ESP.net

4.5K is what I run my forged pistons p2w which is fine till probably 600+whp... not my first engine built.

1991_crxsi

iTrader: (1)

Thought I would share a pic of the P2V interference that killed 2 of my H23A BTs.


I crudely measured where it was hitting and it was about .5mm outside the pocket. I think maybe Honda originally intended to use smaller exhaust valves when they designed the piston... Who knows really.

snobordboy

Wow, did you skip timing at high rpm on that one?

When I clayed my engine, it was very close on the exhaust side, those valve pockets have very little room for forgiveness. That said, I had my exhaust cam gear slip, and it still didn't hit like that, but I had V2V contact on all 16.

1991_crxsi

iTrader: (1)

Nope, neither of my engines skipped timing. I had Pro1s in one and DDTECH customs in the other. Both had stock bottom ends, both of them hit slightly outside of the pocket, and both of them were spun to 8000-8300 RPM. Supposedly the P2V was checked and the cams were degreed in when the DDTECHS were installed, but as you can see something went wrong. Same result as when the Sk2s were installed without checking P2V. However, the Pro1 engine blew for an entirely different reason (my fault)... but there was still pretty bad contact. I'm sure failure was inevitable with the Pro1s installed as they were. With the DDTECHS My guess is that the installer did not account for valve guide play... although my guides on both heads seem fine. Even still, there is always a little bit of play there that should be inspected. I should really have had the reliefs fly-cut just a tad on these engines when going to larger aftermarket cams. Engine lasted less than 1000 miles after cams installed. It is like that on all 4 pistons, with no contact marks on the intake side.

snobordboy

Hmm, decked head or block, or thinner head gasket?

I ask because my engine was a frank H23, with H23A1 crank and rods, and H22A pistons, and Pro1 cams as well, so it should have had .020 less clearance from the start.

I didn't have P2V contact like that, and I ran to 8500 all the time. When I lost a timing tensioner, I was at low rpm though, so I may have had minor contact, as it was down compression after that.

When I clayed, I tried to spin it over without a head gasket, and the exhaust valves were hitting, but the added clearance from the head gasket allowed to it to move fine, and when I did all of the measurements, I did end up with a pretty wide window at .030 or higher gap. Granted, I did have brand new valves and guides in the head as well.

1991_crxsi

iTrader: (1)

Not decked, stock head gasket thickness on both engines. Ahh, you were running H22 pistons. They have the same compression but are designed differently. As long as you ran a head gasket that would put the head at stock distance relative to the piston then you would be in better shape than the stock H23A is regarding the P2V clearance. That is why you didn't end up like me. The H23A BT pistons have different valve reliefs, different skirt, and different dome design. I don't know why Honda didn't just use the H22 piston since the compression ratio and compression height are the same... Perhaps they intended on using a smaller exhaust vale like the F20 Blue top? That is my theory anyway. Realistically, at the stock 6700 rpm (i think that is what it is) with the stock cams and valve train, there would be no reason to worry about interference even with the exhaust valve reliefs being wierd. On both of my H23a BTs I had P2V outside the pockets. It was difficult to measure, and so I cannot be sure how accurate it was, but it looked to me that they hit approx .5mm outside.

ON ANOTHER NOTE:

Does anyone have a good H23a BT crankshaft they want to sell?

Aradin

If I had to guess I would say they designed the different style of piston for strength because of the longer stroke. The H23A blue top pistons have strutted skirts which is a common practice with most aftermarket forged pistons but not with OEM Honda stuff. Longer stroke = more side load on the pistons so the strutted designed was utilized to mitigate wear on the skirts and/or potential out of round issues. With all the tech that went into these engines, it seems like Honda really wanted them to perform within their specifications well and be very reliable. Even going above and beyond by using a light crank(which is even lighter than an F20B crank..), rod bolts, etc to ensure everything was good.

As for the valve reliefs, it could just be Honda engineers doing a dumb thing but I doubt it. The valve reliefs are fine with the stock cams and stock rev limit. Adding higher lift/duration cams and increasing the rev limit is just not a good idea in these motors unfortunately. It's just one of those things.

I like these engines but I've sort of learned my lesson about them in stock form. If you want to beat on these or push them too far outside their limits they won't last. However if you put a better set of pistons and some stronger rods in them they would be very potent since they make gobs of torque and carry power very well. I enjoyed mine will it lasted. Car was insanely quick for such a low amount of boost. Really showed me what's possible with a good flowing engine compared to the single cams I was so used to. Car was faster on 9-10psi than the same F22 setup on 16-17psi.

I'm gonna be building a stroked F20B with an F23 crank and all forged stuff here soon. I'm thinking it's going to remind me a lot of this engine.

1991_crxsi

iTrader: (1)

I like them too, and in NA in stock for they have been good for most folks, even when tuning them and revving them up fairly high. While I'm confident that Honda engineers are certainly smarter than the average bear, they are not above making adjustments in production, especially when changes do not compromise reliability in stock form. The issue I take with the piston design is that the exhaust valve reliefs are not in the right place on the piston and so that leads me to question how could this be. I think even the Domestic guys can appreciate that Honda is awesome at engineering. Here is my guess, which kinda goes along with what you were saying: As long as the stock components are used within stock RPMs there is nothing to worry about even with the valve reliefs where they are. The H22 pistons have their reliefs cut slightly farther from the center of the piston. This makes me think that it is probable that Honda originally designed the piston around the other blue top's smaller exhaust valve size. I think that it is probable that later they decided to go with the larger exhaust valves and did not need to do anything to the piston design since in stock form it was completely safe for its intended use in stock form. The larger exhaust valves are a better fit for this engine, and probably a simple and safe way to get better performance in stock form. It is just a theory, but a fair one. In any event, I'll be getting another one soon. I hope your build situation gets worked out soon. LMK if you need some parts, I have a good bit I could send you for shipping if you need.

Aradin

I was under the impression that the exhaust valves were the same size in all H22/H23A/F20B heads. Only the F20B had a 1mm smaller intake valve. The F22s/H23A1s used the 1mm smaller exhaust valve.

You have to consider also that it's not likely that these engines were pushed to the limit in their original market since they only came in automatic vehicles that had little to no aftermarket support when it came to engine management, etc so it's unlikely that Honda would have even known there was an issue that needed to be resolved by making an adjustment during production. They had a fairly limited run of being in only one generation of vehicle so there wasn't much time for refining. Also it wasn't until a few years after that generation of Accord that people in the US started getting their hands on them. For the longest time there was a huge amount of misinformation about them until people really started digging into them.

Best of luck to you with your next one. Maybe put some Nippon Type-S pistons in it? The additional compression would surely go well with aftermarket cams. The valve reliefs are also in a better spot so maybe that would help with the P2V issues you've been having.

What do you have as far as parts? I believe the only OEM piece I'll be needing is a good F23 crank.

ESP.net

Bingo Bango... Motor was not meant to be rev'd past 6500 rpm in Auto form and probably shifted lower then that... lol Thus it does not have Oil Squirters.

All use same valves... EuroR/TypeS/H23AV/H22A .... All F20B use 1mm SMALLER INTAKE VALVE... possibly same as H23A1

I haven't toyed with the stock pistons in a while... I would imagine may have same valve reliefs as H23A1... The pistons may be from factory deck height 0... H22 is 6k in the hole...bigger valve reliefs...

-------------------- I too need a spare H23V BT mint crankshaft I need to build a bigggggg strokerrrr!!! ------------------------------

There is more to 1991CrxSi story... there is either human error or aftermarket parts issue... I thought someone Setup Cam Gears wrong and thus engine hit? DDtech cams...

New Guides etc... on bigger lift cams is smart... Or they will walk...

O
I
/\

1991_crxsi

iTrader: (1)

Ahhh, thanks guys I was definitely confused and wrong on that. My Honda conspiracy theory has been duly BUSTED. I'll put away my tin foil hat now. I agree that under stock conditions there would never have been a problem.

Yea, I need a crank too so sorry Aradin and ESP. I know a guy selling one that spun a main, I have not inspected it. I don't reuse damaged and repaired cranks in Hondas. If either of you you are interested I could reach out to him.

ESP, I know what you are referring to, and there was a lot of really stupid drama around it from people that weren't even involved. Basically you got the gist. However, that was with a different engine but still and H23A BT. That engine did have Pro1s in it, then had DDTECHS, then spun a bearing because I made a stupid assembly error on the bottom end. Judging by the marks on the pistons it was going to fail soon thereafter anyway. Basically though, with this engine pictured above there really is not more to the story worth mentioning. However, so you are aware these DDTECH cams were installed in the wake of all that drama by a different tuner who is a trusted person sourced from DDTECH. (BTW, I still love my regular tuner... great guy with a strong work ethic who does excellent work generally.) In the end the valves STILL hit in the new engine which only lasted less than 1000 miles. For clarification of any drama DDTECH really tried to do right by me through the whole situation and I have nothing bad to say about him. It was just one of those situations where the unusual and generally unknown condition with the valve reliefs ended in a horrible and expensive disaster for me. Because this situation I always tell people the are putting aftermarket cams in their H23A BTs to check the P2V and either plan on fly cutting or swapping pistons. I thinks that is good advice since both the DDTECHS (installed on 2 different engines by 2 different tuners) and Pro1s hit the pistons in the same fashion. Also, installing new guides with the bigger cams on the H series is a great idea.
Thanks Aradin, That is what I am thinking. I'm probably going to sleeve and run a custom KS Tuned Wiseco with H22 length rods. I'm thinking that I can still get a 3 ring pack with the compression height needed to run the longer rod. As far as parts, I do not have the crank you need. Sorry.

Aradin

If you don't want to run the custom Wisecos you could probably run a DSM stroker piston. It's a common practice on F22 engines with H22 rods. Same geometry applies to the H23A. The pistons have a low compression height and have a few different options. There are asymmetrical skirt styles and full skirt styles. You can get them in 87mm.

1991_crxsi

iTrader: (1)

Thanks! I'll look into that. I'm also seriously considering letting 4Piston build the bottom end for me. Nothing is set in stone as of yet but I have a general idea of what is going to happen. At a minimum I will be running a balanced bottom end with some type of piston upgrade.

ESP.net

I figured this out little bit ago for custom build...

Custom pistons with correct compression height whatever you desire etc is only roughly $100 additional from a Shelf Piston... where ever you want the wrist pin....

Beats a lot of guessing on will it work... will the valve reliefs work etc etc.... for frankenstein 4g63 pistons and K20 etc...

Wiseco and Arias were the cheapest on custom pistons...

Rest are in 800+ range...

If you guys want to post up what setup your trying to do... I can do the math of what piston specs you need... PM me on that...


--- You guys may just see a fairly large 2.7L motor H23VBT motor from me here... sooner then later ------------

1991_crxsi

iTrader: (1)

Thanks for the help. And, that 2.7 would be interesting. Random question: Didn't you have that red turbo H CRX? Still have it?

ESP.net

Yes had the H23VBT Turbo Crx. Nope sold it few years ago. Kid from Texas offered me a price I couldn't refuse. He babys it.

I have this now and couple other cars... DC2 H23VBT Turbo 15 psi 500 hp 373 trq. Pump and Meth injected. PS and Cruise Control

1991_crxsi

iTrader: (1)

Looks like fun a fun street car.

ESP.net

If anyone needs a ESP 4-2-1 Header that makes poWA one in the threads on here on personal car. Looking to downsize goodie stash. PM.

Aradin

I did finally get my F20B in the car a few weeks ago. Ordered it from JDMNewYork on a Friday and it showed up at my shop the following Tuesday. Definitely an awesome company. Price was verrrrrry cheap. They will be getting my business in the near future when I pick up a manual swap with LSD trans for my stroker build.


I went through it with a fine tooth comb while I had it on the engine stand. Everything was super clean. This engine was actually a lot cleaner and more complete than the H23A I had previously that I paid much more for AND had to take a road trip to go get. So overall I was pleased. VTEC solenoid screen was 100% clean, whoever had the engine prior to me took very good care of it and it doesn't appear to have been abused. Oil was changed regularly with no trash in the pan or filter. Even had the OEM plugs in it with very little wear. I'm gonna guess it only has about 40k miles on it. The importer even went as far as putting some ATF in the engine to keep it from seizing while it sat for 10+ years.


As far as comparing it to the H23A, I can see the difference in torque it makes in the fuel maps and curves in Neptune but honestly for street driving it isn't really noticeable at all. Having a turbo setup that starts spooling under 3k rpm really helps pull the car around town. I've only done a few pulls for tuning purposes and on varying boost levels it feels just as quick as the H23A did, but again, I can see the difference in power it makes in the fuel maps. Overall the F20B wanted about ~10-15% less fuel in any given high load to cell to maintain the same AFR that the H23A had but when you think about that it makes sense considering the F20B is 15% smaller. So theoretically I could get the same power adding 15% boost which isn't much. 10psi -> 11.5psi, no big deal at all. The F20B seems to carry power a little better into the higher rpms as it keeps a flatter fuel curve up to 7400 instead of dropping off hard around 7200 like the H23A did.

Another thing to note is that the rods on the F20B look beefier than the H23A rods. Assuming they're both made from the same materials and manufacturing process I'm going to hazard a fairly safe guess and say the F20B rods are a bit stronger. 1.) They're under much less stress in the first place because of engine geometry. 2.)The front and rear outside edges of the I on the rods are thicker and wider than the H23A rods. 3.) The F20B rods appear to have more material around the rod cap. 4.) and finally the size of the beam is consistent from the rod cap up to the pin whereas I mentioned previously in this thread that the H23A rod got thinner around the pin area, presumably to save weight.


With all that said, I'm satisfied with it for what it is. Places are basically giving them away for the price they are currently and they are very potent engines especially with boost added to them. The only complaint I have is that they seem to use the old style hydraulic LMAs which I've noticed are pretty noisy and annoying. They will definitely be getting replaced with the newer spring style when I put valve springs and seals in the head that will go on my stroker engine.


Speaking of that, I'm still not 100% sure on what crank I'm going to use. I'm considering taking the H23A crank to a machine shop and seeing if they will check it/repair it, polish and balance it for less than the cost of an F23 crank. If so, I'll likely go that route instead and use an H22 rod with a .020 over DSM piston to get better overall engine geometry but still add some displacement. I've also found that I can actually use a certain eagle B series long rod with a DSM piston with the stock F20B crank and maintain a 1.60:1 R/S ratio which would be better for high rpm stuff. Not sure what direction I'm going to go but I'm looking into both builds. Still leaning towards the stroker.

1991_crxsi

iTrader: (1)

I'm glad you are up and running again! The F20B is a great engine, and from what people say, they are a good platform for boost. As far as the stroker thing goes, if you stay boosted, you will probably be happy either way so I would suggest making reliability the priority. From what Kaizenspeed said, they make the same power on boosted set-ups with various strokes. What matters to them is where and when you need the power. Sometimes because of tire size, trans configuration, and track length, a shorter stroke makes sense. Remember if you are drag racing then you are shifting at higher RPMS so even if you make power later with a shorter stroke, you are shifting at higher RPMS once you are out of first so it sort-of balances out. Whatever choice you make, I'm sure it will be the right one.
BTW thanks on the heads up about JDM New York! Maybe I'll give them a call next time.

Aradin

Thanks man. Reliability will definitely be the first thing on my list. I really never want to have to build another engine for the car. So I'm going to build something that can handle 500+hp and only run it around 400hp. I've already got it pretty much laid out I just need my bank account to recover from everything that's been going on and I'll slowly start ordering parts a little at a time.

Really the car will likely never see a drag strip. It never has because I'm really not super interested in going fast in a straight line. It's fun briefly but my days of street racing and hot rodding around town are done. What I really enjoy are sweeping backroads/touge kind of stuff so I've been building the car in that direction for awhile. The stroker build is likely the direction I will go. I believe it'll be better to have a wider torque curve and more power at any given RPM. I want the car to be "done" in the next year or two so that I can make it down to the Tail of the Dragon in NC to put it to the test.


Also, if you or anyone else is looking for H23A blue top parts I have some for sale. I have a PDE head in good condition with about 50k miles on it(no cams or sensors), I have a complete OEM H series oil cooler with waterpipe/etc, 3 H23A blue top rods that are like new and a bunch of other misc stuff I'm trying to get out of my shop so I can start funding the new build.

ESP.net

F20B are good motors... but I personally wouldn't downsize displacement... No matter on power... your down big time on torque... its like turbo'ing b16 and hoping for same torque and power as a 2.0LS Vtec... never happen... H23AV motor great motor for torque lol same psi 15 psi SC6176e dynapack 473 whp 373 trq. My latest build 475 whp 373 trq t46266 15 psi. Torque is a pretty big jump over a 90.7/h22 stroke.. I will always likeyyyy....

bottomedout

Hey guys I've got one of these H23A vtec blue tops. While it's ridiculously fast compared to the d16's I'm used to. I seem to have managed to blow some main bearings. I crudely replaced them mains and have been driving it for a couple days now with no issues so far. Anyone know why that would of happened.

Aradin

Yeah. Torque makes it fun. I'll be doing a stroker build. Just not sure which crank I'm going to use yet.
That's pretty much what happened to my engine. Had 2 main bearings squeeze themselves out the side of the journals and the debris appeared to clog up the rod oiling hole on the #4 rod which caused it to let go. It was an otherwise healthy, low mileage engine. I'm wondering if Honda didn't clearance some of these motors correctly. You should pull your VTEC solenoid and check the screen for debris before it ends up elsewhere in the engine.

bottomedout

Aradin, did you fix yours or just scrap it. I was able to change out all the main bearings without pulling the crank. I've been babying it ever since. Seems to be good. But my ecu has a tune on it and I fear someone cranked the redline up to 8500+rpm. Can this engine handle that kind of redline with vtec. Is it worth rebuilding this engine.