Chevrolet Gen I Small-Block Rebuild, RPO codes & tuning
The classic SBC. 262, 265, 283, 302, 305, 307, 327, 350 and 400. The heart of the hot rods, the Camaro, the Corvette and thousands of pleasure boats. 48 years in production. A complete guide with workshop pricing and factory-verified torque figures.
The 350 small-block is the most rebuilt V8 in the world. Robert has seen countless SBCs over the years. A fundamentally simple design with a cam-driven distributor, hydraulic lifters, two-bolt and four-bolt mains and 4.40-inch bore spacing. A cast-iron block that handles 400+ hp on stock bearings with the right components. For the hot rodder, the American-car enthusiast and the boat owner it is the engine you can actually maintain without special tools.
On this page: complete torque figures verified against the Chevrolet Performance SP350/357 spec, factory tolerances, the RPO-code matrix, common faults and a full price list. For general service information see our V8 engine reconditioning page.
The Gen I SBC at a glance
Dimensions and data for the Gen I SBC. Values verified against the Chevrolet Performance SP350/357 factory spec and the Wikipedia RPO matrix.
Displacement by bore diameter
Every Gen I SBC shares the same 4.40-inch bore spacing. Bore and stroke determine displacement.
| Displacement | Bore | Stroke | Year | Common application |
|---|---|---|---|---|
| 262 ci (4.3L) | 3.671″ / 93.24 mm | 3.10″ / 78.74 mm | 1975-1976 | Monza, Nova, Ventura |
| 265 ci (4.3L) | 3.75″ / 95.25 mm | 3.00″ / 76.20 mm | 1955-1957 | First SBC. Corvette, Bel Air |
| 267 ci (4.4L) | 3.50″ / 88.90 mm | 3.48″ / 88.39 mm | 1979-1982 | X-body emissions-era |
| 283 ci (4.6L) | 3.875″ / 98.43 mm | 3.00″ / 76.20 mm | 1957-1967 | Fuelie-eran. Corvette |
| 302 ci (4.9L) | 4.00″ / 101.6 mm | 3.00″ / 76.20 mm | 1967-1969 | Camaro Z/28 Trans-Am |
| 305 ci (5.0L) | 3.736″ / 94.89 mm | 3.48″ / 88.39 mm | 1976-2003 | Camaro, Caprice, Trucks |
| 307 ci (5.0L) | 3.875″ / 98.43 mm | 3.25″ / 82.55 mm | 1968-1973 | Emissions-era base V8 |
| 327 ci (5.4L) | 4.00″ / 101.6 mm | 3.25″ / 82.55 mm | 1962-1968 | Corvette L-76, L-84 Fuelie |
| 350 ci (5.7L) | 4.00″ / 101.6 mm | 3.48″ / 88.39 mm | 1967-2003 | Most common. Camaro, Corvette, C10, Vortec L31 |
| 400 ci (6.6L) | 4.125″ / 104.78 mm | 3.75″ / 95.25 mm | 1970-1979 | Siamesed bores. Trucks, B-body |
350 ci RPO variants (most common)
| RPO | Year | Power | Comp. | Common application | Character |
|---|---|---|---|---|---|
| L48 | 1967-1980 | 250-300 hk | 8.5-10.25:1 | Camaro SS, Nova, Chevelle, Corvette | Original 350 |
| L46 | 1969-1970 | 350 hk | 11.0:1 | Corvette | Performance 350 |
| LT-1 Solid | 1970-1972 | 360-370 hk | 11.0:1 | Corvette, Camaro Z28 | Race-ready solid lifter |
| LM1 | 1969-1988 | 155-255 hk | 9.0:1 | Full Chevrolet line | Standard passenger 350 |
| L82 | 1973-1980 | 205-250 hk | 9.0:1 | Corvette, Camaro | Performance option |
| L83 | 1982, 1984 | 200-205 hk | 9.0:1 | Corvette | Cross-Fire TBI |
| L98 TPI | 1985-1992 | 225-250 hk | 9.5-10.0:1 | Corvette, Camaro, Firebird | Tuned-Port Injection |
| L05 | 1987-1993 | 180-210 hk | 9.0:1 | Trucks, police Caprice | TBI truck engine |
| L31 Vortec | 1996-2003 | 255-350 hk | 9.4:1 | C/K, Tahoe, Express, Escalade | Vortec, the last generation |
305 ci RPO variants
| RPO | Year | Power | Common application |
|---|---|---|---|
| LG3 | 1976-1982 | 130-160 hk | Camaro, Caprice, Impala |
| LG4 | 1978-1987 | 150-170 hk | Full Chevy / Pontiac line, 4-bbl |
| L69 H.O. | 1983-1988 | 180-190 hk | Camaro Z28 H.O., Monte Carlo SS, Trans Am |
| LB9 TPI | 1985-1992 | 205-225 hk | Camaro, Firebird F-body |
| L03 | 1987-2002 | 155-190 hk | Trucks, vans, commercial |
Torque specs
Verified against the Chevrolet Performance SP350/357 factory spec (Part 19367081) plus cross-referenced with BoxWrench, Summit Racing and GTSparkplugs. Values apply to oiled threads (engine oil) unless otherwise stated.
Cylinder head & valvetrain
Engine block & bottom end
Timing
Lubrication system
Intake & exhaust
Other
NOTE - Vortec L31 (1996-2003) intake manifold: Uses a unique 8-bolt pattern. The values 9 + 11 ft-lbs (12 + 15 Nm) in two steps are the factory spec from Chevrolet Performance SP350/357. Over-tightening cracks the lower composite manifold - a classic recurring problem.
NOTE - aftermarket racing bolts: Upgraded head studs are usually run at 80 ft-lbs with a specific anti-friction lube (not ordinary engine oil). Aftermarket rod bolts vary by kit. ALWAYS follow the bolt maker's instruction sheet - lubricant and torque spec go together. We fit upgraded fasteners as part of V8 engine reconditioning.
NOTE - Rocker arm nuts (adjustment): For hydraulic lifters: tighten down to zero lash (lift the rocker, feel it release on the pushrod), then 1/4 to 1/2 turn of preload (preload 0.015 - 0.021 inch).
Factory tolerances & workshop data
Values cross-referenced against the ChevyDIY Pre-Assembly Guide and small-block-chevy.com Assembly Specs.
Cylinders & pistons
Crank assembly & bearings
Valvetrain
Common faults on the Gen I SBC
What we see most often on 350s and 305s from the 70s, 80s and 90s.
Head gasket blows
Most common • High- Symptoms
- White smoke from the exhaust, coolant disappearing with no visible leak, "mayonnaise" under the oil filler cap, overheating under load.
- Cause
- Overheating, an old gasket, or (Vortec L31) an incorrect torque sequence on the 8-bolt intake. The L98 TPI aluminium head is especially prone due to thermal expansion.
Cam lobe wear (flat tappet cam)
Modern oil problem • High- Symptoms
- A ticking sound from the valve cover, misfire on individual cylinders, a power drop in the mid range.
- Cause
- Modern engine oil (post-2008 SN/SP) has low ZDDP content. Flat lifters on the pre-Vortec SBC wear quickly without ZDDP. Most common after a cam swap with new oil.
Cylinder wear & ovality
250 000+ km • High- Symptoms
- Rising oil consumption, blue smoke on acceleration, poor compression (below 9 bar on a healthy 350 is a problem), oil on the plugs.
- Cause
- Natural wear. Made worse by cold running and poor oil maintenance. The 305 with thin cylinder walls and the 400 with siamesed bores are extra prone to accelerated wear.
Harmonic balancer delamination
Maintenance oversight • Medium- Symptoms
- Vibration at idle and low revs, a rattling noise, "slack" in the belt. Worst case: the outer hub flies off.
- Cause
- The rubber ring between the inner and outer hub cracks after 200 000+ km. 80s models are the worst.
Vortec L31 - Intake gasket leaks (composite manifold)
L31-specific • High- Symptoms
- Boils over with no visible leak, coolant disappears. Not the head gasket - the intake gasket.
- Cause
- Thermal cycling on the L31 composite intake. The end-seal RTV boils off; heat cycling cracks the base of the plastic intake. A classic Vortec L31 weakness 1996-2003.
Rod bearing (rod knock)
Neglect • Critical- Symptoms
- Knock-knock-knock at 60 mph cruise, low oil pressure (below 20 psi hot at idle), metal shavings in the oil filter.
- Cause
- A worn oil pump, a neglected oil change, or (worst case) oil starvation. Bearings normally last 200 000+ km on a well-kept engine.
Gen I SBC rebuild pricing
Base prices for the 350 ci (4.0 inch bore, 5-bolt main). Prices exclude VAT and parts. For the 400 ci or other custom builds, contact us for a quote.
Cylinder head reconditioning (per head)
Bottom end
Complete long-block
Performance
Cylinder machining V8
| Service | Price |
|---|---|
| Cylinder boring V8 4.0″ bore | 5 880 kr |
| Cylinder boring V8 4.125″ (400) | 6 580 kr |
| Plateau honing 8 cyl | 1 850 kr |
| Torque-plate boring 8 cyl | 7 350 kr |
| O-ringing block 8 cyl | 4 400 kr |
| Deck resurfacing block V8 | 3 150 kr |
Crankshaft work (5 main + 4 rod)
| Service | Price |
|---|---|
| Crankshaft grinding V8 | 4 480 kr |
| Polishing standard | 1 022 kr |
| Wash crankshaft V8 | 1 050 kr |
| Crankshaft straightening (medium) | 1 190 kr |
| Remove/refit counterweights (8 pcs) | 2 044 kr |
Valve reconditioning (16 valves)
| Service | Price |
|---|---|
| Cutting 16 valve seats (standard) | 1 820 kr |
| Cutting 16 valve seats (large) | 2 772 kr |
| Valve guide replacement 16 pcs (cast iron) | 1 974 kr |
| Valve guide replacement 16 pcs (aluminium) | 2 548 kr |
| Manufacture of valve seat inserts 16 pcs | 3 080 kr |
Resurfacing V8
| Service | Price |
|---|---|
| Resurfacing cylinder head (per pc, standard) | 1 596 kr |
| Resurfacing cylinder head (per pc, large) | 1 974 kr |
| Block resurfacing V8 (standard) | 2 660 kr |
| Block resurfacing V8 (large) | 2 940 kr |
| Resurfacing manifold V8 | 3 250 kr |
Con rod work (8 pcs)
| Service | Price |
|---|---|
| Replace con rod bush 8 pcs | 4 480 kr |
| Replace press-fit piston 8 pcs | 3 164 kr |
| Replace piston ring 8 pcs | 2 212 kr |
| Resize big-end housing 8 pcs | 4 704 kr |
| Full con rod reconditioning 8 pcs | 6 328 kr |
| Shot peening con rods 8 pcs | 4 536 kr |
Balancing V8
| Service | Price |
|---|---|
| Balancing rotating assembly V8 | 5 950 kr |
| Weight matching con rods 8 pcs | 2 632 kr |
| Weight matching pistons 8 pcs | 2 184 kr |
| Flywheel balancing | 2 100 kr |
| Balancing flywheel + clutch | 2 842 kr |
NOTE - internal vs external balance: 1986+ 350 with a 1-piece rear main = neutral balance (internal). The pre-1986 350 has 28 oz-in external imbalance on the damper and flywheel. The 400 ci is always external (28 oz-in front + 23 oz-in rear). The damper and flywheel must match the crankshaft configuration.
Tuning the Gen I SBC
It is no accident that the 350 is the most built performance V8 in the world. From daily cruiser to 1000+ hp dragster - the architecture holds up.
- 1
Carb upgrade + dual-plane intake
Dual-plane aluminium intake + 600-650 cfm 4-bbl carburettor. Keep the stock cam for a low-mid powerband.
300-340 hk - 2
Heads + cam + open-plenum intake
Vortec L31 heads (or aftermarket aluminium heads), sport cam (270-285° @ .050), open-plenum intake, 750 cfm carb. We carry out camshaft grinding to our own profile and cylinder head porting.
400-475 hk - 3
Forged short-block + roller cam
Forged pistons, H-beam rods, racing studs, hydraulic or solid roller cam, race heads. Stock bearings max out safely at 5 500 RPM. A forged build requires cylinder boring, crankshaft grinding and dynamic balancing.
500-650 hk - 4
Stroker 383 / 406 + power adder
3.75″ stroke crank + 4.030″ bore = 383 ci. With nitrous or turbo: 700-1000 hp. Aftermarket blocks from 1000+ hp.
600-1000+ hk
Questions & answers - Gen I SBC
What does it cost to rebuild a Chevy 350?
A complete long-block is roughly 28 000 - 42 000 SEK (labour). Cylinder head reconditioning is 6 500 - 8 500 SEK per head (the SBC has two). Parts (pistons, rings, bearings, gaskets) are always extra and vary from 8 000 - 25 000 SEK depending on spec.
What torque do the head bolts take?
Three-step sequence: 25 / 45 / 65 ft-lbs (34 / 61 / 88 Nm). Verified against the Chevrolet Performance SP350/357 factory spec, BoxWrench, Summit Racing and GTSparkplugs. Oil the threads with engine oil. Use the correct tightening sequence, working from the centre outwards.
What is the difference between the L48 and the LT-1?
The L48 was the standard 350 in the Camaro SS and Corvette 1967-1980 (250-300 hp gross). The LT-1 (Gen I, 1970-1972) had high compression 11.0:1, a solid lifter cam, a hotter profile and 360-370 hp gross. The LT-1 is the "high-performance 350" from the muscle car era - not to be confused with the Gen II LT1 (1992-1997) or the Gen V LT1 (2014+).
What is the difference between a 2-bolt and 4-bolt main?
The 2-bolt has two bolts per main bearing, the 4-bolt has four. The 4-bolt is stiffer and takes higher RPM and cylinder pressure. The 4-bolt normally comes in HD applications (truck, perf 350s like the L48, LT-1). For a rebuild the 4-bolt is the safer choice if you plan to run over 5 500 RPM or boost.
Can I use Vortec L31 heads on a pre-Vortec block?
Yes, but the Vortec L31 uses a unique 8-bolt intake pattern. You need either a Vortec intake or an adapter. Compression height differs by 0.011″ from older heads - piston-to-head clearance needs to be verified. L31 heads give 30-40 hp over older 76cc cast heads thanks to better ports.
Vortec L31 intake gasket - why does it leak so often?
The composite intake (plastic base + aluminium top) cracks over time due to thermal cycling. The end-seal RTV boils off. Often diagnosed as a head gasket, but it is the intake gasket. Use an upgraded MLS lower gasket on replacement. Too much torque cracks the intake - use 9 + 11 ft-lbs in two steps per the factory spec. We replace the intake gasket + carry out cylinder head resurfacing of the sealing surfaces as a matter of routine.
How long does a rebuilt 350 last?
With correctly performed work and proper maintenance: 250 000 - 400 000 km is entirely realistic. The cast-iron block is extremely hard-wearing. A quality rebuild with the right components is effectively like getting a new engine.
Does your Gen I SBC need looking at?
Call us directly or send a quote request. Reply within 24 hours. Quote after inspection.