DOHC F20B Vtec Head Info

[Ernestox6]

Hey guys, I know I kind of just ghost around here and never really post, so I thought I'd break down my JDM H22A and EDM F20B vtec heads and post up any information that I found that people will find interesting. Some of the stuff is already known, but I'll be including it anyway.

First off: The F20b head is from a 97 accord and the H22a head is from a 94 prelude. Keep in mind that my H22a is the first generation H22, so it may not be relevant when comparing to an H22a4 or H22a7 head. Also, I have read that there are 2 versions of this head; One with Type S internals(manual engine), and one with stock H22a internals(automatic engine). I will let you know which of the 2 I have further down the page.

Secondly: In case no one has caught it yet. This head is NOT the single cam F20b found in early accords. This engine is the factory DOHC Vtec head not found in america. The head is not a direct bolt on to the SOHC F20 and F22 blocks, but using the same methods used in installing an H22 head on an F block, you could install it on your block. In fact, it would even be a BETTER idea to use an F20b head rather than an H22 head because the head matches the 85mm bore of the block, where as the H22 head is 86.5mm(pointless if you go boost though, because it is a fact that the F22a heads flow much better than the H series and F20b heads, so just slap an F22a head on and boost it.)

As stated in several places, the H22 and F22b heads are nearly identical, except for the few things I was able to determine were different aside from the bore size that I already talked about above in the previous paragraph.

1)Although I don't have a picture to show you people as proof, the intake valves are 1mm smaller on the F20b than on the H22 head.

2)While I was taking off the rocker assembly, I decided to measure the intake ports. I found that the PCH-1 Head(f20b) had ~.5m larger ports on average compared to the P13 Head(H22a). Pics:
F20B

H22A


3)Under the rocker assembly I found 2 types of tappets. A low tension spring type and a hydrolic type as shown below. As for which one is better, I'd say the hydrolic one would be better because low tension springs have a tendency to sag over time. However, hydrolic tappets can also fail as well, so if anyone would chip in some input, that would be great. Pic:


4)I didn't take a picture of this, but on the exhaust ports, the head is actually ported to match the OEM exhaust manifold gasket perfectly on the F20b head whereas on the H22a head, the ports are a little smaller than the gasket.

5)The rockers look almost identical, but if you notice, on the H22a rockers, the forging marks are actually a lot wider than they are on the F20b. This is pretty consistent with all the rockers, so I can assume with this that the h22a rockers are actually stronger than the F20b ones because they were forged at a higher pressure. Another thing to note is that one the H22a rockers, there is a little pin sticking out of each side rocker to keep the center rocker in place, whereas the F20b rockers only have 1(shown in pic below)


6)The last thing I was able to measure tonight were the cams. I wrote all the info down, but forgot to take a picture, but I was able to determine that both the H22a and F20b had almost the same lobe sizes(+/-.1mm probably due to wear.) This leads me to believe that I have a head from an automatic version of the engine.

I hope this info helps someone, if I get more pics or find anything else, I'll be sure to put it up here. I'm only posting this on CB7tunner because I thought you guys would benefit most from this info. If you guys have any questions, feel free to write a comment or PM me. One last thing; please don't reply with problems you are currently having with your engine. I don't mean to be mean, but I'm trying to keep this thread clean and easy to read through for the sake of everyone on this board. If you're having issues with you F/H head, feel free to PM me instead, I may be of assistance.

[Jarrett]

To add to some things you weren't sure about, there are indeed two types of H22A head. The P13, which you have, and the PDE head. The PDE head is found on the Euro R, H22A Type-S, H22A7 and '00+ H23A VTEC. What's mostly special about the head are revised valve angles and a factory port and polish job. All I listed but the H23A VTEC also came with what we call Type S cams as well.

To keep my response more on topic to the comparison of the F20B, your pictures are a great resource to have. I've been trying to explain to people forever that the H22A head swap is a horrible choice. I actually have both a H22A and an F20B in my garage that I've been pulling apart. As soon as I can find an F23A bottom end then that F20B head is getting slapped on it.

Most of the information about valve sizing and bore differences are readily available here and elsewhere. There's a thread here in the Performance Tech section that has all of the dimensions of all the F and H engines.

The rocker casting differences aren't necessarily a difference between the F20B and H22A. All of Honda's parts are contracted out to different manufacturers and you can actually find rods that are very different appearing (same dimensions where it's important) from the same year H22As.

Your information is good but I recommend that you read through what is here already so that you don't waste time proving things redundantly. Pictures are always fun, though.

[Ernestox6]

Thanks for the tip man. I assumed that Honda used the same manufacturer for all of their internal parts, but it seems like I was mistaken. All that info on the PDE head I already knew and was actually planning on getting my hands on one, but I just decided to stick with the same bore for my build to play it safe. I can always drop in type S(or even higher) cams down the road along with a port and polish If need be.