There are several variables that influence proper pushrod length, i.e. block deck height, head milling, head gasket thickness, camshaft base circles, and even the design of the rockers and lifters. It is necessary to use a pushrod length checker to determine the proper geometry for your application.
Regardless if it is a fresh engine build or a cylinder head swap, piston-to-valve clearance must always be checked for depth and radial interference prior to startup. The use of modelling clay is highly recommended for this procedure. Minimum clearances on depth are .080" on the intake and .100" on the exhaust, radial clearance should be no less than .020" around the perimeter of the valve. If your measurements are below the minimum it will be necessary to notch the pistons or replace them all together. Failure to do so may result in catastrophic engine damage, voiding your warranty.
All AFR assembled cylinder heads come equipped with high quality valve springs, however it is possible that the supplied springs may not be correct for your application/camshaft selection. All valve springs must be checked for compatibility with your specific camshaft prior to installation and engine startup. Failure to do so may result in severe wear of valve train components and/or engine damage, voiding your warranty. Please consult with your camshaft manufacturer for recommended spring pressures. AFR also stock a full range of valve springs which can be selected during order process, besides the standard spring package.
All assembled, stud mount cylinder heads are shipped with ARP rocker studs and AFR adjustable guide plates for optimal valvetrain geometry. These pieces are packed seperately and are not installed. Please make sure to remove all parts from the packaging and confirm no pieces are missing prior to discarding of the box.
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, AFR recommends 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 #3922, or equivalent for engines with high compression, between 13.5:1 and 15:1, or boosted applications over 15psi running Race Gas
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. In addition, (4) one inch longer space fasteners must be used, per side, along the exhaust port(bottom) of the cylinder head.
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.
Your AFR cylinder heads will accept most factory GM components. However, if you require a stud girdle, you must use AFR #6202 which has been designed specifically for AFR V2 castings. Conventional stud girdles will not fit properly.
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, AFR recommends 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.
- NGK #TR55 for normally aspirated, pump gas engines with a compression ratio between 10:1 and 11:1
- NGK #TR6 for engines with high compression(greater than 11:1) or running power-adders using Race Gas
AFR recommends using ARP head bolts or studs versus the factory (torque-to-yield) GM bolts. Make sure to follow the recommended torque specifications supplied with your fasteners.
With the exception of the perimeter valve covers on 97-98 motors, your AFR cylinder head will accept all factory GM components. 97-98 vehicles you must use Center-Bolt valve covers versus the factory covers.
Yes, you can run AFR cylinder heads on your small-bore(3.898"-3.905") block. In order to do so, you must use a head gasket with a 4.125" or larger bore; such as the Cometic #C5318-040 or the Felpro #1041 head gaskets.
- For small bore(3.898" to 3.905") blocks with AFR #1510 and #1660 cylinder heads, AFR recommends using the Cometic #H1294040S head gasket
- For blocks with a 4.00" or larger bore, AFR recommends using the Cometic C5318-040 head gasket
Unfortunately these cylinder heads can only be flat milled, because of fitment issues that would arise with the intake manifold.
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, AFR recommends 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
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, AFR 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.
AFR ELIMINATOR cylinder heads feature unique rocker arm stud locations to accomodate AFR port design.
- AFR 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 AFR #6200, which has been designed specifically for AFR castings.
- AFR 227cc, 235cc, & 245cc NPP cylinder heads feature offset rocker stud locations. For applications requiring a stud girdle, you must use AFR #6208, which has been designed specifically for AFR 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.
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.
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, AFR 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(15+psi) applications running Race Gas
Make sure to use Permatex thread sealant with Teflon.
289ci / 302W (7/16" factory head bolts) - 70ft./lbs. for the short bolts. 80ft./lbs for the long bolts.
351W (1/2" factory head bolts) - 100ft./lbs. for the short bolts. 110ft./lbs. for the long bolts.
For your convenience, AFR stock complete and partial ARP head-bolt kits, studs and washers. AFR 1402 and 1472 cylinder heads are machined for 7/16" head bolt diameters; all others are machined for 1/2" head bolts. When using heads with 1/2" holes on blocks with 7/16" threads, AFR recommend using ARP's 254-3708 or 254-4401 kit with their 200-8598 bushings.
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.
Typically AFR cylinder heads that are equipped with 2.02" or larger valves do not clear factory pistons or aftermarket pistons that mimic a factory style valve pocket. Regardless if it is a fresh engine build or a cylinder head swap, piston-to-valve clearance must always be checked for depth and radial interference prior to startup. The use of modelling clay is highly recommended for this procedure. Minimum clearances on depth are .080" on the intake and .100" on the exhaust, radial clearance should be no less than .020" around the perimeter of the valve. If your measurements are below the minimum it will be necessary to notch the pistons or replace them all together. Failure to do so may result in catastrophic engine damage, voiding your warranty.
The stock rocker arms can be used with AFR #1472 and #1492 cylinder heads, which come with the pedestal style bosses. The other cylinder heads in AFR RENEGADE line require stud mounted rocker arms.
Intake:
165cc Street - AFR #6828 or Felpro #1250
185cc Street, 195cc Comp and 205cc Comp - AFR #6832 or Felpro #1262
220cc Comp - AFR #6812 or Felpro #1262R
Exhaust:
165cc Street and 185cc Street - AFR #6837 or Felpro #1415
195cc Comp, 205cc Comp and 220cc Comp - AFR #6839 or Felpro #1487
Head Gasket:
Factory block (289W, 302W and 351W) - AFR #6808 or Felpro 1011-1
Aftermarket Block - Consult with block manufacturer for recommendations