Proper built hot rods & speed parts
Custom hot rods, resto-mods and performance builds on any make and model, foreign or domestic. Twenty-five years of turning wrenches behind every build.
Specialty services
If it has wheels, we can modify it. Full builds or one piece of the puzzle, on any make and model. Bring us the car and the idea.
Hot rod builds
From a bare frame to a finished car. Chassis, drivetrain, suspension and the details that make it yours.
Fuel injection conversions
Carb to EFI on any engine. Fuel system, sensors, harness and a base tune that starts and idles right.
Wiring & electrical
Clean, labeled, serviceable harnesses. Swap wiring, gauges, lighting and full rewires.
Sheet metal work
Custom sheet metal shaped and fit by hand. Bead-rolled panels, dimple-die work, mini tubs, firewalls, floors, interior panels and one-off pieces.
Welding & fabrication
MIG and TIG. Brackets, mounts, chassis work and one-off parts.
Custom exhaust
TIG-welded stainless steel tubing, custom hangers and mounts, V-band clamps, mufflers and headers built to fit your car.
Performance upgrades
Power adders, intake, exhaust, tuning, gears, shifters, brakes and suspension, matched to how you drive.
Advanced diagnostics
Electrical gremlins, drivability issues and problems other shops couldn't find.
Why the Atlas 4200
We work on everything, but the shop is named for one engine. Ask us about putting GM's Atlas inline-six in your build.
GM's Atlas 4200 came out of the TrailBlazer, Envoy and Bravada: an all-aluminum, dual-overhead-cam straight six with variable cam timing and a long stroke that makes torque low and keeps making it.
It's narrow enough to fit where a V8 gets crowded, smooth the way only an inline-six is, and the bottom end takes boost well. Built right, it's a different kind of hot rod. That's what Atlas Speed Co. is named for.
We plan the swap, fabricate the mounts, wire the harness and tune it, so the engine runs like it belonged in the car from day one.
| Layout | Inline-6, DOHC, 24 valve |
|---|---|
| Displacement | 4.2 L · 4,157 cc |
| Bore × stroke | 93 × 102 mm |
| Block / head | Aluminum / aluminum |
| Cam timing | Variable, exhaust cam |
| Output | 270–291 hp · 275–277 lb-ft |
| Firing order | 1-5-3-6-2-4 |
| Production | 2002–2009 model years |
From idea to shakedown
Every build follows the same path, so you always know where your car is.
Talk it through
What you want the car to do, how you'll drive it, and the budget you're working with.
Plan & quote
A written build plan with parts, labor and a timeline before any wrench turns.
Build
Teardown, fab and assembly, with progress photos along the way.
Wire & tune
Harness, first fire, and a tune dialed in for your setup.
Shakedown
Road miles to sort the small stuff before the keys come back to you.
behind the wrench
Atlas Speed Co. opened in 2026 in St. Louis after twenty-five years of building and wiring cars. We modify any make and model, and we still have a soft spot for the Atlas inline-six the shop is named after.
It's a small shop by design. Your car gets worked on by the person you talked to, and you get straight answers about cost and time.
Start a build
Tell us about the car and what you have in mind. We'll get back to you to set up a time to talk.
- Location
- St. Louis, MO
- Hours
- Mon–Fri · 8 am – 5 pm
By appointment only - Phone
- (314) 472-2640
- @atlasspeedco