The WC-200 Forged 72mm piston was designed by EC Carburetors to enhance further the performance of small block clone engines with 72mm bores.
The WC-200 piston is superior to the factory stock-style cast and Tillotson hypereutectic 72mm pistons, as it is both lighter and stronger than both due to its forging and design. The piston reduces friction with coated skirts and thin, low-tension piston rings. The compression height is shorter than that of the Tillotson piston, allowing for slightly longer rods, which improve the rod/stroke ratio, crankshaft leverage, and reduce wear and friction on the skirts, especially on the thrust side of the piston.
Our goal was to make the piston more durable for high RPMs and increase the performance of your racing engine.
To utilize this piston, we have designed specific rods, stroke assemblies, and bottom-end kits to facilitate easy assembly. Below are the specifications and installation guide for the WC-200 72mm Forged Piston.
WC-200 Piston Specifications Piston Crown Piston Weight Compression Height(4) Wrist Pin Journal(5) Wrist Pint & Cip Weight Flat Top 123.5g .628" .5125" 24g Top Ring Second Ring Oil Ring Assembly RIng Weight Piston Diameter/Piston-to-Wall Clearance Thickness .038"
Recommended
Ring Gap .010"Thickness .038"
Recommended
Ring Gap .012"Total Thickness .082" 11.8g 2.831"/.0035-.004 
Piston-to-Cylinder Wall Clearance
To measure piston size accurately for piston-to-wall clearance:
- Measure from the bottom of the skirt and 90° from the wrist pin.
- Subtract that measurement from the bore diameter.
- Check multiple spots in the bore. The bore may need to be honed to improve bore straightness.
- Most factory piston to wall clearance is .0035-.004” which is recommended for most builds, minimum piston-to-wall clearance is .0025. When the piston-to-wall clearance exceeds .008, rebuilding the next oversized piston is recommended.
Piston-to-Valve Clearance
Check piston-to-valve clearance. Changes in camshaft lift, duration, and centerlines will influence the clearance of your valves. The problem often begins with ratio rockers that increase lift across the profile, thereby tightening the clearance. Ensure they are checked with the rocker arms you plan to run with your engine. Valve float is rare for most combinations running at less than 7000 rpm, so we want at least a .080 piston-to-valve clearance. However, high rpms(8000 rpm+) engines are much more unstable, so we recommend .120” piston-to-valve clearance.
Piston to Head/Spark Plug Clearance
Stacking tolerance, heat, piston/engine speed, and weight contribute to setting piston-to-head clearance. If you are in doubt, we recommend at least 0.040” of clearance, a standard fire-ring gasket that is 0.045-0.050” thick, and the piston has zeroed at the deck. We recommend never allowing the piston to pop up to provide more clearance, rather than worrying about minimum gains in compression.
Crankshaft Counterweight Clearance
Check the clearance between the piston and crankshaft counterweights at the bottom dead center(BDC). Some combinations of pistons and stroker crankshafts may require additional machining to prove clearance. Minimum recommended clearance .050”
Piston Ring End Gaps
The ring gaps are often set tight to compensate for misaligned bores and block distortion, which can increase the ring gap and lead to blow-by, ultimately reducing performance. However, we recommend not setting the rings too tight, especially on high-compression engines. We would rather give up a little power to avoid a stall than risk an engine failure.
Top Ring | 2nd Ring | Oil Ring Rails | |
Application | Minimum Gap Per Inch of Bore | Minimum Gap | |
Low Compression 9:1 or less | Bore x .003 | Bore x .0035 | .015 |
High Performance Racing | Bore x .004 | Bore x .0045 | .015 |
Ring gaps are set by installing the ring in the bore and using a piston or a ring squaring tool to position the ring so that it is square. Measure your gap with a filler gauge. The gap can be increased by using a piston ring grinder or file. Slowly remove material(sneak up on your measurement). Repeat until you achieve the desired gap. Sometimes, oversized rings must be used to get the ideal ring gap.
Piston Assembly Instructions
1. Clean the piston and cylinder bore thoroughly with automotive cleaning solvents, dish soap, and hot water. Dry thoroughly to prevent flash corrosion. We use Maxima MPPL to keep rust from forming in the bore.
2. File fit ring gaps to the bore before installing on the piston. Use a ring expander or spiral method to install rings. Most ring sets are marked 1 and 2, which will face upward. If rings are not marked, the inside chamfer will face up.
3. Use a light coat of assembly lube(Maxima Assembly Lube) or Break-in Oil to coat the piston’s wrist pin, piston, and small rod journal. Install the wrist pin clips and wrist pin. Ensure the clips’ gap is 90° of the pick lock groove and is firmly seated in the piston pin clip groove before and after installing the wrist pin. When installed correctly on the connecting rod, the piston will have a directional arrow pointing towards the push rod gallery.
4. Use a light coat of assembly lube(Maxima Assembly Lube) or Break-in Oil to coat the piston’s skirts, rings, and cylinder bore. Use the appropriate ring compressor to compress the rings. Lube the ring compressor, push the piston into the compression, or squeeze the rings with the compressor. Ensure the crankshaft journal faces away from the rod so that it does not hit. Insert the rod and ensure the compressor is flush with the deck by tapping it around its edge on the block. Most of the time, the piston can be pushed into the bore. At other times, you may need a rubber or plastic dead blow hammer to tap the piston in the bore gently. Be very careful not to damage the rings. If the rings come out of the compressor before entering the bore, you can break them if you use too much force.
5. Complete your rod installation.
Note: DO NOT USE SYNTHETIC ENGINE OILS OR ADDITIVES during installation until after the engine has completed its break-in cycle. This will allow the rings to bed with the cylinder and for anti-wear to form.
Break-In Instructions
Use a good quality break-in oil; we recommend Maxima Break-In Oil.
1. For small block Clones, use 16oz of Break-In Oil.
2. Ensure oil reaches the valve train and cylinder bore. Pull the engine up on the compression stroke to Top Dead Center and tilt the engine towards the valves to allow oil to reach both the valves and the cylinders. Don’t tilt long enough for oil to drip out the breather; only a second will do. If you have already mounted the engine, remove the valve cover and ensure the valve train is lubricated. If the engine was adequately assembled, you should have used assembly lube to lubricate the moving parts during the first start-up.
3. Start the engine on a dyno with a moderate load at moderate rpms(3500- 6000 rpm) or on a kart or mini bike. Do not free-rev the engine without a load, and avoid allowing the engine to idle for too long. The engine should break in within 20-30
minutes before changing to a fully synthetic racing oil. We recommend the Maxima Racing OIL RS-Series. Most small blocks on gas will run Maxima RS 0w-20
