil and filter, because there's metal in there from the rings seating. You check for leaks. You listen for noises. You retighten the head bolts. Then you take it easy for the first few hundred miles. No full throttle. Vary the rpm. Let the rings finish seating against the cylinder walls.

In a sim, the break in is where mistakes you made earlier come home. Loose bearing clearance shows up as low oil pressure on the gauge. Bad cam break in technique destroys lobes. Forgetting to prime the oil pump kills the engine in twenty seconds. The break in scene should be tense in the same way a heist game's escape sequence is tense. Everything you did matters, all at once.

Dyno Tuning

If you want to know what you actually built, you put it on a dyno. A dyno is a machine that loads the engine while measuring torque and rpm, and from that it calculates horsepower across the rpm range. You get a graph. The graph tells the truth.

There are engine dynos, where the bare engine bolts up to the dyno on a stand, and chassis dynos, where you drive the whole car onto rollers. Engine dynos are more accurate but most enthusiasts only see chassis dynos because they're cheaper and easier to find. Either way, you make a pull, you read the numbers, and you start tuning.

Tuning means adjusting the things that affect how the engine makes power. Ignition timing, air fuel ratio, fuel curve at different rpm. With a carburetor you change jets and squirters and accelerator pump cams. With fuel injection you reflash a tune file. You make a pull, look at the data, change something, make another pull. After ten or twelve pulls you have an engine that's making everything it can make.

If you want to read more about the EFI side of this, I covered the basics in what is ECU tuning.

A good dyno session feels like the climax of the build. The engine you spent months on either makes the number you were chasing or it doesn't. If it does, you celebrate. If it doesn't, you figure out why. Maybe the cam is too small for the heads. Maybe the carb is too big. Maybe a bearing is going bad and oil pressure dropped at high rpm. The dyno graph tells you, and you go back and fix it.

Where the Game Lives

The reason I keep coming back to the idea of a hot rod shop sim is that this whole process is already a game. Every build is a series of choices that interact with every other choice. Budget pulls against time pulls against power goals pulls against reliability. The block you picked at the swap meet determines the bore size, which determines the pistons, which determines the compression ratio, which determines the cam choice, which determines the head choice, which determines whether your engine idles smooth at a stoplight or shakes the doors loose.

Most car games skip all of this and just sell you upgrade tiers. Tier one cam, tier two cam, tier three cam. Buy more horsepower. That's not building. That's shopping.

A real engine building game would let you make real choices and live with real consequences. It would simulate the machine shop as a network of relationships. It would let you build a reputation, take on customer cars, and slowly turn a one bay garage into a serious shop. It would have a dyno scene that means something. And the engine you build in week one would be the engine you put in your first project car in week ten, and it would still be running in week thirty, and you would remember it.

That's the game I want. Until somebody makes it, I'll keep watching uncles in garages, reading build threads, and writing about engines that exist only in my head. The 350 in this article is one of them. Maybe next year I'll actually build one for real.