NKB-200 ULTRA HIGH FLOW STRAIGHT PLUG CYL. HEADS FOR SBC 350, 355, 383 ENGINES.
THE BEST FLOWING, BEST QUALITY SBC ALUMINUM HEAD ON THE MARKET FOR THE MONEY.
This sale is for a bare set of straight plug heads (2 heads).
200cc runner size, 64cc combustion chambers. Uses 2.02 1.60 valve size.
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.
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 "something 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, and 406 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.
Our cylinder heads are made from AC4B alloy and tempered to T6 standards. Details about this alloy are in the lower section of this ad.
Our new 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 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, 406 and 421. Many of these engines were dynoed on our new 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.
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 part number is TEK-1003-1206, or for those that favor the MLS multi layer style head gaskets, part number TEK-5219-1206, or any TEK kit that has the 1206 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 1206 is the intake gasket part number, and that is mandatory for use with the sbc NKB heads. Some intake manifolds will set too low due to their design, and the 1266 extra thick intake gaskets may be required. We also offer all of the premium hardware for these heads in our other listings.
Very Important Note.
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 NKB 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.
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. We have sold over 5000 pair of these heads over the past four years.
List of Standard Alloy Characteristics
Alloy +B4: H16
High strength, small elongation
for general purposes
Pressure resistance, corrosion resistance: good
Mechanical properties: good
Pressure resistance: good
Corrosion resistance: excellent,
lighting components, etc.
aircraft parts, etc.
fuel pump bodies, etc.
Parts for overhead contact lines,
parts for ships,
and lighting components for aircraft
These heads can be used with outer perimeter or center bolt valve covers.
Flow chart information.
our flowchart on several different heads. All tests were performed on a
Superflo 1020 bench by our expert head builder. We stand behind the accuracy of the numbers.
We have noticed many other sellers posting what we consider to be false flow
numbers on the heads they are selling. We find this to be nothing short of
outright fraud. Of course, flow numbers can vary a few points depending on
equipment used and testing methods, but not by 15-25 points.
Notice the low
lift flow numbers produced by our new heads. That is as important as the upper
lift numbers, and it's why these heads produce so much peak power and torque.
We are very impressed with the flow numbers of our new heads.
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 Procomp heads. We offer four different cam
choices for your consideration, and every combination has shown an
increase of up to 50 horsepower and no less than 40 hp when coupled with the
various combos. We assumed the new heads would generate a considerable increase
in power, but to our surprise, they generated even 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.
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 no issues with the heads.
ONE YEAR WARRANTY, UNLIMITED MILEAGE.
The warranty will cover the castings and seats.
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 cid engines in the 10:1 to
11.2:1 compression range. All ran on pump gas. Our Stage 2.2 383
engine ad has a selection of four different cams. I have copied this info from
that ad. 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 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.
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
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 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
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.
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 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 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.
The solution to running a hyd. roller cam of decent size in an engine and avoiding valve float is an easy fix, thanks to the Howards Max Effort lifters and our Comp lightweight springs. The cost is only slightly more than the regular Howards street tie bar lifters, and they are undoubtedly the most stable hyd. roller lifters on the market without going to all out racing hydraulic roller lifters. The Max Efforts are also very quiet. Not sure what rpm range they can remain stable at, but we have pushed many of our sbc engines up to the 6,650 rpm range in order to establish the fall off point of a particular build. We now use these lifters with many of our cam choices. We have tried the Morel tie bar hyd. roller lifters on cams in the 550 and higher lift range in the past and found them highly unstable at around 5800 rpm. Well before audible valve float was evident, the horse power numbers were falling sharply due to valve float. Any cam that's approaching the 550 lift or higher range should not use the Morel street/strip lifters. The Max Efforts were very stable well into the 6500 rpm range and higher. The cam in this add is below the 550 lift range but close enough to the limit that we recommend the Max Effort lifters.
Head bolt washer recommendation.
The NKB-200 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.
See our other listings for many of the items needed to complete your engine build. The correct part number for the head bolts to be used with these heads is 2451-W or ARP-134-3601. If you purchase the top end kit we offer for these heads, the head bolts and washers are included.
Guide plate recommendation.
We strongly recommend the use of the Dart guide plates with these heads, or with any aluminum heads for that matter. These guide plates will allow better rocker tip alignment due to the fact the rocker stud holes in them are oval shaped. We use them on every set of heads we install on our engines, including the Dart Platinum Pro-1's. The rocker tip may end up offset to one side more than is acceptable, and the Dart guide plates allow a decent amount of correction. The variances in stud position to valve guide alignment vary on all brands of heads. The rockers could also contribute to this issue, as the trunnion or rocker body could have variance. By having proper rocker tip alignment, you are distributing the pressure on the valve tip evenly. This not only reduces uneven valve tip wear, but also prevents undue stress on the valve guides in the heads.
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. Our prices on them are the best you will find.
The size that you will most likely need with the NKB heads will be 7.250. 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 7.250 length is the most applicable. 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. If you decide to purchase one of our new Comp reduced base cams, then the pushrod length will increase to approx. 7.300 or possibly 7.350 These new custom grind cams are what we now use in all of our engines.
Stud Girdle recommendation.
If you are running full roller rockers, we recommend tall valve covers, and this can cause the oil that is pumped up into the top of the heads to not be deflected back down onto the valve springs, valve tips and roller rockers. The lack of oil on these parts can lead to not only a lack of lubrication but also to a lack of cooling on these parts. Heat transfers up the valve stem from the combustion chamber. This heat is very high in temp, and may cause serious damage to the valve guides, springs and roller rockers.
The cure for this would be to install a low cost set of stud girdles. Stud girdles increase stability to the rockers' studs, eliminating flex that is may be present to some degree when running cams several sizes over stock, not to mention increased spring pressures over stock. Stud flex robs your engine of power and smooth operation in the upper rpm ranges. As mentioned above, another very important aspect of using stud girdles is that they deflect oil directly back onto the valve springs, valve tips and roller rockers. On a stock engine this is not an issue due to the fact that stock valve covers are very close to the top of the rocker arms
NKB-200 64CC 200CC RUNNER SIZE STRAIGHT WITH STEAM HOLES PLUG FOR SBC CHEVY ENGINES
Intake Valve Dia: 2.02"
Intake Port volume: 200cc
Intake Port Dim: 2.2" x 1.2"
Int 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.
Exh Valve Dia.: 1.600"
Exh Port volume: 70cc
Exhaust Port Dim: 1.356" x 1.420" w
Exh Port Location: Stock location & bolt pattern
Exhaust Gasket: Depends on what type exhaust your 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: Must use extended reach with true head bolt washers or head studs. See our other listings for accessories.
Head Studs: PC-2451-STUDS (12pt)
Manifold: MOST ANY
Milling: Min. Down to 58.5cc or 64.5 = .060" See info in this listing for details on this.
Pistons: Most 23°aftermarket pistons.
Push Rod length: 7.9" (also known as +100) if setup as a hyd. flat tappet. if setup as a hyd. roller 7.2 pushrods. Check this!
Push rod Guide Plate: We strongly recommend Dart flat guide plates. See our other listings for many accessories.
Retainers: Steel 10° Comp brand machined locks are used on all of our heads.
Spark Plug: Straight, .750" reach, gasket, Autolite 3923 or NGK 4554 for one step lower heat range than the Autol.
Spring Pockets: 1.550" OD (.030" deeper max)
Springs: Our Assembly: 1.46 outer diameter. single with a damper for hyd. flat tappet cams. Dual spring for hyd. roller cams.
Valve Length: 5.015" (+.100") for hyd. flat tappet cams or + .200 for hyd. roller cams
Valve Stem Dia: .3415" - 11/32"
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 dim. Standard
Valve Seat angles: Int = 32° - 45° - 60° - 70° Exh = 37° - 45° - radius
Stud Girdle: Use any standard girdle
Torque: Head Bolts = 65 ft/lb
Rocker Studs = 55 ft/lb
Manifold = 35 ft/lb
Block Use: Any SBC Iron or Aluminum
Weight: 59-61 lbs fully assembled pair.
Important installation notice.
As with any new heads, you must do a
mock setup with the heads before bolting them on. This is done by setting the
heads on the engine and using two bolts to hold the heads in place. This will
allow you to check your pushrod clearance, and verify that your rocker studs
are all in line. In rare instances, if your pushrods are touching any surface
of the heads, you will have to dremel these spots for clearance. We have seen
this situation with many aftermarket heads, including Dart. There are areas of
the casting that are very close to interfering with pushrods, and it will only
take seconds to correct, but you certainly don't want to have completely bolted
the heads on and find this out. We received a large order of Dart heads that
had an interference issue with the pushrods, and as mentioned, it only takes
seconds to correct this with a dremel tool, but not if you have secured all 34
head bolts. You cannot correct such issues with the heads on the engine due to
the risk of contamination of the rest of the engine. See our other listings for
items you may need to complete your engine build.
IMPORTANT NOTE CONCERNING ROCKER ARM STUDS.
If you have been a regular shopper with us, you will have noticed
we do offer some knock-off products that are made off-shore. We do also sell
many products made in the USA. We have always been very particular as to
the quality and workmanship of such products, while considering the cost. We
scrutinize our products very carefully and refuse to sell products that
simply don't meet our standards. We have
now eliminated another of the low cost knock-off products from our line.
The low cost imported rocker arm studs have shown numerous problems unlike
those in the past. We have looked at several others on the market, and still
find many issues with them that are not acceptable.
The most serious issues included the fact that many of the studs
had run-out in the shaft up to 150 thous. This caused major problems with
rocker alignment, and depending where the position was when the stud tightened,
would determine the direction of the misalignment. If the stud position was
facing the valve, then the roller tip would not run off to the side of the
rocker but it would cause the roller tip not to be centered on the valve. This
would then create a loss of lift.
However, another issue concerned us most of all. The warped
stud shaft of some of these studs would allow the rocker tip to be cocked
on the valve tip depending on the position it was tightened at. This would then
side load the valve tip with undue pressure creating a serious wear problem on
the valve tip and valve guides in the heads. This also side loaded the rocker
trunion and front roller creating an excessive wear issue in the roller
We also found the difference in the tread pitch and depth to
be dramatic compared to the ARP studs. The rocker studs in an engine are under
a tremendous upwards pull and improper thread design may cause the studs to
pull out of the head. The ARP studs screw into the heads with a very precise fit
After thoroughly comparing the ARP studs and several off shore
models, I am convinced that we will never offer them again regardless of the
price difference. They were never as bad in the past as to what we're
seeing now. This run-out was most likely caused by improper heat treating
We are glad to offer many of the low cost items that are
off-shore, but will always give careful consideration to quality,
functionality, and overall value. We will not sell imported after-market rocker
studs going forward.
You will notice that we offer many US-made products, but we may not
offer those same items in off-shore lines. It certainly is not because we don't
have access to the low cost off-shore product, but because of quality issues that
we have discovered. We have rejected
many products that are outright junk and would cause serious issues in your
engine only to see other sellers offering those same exact products. It's all
about learning where to draw the line. We are aware of only one other rocker
arm stud besides ARP on the market of decent quality, and that's from the GM
Performance division, and it's fair to say they are most likely supplied to GM
by ARP under private label.
Stud Girdle recommendation.
If you are running full roller rockers, we recommend tall valve
covers, and this can cause the oil that is pumped up into the top of the heads
to not be deflected back down onto the valve springs, valve tips and roller
rockers. The lack of oil on these parts can lead to not only a lack of
lubrication but also to a lack of cooling on these parts. Heat transfers up the
valve stem from the combustion chamber. This heat is very high in temp, and may
cause serious damage to the valve guides, springs and roller rockers.
The cure for this would be to install a low cost set of stud
girdles. Stud girdles increase stability to the rockers' studs, eliminating
flex that is may be present to some degree when running cams several sizes over
stock, not to mention increased spring pressures over stock. Stud flex robs
your engine of power and smooth operation in the upper rpm ranges. As mentioned
above, another very important aspect of using stud girdles is that they deflect
oil directly back onto the valve springs, valve tips and roller rockers. On a
stock engine this is not an issue due to the fact that stock valve covers are
very close to the top of the rocker arms.
If you have ever removed the valve covers on an engine while it is
running you would notice that the oil sprays up out of the back side of the
rockers and goes in all directions. The most important reason that oil is
brought up into the top of the engine is for lubrication and just as importantly,
to cool the valve train components. The oil temp does have a great cooling
effect, as its temp is only around 215 deg. and the heat that is transferring
up into the valves and springs is far greater than this. If oil were not flushed
onto these parts, lack of lubrication would be just one problem. Valve guides
and stems that are heated up to high temps, and also lack the proper
lubrication may experience excessive wear. We suspect that these parts may be stressed
due to the oil not being redirected back onto them, and stud girdles would
positively protect these parts to a great degree.
We now use them on every engine we build regardless of the degree
of cam and spring pressure. Those running cams that are above 460 lift should use
stud girdles, since this is about the level that stud flex may come in,
especially when running the smaller 3/8's rocker studs. Excessive valve guide
wear along with other valve train components can be very expensive to
A final note...
Our user id is: skipwhite, and our
store name is whiteperformance1. You may have noticed other sellers using
a similar name offering similar products. These other sellers have capitalized
on our name, and many customers searching for us will inadvertently find them,
thinking we are one in the same company. There is only one "Skip White."
We are the original premier seller under this name since approximately
2002. We have no other names, nor are we associated with any other company
regardless of the similarity in the name or location. Our official company name
is Skip White Performance.
We are not responsible for collateral damage caused by the use of this product.