Ok, so I'm currently getting a set of ZE heads built up for my boost project. Well, I have been searching and reading every post I can find that discusses the valvetrain for the KL03 and the KLZE.. As well, I've been researching the aftermarket companies and what they have to offer in terms of parts. Well, I thought it would be good if there was 1 comprehensive thread that sort of listed all pertinent info pertaining to heads and what should be done in terms of building up a good set...
Of course, there are a few questions.. What kind of heads (ZE or 03) do you want to use?? How much do you want to spend?? What do you want to get out of your heads?? I am going to try to answer all of these questions in an easy to read manner, hopefully making this a good thread for many to start with... Preferably this can be made a sticky...
Lets start with the head similarities and differences.
1. 03 Heads have the same size HLAs, valvelocks, retainers, and springs, for both the intake and exhaust side.
2. ZE heads have larger stuff on the intake side. The HLAs are 1mm bigger. The springs and retainers are also bigger on the intake as well. The exhaust valvetrain is the SAME as KL03.
3. The valvelocks are the SAME for all heads, intake and exhaust. This is because all KL valves whether intake or exhaust, ZE or 03, have a standard 6mm stem.
4. Intake valves are larger than the exhaust valves, but, they are the SAME for KLZEs and KL03s.
5. ZE heads obviously have the larger intake ports, making them so popular.
Now, lets discuss the problems or downsides to each head.
1. KL03 heads have smaller intake ports, hence less flow. This is NOT a BAD thing, but its 1 downside compared to the ZE heads
2. KLZE heads have the bigger intake ports, but are harder to find and will cost you some cash... In the $400 range with cams, sometimes more or less
3. KLZE valve retainers have a tendency to crack and break, causing a valve to drop into the combustion chamber, essentially grenading the engine. This is caused by poor valvetrain design. There are two theories on this. The ZE valve spring pressure is 40lbs seat pressure and 140lbs open pressure. This allows for more valve float at high RPMs, where the ZE makes its power. This eventually causes the retainer to crack. Also, the springs were not manufactured well, and many have a burr that wears at the retainer until it finally cracks. This of course can occur at any RPM.
4. As said above, KLZE valve springs are softer. ZE seat pressure is 40lbs, and open pressure is 140lbs. On an 03, the seat pressure is 50lbs, and the open pressure is 150lbs.
Of course, there are a few questions.. What kind of heads (ZE or 03) do you want to use?? How much do you want to spend?? What do you want to get out of your heads?? I am going to try to answer all of these questions in an easy to read manner, hopefully making this a good thread for many to start with... Preferably this can be made a sticky...
Lets start with the head similarities and differences.
1. 03 Heads have the same size HLAs, valvelocks, retainers, and springs, for both the intake and exhaust side.
2. ZE heads have larger stuff on the intake side. The HLAs are 1mm bigger. The springs and retainers are also bigger on the intake as well. The exhaust valvetrain is the SAME as KL03.
3. The valvelocks are the SAME for all heads, intake and exhaust. This is because all KL valves whether intake or exhaust, ZE or 03, have a standard 6mm stem.
4. Intake valves are larger than the exhaust valves, but, they are the SAME for KLZEs and KL03s.
5. ZE heads obviously have the larger intake ports, making them so popular.
Now, lets discuss the problems or downsides to each head.
1. KL03 heads have smaller intake ports, hence less flow. This is NOT a BAD thing, but its 1 downside compared to the ZE heads
2. KLZE heads have the bigger intake ports, but are harder to find and will cost you some cash... In the $400 range with cams, sometimes more or less
3. KLZE valve retainers have a tendency to crack and break, causing a valve to drop into the combustion chamber, essentially grenading the engine. This is caused by poor valvetrain design. There are two theories on this. The ZE valve spring pressure is 40lbs seat pressure and 140lbs open pressure. This allows for more valve float at high RPMs, where the ZE makes its power. This eventually causes the retainer to crack. Also, the springs were not manufactured well, and many have a burr that wears at the retainer until it finally cracks. This of course can occur at any RPM.
4. As said above, KLZE valve springs are softer. ZE seat pressure is 40lbs, and open pressure is 140lbs. On an 03, the seat pressure is 50lbs, and the open pressure is 150lbs.
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