Small Block Chevy 350 Build Pt.2 | Chasing the Head Bolts
This episode focuses on 'chasing' the head bolt holes on a Small Block Chevy 350 to ensure clean, undamaged threads before final head installation. The job covers cleaning the bolt holes, using a thread chaser/tap to restore threads, cleaning debris, and installing new head fasteners and head gaskets in preparation for torqueing the heads to spec.
Build Sequence
1. Vehicle and engine prep / verify heads removed
Ensure the cylinder heads have been removed and the block is accessible. Disconnect any remaining components and protect open oil galleries and coolant passages.
2. Initial cleaning and inspection of bolt holes
Spray penetrating solvent into each head-bolt hole, allow dwell time, then use compressed air and a brush to clear loose dirt, corrosion, and gasket material. Inspect holes for cracked or severely damaged threads.
3. Chase threads with thread chaser or tap
Using a correct-size thread chaser or bottoming tap, carefully chase each bolt hole to restore thread runout. Turn the chaser slowly, back it out frequently to clear chips, and keep the tool perpendicular to the hole to avoid cross-threading.
4. Thorough cleaning after chasing
Blow out all bolt holes with compressed air, wipe surrounding areas, and vacuum up chips. Re-spray solvent and repeat cleaning until no metal debris remains. Protect oil/coolant passages during this step.
5. Prepare fasteners and head surfaces
Confirm you have the correct replacement head bolts or studs and a new head gasket. Apply assembly lube or specified lubricant to bolt threads and under bolt heads as directed by the fastener manufacturer.
6. Set head gaskets and install heads / torque bolts to spec
Place the head gaskets, set the heads, and start fasteners by hand. Tighten in the proper sequence and increments called out by the engine service manual or fastener instructions (use torque wrench and/or angle gauge as required).
7. Final checks and cleanup
Double-check torque on all fasteners, ensure no debris remains in passages, and reattach any removed ancillaries. Refill fluids if removed and run a careful initial break-in or leak check after reassembly.
Frequently Asked Questions
Can I use a cutting tap instead of a thread chaser?
A dedicated thread chaser is preferred because it cleans and reforms threads without removing significant material; a cutting tap can remove metal and potentially damage or change thread fit in cast materials.
VIEW FULL ARTICLE →How do I know if a bolt hole is too damaged to chase?
If threads are stripped, heavily corroded, cracked, or a chaser won't restore full engagement, the hole may require helicoils/coil inserts, oversized fasteners, or professional repair. Inspect carefully before reassembly.
VIEW FULL ARTICLE →Where do I find the correct torque specs and sequence?
Consult the factory service manual for the Small Block Chevy 350 or the head-fastener manufacturer's instructions. Torque values and angle steps vary by fastener type (torque-to-yield vs. reusable studs).
VIEW FULL ARTICLE →What does 'chasing the head bolts' mean?
Chasing means running a thread chaser or appropriate tap through the head-bolt holes to clean and restore the internal threads so fasteners can properly seat and be torqued.
VIEW FULL ARTICLE →Related Builds
Small Block Chevy 350 Build Pt. 6 | This Is How It's Actually Supposed To Be Done
Small Block Chevy 350 Build Pt.3 | Filing rings and checking main clearances
Small Block Chevy 350 Build Pt.5 | Continued frustrations with rod clearances
Small Block Chevy 350 Build Pt. 11 | Installing the intake manifold and figuring out sbc nuisances
Small Block Chevy 350 Build Pt. 7 | Checking Crank Clearance and installing the rods.
Small Block Chevy 350 Build Pt. 8 | Installing Camshaft and timing componentsParts Used (5)
Used on bolt threads and head-bolt seats as recommended by fastener or engine builder.
Replace torque-to-yield head bolts (or upgrade to studs) whenever heads are removed; exact set depends on engine variant.
Full head gasket set appropriate for SBC 350; replace any time heads come off.
For wiping, solvent work, and containing metal chips after chasing threads.