The Chevy small block 350 is the most rebuilt engine in America. Not a close call. Over 50 years of production, fitment in everything from Corvettes to Chevettes to C10 pickups to Camaros, and an aftermarket deep enough to choke a warehouse — the SBC 350 is the engine the country learned on. Cores are cheap ($200-$600 for a running engine), machine shops know them cold, and you can buy every conceivable part at every price point.
This guide covers everything: identifying your block, choosing your build tier, what to ask the machine shop, how to assemble it correctly, and how to break it in without grenading your new cam. Whether you're refreshing a tired Chevelle daily driver or building a street-strip 383 foundation, the process is the same.
Not all 350s are equal. Before you pull it apart, identify your block — this determines what it can safely become.
Casting numbers are on the rear of the driver's side of the block, above the bellhousing flange. Common desirable castings:
| Casting | Year Range | Notes | |---------|-----------|-------| | 3970010 | 1969-1979 | The most common SBC — good 2-bolt main | | 3914678 | 1967-1969 | Early 4-bolt main, pre-smog, desirable | | 14010207 | 1976-1985 | Later two-piece rear main seal | | 10051182 | 1986-2002 | One-piece rear main seal, stronger design |
2-bolt vs. 4-bolt mains: Look at the main caps. Four-bolt main blocks have two extra bolts per cap on the center three journals. For street builds under 450 HP, 2-bolt is fine. Over 450 HP, sustained RPM, or any forced induction — you want 4-bolt, or main stud girdles.
Overbore limits: Standard SBC bore is 4.000". Most castings have enough material for .030" over (4.030"), some will take .060" over (4.060"). Rare thick-wall castings accept .080" over. Your machine shop will measure wall thickness and tell you what's safe. Never guess — a punched-out bore with thin walls cracks under detonation.
Date codes are stamped on the pad at the front of the passenger-side bank. Format is month-day-year (example: K128 = November 12, 1968). The date code must predate the vehicle's assembly date — a replacement block will have a later date.
Three realistic tiers. Pick based on what you want the car to do, not what sounds exciting in the parts catalog.
| Tier | Budget | HP Target | Best For | |------|--------|-----------|----------| | Stock Refresh | $800-$1,200 | 250-300 HP | Daily driver, reliable cruiser, original replacement | | Mild Street Build | $1,500-$2,500 | 350-400 HP | Weekend driver, light autocross, most builds | | Performance Build | $3,000-$5,000+ | 450-500+ HP | Track car, dedicated street-strip |
Stock Refresh: Standard or .030" overbore, cast pistons, stock cam, rebuilt heads (valve job, new seals, stock springs), all new gaskets and bearings. This is the engine that gets back in the Caprice station wagon and runs for another 100,000 miles.
Mild Street Build: .030" overbore, hypereutectic pistons, RV cam or mild flat-tappet (Comp 268H or similar), Vortec iron heads or reconditioned factory heads with 1.94/1.50 valves, Edelbrock Performer intake, 600-650 CFM Holley. Makes 370-400 HP with a timing curve and decent fuel. This is 90% of SBC street builds.
Performance Build: .030"-.060" over, forged pistons, aggressive hydraulic roller cam (220-230° duration @ .050", .520"+ lift), aluminum heads (Dart Iron Eagle, Edelbrock Performer RPM, AFR 190), high-rise dual-plane or single-plane intake, 750-850 CFM carb, ARP hardware throughout. This build requires matched components — a lumpy cam in stock heads and a cast crank is money wasted.
Don't drop the block off and say "rebuild it." Walk in with a list.
What to order:
- Bore and hone: Bore to the next standard oversize (typically .030" over), then finish hone to size. Ask for a torque-plate hone — the shop bolts a steel plate representing the head to the deck surface before honing, so the bores are round under real-world thermal stress. - Deck the block: Mill the head mating surfaces flat. Specification is .0005" max warpage. Most worn blocks need a light cut (.003"-.010"). Ask for the surface finish — cast iron should be 60-125 RA microinch for gasket seal. - Clean and hot tank: Chemical bath strips every casting oil passage. Mandatory on any engine that sat. Verify the shop blows out every passage with compressed air after cleaning. - Align hone: If the main bearing bores are worn or the block was decked aggressively, align honing restores the crankshaft centerline. Not always needed, but ask the shop to measure. - Magnaflux crack test: Especially on any high-mileage block or one pulled from a crashed car. A cracked block is scrap. Find out before you spend $1,200 in parts.
Expected machine shop costs for a 350:
| Service | Typical Cost | |---------|-------------| | Bore + hone (.030") | $80-$150 | | Deck block | $60-$100 | | Hot tank clean | $50-$100 | | Align hone | $80-$150 | | Magnaflux | $50-$80 | | Total | $300-$550 |
### Pistons - Cast: OEM replacement, cheapest, brittle under detonation. Fine for stock refresh at 9:1 compression or below. - Hypereutectic: Silicon-aluminum alloy, tighter tolerances, better heat resistance than cast. The right choice for mild street builds. Runs cooler than forged. - Forged: 4032 or 2618 alloy, required for boost, nitrous, or 500+ HP. Needs more piston-to-wall clearance (.004"-.006" vs .001"-.002" for cast), which means more cold-engine noise until warm.
### Cam Profiles - Stock replacement: Designed for emissions compliance and broad idle quality. About 190° duration @ .050", .390" lift. Quiet, smooth, adequate. - RV cam (Comp Cams 268H or equivalent): The mild street cam. 218°/218° duration @ .050", .447"/.447" lift. More torque than stock, still idles well, works with iron stock heads. This is the cam in 70% of SBC street builds. - Mild performance (Comp Cams 270H or similar): 224°/230° duration @ .050", .477"/.480" lift. Needs valve springs with 120+ lbs seat pressure, slightly lopey idle, pairs well with Vortec heads. Real-world 380-410 HP on a .030" 350.
### Heads - Stock 882/492 castings (1.94/1.50 valves, 76cc chambers): Fine for a stock refresh. Flow 160 CFM @ .500" lift — adequate for under 350 HP. Keep them if they're not cracked; a valve job runs $150-$200. - Vortec 906/062 heads: The best bang-for-buck iron head for street 350s. 170 CFM flow, 64cc chambers (raises compression), requires specific intake manifolds. New pairs run $200-$350 from GM. Worth every dollar over the stock castings. - Aluminum aftermarket (AFR 195, Dart Iron Eagle 200, Edelbrock E-Street): For the performance tier. 210-230 CFM flow, significantly lighter than iron, better heat dissipation. Required above 450 HP. Budget $800-$1,400/pair.
### Phase 1: Disassembly
Remove the engine from the vehicle on an engine stand. Drain oil and coolant. Strip all accessories: intake, heads, valve train, timing cover, oil pan. Label every part bag — you will forget where the rocker arm from cylinder 5 came from. Photograph everything before you remove it.
Pull pistons and rods as assemblies — stamp each connecting rod cap and rod with the cylinder number before removal. The rod cap and rod are a matched set; they must go back together in the same orientation.
### Phase 2: Cleaning and Inspection
Send the block, heads, and crank to the machine shop. While it's there:
- Inspect the crankshaft journals for scoring. Standard main journal diameter: 2.4484"-2.4493". Standard rod journal: 2.0978"-2.0988". Journals that mic undersize need grinding; common undersizes are .010" and .020". - Check connecting rods for twist and bend — machine shops can resize rod big ends for $10-$15 per rod. - Inspect the camshaft bearings in the block. If they show wear, have them pressed out and replaced ($40-$80 at the shop).
### Phase 3: Machine Work
As outlined in the machine shop checklist above. This phase takes 1-2 weeks at a busy shop. Do not rush it.
### Phase 4: Short Block Assembly — Main Bearings and Crank
Start with a surgically clean engine stand. Use engine assembly lube on every bearing surface before it sees metal.
1. Install new camshaft bearings if replaced. Lubricate with assembly lube. 2. Install main bearings — upper half in block, lower half in caps. Apply assembly lube to bearing surfaces. 3. Lower the crankshaft into the block. Set Plastigage across each journal, torque the main caps to spec, remove caps, measure crush. Clearance should be .0010"-.0025". If tight, check for debris. 4. If clearances are good, install the rear main seal. One-piece seals (post-1986 blocks) press into a retainer. Two-piece seals require careful seating in the rear main cap groove — use a seal installer tool, never a screwdriver. 5. Final torque sequence for main caps: start at 45 ft-lbs, work to final spec in sequence.
Main cap torque specs:
| Cap | Spec | |-----|------| | 2-bolt mains | 70 ft-lbs | | 4-bolt outer bolts | 65 ft-lbs | | 4-bolt inner bolts | 70 ft-lbs | | ARP main studs | 85 ft-lbs (with ARP Ultra-Torque) |
### Phase 5: Piston and Rod Assembly
Install new piston rings. Check ring end gap in the bore before assembly — insert each ring 1" down in the bore and measure.
Ring end gap specs (SBC 350, 4.030" bore):
| Ring | Minimum Gap | Maximum Gap | |------|-------------|-------------| | Top ring | .012" | .020" | | Second ring | .010" | .018" | | Oil ring rails | .015" | .055" |
Insufficient gap = ring butts on expansion = seized engine. This is the most common mistake in a home rebuild. Measure every ring.
Stagger ring gaps at 120° intervals. Lube the cylinder walls and piston skirts with clean engine oil. Use a ring compressor to install each piston-rod assembly. Verify rod bearing clearance with Plastigage as you did with the mains (.0010"-.0025"). Torque rod bolts to spec.
Rod bolt torque:
| Hardware | Spec | |----------|------| | Stock rod bolts | 45 ft-lbs | | ARP rod bolts | 45 ft-lbs (2-piece; check ARP instructions) |
### Phase 6: Oil Pump and Timing
Install the oil pump with a new pump-to-screen tube. Never reuse the old screen — it costs $15. The oil pump drive shaft goes in before the pump; verify it seats in the distributor drive tang.
Install the timing chain and gears. Use a new double-roller timing set for any performance build — the factory single-row chain stretches. Align the timing marks (crank keyway at 12 o'clock, cam sprocket mark at 6 o'clock for TDC compression on cylinder 1). Degree the cam if you're running an aftermarket grind.
Install the timing cover with a new front main seal. Do not reuse the old seal.
### Phase 7: Head Installation
Clean the deck surfaces. Verify head gasket compatibility — Vortec heads require specific gaskets with the correct coolant passage locations (Fel-Pro 1094-1 or equivalent). Torque head bolts in sequence, from center outward.
Head bolt torque (stock head bolts, cast iron heads):
| Pass | Torque | |------|--------| | First pass | 25 ft-lbs | | Second pass | 45 ft-lbs | | Final pass | 65 ft-lbs |
ARP head bolts: Follow ARP spec sheet — typically 65-70 ft-lbs with ARP Ultra-Torque lubricant. Do not substitute 30-weight oil; it changes the clamp load calculation.
### Phase 8: Valve Train
Set lifter preload on hydraulic flat-tappet cams: tighten each rocker arm nut until zero lash (lifter just moves), then add 3/4 turn. For hydraulic rollers, follow manufacturer's spec (typically 1/2 to 1 turn after zero lash). Verify pushrod length — deck cuts and head milling change the geometry; a pushrod length checker tool costs $20 and prevents a destroyed cam.
### Phase 9: Intake Manifold and Accessories
Install the intake manifold with new gaskets. The Fel-Pro 1205 is the standard for street 350s; it accommodates both conventional and Vortec head configurations.
Intake manifold bolt torque:
| Pass | Torque | |------|--------| | Initial | 10 ft-lbs | | Final | 25-30 ft-lbs |
Install the carburetor, distributor, valve covers, thermostat housing, and water pump. Torque exhaust manifold bolts to 20-25 ft-lbs, working from center outward.
### Phase 10: Pre-Oiling
Before first start, prime the lubrication system. Remove the distributor. Using an electric drill and an oil pump primer tool (a modified distributor shaft), spin the oil pump until oil pressure registers on the gauge — typically 30-45 seconds. Rotate the crank every 15 seconds to distribute oil to all rod journals.
This step is not optional on a flat-tappet cam. A dry startup with no oil pressure is an immediate cam wipe.
| Fastener | Torque | |----------|--------| | Main cap bolts (2-bolt) | 70 ft-lbs | | Main cap bolts (4-bolt outer) | 65 ft-lbs | | Rod bolts (stock) | 45 ft-lbs | | Head bolts (stock) | 65 ft-lbs | | Head bolts (ARP) | 65-70 ft-lbs | | Intake manifold bolts | 25-30 ft-lbs | | Exhaust manifold bolts | 20-25 ft-lbs | | Rocker arm studs | 50 ft-lbs | | Oil pump bolt | 65 ft-lbs | | Harmonic balancer bolt | 60 ft-lbs |
Wrong ring gap. The #1 failure in home rebuilds. Rings that butt against each other on a hot engine seize instantly. Check every ring in every bore.
Skipping pre-oiling. Flat-tappet cams are not self-lubricating. The first 20 minutes are when the cam lobes and lifters establish wear patterns — no oil means the cam is dead in one revolution.
Wrong cam break-in procedure. A flat-tappet cam needs 2,500 RPM for 20 consecutive minutes on fresh assembly lube. Below 2,000 RPM, the lobes don't circulate oil properly. Don't let it idle. Don't stop the engine. Watch the temp gauge, but keep that RPM up.
Reusing TTY bolts. Torque-to-yield bolts are single-use by design. They stretch permanently during the torque sequence and cannot maintain clamp load on reuse. Any time you see a head bolt or rod bolt spec listed as "torque + angle," replace it. The bolts are not expensive; the engine rebuild is.
Wrong firing order. SBC 350 firing order is 1-8-4-3-6-5-7-2 (standard). It is NOT the 1-2-3-4-5-6-7-8 sequence from your buddy's 4-cylinder. Distributors are installed 180° off on more rebuilt engines than anyone admits. Verify TDC on #1, verify rotor points at #1 terminal, verify wire order going clockwise.
Forgetting rear main seal direction. The lip seal goes toward the oil (toward the engine). Installed backward, it pumps oil out the back of the block. It will look like a crankshaft seal failure. It is not.
First 20 minutes: Keep the engine at 2,500-3,000 RPM continuously. Vary the RPM slightly every 30 seconds — don't hold a steady speed. This seats the rings and breaks in the cam lobes. Change the oil and filter immediately after this period. You will see metallic particles on the drain plug — this is normal.
First 500 miles: Vary throttle and RPM constantly. No steady-state highway cruising. No wide-open throttle runs. Let the engine cool completely between sessions.
First oil change: 500 miles or 30 days. Drain break-in oil (use a conventional non-friction-modified oil — no synthetics, no high-moly additives that interfere with cam break-in). Install a fresh filter.
After break-in: The engine is now ready for normal operation. Verify valve lash (hydraulic lifters should still be at spec), check for any leaks, and re-torque the intake manifold when cold.
[Sealed Power / Enginetech Complete Rebuild Kit](https://www.amazon.com/s?k=sealed+power+350+chevy+rebuild+kit&tag=rusttoroad-20) — $300-$500. Includes pistons, rings, bearings, gaskets, and seals. The correct starting point for a stock refresh or mild street build.
[Comp Cams Xtreme Energy 268H Cam Kit](https://www.amazon.com/s?k=comp+cams+268+hydraulic+flat+tappet+kit+sbc&tag=rusttoroad-20) — $150-$250. The RV/mild street cam. Includes cam, lifters, springs, and retainers. Works with stock or Vortec heads.
[Fel-Pro PermaTorque Head Gasket Set](https://www.amazon.com/s?k=fel-pro+1094+head+gasket+set+chevy+350&tag=rusttoroad-20) — $60-$100. The standard for SBC sealing. Order the correct version for your head casting (conventional vs. Vortec).
[ARP 134-3610 Head Bolt Kit](https://www.amazon.com/s?k=arp+134-3610+head+bolt+kit+sbc+350&tag=rusttoroad-20) — $80-$120. Required for any performance build. ARP makes consistent clamp load possible with proper torque values.
[Melling M55HV High-Volume Oil Pump](https://www.amazon.com/s?k=melling+m55hv+oil+pump+sbc+350&tag=rusttoroad-20) — $30-$50. High-volume pump ensures adequate oil pressure with worn clearances or a performance cam. Install with a new screen and pickup tube.
[Plastigage Green (PG-1)](https://www.amazon.com/s?k=plastigage+bearing+clearance+green&tag=rusttoroad-20) — $8-$12. For measuring bearing clearance. Non-negotiable step. A pack covers an entire engine rebuild.
[Permatex Engine Assembly Lube](https://www.amazon.com/s?k=permatex+engine+assembly+lube+sbc&tag=rusttoroad-20) — $10-$15. Applied to every bearing surface during assembly. Prevents dry startup damage on the first revolution.
[Hein-Werner / OTC Engine Stand (2,000 lb capacity)](https://www.amazon.com/s?k=engine+stand+2000+lb+capacity&tag=rusttoroad-20) — $60-$100. Get a 2,000 lb stand minimum. The SBC weighs 575 lbs bare — a 750 lb capacity stand is a liability when you're torquing heads.
[CDI Torque Wrench (1/2" Drive, 25-250 ft-lbs)](https://www.amazon.com/s?k=torque+wrench+1%2F2+drive+25+250+ft+lbs&tag=rusttoroad-20) — $30-$50. Every fastener on this engine has a torque spec. Guessing with a breaker bar is how you strip threads or warp heads.
[Joe Gibbs Driven BR Break-In Engine Oil](https://www.amazon.com/s?k=joe+gibbs+driven+break-in+engine+oil&tag=rusttoroad-20) — $40-$60 (case). High zinc content (ZDDP) is essential for flat-tappet cam break-in. Modern oils have insufficient zinc for the cam-lobe loading on a fresh flat tappet. Do not skip this.
- [Chevy Nova Engine Swap](/guide/nova-engine-swap) — Dropping a fresh SBC 350 into the best swap platform in classic American cars - [1968 Chevelle Carburetor Tuning](/guide/chevelle-carburetor-tuning) — Getting the right carb on top of your rebuilt small block - [C10 LS Swap Guide](/guide/c10-ls-swap) — When the SBC build is behind you and you're ready for the modern V8
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