1funryd

The block castings between the H and F motors are identical.

The differences will be in the internals like: rod/stroke ratio, pistons, crank and bore size.

The F20b uses an H22 head but with smaller valves, and dome size, as well as higher compression pistons.

It has Type S cams which is why there is a difference in power between the auto F20b(180hp) and the manual(200hp) version is 20hp more.

The three motors that are the same bore and piston sizes are: H22, H23A(vtec Bluetop), H23a1.
The H23 blocks and cranks are the same, the difference is the H23avtec uses H22 pistons, but still uses the same rods, and crank.

1991_crxsi

iTrader: (1)

Good answer, but here are some corrections to that.
H23A has a different pistons from the h22 (same compression but just different design), H23A has a different crank from the H23a1 in that the H23A has 55mm mains and has different counter weights and weighs less overall, the H23A has slightly shorter rods than the H23a1 because the H23A's pistons have the same compression height as the H22's pistons (the H23a1 has a slightly smaller compression height by about .040).

Aradin

Any other input on safe rev limit? I just stuffed a PDE H23A into my Accord. Boosted as well. I've been reading a lot about these and lots of people are taking them to 8k without any issues. I'm a little leery on that since boost will exacerbate the stress on the rods. I was thinking more along the lines of 7500.

ESP.net

Weak point is the Ringlands... ive track'd my motors over the years...so take a lil bit of beaten on within limits... 2 motors I have broken ringlands NA... so boosting stock internals is a gamble... 8-12 lbs always been a rule of thumb with a great tune. Still eventually will give up..rings.. plan for a rebuild ahead of time...

Aradin

Strange. I was having the opposite problem on the F22s I've been running for years. I was chunking rods before having any issues with pistons. Then again I do run an AEM water/meth kit so that probably alleviates a bit of the stress on the pistons from the lower combustion temperatures.

I have no intentions to push this motor very hard simply because I don't want to have to replace it. I'll only be running about 9-10psi on a dinky little T3/T04E 57 trim so it should be alright for a good while. I just don't want to have any issues spinning bearings or anything like that so I think I'm only going to rev to 7500 just for peace of mind.

1991_crxsi

iTrader: (1)

Yup, very true.

backinblue92

iTrader: (1)

I haven't been able to read the whole thread yet, and my h23a research is just beginning so this question may be moot, but the engine will run fine on an obd2 h22 p13 ecu? Obviously tuning is always preferred, but reusing my current ecu would be just fine?

I know there is no factory ecu for the h23a with a manual tranny, or so I've read.

Aradin

Anybody know the valve adjustment specs on these motors? I have the PDE head version so I'm assuming it's probably the same clearances as an H22A4?

1991_crxsi

iTrader: (1)

It is the same.

Aradin

Cool, thanks.

fseriesmotors

i have a h23a1 vtec in a 97 honda prelude 5spd.
compression 215 each cylinder
fuel
air
spark
it will start then when i hit the gas it will bog out and die
the shop has no idea whats wrong

it all began when the blance shaft belt broke
i took it in and they removed the head just to be safe
so they change the timing belt
balance shaft belt
auto tensioner
decked the head
and new head gasket

it will crank and start but dies after ill get maybe 10 feet and then it shuts off and no codes are being thrown i don't get it…
any help would be great!

i would have made my own thread but the site won't let me since i have just registered.

1991_crxsi

iTrader: (1)

I have no idea what is wrong. However, once you make a few posts then you can create your own thread. Just go on GDD and comment on something, then make a detailed thread. GOOD LUCK!

Aradin

What aftermarket fuel rails fit these motors? Or is there an OEM option that would be a better fit for me? I have an H23A w/ a PDE head in my 95 accord. I'm using OBD1 style Precision injectors and they don't fit the greatest with the stock H23 rail since they came with OBD2 style injectors from the factory. I had to use extended studs but the rail still sits at a little bit of a funny angle and doesn't sit completely on the top shoulder/stop of the injectors. My fuel feed line is on the driver side. I was planning to use my stock F22 rail when I did the swap but the mounting points on the intake manifold didn't line up at all. The intake manifold seems to be a little bit different from the USDM H22 stuff from my research.

1991_crxsi

iTrader: (1)

I either used the used the USDM h22 or H23 fuel rail. Whatever combination of parts you use, the 2 key things are to make sure that the injectors are seated properly and that the o rings are sealed. Sometimes just adjusting the size of spacers can fix this. Also, sometimes enlarging the holes on the fuel rail that slide over the posts on the intake manifold can give you a little wiggle room so that you can make sure everything is squared up.

Aradin

It fits fairly well but not up to my particular standards. I did have to extend the spacers with 10mm nuts just to account for the additional length the injectors had versus the stock ones. The intake manifold seems to have the studs at a weird angle to begin with and there are only 2 of them instead of 3 like I've been seeing on USDM stuff. The main thing that concerns me is the 1/8" gap between the shoulder on the injector and the rail itself. I worry that if for some possible reason an o-ring gives out it's going to cause the car to burn to the ground. The AEM and golden eagle fuel rails advertise that they fit all H22/H23 but I'm a little hesitant to buy one since the manifold seems to be an oddball.

1991_crxsi

iTrader: (1)

If I understand what you are talking about, you can swap out the seals as well, and you can adjust the "weird angle" by enlarging the mounting holes on the fuel rail. The fact that there are only 2 post mounts is okay; as long as everything is seated and sealed properly then you are good to go. YOu may have to make custom length spacers which can be made a number of different ways, from grinding down the OEM ones if they are too long, to, cutting a small section of pipe. The manifold is not an "oddball" it is the same exact casting as the USDM. The posts are different, and you can actually remove the posts and swap them out too. There are a quite a few different combinations to get this to work correctly. It just takes a little creativity. In any event, never run your car without the fuel system safely and properly installed. Perhaps you could contact a friend locally that works on cars. It is a pretty simple thing to figure out how to do, but it may require some slight modifications.

Aradin

I'm more than capable of doing it myself. I assemble engines all the time. I was just curious as to what worked for other people and I've been pondering a custom fuel line setup so that aftermarket rail would be beneficial. I had a limited time frame to complete the swap as the car is my daily and this is the only thing that I need to revisit and bring up to my standards. I've seen much worse hacked together crap come rolling through my shop before. I'll take a look at it at some point this week and see if I can get it to fit 100%.

1991_crxsi

iTrader: (1)

You should be able to get it together 100% without it being hacked up with a little time.

ESP.net

To answer the question above. About Fuel Rails... If you have H23AVBT Intake Manifold the injector angles are in a different location and possibly diameter... I believe they use a s2000 type injectors... PDE manifold has IACV in back... for ease of room better to get a normal H22 manifold with it in the front or swap top half plenums.

Its easier to just use a normal H22A intake manifold.

Becareful don't want fuel leaking all over with wrong combo...

Aradin

I got all that sorted out. The IACV being on the back of the plenum is a better fit for my Accord since I have to run a 3 wire to 2 wire adapter anyway. I ended up using USDM studs and spacers off of another H series intake manifold and it fits like stock now.


Another question, I'm thinking about upgrading rods for reliability reasons. Does anyone know if the stock H23A pistons will work with standard F22/H23 eagle rods? I know it will bump compression up a little since they're 141.5mm as opposed to the OEM H23A @ 141mm but I'm fine with that since I'm running water/meth. I also know that they're full floating pin. I see that Eagle lists 2 sets of rods for H22 applications(one for Type S pistons, one for aftermarket pistons) and for all intents and purposes those are close enough, aside from length, to compare. I believe there is a small variation in pin size(.002) between OEM floating pins and the pins that come with aftermarket pistons. I'm assuming here that the H23A floating pins and Type S piston floating pins are the same.

1991_crxsi

iTrader: (1)

The H23 Bluetop OEM rods have been ran over 550WHP... I wouldn't recommend it, but it has been done. I say that to tell you that those rods are very strong. However a couple of internal modifications that might help with reliability is 1) balancing rods pistons and crank and; 2) if you are running a balance shaft eliminator and you regularly race your car then consider getting some bearings with a little more oil clearance since your oil pressure will be higher than originally designed.
To answer your question directly, the short answer is: No, not really.
If you want to upgrade to Eagle rods, then you are going to want to switch pistons. You can modify some things and get them to work, but it is not worth it. There are a few reasons. First, and most importantly is the stock H23A BT piston is less than ideal. The valve reliefs on the exhaust side are too small and need to be fly cut if you run a bigger cam or start messing with anything that affects P2V clearances. Trust me, I found out the hard way. Another reason why is that the compression height on the H22/H23A Bluetop is about .040 taller than the H23A1's pistons. That means that your H22 or H23A Bluetop piston will stick out .040 and thus you need to run a bigger head gasket to accommodate a piston that has poor clearance issues. Furthermore you will be compromising the upper ringlands pushing the piston out of the bore. If you want to run a stock piston with this set-up (Eagle rods or not) you really should consider getting Type S pistons as the valve reliefs are better, and if you have to fly cut, you still have more compression than you would with the Stock BT pistons in the same configuration. As far as the wrist pin situation goes, I have no idea. Anyone else know? Seriously though, I strongly recommend against using the OEM BT pistons for anything other than a stock set-up. If you can wait a few days I can take a pic to show you where the exhaust valves collide with the pistons... I have even seen some marks on pistons with stock cams. At first I thought is was due to valve guide wear, but nope... it is due to the design. To be fair though Honda intended that engine never rev past 6700, I was at 8000 on a stock longblock beating the hell out if it in the 1/4 mile. Good luck.

Aradin

Thanks for the info. I'm not sure which direction I'm going with it yet. I actually ended up with a junk H23A that a friend of mine destroyed from a bad tune. I tore it down and compared the rods to some stock F22 rods I had laying around and the H23A rods were actually not as wide as the F22 rods just under the pin area and about 1" thereafter which was alarming since the last 2 F22 setups I had spit out rods in the high 300whp range. Less material doesn't mean less strength but they just don't look particularly beefy to me so I was concerned that with the extra RPM and added load from boost that it may be too much for them. I'm only revving to 7200 though and likely making less than 350whp @ 10.5psi. I don't really feel like opening it up so here's hoping it lives for awhile.

1991_crxsi

iTrader: (1)

I hear you. That H23A 550 WHP stock longblock was ran on PURE methanol. If I was boosting, me personally, I would either run it stock since they are only like $1000, or re-sleeve and do it right with forged pistons as well. That being said, if I am not mistaken, I think that ESP has built a few with a simple combination of parts, turboed in that power range or greater. Hopefully he chimes in since he has been successful with his engine combination. I think he was running type s pistons, aftermarket H23 rods, and a thicker headgasket... but I'm not sure. It was pretty basic though if I remember correctly.

ESP.net

I wouldn't worry so much about how much material is up top on wrist pin area. Your bigger worry is the rod bolts going. H23VBT has like a s2000 rod bolt from what I understand. Unlike a press in h22 one. H23VBT bolt seems to be a stronger way from what I hear. Your biggest worry will be the ringlands and rings. Like I have said I have busted them even NA. 220 compression down to 180 and still be able to run 13.4 in the 1/4 in a crx. 217 whp 175 trq. Never got her fully dialed in NA. Car still ran decent and still pulled.

If your asking to use the H23AV pistons on a build with a F22/H23A1 rod yes your pistons will stick out of the hole 20k. The wrist pin location to top is same as H22. The H23AVBT rod is about 20k shorter to compensate with the H23AVBT piston to be in hole like OEM. Yes I do think the H23AVBT rods are possibly lil stronger then the H23A1/F22 stockers.

Would I put money or time on a rebuild of stocker parts especially stock pistons new or old and hope to get under 12 psi for somewhat of a lengthy time. Probably not. I know it takes money... but I build my motors for boost. Its a huge gamble... if you don't

Your talking easily of bore/honing... engine rebuild parts... to use stock oem parts probably $800-$1000.

Best thing you can do would be to start over... call around to some engine importers for the H23AV Blue Top find a place that will either send you a video or compression results and all are up and up on compression... then go from there on hoping 10-12 psi on a great tune and tuner. Longblocks are as cheap as $750-$1100. Higher end will be HMO. It is were I got my last one. But there legit. I did get my first NA H23AV from tiger japanese. Was a gamble and paid off. I also purchased for customer to do swap in crx H23AV again from tiger and worked out well too. Made 218 n 175 trq. All were PDE.

Yes all turbo builds have done with the H23AVBT I have used an off shelf H22 9-1 compression piston with a H23A1/F22 rod and have the piston sticking out of the hole 20k. 20k is not a lot. But will need to compensate with correct P2V headgasket thickness. I use 60k thick cometic mls. Overall compression is 9.6-1 at this point. Longer rod is a better idea. I don't think its worth the extra money to go with a custom shorter rod or the better route. I also not sure about moving wristpin with a custom piston is better either.

I have no worries of the setup with piston sticking out of the whole lasting and working with whatever boost and hp you want out of it.... should make no difference tiny bit out of hole or in hole.

Aradin

I already have a good H23A in my car. I've been running a little over 10psi for a couple of months now with no issues. I picked it up from an importer a few hours away in August.

What I was saying was I ended up with another H23A that came out of my friends car. That's how I ended up comparing the rods.

I know all about the compression and P2V issues. I've done the math and research. I wanted to know specifically if the shelf H23/F22 eagles were compatible with the OEM floating pins on the blue top pistons. That was all. I can't seem to find any info about their compatibility. I tend to think they're not immediately compatible because eagle makes a specific rod for H22 applications that is only compatible with Type S pistons, and not aftermarket ones. Leading me to believe that the OEM pins on the H23A & Type S pistons differ from pins used with aftermarket pistons. According to the info on the rods, they are identical except on the small end. The rods for use with the Type S pistons are .005 smaller on the small end, with a .002 smaller pin bore.

Either way it's a bit irrelevant to me now because I've decided against doing anything to it. Thanks for posting the info though.