Bare Casting

SBC CHEVY 327 350, 355 383, 400, 406, 421 ENGINES.

This sale is for one fully assembled set of heads (2 heads).

200cc RUNNERS, 64cc COMBUSTION CHAMBERS.

These heads are available in straight or angle plug style, with and without steam holes.

THE BEST FLOWING, BEST QUALITY SBC ALUMINUM HEADS ON THE MARKET FOR THE MONEY.

Flow Numbers

Below is 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. 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 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.

Springs

Different cam types require different springs and valve lengths. Be sure to pick the correct option.

These heads are not built by Procomp, and have no association with them in any way.

Best "bang for your buck"

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, 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.

Intake Gaskets

The Felpro 1206 is the intake gasket part number is the most common used with these heads Some intake manifolds will set too low due to their design, and the 1266 extra thick intake gaskets may be required. You may also be able to use the Felpro 1205 intake gasket depending on the style of intake used.

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.

Part Number Breakdown

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.

Competition Series PBM valves Available

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 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 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.

Valve covers

These heads can be used with outer perimeter or center bolt valve covers. We offer many types of valve covers .

Recommended Accessories

ONE YEAR WARRANTY, UNLIMITED MILEAGE.

Rocker Arms

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.

Very Important Note About Valve Springs

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 it'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.

Cast from AC4B Alloy

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