I'm new to this so bare with me. I have a 92 Prelude Si with a H23A1. I'm dropping in a new engine soon and looking for some guidance on building it to gain more horsepower and low end torque.
I'm thinking about putting in Crower stage 3 cams, HKS forged pistons and rods, and higher tension valve springs. If you have any suggestions that would be helpful.

 

Can't run forged pistons unless you run a sleeved block.

You're not going to get the best of both worlds with an NA 4 cylinder, especially a non-vtec engine such as the H23A1. If you go with aggressive cams you will sacrifice low end power and midrange to some extent to gain up top.

A better option would be to swap to a VTEC platform, like the JDM H23A VTEC, and build from there. You can keep streetable low end on the low cam lobes, but high cam can be as aggressive as you want for the most part. Swap to Type-S pistons, Skunk2 Pro 2s and valvetrain, and with the right bolt ons it would be an easy 230whp+ to wheels naturally aspirated. Typically even a standard, stock JDM H23A VTEC will put down 200-210whp to the wheels with fbo and a tune.

 

You cannot make Prelude fast na. Its kinda wasting money - good as for hobby if you dont have better things to do but building H engine is not really worth it

 

If I do a JDM H23A swap how would everything fit when dropping in the engine? Also would I need any add ons because it's vtec and because it's an OBD2 engine going into an OBD1 car?

 

The engine OBD does not matter really and it's easy to convert, especially the JDM engines. JDM OBD2 actually uses an OBD1 oil pump. So you would just use your stock harness, alternator, and distributor. Add a couple wires for VTEC, get some OBD1 injectors for the new engine, get a chipped ECU and tune it.

It's not going to be without changing a few other things like the exhaust which may need work to match up, etc but overall it should be relatively simple and easy as your car is already setup for H series. H23A is a very fun and stout engine. Even just swapping one in stock will wake your Prelude up a fair amount.

You may want to search for info on H22 swaps as the swap will be largely the same. The engines are identical externally. The difference comes with the crankshaft, rods, and pistons. You must have a chipped ECU and tune for the H23A swap though. There is no stock USDM equivalent ECU that will run the H23A reliably. No point in doing the swap and then limiting it's potential by running the wrong ECU.

 

Will do and thanks for the tips!

 

H22A4 - H23 VTEC swap:

or you could also get chipped ecu (+tune).

Remember that your swap engine needs to be rebuilded (new clutch, timing things, seals, gaskets etc) also so its going to cost you more than just the price of the engine!

 

That quote is not applicable as OP has an OBD1 4th gen with an H23A1, not an OBD2 5th gen with an H22A4. Even so I would never recommend running an H23A on an H22A1/4 ecu, regardless of OBD1 or OBD2. .1L of displacement may not seem like a big difference but I have seen the consequences of doing as such in person and it's not pretty.

 

it is if its USDM so electrics wont match

 

Do you know where I could find a good chipped ECU and obd1 injectors?

 

Ha motorsport have ecu stuff

 

If I drop a H23a in will my stock trans be fine?

 

Yep. USDM H23A1 transmission is actually a pretty good match for the JDM H23A as far as gear ratios. I ran that combo for a little while.

 

Is there anything else I would need for this swap? Besides thinking about new pistons all I can think of is a new ECU, new engine mounts, and possibly some exhaust work.

 

As mentioned before, the H23A will need a different exhaust manifold or header, so it is a decent time to do any other exhaust changes you want, 2.5" or more all the way back is good compared to a stock exhaust.
With the FRM sleeves in these engines, I would keep the idea of changing pistons out of your head. Keep that bad boy sealed up withe Honda "reliability fairies" trapped inside!
Even on stock compression, you may see some decent gains with some better cams and a proper tune, and obviously with cams you need to be upgrading the valvesprings and retainers as well. To really take advantage of that, going to a larger throttle body, and port matching the intake manifold is a good upgrade as well.
When tuning this combo, you will probably need to go with larger injectors, and the modern Bosch injectors are excellent. I run ID 1000s on my H engine, and am tuned on Hondata S300.

 

To add to this, the reason I recommend Type-S pistons is because they just drop in with stock rods, provide a slight bump in compression, and the biggest thing is that they have much better valve reliefs than the standard H23A pistons. The stock JDM H23A pistons are a one-off design and the valve reliefs are lacking when used in conjunction with aftermarket cams. Piston to valve contact is common when running big cams, high RPM, and the stock H23A pistons.

With that said, the standard JDM H23A pistons are completely fine for stock cams. The Type-S pistons will only really be needed if OP opts for some aftermarket cams and valvetrain as well.

 

Id get rather Type S pistons with stock cams since I like the reliability of stock cams and those pistons also give performance bump even with stock cams

 

Could you link me to those injectors?

 

Yes, of course the Type-S pistons will be beneficial regardless. I was just saying they're not required if staying with the stock cams.

 

ID1000 Injectors - Injector Dynamics

Those are the ones I run. You may not need so big, I know they make 800s as well.

 

Any ideas for improved throttle response?

 

Lightened flywheel and balance shaft delete/belt removal. Removes about 30lbs of unnecessary rotating mass depending on how light you go with the flywheel. Balance shafts are ~18lbs alone. Really transforms how an H/F will rev and respond to throttle inputs.

 

Didn't notice much difference from lightened flywheel

 

Depends on what weight you go with and if you retained balance shafts or not. Removing balance shafts will make more of a difference than any lightened flywheel since they are about 18lbs for the pair. The stock flywheel is about 21lbs and even if you go with the lightest aftermarket flywheel at 8lbs it's not going to remove as much rotating mass as just cutting the balance shaft belt. Doing both things makes a big difference. I'm sure eliminating all that drag picks up some power too.

 

Any good intakes/ throttle bodies in the low to mid price range?