What spark plug should I use with my AFR cylinder heads?
The following list of spark plugs are suggestions for getting your engine up and running. In order to determine the correct heat range for your application, we recommend pulling your plugs and inspecting them a few times under typical operating conditions; commonly known as reading the plug. Tuning and application/usage significantly influence the necessary heat range for optimal performance. Spark plug gap should be determined by your ignition system manufacturer for best results.
- 3/4" reach, 14mm, gasket seat
- Autolite #3924 or equivalent for normally aspirated, pump gas engines with a compression ratio between 9:1 and 11:1
- Autolite #3923 or equivalent for compression ratios between 11:1 and 13.5:1 or mildly boosted(8-12psi) applications running Race Gas
- Autolite #3922 or equivalent for engines with high compression, between 13.5:1 and 15:1, or high boost(10-18psi) applications running Race Gas
What should I torque my bolts to?
All aluminum cylinder heads with factory bolts should be torqued to 70-75 ft./lbs using Permatex thread sealant with Teflon. Be sure to follow the proper GM torque sequence, starting at 40 ft./lbs and increasing by 10ft./lbs until reaching the recommended setting. All engines with high compression or using power-adders should be re-torqued after the first run-in, after it has completely cooled-down. 12 point bolts are recommended in the 3 areas near the exhaust valve springs, where it may be difficult to fit a standard 5/8 socket. If using head studs, 12 point nuts are recommended.
For your convenience, we stock complete and partial ARP head-bolt kits, studs and washers. ARP part numbers for the bolt kit are #134-3701 and the stud kit is #234-4301.
If you are using ARP hardware, follow their recommended torque specifications. Rocker studs should be torqued to 50-55 ft./lbs using Permatex thread sealant with Teflon. Spark plugs and all intake and exhaust bolts should be tightened with a standard wrench or socket versus a torque wrench as these smaller threads can easily strip. Be sure to apply anti-seize to all threads prior to tightening.
Will I need to use offset rockers with my ELIMINATOR cylinder heads?
Our ELIMINATOR cylinder heads feature unique rocker arm stud locations to accomodate our port design.
- Our 180cc, 195cc, 210cc and 220cc cylinder heads do not require an offset rocker arm and will accomodate a conventional stud mount rocker arm. For applications requiring a stud girdle, you must use our #6200, which has been designed specifically for our castings.
- Our 227cc, 235cc, & 245cc NPP cylinder heads feature offset rocker stud locations. For applications requiring a stud girdle, you must use our #6208, which has been designed specifically for our castings. Due to the 60/40 stud and valve locations, a shaft mounted rocker system is highly recommended (shaft mount required on 245cc heads).
If you are only drag racing, you can run a .050" offset stud mounted rocker on the intake and a standard rocker on the exhaust with the supplied AFR guideplate. Please note that when using the .050" offset rocker(intake), the roller tip will not be perfectly centered and will not sit squarely on the valve; causing increased side-loading and wear. This setup is not recommended for race, endurance or street applications that see a lot of mileage.
Will my 400ci block need steam holes?
Steam holes are recommend for all factory GM 400ci block applications. Using the head gasket with the steam hole openings, properly locate the positions on the head that require drilling/modifications.