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19 Posts
Discussion Starter · #1 · (Edited)
Heya guys,

Thought itd be fun to document and share my Prelude build since usually people swap H22s or H23s in, instead of my planned K24A3.

The car:
My Prelude is a 5th gen base model built in 2000. It currently has an F20A4 engine (SOHC, no VTEC, 133bhp). And is my daily driver currently. It currently has about 220k miles on it and has no rust issues beleive it or not. Currently i already swapped out the headlights for angel eyes, and put Koni Yellow struts with Ground Control springs on her. The color is Crystal Blue metallic.

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The Engine

I bought a K24A3 from someone from Belgium who needed money to buy himself another car. The engine came mostly disassembled, with some new parts in boxes like ACL racebearings and new seals. The engine is the EU equivalent of the K24A2 with only minor differences. Stock the engine should produce 200bhp, is DOHC and has I-VTEC.
So far, i`ve taken everything apart and redid the valve seals and cleaned and reseated the valves. I also took the head to a machine shop to have the mating surface with the block leveled out (It was really bad according to the guy who did it). I also did some painting as you`ll see in the pictures below.
When taking this engine apart, apperantly it had a blown head gasket, and coolant had leaked onto one of the pistons

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The engine how i bought it. Not shown is the boxes of parts.

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The engine block fully disassembled

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Painted the oil pan, fuel rail, an engine mount, and air intake

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Previous owner had carefully engraved a honey comb structure into the valve cover. So i went with yellow as the color i wanted it to be. Spark plug cover is loosely mounted here just to see what it would look like.

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Used ducttape to plug the holes and threads before taking it to someone to be sandblasted. I dont have a picture of it, but i did paint the engine in silver.

So thats the progress up untill now. I`ll keep updating this post as i progress. For now, im gonna try and find a machine shop who can hone the cylinder walls for me, and thouroughly clean it so theres no sandblast grit left anywhere.

Questions i still have:
The previous owner supplied K20A3 camshafts aswell as the K24A3 camshafts. He said he wanted to combine the camshafts and use one K20 cam and one K24 cam since one of the camshafts of the K20 is more aggressive than the K24 (cant remember if it was exhaust or intake cam). Is this a feasable combination?

Update 1: 01-02-2022

I forgot to take pictures, but i took my block to the machine shop to have it honed. Unfortunetly this means i have to repaint the block since the paint got removed due to the chemicals used to clean. No big deal though.
I also got around to measuring the crankshaft, and crankshaft bearing clearance. To measure the crankshaft bearing clearance i used green plastiguage. Before doing so i found out i was missing all the outer bolts for the crankshaft girdle. They are 8x35mm, except for 4 bolts, for which i`ll be using 8x50mm bolts. The clearance came out to be 0.038mm on all points. According to my manual, this is within spec, so i wont have to get different bearings or a new crankshaft. I havent measured crankshaft end play yet since the engine came disassembled. But since i`ll be using new thrust washers, im convident enough to put them in place, put in the crankshaft together with honda bond and bolt everything to spec, and then measure crankshaft end play.

So next thing up the list is bolting down the crankshaft for the final time, and measuring crankshaft end play. If that checks out, i`ll have to go buy some new piston rings, and start on measuring the piston bearing clearance, aswell as installing the pistons. I will be going turbo later so i`ll be using the OEM pistons as they have low enough compression. I dont need a ton of power so i`ll be fine using the OEM.

19 Posts
Discussion Starter · #3 ·
Update 2: 03-05-2022
Hey all! Im back with another update! Things have been a little slow. Havent had much time or money to spend on the K24. This time though i have some pictures and some shiny stuff i want to show! So first things first! In the last update i left you guys with mounting the crankshaft for the final time, and measuring the piston bearing clearnces aswell as crankshaft end play. In short, they measured perfectly fine. I used standard sized ACL racebearings that i got with the engine. Also the thrustwashers that i got measured up aswell, and everything works out fine. Again, i didnt go with super tight the clearances since im not looking to get a ton of power out of the engine, and i`d like it to be somewhat reliable. So the crankshaft is mounted up, and the cradle bolted down together with Hondabond.

The old pistons were probably good, but i wanted to make sure so i bought new DNJ piston rings to make sure everything was good since i had my engine block honed. It would suck if my piston rings ended up leaking because i didnt replace them. So out with the old, in with the new as ChrisFix usually says. However, while i was busy replacing the rings on the pistons,i noticed one of the pistons had a piece chipped out of it:
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So i stared at it in disbelief, cried, and went and looked up some new pistons. Luckily i found DNJ pistons that were standard size, aswell as same compression as the OEM ones for a good price. So i ordered those, and oh boy... shiny stuff always looks soo good.
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After looking and drooling at the new shiny pistons, i went and installed the piston rings, and transfered the piston rods. The set came with new piston wrists and clips as you can see the in picture above, so why not use them?
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Obviously before i installed the piston rings on the new pistons, i measured the ring gaps to make sure there were no issues there. Since they are also standard sized, there were no issues at all and i didnt even need to gap them. All gaps were within factory spec. Now i could`ve gotten new piston rods aswell, but as i said, im not looking to get a ton of power out of this engine. Yes ì`ll be going turbo down the road, but even then, i probably end up going low boost anyway. Plus new rods would`ve added 7-800 euro`s to the costs, and the old ones still look good.

Since i dont own a ring compressor to get the pistons in, i had to borrow one from a ex co-worker to get the job done. It was a bit of a pain at first since i didnt have a hang of how the ring compressor worked best, and ended up having one of the rings not compressed far enough. This meant i couldnt get the piston in, had to take it out, recompress the whole thing, and retry. In the end, i got it and got all 4 pistons in.
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I have to say, it looks sooo good. Bit of a shame i cant turn the crankshaft by hand anymore, but oh well...

So, pistons are in, and now it was time to put on the piston rod bearing caps, torque them down to specs, and give them an extra turn. After that i installed a K20 baffle plate that was supplied with my engine. Once that was installed, i got to modifying the K20A oil pump that was also supplied with my engine. For those of you who dont know, the K20A oil pump wont mount up without cutting away some bits and pieces. If you`re doing this yourself, it will be very clear what you need to cut away in order to make it fit. Be carefull around the parts where the bolt threads are. You do need those, and if you cut away too much, you`ll have to buy another pump.
After that, i wanted to fit my oil pump chain. It became very clear that the K24 oil pump chain DOES NOT fit on the K20 oil pump. I mean, it fits the teeth of the gears, but the chain is too short. So i have to save up to buy a K20 oil pump chain, and guide in order to fit this oil pump.

So whats next? Well.. after the K20 oil pump chain and guide, i have to get the bolts for the oil pump, bolt it down, and then mount the oil pan. For the top end, im still struggling to get the valves leak free. I test them under no pressure by pouring some water into the intake and exhaust ports. I know i should probably test them under pressure, but if they leak under next to no pressure already...Even after lapping them, they still leak. So i might just save up for a K20A2 head to put on it and go from there. They do cost a bit though, so it will probably take a little bit if i do end up going this route. Another thing i can do is just take my K24A3 head to a machine shop and have them do the work for me. Though it might not be worth doing so because i had the machine shop resurface the head. They told me it was really bad and they had to shave away quite some metal from the mounting surface (where it bolts up to the engine block). If you have any idea`s on whats best to do in this situation, let me know. Valves look good,and arent bent. No pitting. Same for the surface on the head where the valves seal.
Anyway, be on the look out for a new update!

19 Posts
Discussion Starter · #5 ·
Update 3: 30-06-2022
So in update 2 i mentioned i finally installed the pistons back into their homes. I managed to get some missing bolts for my oil pump, K20 oil pump chain, and a K20 oil chain tensioner. They fit awesome. Unfortunately after fitting the oil pump, i checked to see if the crankshaft would still turn (i managed to buy a crankshaft bolt so i can turn it with a wrench). Unfortunately it seized. So i had to take apart the oil pump, baffle plate, and find out what was causing the issue. Turns out, somebody forgot to lube the nr 4 piston connecting rod bearings... So it meant that the bearings had spun. Fortunately the only damage done was the little positioning tang on the bearing being bent. I went and bought some new bearings since i don`t want to bend it back and risk it spinning again due to metal fatigue.
With that out of the way, i bolted the baffle plate and oil pump back onto the block, fitted the oil chain with guide and tensioner, and even mounted up the oil pan.
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So with that done, the bottom end is finally done! Feels like a major milestone has been reached. I still need to bring my cilinderhead over to a revision company to have it checked out. Depending on the costs i might have them fix the leaking valves for me, or junk the cilinderhead and get a K20A2 head. Anyways, thats it for this update. Next update will either be mounting the entire top side, or i might feel like disassembling the transmission and see what needs to be done to that.
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