AFR Enforcer Cylinder Heads

200cc/65cc Straight Plug

For SBC Chevy 327, 350 & 383 w/ hydraulic flat tappet cams up to .550" lift.

Not for use with roller cams.

After receiving many recommendations from our engine builders, we came up with the best quality, best flowing heads on the market relative to cost. The only way you're going to get a set of heads that flow as well or better will be to spend at least double the cost or more. We have installed these heads on all of our 383 and most of our 406 engines for the past 2.5 years. Many of these engines were dyno'd on our Superflo dyno . The engines had every possible combination of cam, intake and carb. The results have been amazing. These heads are excellent in design and quality. Our choice of hardware and precision assembly also contribute to the performance and reliability of the heads.

These heads can be used with outer perimeter or center bolt valve covers.

Fully assembled with the identical components found in our higher end CNC ported cylinder heads; such as ARP rockers studs, PAC Racing springs, Viton valve seals, AFR adjustable guide plates, machined bead valve locks (not stamped), hardened spring cups our one piece 8mm 21 4N Stainless Steel valves. They are available in straight or angle plug and bare without any parts for the DIY. Sold as a single piece, 2 are required per engine.

• ARP studs, 3/8's or 7/16's, (you pick)
• AFR 2pc. adjustable guide plates included
• Material: A356 Aluminum, see more details on alloy below.
• Intake Port Volume: 200cc true actual runner size.
• Intake Port Dimension: 2.080" H x 1.270" x 5/16 Radius
• Intake Port Location: Stock
• Exhaust Port Volume: 76cc
• Exhaust Port Dimension: 1.380" H x 1.420" W
• Exhaust Port Location: Stock
• Combustion Chamber Size: 65cc
• Valve Cover Bolt Pattern: Perimeter Bolt
• Valve Angle: 23°
• Valve Spring Pocket Diameter: 1.580" O.D
• Max Valve Spring Pocket Machining: 1.600" O.D
• Deck Thickness: .450"
• Minimum Bore Diameter: 4.000"
• Flat Mill: .006" per cc 56cc Maximum
• Spark Plug Dimensions: 14mm x .750" w/Gasket Seat

See our many listings for the AFR Enforcer heads for use with hyd. flat tappet cams, solid roller cams, with angle or straight plug design, and non steam hole applications.

Rocker Studs

These heads will include a full set of genuine ARP rocker studs. Choose the stud size, 3/8's or 7/16's.  Adjustable AFR guide plates are also included.

Intake Gasket

The 1206 is the intake gasket part number, and that is mandatory for use with the Enforcer heads. Some intake manifolds will sit too low due to their design, and the 1266 extra thick intake gaskets may be required.

Head Bolt Washers

The AFR/NKB-27X heads require the use of special head bolt washers, and extended reach head bolts. Using stock length head bolts will not allow the use of the special washers required, as the OE bolts have a limited amount of thread on them. Not using the special head bolts and washers may cause serious damage to the cylinder heads.

Pushrods

We recommend not using stock GM pushrods with these heads. The spring pressures on aftermarket heads are somewhat higher than on OE heads. Combine this with the larger lift and duration cams often used, and stock pushrods may flex or permanently bend. The stock pushrods are usually made from a mild 1810 steel that has been heat treated. Under high rpm they will usually flex and cause a loss of lift resulting in a power loss. The engine will usually run erratically when pushrods are flexing. The Spintron valve train dyno proves that inadequate pushrods will flex to a great degree as engine rpm increases.

Some GM pushrods have a welded ball on them, and they stand a greater chance of breaking off with the use of larger than stock cams, and increased spring pressure.

We offer pushrods made from 4310 chromoly with an .080 wall thickness. They are superior to any stock pushrod.

The size that you will most likely need with the AFR/NKB heads will be 7.900". This size has worked well for us when using the Comp high energy or Scorpion brand rockers. There are many low cost pushrods on the market in the $29-$39 range. These low cost pushrods are totally unsuitable for use with these heads for the many reasons mentioned above, and they are not guide plate compatible.

They usually have a wall thickness of only .065"! These pushrods will cause problems when used on a high performance setup. There are many factors that can determine pushrod length requirements. The 7.900" length is the most applicable for those using a hyd. flat tappet cam.

Should you purchase a set of pushrods from us and find that the length is not suitable, you may return them, and we will send out the size you request. It is strongly recommended that you use a pushrod checking device to determine the exact size pushrod needed.

Stud Girdle recommendation.

Edelbrock Performer EPS Intakes

If you are using an Edelbrock Performer EPS intake then you will need to use a 1205 intake gasket instead of the 1206. This is due to intake flange not covering the top of the 1206 intake gasket properly.

The 1205 is slightly small for the AFR Enforcer heads, and may need a very slight amount of trimming to avoid any gasket materiel hanging over into the intake runner. We have been through this procedure in our engine room many times for engines using the Performer EPS intake.

Part Number Breakdown

We offer 3 major types of SBC AFR heads, 272, 274 and 919.

272 designates the use of standard length valves, and single springs with a damper setup for hydraulic flat tappet cams.

274 designates the use of longer valves with dual springs with a damper, setup for hydraulic roller cams.

919 is a solid roller cam setup.

The heads come in angle or straight plug. Some blocks require steam holes. Be absolutely certain of what you need before buying.

Contact us if you need assistance deciding what you need for your build.

Recommended accessories

Alloy Information

Our cylinder heads are made from AC4B alloy and tempered to T6 standards. You may have heard the alloys 355 and 356 being used on many heads. The alloy used on our heads is similar but slightly different. The AC4B alloy is commonly used by automakers in Europe and Japan. Take notice of the Rm value. This value indicates the tensile strength of an alloy. As you can see, it's higher than all the other common alloys in this chart. It's no surprise as to why we have never experienced a failure of any kind with these heads. Zero failures in the casting, zero failures in the seats and guides.

Flow Numbers

The difference in horsepower and torque generated by the AFR Enforcer heads is monumental compared to any of the low cost SBC heads on the market.

Dyno Numbers

Below you will find 5 different cams paired with these heads. We've found a 350 engine build will produce approx. 350-440 hp. on pump gas depending on cam, intake, rocker ratio, and carb.

When combined with a 383 stroker engine, the horsepower and torque numbers increase dramatically.

We have achieved 550 hp in our Stage 2.2 383 Super Stroker engine, setup for street use with the AFR/NKB heads, and able to run premium pump gas.

Our team has thoroughly tested these heads on our Superflo 902s Dyno . The results have been amazing with each and every cam combo possible.

They performed faultlessly. Cam, carb, and ignition tuning led to so much testing, and we also took the opportunity to make sure the new heads would not have any reliability issues whatsoever. Our head builder noted the excellent style of cutting on the seats in these heads. He also told us that our line of intake manifolds mounted very well on the heads, and the heads mounted perfectly onto the block.

It's critical to match the engine components together for each application. We know the combinations and will work well. Take a test drive in a car with over 500 hp vs. a 300 hp or less and you will then see what you're missing. The exhaust sound under load is very pleasing. These heads will generate the power you need without spending a fortune.

Our Stage 2, 2.2, 3.0 engines are all now built using these heads. Read the full story on how these heads performed on our 383 Super Stroker pump gas engine. See our Stage 2.0 engine listing and the Stage 3.0.

Your results may vary

The results produced by these heads will vary greatly depending on the type of setup you are running. The engine combos we have dynoed are what most people use for cam and intake selection, and the results are listed below. The engines dynoed were many 383's, and several 406 and a few 421 cid engines in the 10:1 to 11.2:1 compression range. All ran on pump gas. This will give you an idea about the capabilities of these heads with combinations of cam, intake, rockers, and carb. This may also help you select the proper cam for your build.

As mentioned, below is just an excerpt from several of our engine adds using the AFR Enforcer heads. We also built and dynoed a 350 engine recently with the new AFR/NKB-200 heads for a customer, and will have the actual dyno results in this ad soon. The cams mentioned below are all hyd. roller cams. If you're using a lower lift than those listed below, then it would be fair to say the hp will drop, but not by much, providing your lift and duration are somewhat close to any of the cams mentioned below. This will give you an idea of what kind of power to expect with these heads, and it can certainly help you choose a cam and intake. These dyno reports show the heads to be the NKB heads. They are the exact same castings as the AFR Enforcer heads. The main difference between the two brands is the hardware used in AFR brand. This hardware used is of exceptional quality. The valves are 8mm metric size, and the valve springs are the Pacaloy high end series, same as used in their top of the line AFR Eliminator heads. The flow numbers picked up just a bit also over our NKB heads, and these high end valve train components also had a 810 gram weight reduction off the valve train. This has many benefits such as the reduction of valve float coming in sooner, and has a great effect on the ability of the lifters to stay operational at higher rpm.

Just to be clear, a cam is not included with the heads. This is just a guide to show what you may expect with a given combination when building an engine using the NKB heads.

Cam #1

Howards Cams

PART # 180345-10 This is a hyd. roller cam for use with OE roller blocks.

PART # 110345-10 This is a retro hyd. roller cam for use with non roller blocks.

Valve lift with 1.5 Rockers: Intake .565/Exhaust .580

Duration @.050": Intake .245/Exhaust .253
Lobe sep. angle: 110º
Recommended springs #: 274, See our other listings.

Below are our dyno results on one of our engines with a set of our AFR/NKB heads using this cam and a single plane intake. The horse power numbers will usually improve anywhere from 5-10 more than what the dyno results show after the rings have fully seated.

Official Dyno report on our 406 engine with this cam, flat top pistons, and a single plane intake.

Official Dyno report on our 383 engine with this cam and a single plane intake.

Valve lift with 1.5 Rockers: Intake .530/Exhaust .545

Duration @.050": Intake .233/Exhaust .241
Lobe sep. angle: 110º
Recommended springs #: 274, See our other listings.

Official Dyno report on our 406 and 383 engines with the cam mentioned above. The 406 engine had a dual plane intake, yet still achieved over 500 hp with the NKB heads.

Cam choice #2 and a dual plane intake.

This cam and a single plane intake.

Cam #3

Howards Cams

PART # 180245-10 This is a roller cam for use in OE roller blocks.

PART # 110245-10 This is a retro style roller cam for use in non-roller blocks.

Valve lift with 1.5 Rockers: Intake .500/Exhaust .510

Duration @.050": Intake .225/Exhaust .231
Lobe sep. angle: 110º

Official Dyno report on our 383 engine with our AFR/NKB heads and a single plane intake. Considering the low lift and duration of this cam, the hp numbers are excellent.

Cam #4

One of our COMP custom ground street rod cams. This cam has a somewhat low lift and duration, and produced amazing hp and torque numbers when using the AFR/NKB heads.

SBC Comp Cam OE HYD. ROLLER 520/540 Lift 236/242 Duration

110 Lobe Sep.

This cam has a step nose for use in OE roller blocks. Reduced base circle cam. (1.050)

AFR/NKB heads, a dual plane intake, a 770 cfm Brawler carb, and an MSD distributor.

This engine made 533 hp, and an amazing 549 lb. feet of torque at 4100 rpm. This engine had a dual plane intake on it. The single plane intake would have brought the hp numbers up to around 555.

Cam #5

Special Grind # 33161

PART NUMBER: 08-000-8-11323

520/540 lift

236/242 duration

110 lobe separation

Listed below is our 2.0 383 pump gas engine making 508 horse power at 5900 rpm.

You would be hard pressed to find a cam of this lift and duration to produce these hp and torque numbers in a 383.

We find this size cam to be the perfect all around size to give good drivability yet make outstanding performance numbers.

Very little strain on the valve train components with a cam of this size.

This engine had our AFR/NKB heads on it, and the regular Speedmaster single plane intake.

The 421 listed below made 526 horse power with this cam and had a set of our low cost 200cc AFR/ NKB heads on it with the 1.5 rockers.

Very impressive considering the low cost heads, and size of this cam.

Notice the torque numbers in produced. A fairly flat line from 4100 up to 5500 rpm.

Specification	Details
Intake Valve Dia	2.02"
Intake Port Volume	200cc
Intake Port Dimensions	2.2" x 1.2"
Intake Port Location	Stock
Intake Gasket	Felpro# 1206 fits perfectly with most intakes. Should your intake drop too low, then the 1266 gasket will correct this problem. Our line of intakes have worked very well with the Felpro 1206 intake gaskets.
Head Gasket	Felpro# 1003 for 327, 350 & 383 builds.
Exhaust Valve Dia.	1.600"
Exhaust Port Volume	70cc
Exhaust Port Dimensions	1.356" x 1.420"
Exhaust Port Location	Stock location & bolt pattern
Exhaust Gasket	Depends on what type exhaust you're using. Best to try and match up the gasket to your header or manifold.
Flow, Intake	See chart above.
Flow, Exhaust	See chart above.
Head Bolts	We strongly recommend ARP # 134-3601 head bolts. Must use extended reach with head bolt washers or head studs.
Head Studs	PC-2451-Studs (12pt) or ARP brand.
Manifold	Most any. Our line of intakes fit very well on the AFR/NKB heads.
Milling	Min. down to 58.5cc or 64.5 = .060". See info in this listing for details.
Pistons	Most 23° aftermarket pistons.
Push Rod Length	When running a hyd. flat tappet cam use 7.900 length. This may vary depending on many factors.
Push Rod Guide Plate	These heads include a full set of AFR adjustable guide plates.
Retainers/Locks	Chromoly Steel Retainers, with 7 degree AFR brand machined locks are used on all of our heads.
Spark Plug	.750" reach, gasket, Autolite 3923 or NGK 4554 for one step lower heat range than the Autolite.
Spring Pockets	1.550" OD (.030" deeper max)
Springs	Pacaloy premium springs.
Valve Length	5.015" (+.100") for hyd. flat tappet cams or + .200 for hyd. roller cams.
Valve Stem Dia	8mm Metric
Valve Train	STD SBC 3/8" or 7/16" stud mount
Valve Guides	1/2" OD Int = Mag-bronze, Exh = Phos-bronze (.002" press)
Valve Guide Length	1.950"
Valve Guide Clearance	.0014" - .002" (with our .3415 dia. valve stem)
Valve Guide Spacing	1.890" moved .030" from stock
Valve Seats	Hardened Ductile Iron, .006" press
Valve Seat Dimensions	Standard
Valve Seat Angles	Int = 32° - 45° - 60° - 70°, Exh = 37° - 45° - radius
Stud Girdle	Most all stud girdles will work on these heads with the exception of the AFR Eliminator stud girdles.
Torque	Head Bolts = 65 ft/lb, Rocker Studs = 50-55 ft/lb, Manifold = 30 ft/lb
Block Use	Any SBC Iron or Aluminum
Weight	59-61 lbs fully assembled pair

Product Information