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Racing Head Service
Flat milling : .006" per cc Angle milling: .0075" per cc
Excessive milling can cause intake manifold port misalignment, which may require corrective machining to the intake side of the head, the manifold or other measures in order to achieve proper intake gasket sealing.
Different thickness head gaskets and/or intake manifold gaskets will also affect port alignment.
Refer to cylinder head bolt manufacturer"s specifications for torque setting.
Torque head bolts/studs to specified setting in 10 lb/ft increments, starting at 35-40 lb/ft. GM factory torque sequence must be followed for proper head gasket sealing. Bolts/studs that enter coolant passages should be coated with a thread sealant such as Permatex.
Bolts/studs that are being threaded into aluminum should be coated with anti-seize lubricant to prevent thread damage. All other bolts and studs should be lightly lubricated with 30 weight engine oil.
Intake manifold bolts should be torqued to 35 lb/ft in 5 lb/ft increments, starting at about 20 lb/ft. GM factory torque sequence must be followed, and all bolts that enter the water jacket should be coated with a good thread sealant such as Permatex, in order to prevent coolant leaks.
Torque specification is 45 lb/ft.
Be sure to put thread sealant or RTV silicone sealer on any stud or shaft bolt that threads into an intake runner, and use anti-seize lubricant on any stud or shaft that is being threaded into aluminum.
Installed height, coil bind clearance, seat/open pressure, and spring rate must all be verified and correct before the engine is run, or severe engine damage will result.
Call RACING HEAD HELP™ toll free at 1-877-776-4323 if you are not sure that your valve springs are correct for your application.
Valve spring pockets can be machined to 1.625" maximum diameter, but cannot be machined any deeper. If additional valve spring installed height is required, valves with longer stems or valve locks/keepers that provide increased installed height should be used.
There is no “standard” or recommended pushrod length unless your engine is completely stock. Pushrod geometry must be verified!
All cylinder heads that are run with guide plates must also use hardened steel pushrods that are intended for use with guide plates. Failure to use hardened pushrods will result in premature wear of the pushrod where it contacts the guide plate, which will result in severe engine damage.
Piston-to-valve clearance must be verified – the minimum clearance is .080" on the intake side and .100" on the exhaust side. Technically, engine builders have found that all you need on the intake is the total amount of deck clearance plus .010”-.015” for piston rock (pivoting in the bore wall). On the exhaust side, you need 2 to 2 ½ times the clearance you have on the intake.
When running domed pistons, chamber to dome clearance should always be checked prior to final engine assembly. Clearancing may be necessary.
The distance between the bottom of the valve spring retainer and the top of the valve guide or valve stem seal must be greater than the valve lift. Clearance measurement is strongly recommended.
Valve guide clearance must be checked due to the variance in valve stem diameters between manufacturers. Recommended clearance is .0015"-.0016" for the intake valves, and .002"-.0025" for the exhaust valves.
Valve head margins and dishes will have an impact on advertised combustion chamber volume. For accurate compression ratio calculation, the combustion chambers must be CC’ed with valves installed in the cylinder head to verify the exact combustion chamber volume.
Water jackets require flushing prior to cylinder head installation, and the entire cylinder head should be thoroughly blown out with compressed air prior to installation.
Use the spark plug application chart below to determine which spark plug best fits your application. Note that forced induction or nitrous engines should use spark plugs 1-2 heat ranges colder than those listed in the chart.
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Be sure to use anti-seize lubricant on the threads of spark plugs installed into aluminum cylinder heads.