BBC Cylinder Head Footnotes
- General special parts/requirments
- As with all aftermarket heads, a different lenght pushrod might be required.
- Due to many available factory OEM style/variations your existing stud girdle may not fit.
- 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 footnotes and the specific product page your researching for specific variences 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.
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Air Flow Research
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28611 W. Industry Drive
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Valencia, CA 91355
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661-257-8124
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