SBC CHEVY 350 383 406 NKB-200cc ALUMINUM HEADS 64cc STRAIGHT PLUG NKB-274
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NKB 200cc/64cc ULTRA HIGH FLOW CYLINDER HEADS,
STRAIGHT PLUG, FOR SBC CHEVY 327 350, 355 383, 400, 406, 421 ENGINES.
Setup for hydraulic roller cams.
200cc RUNNERS, 64cc COMBUSTION CHAMBERS.
THE BEST FLOWING, BEST QUALITY SBC ALUMINUM HEADS ON THE MARKET FOR THE MONEY.
This sale is for one fully assembled set of heads.
The springs in these heads are set up to operate with hydraulic roller cams up to .600 lift. For those running hyd. flat tappet cams, see our other listings for these heads with the part number NKB-200-272.
The NKB aluminum heads have 64cc combustion chambers with 200cc runners, 2.02/1.60 stainless valves. These heads are not built by Procomp, and have no association with them in any way.
PART NUMBER # NKB-274
We certainly know where to draw the line with low end products, and we continue to eliminate parts that we once accepted but that eventually had problems. Sometimes it's not that a particular product has had a problem that leads to its elimination; something better just comes along. The NKB cylinder heads are that â€œsomething better" coming along. Considering the price is only slightly higher than our former line of heads, this has to be the best value in a set of cylinder heads we have ever offered. We now use the NKB heads on all of our 350, 383, 400, 406, and 421 engines. The performance has been outstanding on every combination we have tried them on. We have been selling the NKB heads for around 4 years. We have sold approximately 5500 sets, and problems have been near non-existent.
We have complete top end hardware kits available for the NKB-200 heads in our other listings. The kit has the correct head and intake gaskets, head bolts with special washers, and stainless intake bolts. The most popular kit is the TEK-1003-1205, or for those that favor the MLS multi layer style head gaskets, part number TEK-5219-1205, or any TEK kit that has the 1205 part number in it. The first number is the type of head gaskets, and we offer around 5 different head gaskets that will work with the NKB heads. The 1205 is the intake gasket part number, and that is mandatory for use with the sbc NKB heads. Some intake manifolds will sit too low due to their design, and the 1266 extra thick intake gaskets may be required.
These heads are also available in angle plug style, and with steam holes.
A breakdown of the part number.
The NKB stands for "New Kid on the Block"; 200 represents the runner size, 272 designates the use of standard length valves, and single springs with a damper setup for hyd. flat tappet cams. You will also see the heads listed with the number 274. The 274 designates the use of longer valves with dual springs with a damper, setup for hyd. roller cams. We also have the valve train setup for solid roller cams, and will have the number 583 rather than 272 or 274. The heads listed with the letter "A" in the part number are angle plug design. We also offer these heads with steam holes for GM 400 blocks. These will have the letters SH (Steam Holes) in the part number. Be absolutely certain of what you need before buying. Feel free to call us if you need assistance deciding what you need for your build.
See our other listings for these heads with our Competition Series PBM valves.
Our NKB-200 heads have been designed especially for us. 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 youâ€™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 4 years. Many of these engines were dynoed 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.
Recommended accessories for these heads.
Please see our other listings.
Flow chart information.
In the flowchart above, the NKB-200s are superior to the Procomp heads in flow numbers, and also edge out the Dart SHP heads on the intake side. The intake numbers are far more important than the exhaust. The overall average flow numbers on the NKB-200 heads are higher than most any brand of non cnc'd cast aluminum heads on the market. We guarantee the flow numbers to be accurate, as well as the horsepower numbers produced by them.
Most importantly, all three of these heads were tested by the same person, on the same machine, (Superflo bench 1020) using the same testing method, on the same day. These numbers show the true difference between each brand, and that's what counts.
The difference in horsepower and torque generated by these new heads is monumental compared to the 210cc Procomp heads. We offer several different cam choices with our 383, 406 and 421 engines, and every combination has shown an increase of up to 50 horsepower and no less than 40 hp over the Procomp 210cc heads. We assumed the new heads would generate a considerable increase in power, but to our surprise, they generated more power than expected.
We tore down the heads that were on our 383 house engine and checked the guides as this was an area we are most concerned about, and found zero wear. The seats were also in perfect condition. We tested the spring pressure to see how much was lost after a brutal 80 or so dyno passes, and saw approx. 5 lbs of pressure drop on the nose, and even less on the seat, and this is to be expected.
Many of the dyno passes were run to 6500 rpm as the large cam needed 6300-6400 rpm to make peak power, and you must run past this to determine the fall off point. The super sized cam (choice 1) was run on the heads towards the end. Considering the size of this cam, it was very impressive to see zero issues with the heads or hardware. We made a good 25 passes with the big cam trying out different carb sizes, jetting, intake manifolds, timing setting, and adding the Super Sucker plate last.
ONE YEAR WARRANTY, UNLIMITED MILEAGE.
Here is a rundown on the hardware used in these heads and the assembly process.
Comp High Performance Dual Springs, Part Number 987-16
Our Comp springs are 1.43 diameter, with an inner spring and internal damper. Others are using springs that are much smaller in diameter. Smaller diameter springs may be in the correct spring pressure zone, but they usually have a shorter life. Comp springs are made in the USA. All of our engines using the NKB heads use these springs. Spring failures are near non-existent.
COMP CAMS "POSITIVE STOP" VITON VALVE STEM SEALS. # 529-16
We purchase most of our valve train hardware in bulk for our engine program. Below is a copy of one of our invoices from Comp Cams showing several of our rather large purchases of valve train hardware. We have removed the price and our account number for privacy reasons. This is the best way we can prove to our customers that the valve train products we use and sell are genuine Comp Cams products.
IMPORTANT NOTE, MUST READ!
We have noticed several sellers offering these heads with a one size fits all valve springs for dual use on hydraulic flat tappet and hydraulic roller cams.We are sure this is not the proper way to setup the heads.
If they have this one size fits all setup somewhere in the middle spring pressure values of what is required for a hyd. flat tappet and a hyd roller cam, then it would be too much for the hydr. flat tappet cam, and create a wear issue. Putting too much pressure on flat tappet cams is a sure way to kill the cam. If these middle of the road springs were used on a hyd. roller cam, then the spring pressure would be too low. Valve float and its damaging effects, along with a loss of performance, are sure to occur.
We use the correct spring for your setup and it is never the same on a hyd. flat tappet as it would be on a hyd. roller cam. As mentioned above, the spring requirements between a roller cam and flat tappet cam are dramatically different. Even the odd ball solid flat tappet cam has its own unique setup depending on the lift. The one size fits all hardware claims also to work on these cams. We know of several sellers offering this insane setup to unsuspecting buyers, and itâ€™s not the proper way to set up a set of heads. We would not even consider using a spring setup like this, and believe me, the simplicity of it is appealing.
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 NKB heads. We also built and dynoed a 350 engine recently with the new 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 youâ€™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.
Please do understand that 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.
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
Below are our dyno results on one of our engines with a set of our 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.
Cam choice # 1 and a single plane intake.
PART # 180265-10 This is a hyd. roller cam for use in OE roller blocks.
PART # 110265-10 This is a retro hyd. roller cam for use in non-roller blocks.
Valve lift with 1.5 Rockers: Intake .530/Exhaust .545
Duration @.050": Intake .233/Exhaust .241
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.
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
Official Dyno report on our 383 engine with our NKB heads and a single plane intake. Considering the low lift and duration of this cam, the hp numbers are excellent.
This cam and a single plane intake.
Check out the results on the dyno reports below using the NKB heads with one of our new Comp custom ground street rod cams. All of our engines now use the Comp custom ground cams. This cam has a somewhat low lift and duration, and produced amazing hp and torque numbers when using the 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)
See dyno results below.
Special Grind # 33161
PART NUMBER: 08-000-8-11323
110 lobe sep.
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 low 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 low cost 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 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.
Listed below are a few important solutions to preventing valve train issues while having maximum performance and longevity in your engine when running medium to large lift cams.
Head bolt washer recommendation.
Guide plate recommendation.
Stud Girdle recommendation.
NKB-200 64CC 200CC RUNNER SIZE STRAIGHT PLUG FOR SBC CHEVY ENGINES
Intake Valve Dia: 2.02â€
Intake Port volume: 200cc
Intake Port Dim: 2.2â€ x 1.2â€
Int Port Location: Stock
Intake Gasket: Felpro# 1205 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 1205 intake gaskets.
Head Gasket: Felpro# 1003 or our line of GR-30 and GR-40 heads gaskets. Must use head gaskets that are suitable for use with aluminum heads.
Exh Valve Dia.: 1.600â€
Exh Port volume: 70cc
Exhaust Port Dim: 1.356â€ x 1.420â€ w
Exh 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 NKB heads.
Milling: Min. Down to 58.5cc or 64.5 = .060â€ See info in this listing for details on this.
Pistons: Most 23Â°aftermarket pistons.
Push Rod length: When running a hyd. roller cam use 7.250 length. See our other listings for the best deal on premium pushrods.
Push rod Guide Plate: We strongly recommend Dart flat guide plates. See our other listings for many accessories.
Retainers/Locks: Chromoly Steel Retainers, with 10Â° Comp brand machined locks are used on all of our heads.
Spark Plug: Straight, .750â€ reach, gasket, Autolite 3923 or NGK 4544 for one step lower heat range than the Autolite.
Spring Pockets: 1.550â€ OD (.030â€ deeper max)
Springs: Comp 1.43 outer diameter. Dual springs with an internal damper.
Valve Length: 5.015â€ (+.100â€) for hyd. flat tappet cams or + .200 for hyd. roller cams
Valve Stem Dia: .3415â€ - 11/32â€
Valve Train: STD SBC 3/8â€ or 7/16â€ stud mount
Valve Guides: 1/2â€ OD Int = Mag-bronze Exh = Phos-bronze (.002â€ press)
Valve Guide length: 1.950â€
Valve Guide clearance: .0014â€ - .002â€ (with our .3415 dia. valve stem)
Valve Guide Spacing: 1.890â€ moved .030â€ from stock
Valve Seats: Hardened Ductile Iron, .006â€ press
Valve Seat dim. Standard
Valve Seat angles: Int = 32Â° - 45Â° - 60Â° - 70Â° Exh = 37Â° - 45Â° - radius
Stud Girdle: Use any standard girdle. Our Gold Series Stud Girdles work very well on these heads.
Torque: Head Bolts = 65 ft/lb
Rocker Studs = 55 ft/lb
Manifold = 30 ft/lb
Block Use: Any SBC Iron or Aluminum
Weight: 59-61 lbs fully assembled pair.
A final note...
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