EC Cylinder Head Instructions
Thank you for buying an EC Performance Cylinder Head. To get the most performance from your new head, we want to provide you with information to help complete your assembly or build
Installation Check List
A. Spring Install Height/Coil Bind: The installation height of your springs is determined by the valve length, retainer dimension, and lock position relative to the mounting position in the cylinder head. Choose the springs designed for your installation height, or you may need to modify your cylinder head to change the installation height. Changing the installation height will change the valve spring pressure and the amount of lift before the coil binds. We recommend having at least .060” before coil binding.
B. Retainer Clearance: Check the bottom of the retainer and the top of the valve guide. With high lift cams, the retainer may hit the top of the valve guide, damaging the retainer and dropping a valve. To resolve this issue, machine the top of the guide to provide clearance; do not machine the retainers. Check your clearance before running the cylinder head. (We recommend .050” between the retainer and guide before the coil binds at max lift.) You could also use longer valves, but this will change your install height and rocker geometry.
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C. 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 starts with ratio rockers that increase lift across the profile, which tightens the clearance. Ensure they are checked with the rocker’s arms you plan to run with your engine. Valve float is rare for most combinations running less than 7000rpms, so we want at least .080 piston-to-valve. However, high rpms(8000rpms+) engines are much more unstable, so we recommend .120” piston-to-valve clearance.
D. Piston-to-Head 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 .040” of clearance, which would be a standard fire-ring gasket that is .045-.050” thick, and the piston has zeroed at the deck. We recommend never having the piston pop up to provide more clearance rather than worrying about minimum gains in compression.
E. Rocker Geometry/Push Rod Length: Check to ensure the rocker arm has suitable geometry and doesn’t contact the retainer. Our EC Rev Rockers have instructions on correctly setting up your rocker arm geometry. The cam’s base circle, lifter, deck height, head gasket, cylinder head, rocker arms, and rocker geometry will determine the push rod length. Once your rocker geometry is set and the engine is assembled, you can use the EC Adjustable Push Rod Tool to measure the correct pushrod length.
F. Torque Specs and Mounting: Some blocks(Tillotson R-Series) will not allow bolts to be installed at full length, preventing the cylinder head from clamping. Blocks may need further tapped, or shorter hardware may be required. If you are using a stud kit, check to ensure the nuts are clamping the head and not bottoming out on the non-threaded part of the stud. This problem can occur if you use a thin head gasket, the head has been shaved, or the studs are not low enough in the block. You may need to machine the block so the studs can sit lower or use washers under the nuts. We highly recommend using Nord-Lock washers to help clamp the head and prevent the bolts or nuts from backing out.
G. Copper Head Gasket: The Copper Head Gasket must be annealed. Copper head gaskets require the cylinder head to be grooved and cut for an o-ring to seal. Gasket makers(Permatex, Hondabond, etc.) or sealants (Edelbrock Gasgacinch) may be used in addition to o-ringing but should not be considered a replacement for an o-ring
H. Compression Ratio: We recommend using 91 octane at minimum—measure for an accurate compression ratio to choose the fuel best suited for your engine.
Listed below are part and tuning recommendations to utilize your head’s performance.
These recommendations are general guidelines. All combinations require tuning and testing for the best results.
Carburetors
Carburetor bore sizing is based on the measured area of the inlet to the cylinder head. For example, the inlet area is 22mm, and we spec a bore size of 90% of the inlet equals 19.8mm or 20mm. Most aftermarket slide and butterfly carburetors will outflow your cylinder head even when the carburetor is slightly undersized. For example, our PWK24 flows 107cfm, which is more than most 32mm valve cast heads will flow at .450 lift, and most do not have an inlet to the head that exceeds 24mm. The exception would be welded-up cylinder heads.
Gas Carburetors
Off-Road Trail Riding - 80-85%
Street Cruising - 85-90%
Racing - 90-100%
PK-875G - Stock Appearing
Methanol Carburetors
Methanol carburetors will run 10-15% larger bores than gas equivalents
HL-304WX-5 - 1-inch Diaphragm/Butterfly - Small/Mid Size Track Kart Racing
XR-28-1K - 28mm Diaphragm/Butterfly - High Rpm Kart Racing
PWK-28-4K - 28mm Flat Slide - Karting/Drag Racing
PK-875A - Stock Appearing
Exhaust
We recommend using no less than .900 ID headers, ideally .960-.990 ID. If possible, no muffler will offer the best performance; if a muffler must be used, it must have an ID larger than the pipe with as few baffles as possible—no threaded or lawnmower-style mufflers. Restrictive mufflers may require extensive carburetor tuning and/or a smaller carburetor.
Camshafts/Rockers/Spring Kit
Check the EC Website for the latest camshaft profiles and recommendations. Camshaft recommendations depend on class or application, engine displacement, compression, fuel, rpm range, clutch engagement, etc.
Fuel
Minimum 91-93 Octane Non-ethanol. Check your compression ratio before choosing an octane for your engine.
DO NOT BUY METHANOL WITH TOP LUBE. Use only 100% methanol. Alcohol(methanol & ethanol) Fuels must be flushed after racing to prevent corrosion.
Ignition Timing
Ignition timing will vary with fuel volatility, compression ratio, and cam timing.
28-34° Gas
34-36° Methanol
Spark Plug/Gap
Torch K7RTI .028”
NGK BPR7EIX .028”
Disclaimer: Following our guidelines and instructions does not guarantee problems or failures will not occur. There are no warranties implied or expressed for any reason. Inspect your cylinder head the moment it’s received. If the head has been installed or modified, it cannot be returned or exchanged.
These industrial-based engines are not designed to run above 3600rpms, and the cause for failure is increased with modifications and higher RPMs. Lean Conditions from carburetor tuning, high compression, low octane, and high ignition timing can increase the chances of detonation. Incorrectly measuring and installing components can lead to a failure caused by interference or fatigue.
Modifying engines and racing are hazardous. By buying this cylinder head, the buyer assumes full responsibility and liability for any damages or harm caused by installing and running it on any engine.
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