thinking of doing DX to SI swap? please read

I have looked and looked on this forum and redpepperracing to find something showing a DX to Si (carb to pgm-fi) swap and the only thing I ever see is people being told: "Dude, you should use the search". Well I did use the search and I still couldn't find any accurate info. So I am posting this for everyone thinking about doing this relatively "common" swap so that you can hear the painstaking labor involved, and how it is going to quickly push me to the brink of insanity! And hopefully some of the experts like lxndr, cvcc and all you other 3G disciples will be as kind and gracious as you've been in the past and answer any questions I have along the way. I am going to thourougly describe this so all the rest of the "noobs" that come along like me can have a 1 stop description of everything involved. Then it can be updated and documented for everyone again!

I figure I am currently about 40% through the transition. I bought an 87 Civic Si and pulled the engine, tranny, stripped the interior and labled and pulled the entire wiring harness. I have the D15A3 disassembled and it is currently at the machine shop where they checked the crank (they said it was perfect), they rebuilt the head, bored out the cylinders at .040 over and are sending it back for me to do the bottom end and gaskets (not a necessary step for a swap, but I decided to rebuild the engine while I had it out and maximize it's power). I also ordered EVERYTHING for this engine so it will essentially be brand new (a/c compressor, water pump, oil pump (comes in rebuild kit) radiator, fuel pump, starter, distributor, stage 2 clutch, flywheel, headers, alternator, cam gear/timing kit, ECU, cold air intake, blah blah...you name it I bought it). I now have my DX up on stands with the hood and fenders off (to protect the paint, once again not a necessary step) and am getting ready to start pulling the D13 carb-o-riffic fuel sipper out and getting the wiring out as well.

A couple of snags so far...the oil pan and gas tank in the Si is dented and I don't trust them, so I thought I would just use the ones off the DX...fine for the gas tank but apparently not the oil pan. I have heard that the Si pan is deeper and the oil lift slightly longer although I have yet to put the 2 side by side to see. So I guess I might have to buy another oil pan. Also, the fuel pump is in the rear of the Si and I haven't really looked at the DX, but not sure how easily that will convert. Maybe some expert advice from one of the advisors on this????? Is there any other components that I need to swap that I've missed???? And is it necessary to swap out the wiring from headlight to taillight or just a specific portion???

So that is where it stands for now, I think I am deliberately procrastinating doing the wire harness swap...not looking forward to that. I am curious to see how much extra HP that engine will have with all the mods. Also, I have a friend that works for a muffler shop and he is going to run a custom dual exhaust once it's ready. DUAL PIPES OUT THE BACK OF A 3G, HOW SWEET WILL THAT BE??? I'll keep updating and any advice from the advisors would be greatly appreciated.

You need to use the Si's tank, or an inline fuel pump capable of handling fuel injection.

The oil pan, iirc, can be used, as long as you use the oil pickup tube that goes with it.

You need to use the Si's tank, or an inline fuel pump capable of handling fuel injection.

Thanks for the reply...that will save me from spending any unnecessary cash on an oil pan. But regarding the fuel system, isn't the fuel tank itself the same in the 3rd gen Dx and Si? I know in the 88-91 Civic the fuel pump is inside the top of the tank on all models, so if was doing any kind of a d16 or ZC swap I know swapping the whole tank is necessary. But since the 87 Si uses an external pump can I just swap fuel lines or just splice the pump into the current fuel lines without the whole tank?

I have never done this swap, but I have a friend that swapped a D16A1 into a sedan. He said the hardest part was swapping the fuel lines. He had a donor car for the fuel lines/pump, but apparently there was an issue with the length and fittings. I'm sorry, I don't know the specifics of his issues.

He also had issues with the wiring and ended up swapping the entire dash and engine harnesses. He had an Integra donor so when he swapped the dash harness he also had to splice in the correct connectors for the gauges and heater.

That's about all I know about this swap, but I'll try to help you however I can.

Everything behind the dash is the same, because I've already swapped the entire interior from the Si over to the Dx, and everything from the cluster to the dash clock had a plug ready to go. But under the hood there are a few differences. I was just hoping that it was possible to only move what is necessary rather than pull out and re-run the whole thing from head to tail. Then again it might be more complicated to try to figure that out. One other question that just came up. Will any PE7 ECU work or does every number have to match?

Any PE7 will work.

You have to swap the tank or use an inline fuel pump that will handle fuel injection. You'll have to swap the lines so they match up and can hold the pressure of the fuel injection system.

Basically, anything remotely related to the intake side of the engine, you'll have to replace... that includes the entire fuel system.

The electrical system, You can either swap the car's harness or rewire the existing harness to accept the FI system... you WILL need to change the wiring in the chassis, as the carb'd model does not have the plugs for the ECU.

So here I am, entering the third month of this thing...but at least I am seeing the light at the end of the tunnel! Got my block and head back from the machine shop. Had the block bored, pistons and crank set and head redone for a total of $757 including parts. I spent another $500 on a stage 3 ceramic 6 puck ACT racing clutch kit, flywheel, high pressure fuel pump, radiator, water pump, upper and lower radiator hoses and a spool of vaccuum line. With the headers and a few other odds and ends I picked up, I am in this thing for about $1500...the custom dual exhaust is gonna be about another $350...so less than 2 grand total. But that is with some major modification, a normal rebuild and swap would probably cost less than $1000. The Si motor is almost completely put back together and the DX engine is ready to come out. It is amazing how many parts are interchangeable between these 2 cars, which comes in handy since I have managed to break a couple of things along the way (turns out the oil pump has 5 bolts, not 4...ha ha). So Tuesday, the plan is to do the actual motor swap and Sunday I have a friend who is an electrical specialist that is pulling up the All-Data and coming over to do all the electrical. Hopefully, I will be driving it by next Monday! I am in the home stretch, and I'll give a final update and maybe a couple pics when this thing is done. I have also come to realize that if you had the time, this swap would probably only take a long weekend (without having any machine work done, about a week or two if you decided to bore it like I did). I have never done anything like this, and it was not beyond my capability. Of course, having a friend who has Master Mechanic status do the wiring is a major plus! My 2 biggest words of advice: 1) you can NEVER label too many things or take too many pictures...put a label on EVERYTHING...and 2) SAVE EVERYTHING...so much is compatible that you can pick and choose the parts you want to re-use (cam gear, pully, front axles, timing gear, oil pan (3/26 OIL PAN WILL BOLT UP, BUT YOU MAY HAVE EXHAUST CLEARANCE ISSUES), starter, alternator (3/26- ALTERNATOR NOT COMPATIBLE WITH Si HARNESS), upper radiator feed are all coming off my DX). I'll hopefully update this with a successful ending in a week or so...keep your fingers crossed for me...

THE NEW ENGINE IS IN!!! It was a tight fit with the new headers and I did minor damage to my header wrap, but nothing that couldn't be resprayed with silicon. I did end up having to buy a new oil pan ($202 from Honda...$63 FROM AUTO ZONE!!!). The Dx pan does line up perfectly, but the shape on the underside is slightly yet CRUCIALLY different for my case. There is about 1/2" more clearance for the exhaust with the Si pan and my headers wouldn't line up with the Dx pan on, (which might not be a problem with a factory exhaust, I'm not sure). The oil pick up tubes are identical though, the one from the Dx being in better shape so I used it. All that is left to do is the wiring and I'm going to mount the new fuel pump on the firewall, which should be happening this Sunday. My biggest fear is having the nicest "paperweight" in SC...let's hope it runs...

Typically a fuel pump will be mounted as close to the fuel tank as possible.

Typically a fuel pump will be mounted as close to the fuel tank as possible.

Is there going to be any repercussions to mounting it on the firewall? Also, found out during the wiring process that the alternator is NOT the same...the Si is a little smaller and has a slightly different plug...had to get a new one...for some reason I remember lxndr telling me that a long time ago, lol...

Well, today was the day I finally turned the key...AND...(anticipation)...***wah wah wah***, it didn't start! It's turning over very slow, even with a brand spankin new battery. I'm thinking that has to do with either everything (bearings, piston rings, etc) being so new and tight -OR- from boring the engine it may require a stronger starter or higher than a 520 CA battery to move everything...anyone have any thoughts on that? On the plus side, I'm getting MAD spark. Compression?...enough to almost suck the finger off my hand and into #1 cylinder through the spark plug hole, so that's good. Oil?...pumping up beautifully and draining through nicely as well. On the possible down side: the timing was set exactly to spec, but it could need some fine tuning on the distributor. On the DEFINITE down side...fuel?...not so much. There seems to be too much air in the line yet and the pump just isn't pulling fuel without the car running to some degree. So I think tomorrow is the day I go get a can of starting fluid to see if it will fire up. If anyone has any thoughts on any of this, feel free to throw down a post!

So, my new fuel pump was bad and I took it back. It was a special order pump, he was quoting me $150-700 for a high pressure pump that he didn't stock. BUT, he gave me an awesome tip that I want to pass on. The early 90's (approx 1991) Ford F-350 has duel fuel tanks. One is an in tank pump, HOWEVER, the other fuel pump is an in-line frame mounted pump. The frame mount pump is 95 psi max (more than twice what a stock Si pump is) and any local auto part store will have PLENTY of them in stock. Plus, I was quoted $227 from Advance for the equivilant aftermarket pump and at the exact same store paid $93 for the Ford pump! This thing is more universal than any of the aftermarket pumps that CLAIM TO BE UNIVERSAL.

I've been having trouble logging in lately, so I haven't been able to update the thread. I got it finished up about a month or so ago. I ended up taking lxndr's advice and moved the fuel pump to the rear by the tank, and was able to reuse the Si regulator and added an aftermarket glass fuel filter. I had to replace a bad oil pan gasket already. Also, I installed a cold air intake and it runs and sounds great! Right now I just have the header bolted into the factory exhaust, so this Wednesday I am having the exhaust done because it is just choking the air flow. I am going to run a single in-duel out muffler and have duel pistol tips on either side of the license plate. I am trying to do some research on mufflers because I really don't want it to sound like that stereotypical Auto Zone "wanna be" import muffler sound, but a nice throaty, less obnoxious sound. I have always been an 8 cylinder guy until this, so I'm not sure what I'm looking for yet. Other than that, I still have some wiring to finish up, the distributor leaks a little oil so I need to put a new o-ring in it, and my water pump is slightly leaking, but that's all that's left. Every day I run it, it wears in more and keeps getting stronger. I am anxious to see where it tops out. Any muffler advice would be appreciated as I need to make that decision in the next couple of days.

mangaflow makes a muffler that is popularly used think you can search youtube for itit to try and hear what it sounds like but i might be wrong i once searched for mufflers for my '85 rex and found the magnaflow but i can rememeber the exact number for the muffler

Thanks for the advice! I also had a friend tell me about Borla and I really like that as well, but as it turned out for me to get the duel exhaust that I was looking for, neither would work well. So we actually ended up putting on a stock Z28 muffler because it was set up with a 1 in 1 out all on a single side, the other out being on the opposite side. It looked perfect, ran incredible, had the low throaty sound from the engine but out the back sounded very poppy like the "cheap" sound I was trying to avoid. So we decided to add a resonator back in and it mellowed out perfectly. I have yet to have the pistol tips welded on, but as soon as I do I'll post some pics.