AFR Cylinder Head Footnotes
- General special parts/requirments
- AFR Titanium valves REQUIRE lash cap
- Marine Applications: We strongly recommend Inconel exhaust valves.
- Boosted/NOS Applications: We strongly recommend upgrading your springs since boosted or NOS applications accelerate the RPM so quickly, additional spring pressure is required.
- Boosted/NOS Applications: We strongly recommend considering Inconel exhaust valves and AFR's optional heavy duty intake valves for high power applications.
- Boosted Applications: We strongly recommend increasing your valve spring pressure since boost pressure on the valves reduces your spring tension. For example, 15 lbs on a 2.125 O.D valve reduces the springs closed seat pressure by approximately 40-50lbs.
- Valve Guide Clearance: Your AFR heads come with .0125 to .0150 valve to guide clearance. Boosted/NOS application might require additional clearance.
- Intake runner volumes can vary 2-3cc from advertised sizes. The reason for this is different combustion chamber volumes require different intake runner length for proper alignment with the intake manifold.
- For all applications we strongly recommend true roller rocker arms, not just roller tip rockers with stock style bodies.
- As with all aftermarket heads, a different length pushrod might be required.
- As with all aftermarket heads, your self aligning rockers will no longer be compatible.
- As with all aftermarket heads, check pushrod clearance with heads placed on the block before final assembly.
- As with all aftermarket heads, milling the head deck might affect air flow. Flat and angle mills might require a .120 thick gasket.
- Shaft Mount Rockers: As with all aftermarket heads, shaft mount rockers might require additional clearance for proper pushrod fitment. Be extremely careful, the port wall thickness at pushrod is .060 thick, don't clearance this area at all!
- Due to many available factory OEM style/variations your existing stud girdle may not fit.
- As with all aftermarket heads with 1.550 O.D. springs, head bolt, or studs with smaller diameter head might be required for easier installation. As with all aftermarket SB Chevy or Ford heads with 1.625 O.D. springs might require the spring to be removed to install the head.
- Valve Springs: AFR springs that come standard with our assembled packages are very high quality and are sufficient for most applications. However, forced induction applications and cams with aggressive ramp rates (some cam manufacturers now offer much faster ramp designs and more aggressive cam profiles) 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 more ideally suited to your application.
- 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 .200 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.
- See below what factory OEM head AFR used for CAD/CAM modeling.
- Please see the page for the product you're researching for specific variances from OEM heads.
BBC Cylinder Heads
- Was modeled after the GM LS6 open chamber rectangle port castings.
- With some domed aftermarket pistons, it may be necessary to slightly clearance or modify the piston due to our more modern (efficient) heart shaped combustion chamber design. Most of the newer manufacturer's dome profiles will clear, however the middle peak or crest of the chamber directly adjacent to the spark plug (between the intake and exhaust valve) is typically the problem area in some of the older piston designs. Note that the typical amount of material needed to be removed is very small usually less than 1 cc of aluminum is removed which only equates to a weight reduction in the piston of one to two grams. If your rotating assembly is already balanced this is a non-event and creates a VERY slight overbalance which in theory brings your engine into a better balance situation at slightly higher RPM. You could easily be off three times that amount by simply setting up your rotating assembly on a different shop's balancing machine. In short, don't worry about the slight removal of material effecting the balance of your rotating assembly. While some of you might be inclined to remove the material from the actual cylinder head, note that all of the combustion chambers shapes are very critical to flow and altering the cylinder head can and will effect flow and power production. We advise and recommend that you remove the material from the piston in the event you have piston dome to head interference. The easiest way to check for this is turning the engine over slowly with the cylinder head installed without the head gasket.
- Was modeled after the GM LS6 #243 aluminum cylinder head.
- AFR LS1 cylinder heads do not have provisions for 1997-1998 perimeter bolt valve covers, conversion kits available.
SBC Cylinder Heads
- Was modeled after the GM L-98 aluminum cylinder heads.
SBC LT-1/LT-4 Cylinder Heads
- Your factory accessory bolts and center bolt valve cover bolts need to be shortened 3/16" or they will bottom out.
SBF Cylinder Heads
- Was modeled after the Ford GT 5.0 cast iron cylinder head.
Air Flow Research
28611 W. Industry Drive
Valencia, CA 91355