Adjustable Cam Gear

This is Nissan Motorsports KA24E adjustable cam gear. The OE KA24E camshaft sprocket has been modified to use a selection of offset bushings from ISKY Racing Cams for adjusting cam timing. The package includes 5 bushings. One is for stock timing, the others advance timing in 2 degrees (natural steel), 4 degrees (copper), 6 degrees (cadium), and 8 degrees (black oxide). This will allow us to dial in the cam to the most optimal setting when it comes time for final assembly. The price is very affordable.

For my new camshaft, Geoff, from Colt Cams, told me the camshaft intake centeline was 105 degrees (+/- 1 degree). I installed it "straight up"...aka Nissan's "fool's proof" method by using the punch marks and gold links on the timing chain. And the camshaft centerline was way off from what Geoff said it should be at....meaning it was not set at 105 degrees when installed "straight up". We used the most retarded bushing in the cam gear kit, and we still could not get it down to 105 centerline degree. Seeing how we could not retard the cam anymore, I used an old trick I learn from Takao when he was explaining to me the rules about motor modification for his racing class. So we decided to advance the cam gear itself up one tooth against the timing chain. So now the timing chain gold link sits one tooth trailing the punch mark on the cam gear. Then we check the cam centerline again with the 0 degree advancement bushing to simulate the stock OEM cam gear. Once we did this, we found that the cam centerline was off by an advance degree of 8 degrees. Luckly the cam kit included a retard bushing (black) for 8 degrees. Using that bushing it brought the cam centerline down to the recommended 105 degrees, the cam now sits clocked correctly in relationship to the crankshaft. According to Colt Cams, this is where this cam will run best. This is what degreeing in the cam means and the adjustable cam gear made this possible.
Nissan Motorsports Parts Store

Colt Cam Tri-Flow Solid Turbo Regrind Camshaft

The camshaft is the personality of the motor. The wrong camshaft will make the car unenjoyable to drive. So I turned to Geoff at Colt Cams in Canada. With his experience, he was able to work with me to do something for the first time ever that he has never done for the KA24E before. He custom machined my KA24E camshaft to meet 3 areas of my application. First, the cam had to be a cross between a stock streetable profile and a full out drag profile for top-end flow, hence calling for Colt's Cam Tri-flow design. Second, the cam's profile had to different from the stock profile to make better use of the solid rocker arm lifters since these lifters don't bleed. And Third, the duration and valve lift need to compliment the CFM flow curves of the newly turbo port and polished head.

The Tri-flow design changes the intake side by staggering the opening times of the two intake lobes, and this causes a change in the system. The principle behind this design is to open the intake valves progressively. By opening the one valve directly across from the spark plug first, this allows the fuel to travel across the chamber at a greater velocity. After the first valve opens, the "secondary" valve opens and then quickly catches up to the first valve so that they both open fully at peak duration and lift to simulate the flow of a race cam. The engine has better vacuum at idle since there is less overlap, throttle response is greatly increased, and turbos’ have noticed less lag and faster spool up time. This design gives me low end torque and top end flow.

The hydralic valves carry too much slack. The hydralic valves bleed off individually at different rates and at different times. So the valve timing will always be different at all times and from cylinder to cylinder. To solve the headache, the solid lifter conversion was done (read below). Since my motor has solid lifters, the camshaft lobes were machined to take advantage of this valve train feature so that the duration and lift are the true specs the motor will see instead of being changed by the slack caused by the stock hydralic rocker arms.

The specifics of the cam's duration and valve lift were decided by reviewing the flow bench charts of my head. Now knowing how my head flows, the final specs can be figured out.

VALVE LIFT:

How much lift should I get in my cam? Well that will depend on your heads' flow characteristics. To choose the correct turbo camshaft, you really need to know how your cylinder heads flow. Reason is if your cylinder head flows "X" amount of air at "Y" lift, choosing a cam that has a lift much greater then "Y" will gain you nothing but extra heat and premature wear of the valve springs. Air flow through a head reaches its maximum flow when the valve opens at its peak position, then starts to drop off as the valve is lifted beyond that peak. Most of this of this will hold true to definition, but with a forced induction motor, valve lift is not as critical since the incoming air is pressurized. So how does this apply to me, well look at the graph chart below at the bottom of this page and look on the right hand side of flow chart data. After my head was ported and polished for forced induction, I was given flow charts to show the new flowing ablilites of my KA24E head. I gave these charts to Geoff to help him produce a cam regrind that will compliment my new heads ablities. Using the stock cam with a ported head could limit the heads true ablities. I will use the Ported and Polish Intake side of the flow chart below as my example. If you look at X-axis, you can see the recorded flow of my head stops at .450 inches of valve lift. Geoff was concerned that even though the recording stop at .450 of an inch, beyond this point, regardless of how small it could be, the head could still possible flow more. So he decided to give the valve lift on the camshaft a bit more lift just incase would flow more beyond this point. A good rule of thumb is to select a cam that will lift the valve 20-25% past its peak flow point. The reasoning behind this is, if you lift the valve only to its peak flow point, then the valve only flows best when it's wide open. The cycle is brief and would only happen once per stroke. So to benefit from you peak flow the most, you want to lift the valve past its peak. That way the valve will pass its peak flow twice in the cycle. The result is more flow during the opening and closing event of the valve. You do not want to raise the valve much past the peak flow though, or you lose total flow by going too high.

Hence the final valve lift specs became to be .477" on the primary intake valve and .468" on the secondary intake valve and exhaust valve. When you convert that over to MM it turns out to be 12.11mm and 11.88mm. Thats huge!

VALVE DURATION:

Duration is critical to a turbo setup since its probably the single most important event of a turbo motor (i.e. time valve sits open and closed). Since the air is being forced instead of drawn into and out of the combustion chamber, duration will be your largest variable on how that incoming/outgoing air is managed.

Duration on most turbo cams that are using a log design turbo manifold, will usually have 6 degrees more intake duration than exhaust duration (ie:226/220).This is know as reverse split duration. This is mainly because a log manifold design will typically see higher then a 2:1 pressure ratio in the exhaust ( as high as 4:1 with some logs). By using a reverse split duration this will somewhat help prevent from getting exhaust gas reversion.

Duration on turbo cams when using an efficient lequal length, individual exhaust runner header design, will usually have matching durations (ie:230/230), or better known as a dual pattern cam. The thinking is with the exhaust backpressure being only 2:1 you can leave the exhaust valve open a little longer than if the exhaust backpressure was 3:1 or higher. Also some of the new turbo designs produce a much lower backpressure with the advent of better flowing turbine wheels and housings which further decrease the total amount of backpressure created by the system.

With that being said, the camshaft with its new Tri-Flow design for better low end torque, decrease in turbo lag and little quicker spool up responce, was ultimately spec'd out at a duration for the:

Primary Intake valve: 220 Degrees @ .050
Secondary Intake valve: 213 Degrees @ .050
Exhaust Duration: 213 degrees @ .050

I have the best of both worlds, reverse split and dual pattern duation all in one camshaft.

Nissan 240SX 12v SOHC Turbo Tri-Flow Solid
Grind Number: C.509.556.S

Rocker Arm Ratio: 1.500:1
Primary Intake Duration: 220 degrees @ .050 (0.477 Lift)
Secondary Intake Duration: 213 degrees @ .050 (0.468 Lift)
Exhaust Duration: 213 degrees @ .050 (0.468 Lift)
Colt Cams

Solid Adjustable Rocker Arm Conversion

With changes to the stock cam profile and machine work to the backside of the valves and valve seats, the geometeric alignment of the valve train has been changed. The stock hydraulic valve lifters and rocker arm lashes will no longer work as a direct OEM bolt on. So I decided to send my hydraulic rocker arms to Gabe at Hybrid KA. Once there, he did the awesome job of converting the stock hydraulic lifters to solid lifters. This coversion offers many pros. Solid lifters can read the camshaft much more accurately which means the valves will get the true duration they are ment to have as they move up and down. Plus with solid lifters, the valves are less prone to valve float. This will give the valve train the ability rev higher to produce more power. Also, the solid lifters are adjustable which allows me to use any cam profile and custom valve train machine work and yet be able to keep the correct alignment of the valve trian without constant machining to individual parts to make everything fit to working order. Hybrid KA

Performance Valve Springs

Finding performance valves springs sure did take some time. But we finally found them. After taking measurements of the install height and physical dimentions of the stock springs and retainers, we were able to find stiffer valve springs. The new springs are the same size as stock spring and work with the factory retainers. They increased the pressure by about 20 lbs over the stock springs for the intake and exhaust sides. This also will help to prevent valve float and also allow the valve train to rev higher. We decided not to get too crazy increasing the valve seat pressure, because it can cause premature wear or damage to the cam. So the decision was made to only replace the outer springs with stiffer ones. The inner springs will remain stock. I took a pair of used stock inner and outer intake and exhaust valve springs and compared them to the Pioneer Outer Springs with brand new stock inner springs. We mashed them down on the spring scale and here are my finding.

------------Intake---------Exhaust
Stock:------132 lbs---------100lbs
Upgrade:---160 lbs---------128lbs

As you can see, it increases pressure on both sides by 28lbs. This gives you a base line for spring pressure differences using the Pioneer outer springs on both sides with stock inners.

Pioneer Inc Automotive Products
Intake Part Number:RV-1034-4
Exhaust Part Number: RV-611-4

I got the specs back from the shop using the Pioneer outer springs with Stock OEM inner springs.

Intall Height ( No Shims)
1.930 Intake
1.820 Exhaust

Install height will change and vary depending how much material is machined from the valve seats. But this was my measurements with a 5 angle valve job.

Open and Closed Pressure with factory shims (0.040)
Intake:
105 lbs @ 1.890 Closed
250 lbs @ 1.440 Open

Exhaust:
105 lbs @ 1.780 Closed
260 lbs @ 1.335 Open

My engine builder said after a few heat cycles and breaking in the motor, most springs lose pressure right off the back. So we upgrades the factory shims to 0.060 shims to get back any pressure we may lose once the motor is broken in. The shim change should add about 10 lbs.

FYI: The KA24E exhaust side can accept any performance L or Z series dual spring, also L or Z series custom retainers. You can also have good results with upgrading the exhaust side only with the l spring. The valve weight/spring rate ratio is more of the problem on the exhaust side. The exhaust valves will always be the first to kiss a piston on the KA SOHC, unless the chain breaks.
Pioneer Auto Inc

SI Valves

I didn't think they existed, but I am glad I have found them. These are stainless steel intake and exhaust valves for the KA24E. They are performance series featuring undercut stem in the head, reducing the valve weight (which provides benefits in opening rate and RPM limits) the radius of the head is such that is significantly improves air/fuel flow. Fully swirl polished. Chromed stems and Stellite tips. I talk to the manager via email. These valves usually run $12.99 per valve, but the manager gave me a discount at $11.50 per valve plus these valves feature a 0.50MM OVERSIZE Head diameter. The valves look awesome when installed in the head.

SI Valves Website

Toga Valve Seals

The stock valve seals were upgraded to the Toga Performance Valve Seals. They are made out of a better material than the stock seals. Import Performanceparts

New Clevite Valve Guides

After disassembling the head, all the stock valves slid out just fine except for the ones in cylinder #3. I am not sure if the valves were slightly bend or if the guides were damaged, either way, I replaced the stock valves with the Stainless Steel SI valves, and the valve guides were replace with new ones from Clevite.

Port and Polish

With all the parts in place, now its time to turn our attention to the head itself. The first thing we did was to clean the head and check it for internal cracks. None were found, so the head was good to go. We did find some strip valve cover threads and one spark plug threading was also strip. These repairs were easily made. Next, I spent many hours researching the best performance shop that could accomplish the best port and polish for my application. Many shops out there claim to do best head work. Few will admit that N/A and Forced Induction applications use different port and polish finishes. After it was all said and done, I finally found the best shop and it turn out to be in my own back yard.

Port Pros is the best cylinder head shop around. They flow bench my head in stock form so that they know where to begin with improvements in terms of better flow. Between every machine stage, they flow bench the head again and again to ensure at the end, the head will flow to its full potential. Since this is for a forced induction application, they will do a port and polish finish specificly for my turbocharger system. They provide me with charts and graphs to show the extent of their work and to validate it. I always dealt with the owner himself, Harold. He treated me on a first name basis. That was a very big plus.

As you can see from the flow charts, the intake and exhaust ports have been improved to flow more air. The exhaust side will end up flowing 15 to 20 CFM more with the turbo manifold due to a vaccum effect that is not featured in s flow bench. Port Pros