Automotive Borescopes — Engine & Vehicle Inspection Cameras | Ralcam

Which Automotive Borescope Fits Your Access Point?

Start with the hole you have to get through. Modern gasoline spark plug wells take a 3.9 mm or 5.5 mm probe; most general engine work runs on 6.2 mm; diesel bores and larger service ports take 8.5 mm. Cable lengths run from 1 m for bench-side checks to 3 m for reaching across a heavy block, in flexible, semi-rigid, and rigid configurations. Semi-rigid is the default for engine work: it holds the bend you give it, so the tip stays pointed at the cylinder wall instead of sagging into the bore.

Auto Borescope Models at a Glance

Steering: 2-way or 4-way

2-way articulating models bend the tip in one plane — enough to clear a bend and angle onto a cylinder wall, and the right call for most day-to-day diagnostics. 4-way models add left and right for a full 360° sweep, which is what you want when you have to look back along a valve face or work a combustion chamber methodically.

Display: built-in screen or your phone

Screen models from 3.5" to 5" power on and work standalone — no app, no pairing, and your phone stays out of the engine bay. Phone-connected probes plug into an iPhone or Android by cable for a lighter, lower-cost kit.

How to Inspect a Cylinder Through the Spark Plug Hole

1. Let the engine cool completely, then disconnect the coil and remove the spark plug.
2. Turn the engine by hand until the piston you are checking sits near the bottom of its stroke — that exposes the most cylinder wall.
3. Pre-bend a semi-rigid cable slightly, feed it in, and articulate the tip toward the wall. Rotate the probe body to sweep all the way around.
4. Look at the piston crown, then tip up to see the valves and the combustion chamber roof.
5. Record each cylinder so you can compare them side by side afterwards.

The full step-by-step, with what to look for at each stage, is in how to inspect engine cylinders with a borescope.

What an Automotive Endoscope Shows You

Vertical scoring on the cylinder wall from a failed ring or debris. Heavy carbon buildup on pistons and intake valves, common on direct-injection engines. A piston crown that is unusually clean compared with its neighbors — often a sign that coolant is getting in. Cracks, burnt valve edges, and damage from a dropped object. How to read borescope images walks through what each of these looks like on screen.

Borescope for Mechanics: What a Shop Actually Needs

A mechanic camera earns its place on the cart when it cuts diagnosis time and backs up the quote. For shop use, look for a built-in screen so your phone stays out of the engine bay, a semi-rigid 6.2 mm probe for spark plug work, a probe lock or 4-way joystick to hold the shot steady, and TF card recording so every inspection ends up as evidence on the job file. Pair it with a 3 m cable option if you see trucks and diesel work. The N505 and H406B cover everyday bay work; the F606B and M6X add full 4-way steering for valves and combustion chambers.

Working on diesel or heavy-duty?

Deeper bores and longer reaches have their own sizing rules — see truck and diesel engine borescopes.

Every probe in this range is IP67 rated against oil, coolant, and fuel, with adjustable LED illumination for dark engine bays. Always inspect a cooled engine.