The core of a 350 stroker involves increasing the displacement of a smaller-block Chevrolet engine (typically a 305, 327, or 350) beyond its original 350 cubic inch displacement. This is achieved primarily by increasing the stroke length of the crankshaft.
Here's a breakdown of the major steps:
1. Disassembly and Component Inspection:
* Completely disassemble the engine: Remove the heads, intake manifold, oil pan, timing chain/belt, pistons, connecting rods, crankshaft, and all other components.
* Inspect all parts for wear, damage, or defects: This is critical. Reusing damaged parts can compromise the entire build. Consider replacing worn bearings, rings, and seals.
2. Selecting Components:
This is where careful planning is paramount. The choice of components dictates the final displacement and performance characteristics. Key components include:
* Crankshaft: The heart of the stroker. A longer-stroke crankshaft is the foundation, often requiring a custom-forged unit to handle the increased stress. The stroke length and rod length determine the final displacement.
* Connecting Rods: Need to be compatible with the chosen crankshaft and pistons. Forged rods are generally preferred for their strength and durability. The rod length is critical in determining the proper piston-to-wall clearance.
* Pistons: Must be custom-made or specifically chosen to work with the increased stroke length and connecting rods. These will likely require custom machining to clear the deck and maintain proper compression ratio. Consider the piston material (forged or hypereutectic) based on your performance goals.
* Cylinder Heads: May need porting and polishing for improved flow, or even upgrading to aftermarket performance heads.
* Camshaft: Needs to be selected to complement the chosen piston/rod/crank combination. The camshaft profile affects the powerband and the overall engine's performance characteristics.
* Rings and Bearings: High-quality rings and bearings are crucial for reliable performance and longevity.
3. Machining (Often Requires Professional Assistance):
* Block Machining: The engine block may need machining to accommodate the longer stroke crankshaft and pistons. This often includes:
* Deck surfacing: To ensure a perfectly flat surface.
* Clearance machining: To prevent piston-to-cylinder-wall interference.
* Line boring: To ensure accurate alignment of the main bearing bores.
* Block alignment honing: To ensure proper cylinder alignment.
* Crankshaft machining (if necessary): Balancing and possibly other machining processes to ensure smooth operation.
* Connecting Rod machining (if necessary): Balancing, machining, and possibly resizing.
4. Assembly:
This is a meticulous process requiring precise torque specifications and careful attention to detail. Errors here can lead to catastrophic engine failure. Steps include:
* Installing the bearings: Main and rod bearings must be installed correctly and torqued precisely.
* Installing the crankshaft: Precisely aligned and secured.
* Installing the connecting rods: Proper alignment and torque are critical.
* Installing the pistons and rings: Proper ring orientation and gap are crucial.
* Installing the cylinder heads: Proper head gasket installation and torque are critical.
* Installing the remaining components: Timing chain/belt, valve train, oil pan, intake manifold, etc.
5. Balancing:
* Dynamic balancing: The rotating assembly (crankshaft, pistons, connecting rods) should be dynamically balanced to ensure smooth operation and prevent vibrations. This is typically done by a professional engine builder.
6. Break-in:
A proper break-in procedure is essential for the longevity of the engine. This usually involves a controlled period of running at various RPMs to allow the components to seat properly.
7. Testing and Tuning:
The engine will need to be tested and tuned to ensure proper operation and performance. This might involve adjustments to the carburetor or fuel injection system.
In summary: Building a 350 stroker engine is a complex project best left to experienced engine builders. The costs can quickly escalate due to specialized parts and machining requirements. Improperly built stroker engines can suffer from premature wear, vibration problems, and even catastrophic failure. If you are serious about this project, seek professional guidance and use high-quality components.
