Editing Vortec L31 cylinder head (section)
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==Upgrading and compatibility== The L31 Vortec head can be used on any SBC engine from 1955 through the end of Vortec production, with the exception of the Gen 2 LT1/LT4 engines used in some vehicles between 1992-'97. They are also not compatible with any of the current LS engines. There are some inherent costs associated in swapping from 1995-back heads to the L31 Vortec heads. Here is a list of items to be purchased and/or labor associated with the upgrade: * L31 heads * Springs if the cam has a valve lift over about 0.440" * 1987 to present center bolt style valve covers if the heads used previously were perimeter style (1986 and earlier including the current production Goodwrench 350 crate motor) ** Note: [http://www.crankshaftcoalition.com/wiki/Vortec_L31_cylinder_head#Small_port_Vortec_head_p.2Fn_25534351_.28bare.29_and_p.2Fn_25534421_.28assembled.29 GMPP small and large port Vortec heads] and other aftermarket Vortec heads accept either perimeter or center bolt valve covers [[File:Vortec valve-rocker.jpg|thumb|right|300px|Self aligning stamped steel rockers]] *Self aligning rocker arms (SBC and 4.3L since the 1988 model year use the self aligning rockers and the pushrod holes are round instead of oblong - self aligning rockers do retrofit to the earlier heads but recommended for a stock rebuild * Valve cover gaskets (again 87+ centerbolt style) * Vortec specific intake manifold. While some aftermarket heads have both 12 and 8 bolt intake bolt patterns, the height of the Vortec ports require a tall, "raised port" type early intake manifold (along with porting/port work to the intake manifold and/or head), to even come close to fitting correctly. See '''[[Vortec_L31_cylinder_head#Using an early style intake on an aftermarket Vortec-type head|Using an early style intake on an aftermarket Vortec-type head]]''' for more info; some applications require the stock SBC intake to have the upper section rewelded with a chunk of metal which covers the intake ports as demonstrated with the SyTy 4.3L or TPI intake base (it is common for the SyTy 4.3L lower intake to be modified with extra material when used with Vortec heads) * Vortec specific intake manifold gasket * Vortec specific intake manifold bolts * Head bolts (required only if the original head bolts are either missing or unusable for some reason - 1996+ head bolts are torque to yield unlike 1995 and older) * Head gaskets ([http://www.crankshaftcoalition.com/wiki/Head_gasket#Re-using_head_gaskets generally required] any time heads are re-installed) * Machining valve guide boss or the use of different retainers and springs, or ghetto grinding the stock retainers, etc., to work with a camshaft having somewhere around 0.450" or more valve lift. {{Note1}} The clearance between the retainer and the seal has to be checked during the engine mock up phase of the build to determine exactly what the clearance is with the cam, retainer, valve stem seal, valve locks and rocker arm/rocker arm ratio used.
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