F23a1 with A6 head

[Thormx353]

Hey guys I'm looking to buy a 93 CB on Friday and just would like some insight on the set up. It's a freshly built f23a1 (all oem parts) with h23 intake manifold, a6 head, and p12 ecu. I've done my fair share of searching the last couple days and haven't been able to come up with much for this combination. I have an 07 Si that I'm putting in the garage and no longer DD'ing (starting to get up there in mods) and I'm really just looking for something with some get up and go around town and reliability. Now I may plan on boosting down the road but that will be awhile, especially because the k20 isn't boosted yet. I'm really just looking for some insight, maybe even some things to look for and ask about when I go and see the car. Appreciate your help.

[deevergote]

There's a thread talking about this exact combination about 6 threads down... and the same reasons why that engine is a bad idea would apply to this.

[Tippey764]

That .01 liter is not worth the effort.

[Jarrett]

I disagree with the typical hybrid consensus in the case of this swap. This is actually a combination I like. The 97mm stroke lends itself to being a perfect highway cruiser in 5th gear while also being able to squeeze off some decent torque numbers when air flow is improved. Using the F22A head allows better cam and intake options and in this case the intake has been done. So I'd say that this has met those considerations and should be a pretty decent performer.

In the case of that car, though, I would buy a PT6 and wire up the IABs so that they are functional on the H23A1 intake manifold. If the F22A6 head it has came with the cam as well them it's what that engine needs to perform "optimally". As optimally as it can given that you've increased displacement.

If you're wanting to boost then do so knowing that the cast F23A1 pistons are just as susceptible to breaking ring lands as any other cast Honda piston. It may last for a while, but eventually it's going to give.

If you want to delve further into my reason as to why I like this combination so much then I'll tell you. Cam duration in an interference engine (most Honda engines, for example) is limited by the stroke of the engine. The piston inside of an engine with an increased stroke will travel away from TDC much faster if it is to complete the same rotation as that of an engine with a shorter stroke at a given rpm. This allows you a little more flexibility with camshaft duration as you've increased the window of time that you have to keep valves open. Of course, what I neglected to say is that they return to TDC on the upswing much faster also. An adjustable camshaft gear can solve this issue by moving the camshaft actuation to favor the time when the piston is moving down in the cylinder even more so.

The OEM gives us a couple blessings here. The 4B camshaft found in the F22A3/7 and F22B5/8 has considerably more duration than the 4A cam in the F22A6. Not to mention, the ECUs that come with those applicable F22A3/7s will also be tuned for 9.8:1 compression. A figure that you could easily be at with a resurface. Are these parts feasible to achieve? Not really. But it could be done and be a capable performer that would drive like stock.

[deevergote]

I'm still not a fan of the different bore sizes. That can be a recipe for disaster, especially with boost.

[Accord problems]

I'm sorry Jarrett i would half to agree with deev and for once with tippey764 . this is not a good idea . i have read about these hybrids and if they do have success they don't last long . from what i read they don't have much success .

[Jarrett]

The bore size issue is not really an issue when the head is what's smaller. Have you seen the underside of the LS2 head? There's plenty of flat surface that extends over the bore. It creates a quench effect on otherwise inefficient pistons. To describe it crudely, the angles of the ridges that extend over the bore are much more obtuse than the effective 90-degree angle of the cylinder walls when the head is larger.

You know how strongly I support the same opinion as you do on the H22A headswap theory. This is just not the same, in my opinion. Once a PT3 head has been applied to this block it's essentially the same thing as someone boring out their F22A/B and putting 86mm pistons in it.

And unlike most other hybrids that I argue against, the oil drainage ports and coolant ports match up. The coolant holes in the gasket aren't the same size in all places but if you know what he underside of a cylinder head looks like you know this doesn't matter.

Accord Problems, you said something without really even saying anything. I know Deev's stance on this issue as it is 90% shared by me. However, I don't know yours and I'd like something a little more technical than what you "half to" agree with.

I am going to try this weekend to remove the head on my spare F23A1 and I'll do a picture comparison of both headgaskets on the block.

The same attitude I take on other hybrids still applies here to the extent that if you have to ask 1000 very basic questions then you have no business trying to pull something like this off. In the case of the OP, it's in a vehicle that's already got it done and running. Assuming timing components were transferred from an F22A as well as the water neck and thermostat housing then this thing should be good. Talking with the guy who built it could tell you a lot, though.

[SOHC-FTW]

They're all sorts of weird shaped combustion chambers on heads and all piston's/bores are pretty much a perfect circle (Give or take a very tiny amount). As jarrett said it's not really an issue i see with said swap or even vise versa for that matter.

[Thormx353]

Thanks for the input so far. From my reading it seems as if the only issue here was the different bore sizes between the block and head, and with that reading came no really concrete answers but rather "theories" and pretty pictures people made on Microsoft paint. The guy is a mechanic and is into the scene a bit, so assuming he knows what he is doing and assuming the motor is healthy like he claims it is, there really shouldn't be any issues here. Correct? He mentioned another ECU he is going to give me but didn't specify what is was. This is a completely new car and engine to me so I'm just trying to go into this with as much knowledge as possible. I will ask about the IAB's. Are the disadvantages of not having it hooked up that significant?

[wildBill83]

If the IAB is gutted there is no reason to hook it up.

My opinion is that once you get into someone elses project, you had better keep in touch with them.

There may be things that necessitated the swap and can confuse a regular tech.

Also don't expect a repair shop to want to touch anything custom, so be prepared to do your own labor from here on out.

[Thormx353]

I've done my own labor since my first car when I was 16 (I'm lucky enough to have a lift.) Aside from Honda replacing my 3rd gear in my Si when I first bought it, all work has been done by yours truly. Even built a 420a eclipse from the ground up myself. I wouldn't trust any mechanic around here anyway since most of them only believe in v8's and classic rock. Anyway everything looks clean done well from the pictures he sent me but we'll see for sure when I go and see it in person. As far as the IAB is concerned; If it's gutted leave it alone, if it's not gutted I should hook it up?

[Jarrett]

Yes, hook it up. It's a bit of work but too much airflow is effecting your torque numbers down low. That's really the whole point of having that bottom end. If they are hooked up and running properly they should open up the secondary runners around 3900 rpm.

[deevergote]

Is the engine already assembled?
If not... I would personally stick to a full F23A1. Especially if you're boosting it. The F22A head does have a reputation for being able to outflow most other Honda heads when modified... but in stock form, the F23A1 likely flows better. With boost, it matters very little which flows better. Either one will allow far more power than you'll ever need on the street... especially if you want a reliable daily driver!

If this was to be a fun project that you're willing to break and stuff into your garage every other month while you fix it, I'd say go ahead... but you're buying someone else's project, planning on doing MORE custom stuff to it... and expecting reliability? These cars can take a lot before they give out, but honestly, that's just asking for trouble.

You seem to be fairly competent mechanically, which is good... but don't go into this expecting it to be a flawless project. Chances are VERY good that it will break on you a few times.

If you want it to be reliable, keep things as simple as possible.

[wildBill83]

Also, is the current owner a mechanic?

I noticed you posted the motor was freshly built. Does this mean bottom end? Or he just slapped bolt ons on it? Did he use OEM internals or aftermarket anything?

If he did rebuild the bottom end, did he have a shop do it? If not how well do you trust the average shade tree mechanic to build the heart of the car?

[deevergote]

I had professional mechanics do my H22 swap back in 2003 (before CB7tuner... when everyone on every forum in existence said "it's too hard for you to do yourself!")
These were not only professional mechanics, but professional HONDA mechanics. Former employees of the dealership I currently take my Fit to. They said they had done swaps before, as well.
I dropped off my car, and spent the next two weeks researching the swap in-depth so I could hold their hands and guide them through it step by step (big thanks to Willie from Twisted Imports there... I'd never have been able to do it without him.) After two weeks, I got my car back. It worked, and has continued to work...
However, they didn't bother changing the 9 year old timing belt ("it looked fine", they said.) They ignored my mount instructions, and mounted the transmission using 1 of the 3 studs (they did not tap a new hole, and used the Prelude mount.) They were incapable of hooking up my AC. My IAB system has never been functional (I just learned this... never even thought to look!) Any spliced wires are taped up haphazardly, and any additional wires added seem to be random bits of wire that were sitting around the shop. None of the gauges match.

My point? Even a professional mechanic can do a shitty halfassed job, ESPECIALLY with something custom.

Such an undertaking is bad enough when you do it yourself... but to pick up where someone else left off is scary. Don't pull the registration and insurance on that Si just yet!