How to Build a Small Block Chevy for Low End Torque

Building a Small Block Chevy engine for optimal low-end torque can transform a mild mannered vehicle into a stump pulling monster. With the right combination of parts, you can get massive amounts of torque just off idle, giving you incredible pulling power and acceleration.

In this comprehensive guide, we’ll cover everything you need to know to build a high torque, street-friendly Small Block Chevy from top to bottom.

Chapter 1: Block Selection and Prep

The foundation of every engine build is the block. For our high torque Small Block, we want something strong and durable that can handle the stress of producing massive torque.

Block Options

  • Factory Cast Iron Blocks: The old school way to go. Cast iron blocks from the 60s/70s era 350 blocks are affordable and plentiful. They are strong, but can be prone to cracking between the cylinders at very high torque levels.
  • Aftermarket Cast Iron Blocks: Companies like Dart offer cast iron blocks with upgraded features for high performance builds. The added material makes them extremely rigid and durable for high torque applications.
  • Aluminum Blocks: Save weight, but sacrifice some durability and rigidity versus cast iron. The reduced friction can add a slight power increase. Popular aluminum blocks come from Dart, World Products and Brodix.

For most high torque street builds, a factory 350 4-bolt main block or affordable aftermarket cast iron block like Dart SHP will work excellently.

Block Prep

To prep a block for our torque-focused build:

  • Bore to Desired Size: Bore the block to achieve the desired cubic inch displacement. 383-400 CID is ideal for maximum street torque.
  • Deck Block: Deck the engine block to ensure a straight and true mounting surface for the cylinder heads.
  • Line Hone: Line honing aligns the main bearing bores and ensures proper oil flow to the main and rod bearings.
  • Lifter Bore Bushings: Upgraded bronze or ductile iron bushings prevent wear and ensure proper lifter rotation.
  • Cam Tunnel Alignment: A precision cam tunnel alignment fixture positions the cam bore in the exact center of the lifter bores for smooth, precise operation.

With the block prepped, it’s ready for the rotating assembly and other components.

Chapter 2: Rotating Assembly Selection

The rotating assembly consists of the crankshaft, connecting rods, pistons, and piston rings. Optimizing these parts works together to generate massive torque.

Crankshaft

For our high torque build, a cast iron crank provides great rigidity and damping for smooth power delivery. Some top options:

  • Stock Cast Crank: Affordable cast cranks can handle over 500 ft-lbs torque. Inspect carefully for any cracks.
  • Aftermarket Cast Crank: Upgraded iron cranks from Scat, Eagle, and Lunati feature heavier counterweights for smoothness.
  • Stroker Cranks: Increasing the stroke adds cubic inches for more torque. Common strokes are 3.75” and 4.00”.

Connecting Rods

  • Stock I-Beam Rods: Can handle up to ~500 ft-lbs torque. Upgrade if going beyond that.
  • H-Beam Rods: Stronger than stock I-beams. Come in affordable steel and lighter aluminum.
  • Billet Rods: The ultimate in strength for high horsepower applications. Overkill for most street builds.

For street use, a set of 6” length H-beam rods from Scat, Eagle, or Lunati are recommended. They offer a great balance of durability and value.

Pistons

  • Forged Flat Top: Most affordable option. Great for budget builds making under 600 ft-lbs torque.
  • Forged Dome: More expensive, but stronger. The dome shape optimizes combustion chamber efficiency.
  • Forged Dish: Great for maximizing compression on stroker builds. Produces huge torque when paired with cylinder heads optimized for dish pistons.

For our high torque build, a set of forged dish pistons from Ross, JE, or Wiseco will work well. They allow us to run optimal compression with the cubic inch increase from a stroker kit.

Piston Rings

Upgrade to moly rings or gapless rings to handle higher cylinder pressures from our torque-focused build.

With the rotating assembly selected, we’re ready to move on to the valvetrain and cylinder heads.

Chapter 3: Cylinder Heads and Valvetrain

The cylinder heads and valvetrain play a huge role in generating low RPM torque. Careful component selection here can really optimize the engine’s torque band.

Cylinder Heads

For small block Chevys, the 23° factory heads work great for maximizing low end torque. Look for heads with:

  • Big Intake Ports: 185-200cc+ intake runners optimize airflow and torque.
  • Smaller Exhaust Ports: 65-75cc exhaust ports enhance low end power.
  • Rectangular Port Shape: Improves low lift flow for great torque.
  • Large Valves: 2.02-2.05” intake valves and 1.60” exhaust valves provide ample flow.

Some top 23° head choices are:

  • Vortec Iron Heads: Great bang for the buck. Affordable cast iron heads that flow very well.
  • Edelbrock E-Street: Aluminum heads with great low lift flow numbers and rectangular ports.
  • Trick Flow 23°: One of the best flowing 23° heads. Great for making big power while retaining low end grunt.

Valvetrain Components

To get the most from our cylinder heads:

  • Roller Rockers: Reduce friction for more power. Look for 1.5-1.6 ratio rockers.
  • Roller Camshaft: Reduces friction and allows more aggressive lobe profiles. Aim for 230-240° duration, .050” lift around .280” intake and .290” exhaust.
  • Valve Springs: Need to match the camshaft and handle higher RPMs. Look for dual springs rated up to .600 lift.
  • Pushrods: Go with 7.4” length pushrods for most Small Block builds. Hardened pushrods can handle higher valve spring pressures.

Choosing the right heads and valvetrain gives us an optimized torque-producing top end. Now let’s look at some other supporting mods and final assembly.

Chapter 4: Additional Modifications and Final Assembly

To complete our high torque Small Block Chevy, we need to make some additional modifications and finalize the assembly.

Additional Modifications

  • Port Matching: Blend and match the intake ports to the intake manifold to optimize airflow.
  • CC Chambers: Check and adjust the combustion chamber size to get the desired compression ratio.
  • Deck Clearancing: Clearance the piston to deck surface to achieve ideal quench and combustion efficiency.
  • Cam Degreeing: Degree the camshaft to ensure optimal valve timing and lift at low RPM.
  • Balancing: Balance the rotating assembly to prevent excess vibration at high torque levels.

Final Assembly

For final assembly:

  • Piston Rings: File fit, gap and install the rings per the manufacturer instructions. Stagger the end gaps.
  • Bearings: Install the cam and main bearings and check clearances.
  • Pistons: Install pistons with proper orientation, making sure to lubricate well.
  • Oil Pump: Prime the oil pump and install with the correct distributor gear for the cam.
  • Timing Set: Install the camshaft and timing set using the proper procedure.
  • Lifters and Pushrods: Install lifters and pre-lube. Install pushrods and set preload.
  • Heads: Install heads using multi-layer steel (MLS) head gaskets for max sealing.
  • Valvetrain: Install rockers, valves and retainers. Set lash to spec.
  • Oil Pan: Install oil pan and pickup tube with windage tray.
  • Valley Pan: Install valley pan and other accessories.

With careful attention to detail during assembly, our high torque Small Block will be ready to fire up!

Chapter 5: Supporting Mods and Tuning

To fully realize the potential of our torque-focused engine, supporting mods and proper tuning are essential.

Supporting Modifications

  • Intake Manifold: Single or dual plane manifolds optimized for low-mid RPM flow.
  • Carb/Throttle Body: Sized appropriately for displacement and desired power band.
  • Headers: Properly sized headers optimized for scavenging at lower RPM.
  • Ignition: Performance distributor and coil matched to the camshaft and RPM range.
  • Oiling: High volume oil pump, pan and pickup to maintain oil pressure at higher RPMs.

Tuning and Break-In

  • EFI Tuning: For EFI engines, optimized fuel and spark maps to maximize torque production.
  • Carb Tuning: Adjust jetting and air bleeds to sync carburetion with the cam profile.
  • Timing: Set initial timing at 12-14° and bring in 2° increments till optimal.
  • Break-in: Following proper break-in procedure ensures long engine life. Limit RPMs and load initially.

With the right supporting mods and tuning, our torque-focused Small Block will really come alive and produce mountains of low end grunt.

Sample Combinations and Results

Here are some sample combinations and the incredible torque results that can be achieved:

383 SBC with Vortec Heads and Cam Package

  • 383ci SBC 4-bolt Block
  • Scat 3.75” Stroker Kit
  • Vortec Iron Cylinder Heads
  • Comp Cam XE274H Camshaft
  • Peak Torque: 515 ft-lbs @ 4,200 RPM

406 SBC with Edelbrock E-Street Heads and Cam Package

  • 406ci SBC 4-bolt Block (0.030” overbore)
  • Scat 4.00” Stroker Kit
  • Edelbrock E-Street Alum Heads
  • Comp Cam XE288H Camshaft
  • Peak Torque: 550 ft-lbs @ 4,100 RPM

400 SBC with TFS 23° Heads and Cam Package

  • 400ci SBC Dart SHP Block
  • Eagle 4.00” Stroker Kit
  • TFS 23° 210cc Heads
  • Comp Cam Custom Grind
  • Peak Torque: 590 ft-lbs @ 4,500 RPM

As you can see, with the right combination of parts, impressive low end torque numbers can be achieved!

Key Takeaways:

  • Start with a strong block, bore and stroke to desired cubic inches (383-406ci optimal)
  • Stroker kits with longer strokes can dramatically increase torque
  • Rectangular port heads with big intake runners flow lots of air to make torque
  • Roller cams, 1.5+ ratio rockers, and big valves enhance airflow
  • Careful assembly and tuning unlocks the full potential of the build
  • With the right parts combos, 550+ ft-lbs torque is achievable!

Conclusion

Building a high torque, street-friendly Small Block Chevy is an exciting endeavor. With this guide, you have all the information needed to put together an incredible torque monster in your garage. From selecting the optimal block and rotating assembly to topping it with the right cylinder heads and valvetrain components, we’ve covered it all. Applying the modifications and techniques detailed here will allow you to easily achieve 500+ ft-lbs of earth twisting low end torque! So get out there, find the right parts for your build, and get to wrenching – massive low end power awaits!

Citations: [1] https://www.motortrend.com/how-to/500-lb-ft-in-six-easy-steps/ [2] https://itstillruns.com/build-chevy-low-end-torque-7988109.html [3] http://67-72chevytrucks.com/vboard/showthread.php?t=729903 [4] https://www.chevelles.com/threads/best-small-block-combo-for-low-end-torque.1161970/ [5] https://youtube.com/watch?v=zC-so_zC_zs [6] https://www.jalopyjournal.com/forum/threads/building-a-torque-motor.1002928/

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