garagelu

S13 and S14 head differences: I believe the most significant difference between the two is the design of the intake manifolds. I believe the difference is going to be the most significant change if any in horsepower and torque. The s14 IM has significantly longer runners and a notably larger plenum.







Another difference that correlates to the IM is the fact that the s13 is a high port head and the s14 is a low port head. This difference affects the angle the air and fuel enters the chamber. I also want to point out the fact that the s14 ports have a significantly improved casting compared to the s13 ports. I want to state that I am only basing this observation on what is in front of me. I know castings, depending on how tight quality control is, can vary quite a bit.

PLEASE READ: A while ago when I was thinking about doing this swap, I was scouring the forums for more information on this swap. I kept seeing a lot of misinformed posts. One misconception was something about a VTC hole on the head. The only difference between the surface that mates to the block is one hole and that is a oil hole for the timing chain tensioner. On the s13 there is only one hole for oil pressure. On the s14 it looks like one hole is for pressure and the other is for lubrication. Other than that every hole lines up just as it would on the s13 head.

I also want to note how much more user friendly the s14 head and manifold is. Especially the coolant hose routing under the manifold was so much better in my opinion on the s14. In my situation, I am going to run a ¾ inch coolant hose from the lower coolant neck to the coolant port on the firewall. The other line goes from the firewall to the port on the intake manifold. Two other things that clean up the coolant hose routing is on the s14 there are no coolant lines running through the IACV and on the s14 the turbo coolant line doesn’t go behind the head. It routes from the upper coolant neck to the turbo.




Initially I had thought that the IACV differences were going to pose a problem. On the s13 IACV there is only one plug where the s14 one has two separate plugs. Upon closer inspection they just integrate the two sensors/solenoids into one plug. Luckily my friend that I bought all this stuff from pulled two plugs off some random Nissan harness that worked with the s14 IACV. In this situation, you have two choices. My first and recommended choice is to solder the plugs onto the s13 harness. Your second choice is to swap the sensor/solenoid over to the s14 IACV body. Also there are some differences between the two IACV which is the fact that the s13 IACV has coolant in and out lines but the s14 one doesn’t. The s13 IACV has a port that pulls air from the coldpipe but the s14 pulls air through a hardline on the IM.



Another problem I have run into is differences between the s13 and s14 throttle body. The s13 throttle pulley design does not allow me to use it. This poses a problem in my comparison. The s14 butterfly is 2 inches compared to the 2.5 inch butterfly on the s13. This .5 inch difference will definitely cause a skew in the results. I might have to just run with it unless someone can find me a s14 NA throttle body or donate one to me.





And finally this is what my kitchen looks like right now....


I will be updating with more information on this swap. Right now I am waiting on my valve spring compresssor to change over everything on my s13 head over. After that I can shine a light through my glass table and get good lighting for an in the port picture. And following, my head will be sent to the machine shop for decking and solvent washing.

So now to give some data behind this head swap, I will be taking this up to my original tuner hopefully and get it dynoed tuned. My setup is almost exactly the same from last year when I tuned. The things I changed on the car should not affect my hp or torque number much. Here is just a brief list of things I have changed: upgraded from evc 5 to evc 6, changed my blitz downpipe to a XS engineering downpipe, replaced my cracked exhaust manifold with a dc sports one. Hopefully this will give me some hard evidence on which head is better. I know there are many variables that can affect it but I will take them into consideration.