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CADAM-master/benchmarks/13-v8-engine.md
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# 13 — V8 engine
> **Prompt**
>
> A complete V8 internal combustion engine: two banks of four cylinders in a 90° V, cylinder heads with ribbed valve covers, an intake manifold in the valley, exhaust headers down each bank, a crankshaft with counterweights, pistons and connecting rods, a front pulley, and an oil pan.
Fully parametric OpenSCAD built from the prompt above — adjustable dimensions and colours, exported as `.SCAD` and rendered to the orbiting preview with [`render.sh`](render.sh).
<p align="center"><img src="13-v8-engine.gif" alt="V8 engine — orbiting render" width="380"></p>
**Parametric controls:** 22 dimensions · 8 colours
**What it demonstrates**
- A complete V8: 90° cylinder banks, heads, ribbed valve covers, intake manifold, exhaust headers, and oil pan
- Even the internal rotating assembly — crankshaft with counterweights, pistons, and connecting rods — modelled inside the block
- 22 parametric controls across 8 part colours; ~460 lines of OpenSCAD — the most complex benchmark here
**Editable parameters**
| Parameter | Default | Range / options | Description |
| --- | --- | --- | --- |
| `crank_angle` | `45` | `[0:1:360]` | Rotate the crankshaft to see the pistons move |
<details>
<summary>OpenSCAD source — <code>13-v8-engine.scad</code></summary>
```scad
// V8 Engine Model
/* [Visibility] */
// Enable cutaway view to see internal mechanics
cutaway = true;
/* [Animation] */
// Rotate the crankshaft to see the pistons move
crank_angle = 45; // [0:1:360]
/* [Colors] */
block_color = "Silver";
head_color = "DarkGray";
valve_cover_color = "FireBrick";
intake_color = "DimGray";
exhaust_color = "Peru";
pulley_color = "Black";
oil_pan_color = "DarkSlateGray";
internals_color = "LightSteelBlue";
/* [Hidden] */
$fn = 32;
bore = 10;
stroke = 15;
crank_r = stroke / 2;
conrod_len = 35;
cyl_spacing = 28;
deck_height = 50;
bank_angle = 45;
pin_angles = [0, 90, 270, 180];
main_y = [0, 28, 56, 84, 112];
pin_y_start = [8, 36, 64, 92];
// Core kinematics calculation for piston position
function get_D(crank_ang, bank_ang) =
let(Px = crank_r * sin(crank_ang),
Pz = crank_r * cos(crank_ang),
K = Px * sin(bank_ang) + Pz * cos(bank_ang))
K + sqrt(K*K - crank_r*crank_r + conrod_len*conrod_len);
module assemble_engine() {
engine_stand();
engine_block();
heads();
valve_covers();
spark_plugs();
oil_pan();
intake_manifold();
exhaust_headers();
front_accessories();
alternator();
belt();
front_pulley();
fan();
flywheel();
internals(crank_angle);
}
module cutaway_cutter() {
if(cutaway) {
intersection() {
// Diagonal cut plane along cylinder axis
translate([0, 50, 0])
rotate([0, bank_angle, 0])
translate([0.1, 0, -50])
cube([80, 100, 150]);
// Limit strictly to right half to preserve left side
translate([0, 50, -50]) cube([100, 100, 150]);
}
}
}
module engine_block() {
color(block_color)
difference() {
union() {
// Main block body
translate([-25, 0, -10]) cube([50, 120, 20]);
// Banks
intersect_bank(bank_angle);
intersect_bank(-bank_angle);
// Side reinforcement ribs
for(y = main_y) {
translate([-26, y-2, -10]) cube([52, 4, 15]);
}
// Rear bell housing flange
translate([-26, -4, -10]) cube([52, 4, 30]);
}
// Hollow out valley
translate([-10, -1, 20]) cube([20, 122, 40]);
// Hollow out crankcase
translate([0, -1, 0]) rotate([-90,0,0]) cylinder(r=18, h=122);
translate([-18, -1, -20]) cube([36, 122, 20]);
// Cylinder bores
for(i=[0:3]) {
y_s = pin_y_start[i];
// Right bank
translate([0, y_s + 7.5, 0])
rotate([0, bank_angle, 0])
translate([0, 0, 10]) cylinder(r=bore, h=deck_height+10);
// Left bank
translate([0, y_s + 12.5, 0])
rotate([0, -bank_angle, 0])
translate([0, 0, 10]) cylinder(r=bore, h=deck_height+10);
}
cutaway_cutter();
}
}
module intersect_bank(ang) {
rotate([0, ang, 0])
translate([-14, 0, -20]) cube([28, 120, deck_height + 20]);
}
module heads() {
color(head_color)
difference() {
union() {
head_shape(bank_angle);
head_shape(-bank_angle);
}
cutaway_cutter();
}
}
module head_shape(ang) {
rotate([0, ang, 0])
translate([-14, 0, deck_height])
difference() {
cube([28, 120, 18]);
// Spark plug recesses
for(i=[0:3]) {
y_s = pin_y_start[i] + 10;
translate([14, y_s, 9]) rotate([0, 90, 0]) cylinder(r=4, h=10, center=true);
}
}
}
module spark_plugs() {
color("White")
for(i=[0:3]) {
y_s = pin_y_start[i] + 10;
// Right
rotate([0, bank_angle, 0]) translate([14, y_s, deck_height + 9]) rotate([0, 90, 0]) cylinder(r=2, h=8);
// Left
rotate([0, -bank_angle, 0]) translate([-14, y_s, deck_height + 9]) rotate([0, -90, 0]) cylinder(r=2, h=8);
}
}
module valve_covers() {
color(valve_cover_color)
difference() {
union() {
valve_cover_shape(bank_angle);
valve_cover_shape(-bank_angle);
}
cutaway_cutter();
}
}
module valve_cover_shape(ang) {
rotate([0, ang, 0])
translate([-12, 0, deck_height + 18]) {
// Base
hull() {
cube([24, 120, 2]);
translate([2, 2, 8]) cube([20, 116, 2]);
}
// Ribs
for(y=[5 : 10 : 115]) {
translate([4, y, 10]) cube([16, 4, 2]);
}
// Oil cap
if(ang > 0) {
translate([12, 20, 10]) cylinder(r=5, h=4);
}
}
}
module oil_pan() {
color(oil_pan_color)
difference() {
union() {
hull() {
translate([-25, 0, -10]) cube([50, 120, 1]);
translate([-15, 10, -30]) cube([30, 100, 1]);
}
for(y=[15:5:105]) {
translate([-15, y, -32]) cube([30, 2, 4]);
}
}
// Hollow inside
hull() {
translate([-23, 2, -10]) cube([46, 116, 1]);
translate([-13, 12, -28]) cube([26, 96, 1]);
}
cutaway_cutter();
}
}
module intake_manifold() {
color(intake_color)
difference() {
union() {
// Central plenum
translate([-10, 10, 35]) cube([20, 100, 15]);
// Runners to Right head
for(i=[0:3]) {
y_s = pin_y_start[i] + 10;
hull() {
translate([10, y_s-4, 40]) cube([2, 8, 8]);
rotate([0, bank_angle, 0]) translate([-14, y_s-4, deck_height-2]) cube([5, 8, 12]);
}
}
// Runners to Left head
for(i=[0:3]) {
y_s = pin_y_start[i] + 10;
hull() {
translate([-12, y_s-4, 40]) cube([2, 8, 8]);
rotate([0, -bank_angle, 0]) translate([9, y_s-4, deck_height-2]) cube([5, 8, 12]);
}
}
// Throttle body
translate([0, 110, 42.5]) rotate([-90,0,0]) cylinder(r=8, h=15);
}
cutaway_cutter();
}
}
module exhaust_headers() {
color(exhaust_color)
difference() {
union() {
// Right bank
for(i=[0:3]) {
y_s = pin_y_start[i] + 10;
header_pipe(bank_angle, 1, y_s);
}
// Right Collector
translate([50, 10, -25]) rotate([-90,0,0]) cylinder(r=6, h=100);
// Left bank
for(i=[0:3]) {
y_s = pin_y_start[i] + 10;
header_pipe(-bank_angle, -1, y_s);
}
// Left Collector
translate([-50, 10, -25]) rotate([-90,0,0]) cylinder(r=6, h=100);
}
cutaway_cutter();
}
}
module header_pipe(ang, dir, y) {
gx = dir * (14*cos(45) + (deck_height+7.5)*sin(45));
gz = (deck_height+7.5)*cos(45) - 14*sin(45);
hull() {
translate([gx, y, gz]) rotate([0, 90, 0]) cylinder(r=4, h=2, center=true);
translate([gx + dir*5, y, gz - 5]) sphere(r=4);
}
hull() {
translate([gx + dir*5, y, gz - 5]) sphere(r=4);
translate([dir*50, y, -25]) sphere(r=5);
}
}
module front_accessories() {
color(block_color)
difference() {
union() {
// Timing cover
hull() {
translate([-25, 120, -10]) cube([50, 4, 20]);
translate([-15, 120, 40]) cube([30, 4, 10]);
}
// Water pump
translate([0, 124, 30]) rotate([-90,0,0]) cylinder(r=12, h=8);
// Water pump pulley
color(pulley_color) translate([0, 132, 30]) rotate([-90,0,0]) {
cylinder(r=10, h=8);
translate([0,0,8]) cylinder(r=8, h=2);
}
}
cutaway_cutter();
}
}
module alternator() {
color("LightGray")
difference() {
union() {
translate([20, 125, 40]) rotate([-90,0,0]) cylinder(r=8, h=10);
color(pulley_color) translate([20, 135, 40]) rotate([-90,0,0]) cylinder(r=6, h=5);
}
cutaway_cutter();
}
}
module belt() {
color("#222222")
difference() {
hull() {
translate([0, 134, 30]) rotate([-90,0,0]) cylinder(r=10, h=4);
translate([0, 134, 0]) rotate([-90,0,0]) cylinder(r=16, h=4);
translate([20, 135, 40]) rotate([-90,0,0]) cylinder(r=6, h=4);
}
hull() {
translate([0, 133, 30]) rotate([-90,0,0]) cylinder(r=8, h=6);
translate([0, 133, 0]) rotate([-90,0,0]) cylinder(r=14, h=6);
translate([20, 134, 40]) rotate([-90,0,0]) cylinder(r=4, h=6);
}
cutaway_cutter();
}
}
module fan() {
color("Silver")
difference() {
union() {
translate([0, 142, 30]) rotate([-90,0,0]) cylinder(r=5, h=2);
for(a=[0:72:359]) {
rotate([0, a, 0])
translate([5, 142.5, 30])
rotate([20, 0, 0])
cube([25, 2, 8]);
}
}
cutaway_cutter();
}
}
module front_pulley() {
color(pulley_color)
difference() {
translate([0, 124, 0]) rotate([-90,0,0]) {
cylinder(r=12, h=8);
translate([0,0,8]) cylinder(r=16, h=8);
}
cutaway_cutter();
}
}
module flywheel() {
color(pulley_color)
translate([0, -5, 0]) rotate([-90,0,0]) cylinder(r=25, h=5);
}
module engine_stand() {
color("Orange")
union() {
// Floor base
translate([-40, -40, -60]) cube([80, 160, 5]);
// Upright
translate([-15, -30, -55]) cube([30, 15, 75]);
// Stand head
translate([-10, -15, -10]) cube([20, 10, 20]);
// Standoff mounts to bell housing
for(x=[-15, 15]) {
for(z=[-5, 15]) {
translate([x, -15, z]) rotate([-90,0,0]) cylinder(r=2, h=15);
}
}
}
}
module internals(crank_angle_offset=0) {
color(internals_color) {
// Main journals
for(y = main_y) {
translate([0, y, 0]) {
translate([0, 4, 0]) rotate([-90,0,0]) cylinder(r=5, h=8, center=true);
}
}
for(i = [0:3]) {
ang = crank_angle_offset + pin_angles[i];
y_s = pin_y_start[i];
// Web 1
web(ang, y_s);
// Crank Pin
translate([0, y_s + 5, 0])
rotate([0, ang, 0])
translate([0, 0, crank_r])
translate([0, 5, 0]) rotate([-90,0,0]) cylinder(r=4, h=10, center=true);
// Web 2
web(ang, y_s + 15);
// Piston 1 (Right Bank)
piston_and_rod(ang, bank_angle, y_s + 7.5);
// Piston 2 (Left Bank)
piston_and_rod(ang, -bank_angle, y_s + 12.5);
}
}
}
module web(angle, y_pos) {
translate([0, y_pos, 0])
rotate([0, angle, 0]) {
hull() {
translate([0, 2.5, 0]) rotate([-90,0,0]) cylinder(r=6, h=5, center=true);
translate([0, 2.5, crank_r]) rotate([-90,0,0]) cylinder(r=6, h=5, center=true);
}
// Counterweight
translate([0, 2.5, -crank_r/2 + 1])
cube([16, 5, crank_r + 10], center=true);
}
}
module piston_and_rod(crank_ang, bank_ang, y_pos) {
D = get_D(crank_ang, bank_ang);
Px = crank_r * sin(crank_ang);
Pz = crank_r * cos(crank_ang);
Wx = D * sin(bank_ang);
Wz = D * cos(bank_ang);
rod_ang = atan2(Wx - Px, Wz - Pz);
translate([0, y_pos, 0]) {
// Conrod
translate([Px, 0, Pz])
rotate([0, rod_ang, 0])
translate([0, -2.5, 0]) {
hull() {
rotate([-90,0,0]) cylinder(r=4, h=5);
translate([0, 0, conrod_len]) rotate([-90,0,0]) cylinder(r=3, h=5);
}
}
// Piston pin
translate([Wx, 0, Wz])
rotate([0, bank_ang, 0])
rotate([-90,0,0]) cylinder(r=2.5, h=10, center=true);
// Piston body
translate([Wx, 0, Wz])
rotate([0, bank_ang, 0]) {
translate([0, 0, -6]) rotate([-90,0,0]) cylinder(r=bore-0.5, h=12, center=true);
translate([0, 0, 6]) rotate([-90,0,0]) cylinder(r=bore-0.5, h=4, center=true);
}
}
}
assemble_engine();
```
</details>