[SR20DET Head Parts]
After performing many tests through competing in D1GP, SR20DET Head Systems are now available to extract maximum power at high rpm. Further engine performance can be obtained when using with Step 3 camshaft.
SR20 engines feature a Y shaped rocker arm which is unseen in most other engine types and reducing rocker arm trouble has become the key in SR20 tuning.
■SR Engine - Problems and Solutions
(1) Hydraulic Lash Adjusters
The stock engine uses a hydraulic lash adjusting system which uses oil pressure to press the cam against the rocker arms. This means that there are no tappet clearances to worry about. As the engine ages and wears, the hydraulic system can absorb the increasing tappet clearance and so engine noise is reduced but this is not necessarily a good thing to extract performance on a tuned engine.
When strengthen Valve Springs are combined with continuous high revving, the load from the rocker arms can be too much for the lash adjusters causing the clearances to open too much and cause eventual damage to the engine. In order to prevent this, HKS recommend that the hydraulic system is replaced with mechanical tappets using the HKS Lash killer kit.
(2) Rocker Arm Damage
A lot of problems from SR engines come from the rocker arms. If the rocker arm breaks it can often lead to further problems causing complete engine failure.
Valve float can make a rocker arm come loose and stronger Valve Springs are usually used but this does not completely solve the problem. HKS has developed a spring retainer that prevents shims from falling off the upper part of the valves. This prevents engine damage if the engine should be accidently over revved and the valves float. On the other hand, using high strength double Valve Springs increases pressure and load on the cams and rockers causing other issues.
The black coated rocker arms overcome this issue by reducing friction where it contacts with the cam whilst increasing surface strength.
* To be discontinued
- Head System Step 2 is for those who already installed Step 3 of the Camshaft for Lush Killer.
- Or, for those who already installed Step 1 Camshaft for Lush Adjuster or Step 2 Camshaft.
- Capable Engine RPM: 7000rpm〜8000rpm
- HKS Camshaft: STEP2〜STEP3
The Head System is mainly for HKS Step 2 Camshaft which is high lifted to respond to the engine output increase at high rpm. The camshaft's lift volume was increased to ensure accurate valve movement and reliable durability. (Camshaft is available separately.)
* Kit Parts: Valve Spring (outer), Valve Spring Retainer
* To be discontinued
- Head System Step 3 is for those who plan to use this system with Step 3 Camshaft for Lush Killer to avoid possible troubles.
* Installation of this system may shorten the life of the rocker arm and/or NVCS unit due to high load to these parts.
- Capable Engine RPM: 8000rpm〜9000rpm
- HKS Camshaft: STEP3
The Head System is mainly for HKS Step 3 Camshaft which was designed to achieve higher engine output at high engine rpm for drag races or circuit driving. Lush Killer Kit is included to avoid any trouble that may arise especially at high engine rpm range. (Camshaft is available separately.)
* Kit Parts: Lush Killer Kit, Valve Spring (inner & outer), Valve Spring Retainer, Valve Stem Seal, and Black Coated Rocker Arm
As valve train dynamics change with the use of high performance cam profiles and greater lift, stiffer Valve Springs are needed to optimize valve movement. Combination use of outer springs and inner springs can provide benefit to high revving engines, as the risk of valve-float is greatly reduced.
Black Coated Rocker Arm
HKS Black Coated Rockers Arms have been specially treated to increase strength and durability so no scratching should be found after reassembling camshafts. When using with the upgraded Valve Springs, this rocker arm can avoid damage may be caused by insufficient oil film at high contact surface pressure.
Valve Spring Retainer
HKS Valve Spring Retainers can provide superior security for shims over stock retainers so possible rocker arms trouble can be avoided. This retainer was made from heat-treated chromium molybdenum steel for better abrasion-resistance. Its unique shape can provide a 10% decrease in weight compared to the stock retainer.
HKS Valve Stem Seals are made from fluorine-contained rubber and utilizes redesigned lip's shape. The appropriate amount of oil to lubricate the valve seat at high RPM is provided for the SR20 engine.