AFR® 2020-TI - Magnum 24° Rectangular Port Cylinder Heads with Full CNC Chamber

Recommended Components:

• Intake Port Gasket:
• AFR #6854 (.120" Thick)Intake Port Gasket: AFR #6856 (.060" Thick)
• Exhaust Port Gasket AFR #6858
• Head Gasket, Fel-Pro #1047 (Mark V and VI) AFR #6849
• Head Gasket, Fel-Pro #1017-1 (Mark IV) AFR #6850
• Head Bolts, ARP 135-3703 (Mark IV) AFR #6306
• Head Bolts, ARP 135-3707 (Mark V) AFR #6308
• Head Studs, ARP 235-4713 AFR #6307
• Head Bolt Washers, Manley AFR #6320
• Stud Girdle, (AFR Specific) AFR #6202
• Suggested Manifold Victor Jr
• Suggested Manifold Super Victor
• Spark Plug Starting Range Autolite 3932

AFR Big Block Chevy

• With some domed aftermarket pistons, it may be necessary to slightly clearance or modify the piston due to our more efficient heart shaped combustion chamber design. Most of the newer designed dome profiles will clear. AFR strongly recommends material be removed from the piston and not the cylinder head. Our combustion chamber shapes are very critical to flow and altering the cylinder head can adversely affect flow and power production. It is the customers responsibility to verify proper piston to head clearance.
• Heads are designed for 3/8" pushrods. Larger pushrods will not fit without clearancing and is not recommended since some areas are very thin. AFR recommends the use of .120" thick-wall pushrods.
• Modeled after GM LS6 Open chamber rectangle port castings.

General Recommendations for AFR Cylinder Heads:

• Bar Codes - Please keep the bar code & paperwork shipped with your head, these contain all the specs for your heads when calling AFR.
• Pushrods - Different length pushrods might be required, always check pushrod length. Check pushrod clearance with heads placed on the block before final assembly. Larger pushrods will not fit without clearancing and is not recommended since some areas are very thin. AFR recommends the use of .120" thick-wall pushrods.
• Mills - Flat or angle mills could affect flow numbers and might require a thicker intake gasket.
• Stud Girdles - Due to many available factory OEM and aftermarket style/variations your existing stud girdle may not fit (AFR heads require AFR Stud Girdles)
• Boosted/Nitrous Applications - We strongly recommend considering Inconel exhaust valves and AFR's optional heavy duty intake valve for power adder applications. Since boosted or nitrous oxide applications accelerate RPM quickly, additional spring pressure is required. We strongly recommend upgrading your valve springs or increasing your valve spring pressures since boost pressure on the valve reduces spring tension. For example, 15lbs boost on a 2.125 OD valve reduces the springs closed seat pressure by approximately 40-45lbs.
• All MARINE Applications - We strongly recommend Inconel exhaust valves & also offer a hard anodized coating to slow the effects of corrosion. Please see note on guide clearance below.
• Valve Guide Clearance - Your AFR Heads come with proper guide clearance (.0012"-.0016") for most applications. Boosted/Nitrous or marine applications might require additional clearance and it is the customer's responsibility to verify proper clearance in these applications.
• Valve Springs - Forced induction, nitrous oxide and cams with aggressive ramp rates may require additional spring pressure. We offer optional valve springs for these types of applications. AFR also recommends the use of billet cam cores which tolerate higher spring loads. Please don't hesitate to contact us directly if you question which spring is correct for your application.
• AFR Titanium Valves - Might require lash caps and different length pushrods. Titanium valves are coated, do not grind valves because it removes the protective coating.
• Piston to Valve - AFR assumes no responsibility for damage if the end user builds an engine without properly verifying he has enough piston to valve clearance (depth and radial clearance both checked). We recommend a minimum depth of .080" on the intake valve and .100" on the exhaust with a radial clearance of .020" minimum around the perimeter of each valve. Clay is recommended to visually verify both depth as well as radial clearance. Just checking depth is not enough, the position of the valve pocket must also be addressed. It is the customers responsibility to verify proper piston to valve clearance.
• CNC Porting - Occasionally a 100% CNC ported head might have a very small area left "as cast", this in no way affects performance.
• Shaft Mount Rockers - Shaft mount rockers might require additional clearance for proper pushrod fitment. Do not clearance the push rod area as the wall is .060" thick.
• Spring Installation - To ease installation with 1.550" O.D or larger springs, 12 pt head bolt or studs are recommended for extra clearance. Beveled or ground washers might be needed (ARP #200-8504 comes with smaller O.D and doesn't need to be ground)
• Runner Volume - Intake runner volumes can vary 2-3cc from advertised specs. The reason for this is that different combustion chamber volumes require different intake runner lengths for proper alignment with the intake manifold.
• Rocker Arms - Use full roller rocker arms, roller tip rockers with stock style bodies are NOT recommended.