Frequently Asked Questions

Big Block Chevy Aluminum Heads

1. What spark plug should I use in my AFR BB Chevy Cylinder Head?
2. What should I torque my fasteners to?
3. Will my new AFR cylinder heads accept all of my factory components?
4. Do I need to re-torque all my head fasteners after first start up?
5. How do I determine correct pushrod lenght?
6. Where can I purchase AFR Cylinder Heads?

 

Answers

1) Spark Plugs:

All AFR BBC Cyilnder Heads accept spark plugs with a flat gasket seat and washer (not the tapered seat style) and a .750 long reach. Projected tip plugs can only be used if you check for adequate piston dome to spark plug clearance. Some initial plug recommendations are as follows:

Autolite #3932 Std. Tip, Race Application
Autolite #3935 Std. Tip, Street / Strip Application
Champion #C59C Std Tip, Race Application
Champion #C59YC Projected Tip, Race Application
Champion #RC12YC Projected Tip, Street Application

2) Head Fasteners Torque:

All Seventeen fasteners per cylinder head can be torqued down to 75 ft./lbs. using the standard General Motors BBC torque pattern. The best choice of fasteners being a quality kit of aftermarket studs (ARP, B&B, Milodon, etc.) Don't forget to use a non-hardening sealer on studs or bolts that enter into the engine block water jacket. Also, be aware that you need (4) one inch longer space fasteners per side along the exhaust port (bottom side) of cylinder head. The recomneded bolt kit does not work on Dart BBC as the holes are not deep enough.

3) Factory Components:

Yes, your AFR cylinder heads will accept all factory components with the exception to the rule being a stud. Only a stud girdle designed for a 2 degree rolled over valve andle will properly fit. We sell one under our AFR Parts and Accessories Section. Also, be aware that our exhaust port location has been raised .300 over stock height to improve flow characteristics. If you are currently running stock heads and you have a very tight header/exhaust manifold clearance, you might be forced to modify them to fit.

4) Re-Torque head fasteners after start up:

If you are running copper head gaskets the answer is YES, with a Capitol "Y". If you are running the Felpro Permatorque style gasket, it is certainly a good idea on a normally aspirated engine and should be considered a must on any blown, turbo, or nitrous motor. any motor subject to severe usage should have the heads re-torqued for improved reliability and a longer head gasket life.

5) Pushrods:

Visit the following sites for information regarding choosing the correct push rod length.

Holley Valve Train Technical Info
Holley Valve Train Geometry Info

6) Purchasing AFR Heads:

You may purchase your AFR Aluminum Cylinder Heads directly from Air Flow Research or any one of our authorized distributors.