Hello All,

I have been a member of this forum for a while but got out of the honda scene for quite some time. You know, marriage, family, new born, school, work, etc. Anyway, I am back and looking to start venturing on a K24 project on a 2002 Civic ES1 (4 door).

I don't have a horsepower goal in mind but want to get the most on pump and alcohol on a turbo setup. I recently purchased a K24a4 since I am going to take the block apart and do it all over with forged internals. So, there was no sense in getting the K24a2 block.

Now, the A4 block has the A4 head. I have been contemplating on getting the A2 head (TSX) since it produces more airflow and has the 3 lobe vtec system. My question is the following:

Should I really venture into getting the A2 head for what I am planning to do? Is it worth getting the A2 head just because it flows better and has 3 lobe vtec? I am going to be porting out the head, getting new cams, retainers, springs, etc. With that being said, I don't see the reason to really go with an A2 if I am going to take that head apart and rebuild it. Any thoughts?

Again, haven't done this in a while since the B series era so I may be missing some pros/cons to the K series.

 

Ok, here is what I have gathered so far from doing a little reading. From what I understand, a K24A2 head vs K24A4 head stock to stock, you'll see significant changes as far as power numbers is concerned. So, when trying to output the most power based on stock internals, it is wise to swap the k24a4 head for a k24a2 head due to the cam profile and better head airflow.

Now, if you are going to run a turbo setup and plan on changing the internals of both the block and the head, it makes sense to just keep the k24a4 head. If you do a port/polish/valvetrain job to the k24a4, you can expect the same performance as if the same is done to a k24a2 head. In summary, if staying stock and want to gain more performance, then a head swap is the way to go, if building the entire engine from head to bottom, then keeping the k24a4 head instead of swapping it out for a k24a2 head doesn't matter.

That is what I have gathered from my research so far, can someone shine some light on this subject? Am I on the right track?

 

No one has any suggestions? I am also curious to know if I can order parts (internals) for a k20a1/2/3 head to use on a k24a4 head? The reason I ask is because I am having a hard time finding parts specifically for a k24a4 head. Everything seems to be for a k20a1/2/3

 

Still waiting to see if anyone has any thoughts.

 

Bump for a new day, still hoping for advice

 

Ok,

After hours of reading, looks like I am going to search for a K20A2 head instead of using my k24A4 head. Here is why:

The A4 head seems to open up only 1 intake valve per cylinder when not in vtec. When vtec engages, it opens both valves on the intake side. On the K20A2 head, when vtec engages, the valves open on both exhaust and intake side (4 valves). So, the 3 lobe vtec mechanism is definitely a huge factor besides just head flow and the power gains would be a lot more than just 5-10HP. The A2 head will also allow a larger turbo setup to spool faster because of the 3 lobe vtec mechanism (since more air is flowing).

All in all, if porting and completely building a K20A2 head and K24A4 head, the K20A2 head will perform better anyway because of the 3 lobe vtec engaging all of the valves.

 

Hmmm...the A2 head still looks better than the A4 even if porting. After looking at some pictures and reading some info, the A4 head intake ports seem to have a split in the port wall. The A2 head doesn't. This is because since the A4 head is an economic vtec mechanism, one of the valves on the intake side stays closed during non vtec engagement. If that valve is closed, the air has to go somewhere so that it doesn't produce back gases or turbulence. This is why it has a split in the intake port wall so that when the valve is closed at low RPM, the only open valve can receive the air through the wall split of the intake port from the valve that is not receiving any air through the valve. In other words, it becomes a dead end.

On the A2 head, the intake port doesn't have this split in the intake wall that separates the two intake valves because both valves open all of the time. So, the A2 head would still be better with any mod because air flow is directed through two intake valves at all time where as the A4 it only happens when vtec is engaged.