Two 7/16-20 bolts are standard for mounting a Chevy small-block 350 starter. They’re typically about 1.5–2 inches long and torqued to roughly 25–35 ft-lbs.
That size covers most factory and many aftermarket starters, but variations exist depending on the specific starter model, year, and whether an adapter or different flange is involved. Always verify with the starter manufacturer’s spec and the engine block you’re working with before reassembly.
Starter bolt size basics
Understanding the sizes helps you replace or verify hardware without delays. Below are the key details you should know.
Common configurations you’ll encounter
The two-bolt mounting is the baseline. However, some combinations differ in diameter, thread pitch, and length depending on the starter flange and bellhousing gap.
- Thread size: typically 7/16-20 UNC for most factory and many aftermarket starters.
- Alternative: some units use 3/8-16 UNC bolts; verify with your starter’s mounting flange.
- Bolt length: commonly around 1.5"–2" to accommodate the starter’s flange height.
- Torque: generally 25–35 ft-lbs, with manufacturer specs often around 30 ft-lbs.
Conclusion: while 7/16-20 is common, always measure or consult the manual for your exact starter model.
How to verify on your engine
Reliable confirmation comes from measuring the bolt holes and the starter’s mounting bolts, or consulting the service manual for your exact year and model. If you’ve swapped the starter, bring the old hardware to the parts store for an exact match.
- Remove the starter mounting bolts and inspect the diameter and thread pitch on the bolts and the block threads.
- Measure the bolt length needed by placing the bolt on the flange and checking clearance to the block and exhaust manifold.
- Match the starter to a hardware kit that lists the correct diameter, pitch, and length for your assembly.
Tip: Do not use threadlocker on starter bolts; clean threads and use a light anti-seize compound if recommended by the manufacturer.
Summary
For a Chevrolet small-block 350, the standard starter mounting bolts are typically two 7/16-20 UNC bolts, used in a two-bolt configuration with lengths around 1.5–2 inches and torque near 25–35 ft-lbs. Variations exist, so verify against your exact starter model, year, and block to ensure a proper fit.