View Full Version : 84 Prelude Auto to Manual

02-05-2019, 06:34 PM
I recently bought an 83 prelude parts car with a manual transmission in it. The motor and transmission have about 130k miles on it. I pulled the motor last weekend and realized there are a few differences between the 83 and 84. One of the differences was the engine code, the '84 being a et2 and the 83 an es1, 2, or 3. Looking through engine parts, the only differences I could see were either in the intake manifold gasket or the exhaust manifold gasket. I'm wondering if the transmission will bolt up to the et2 block. I think it will, but I would like to confirm it here.

The 84 prelude has 50k miles on it. I'm torn on if I should see this project to the end, or just leave it untouched.

My possible plans are rebuilding the es1 motor, and installing a weber carb, or only swap the transmission in there.


02-08-2019, 10:45 AM
Trans should be the same... The carb ones have smaller axles and flyweel/clutch. Way back when I was broke and crazy I swapped the larger diff into my carb trans and ground down the housing to fit 2.0 axles and flywheel.
Although, that said, I know 84+ is the same, 83 did have some oddities but I believe you should be fine. I've only ever seen an 83 one time, long ago. The 83 is CVCC, you are not going to want that head.

02-08-2019, 04:00 PM
I've decided to stick with the motor in the '84. I will probably start working on this project again next week starting with taking the glass out. Then I have to get rid of the parts car so I have room to work.

05-12-2019, 10:58 AM
Here's an update after a few months. I got the transmission rebuilt, and repainted the shift linkage, brackets, pedal assembly, etc. I don't have much pictures. Mostly I've been gathering parts and now I can get going with the project. This weekend I started removing the automatic and ended up getting stuck on the converter plate bolts. I will get that part figured out though.

The only thing I'm not so sure about is the speed sensor and how to re-route the power steering lines. The manual speed sensor has two lines going into it, while the automatic speed sensor has two lines similar to the manual sensor, but just one more larger line. I can't upload a picture of it for some reason though. I know some people bypass that system by looping the lines together, but that won't help with the third line hanging around.



05-17-2019, 08:06 AM
Isn't the larger line just a vent?

05-18-2019, 02:47 PM
The larger line actually refills the reservoir after reading about it. There is a pump in the speed sensor that reduces steering assist as you gain speed, so I'm thinking the two smaller lines recirculate or reduce pressure somewhere else in the system.

That being said I'll try out using the automatic speed sensor since the one that came off the manual transmission doesn't even have a third line.

The guy who sold me that parts car gave me a shop manual for an '83. Even the speed sensor shown there has 3 lines, so I'm starting to think that speed sensor never belonged to that car anyways. He was having issues with the power steering system's reservoir cap blowing off.

05-18-2019, 06:17 PM
Mine only has 2 lines on the manual trans. I 5 speed swapped it at the end of last year. Maybe it's a Prelude thing but the auto speed sensor that came off my accord only has 2 lines as well and from what I've read are not interchangeable.
As far as I can tell, the assist reduction is done in the sensor. My evidence is that I swapped the lines by mistake recently when I had to fix my clutch. It would give me no assist at a stop but full on assist at higher speed. Doing 70 and barely touching the wheel was an adventure.
Are you talking about the post right in the center of the sensor? Cause that's where the speedometer cable goes..

05-19-2019, 10:33 AM

Whenever I take a picture of the speed sensor in my car it will not upload on this site.

I did take a picture of what it looks like in the shop manual, and its the same.

Yes, in the picture attached before is the hole for the cable.

05-19-2019, 01:45 PM
I've never seen one with three lines like that. Funky.

05-25-2019, 11:49 AM
Well got all the bolts out of the crank today. Then I looked at my parts and the clutch pilot bearing fits on the transmissions output shaft, but does not go into the flywheel. Grr... The ID on my flywheel is 0.750... and not 1.260 like the bearing OD. Was wondering if anyone has dealt with this before. I may just make a bushing out of bronze or some other soft metal and send it.

Also working on searching around too.


After searching these cars do not use pilot bearings. They use bushings. I found a part number on NAPA that matches the OD and ID that I need, so no need to turn one. yay.

06-02-2019, 11:18 AM
Project is dead. '83 transmission does not bolt up to an '84 block.

I seriously doubt i will be able to find a transmission for an ET2 block.

06-02-2019, 01:42 PM
Why not have an adapter plate fabbed up?

06-02-2019, 04:36 PM
I'd really prefer that to be the last resort. But yes, it is possible. I would definitely outsource that job though.

06-02-2019, 09:21 PM
What about using the 84 bellhousing on the 83 gearbox?

06-03-2019, 03:10 PM
Its possible, its just a matter of getting my hands on one. Out of all the yards I called, no one has a transmission. Might have to go farther than my local ones. I did see a motor on ebay but I asked the seller some questions and he hasn't gotten back to me. May be a riskier option there. I'll keep hunting locally.

My other option is taking this non-running car with the right transmission, but I don't want to take on another parts car.

I'm sure one will come up eventually.

06-05-2019, 06:10 PM
Have you used Car-Part.com--Used Auto Parts Market (http://www.car-part.com) to search all the junkyards around your area.

06-06-2019, 04:49 PM
OOF. There's literally a local junkyard that I did not call that popped up on that list from car-part.com. The three junkyards within 15 miles to me just throw these cars away...

I already ordered a JDM engine and transmission and it should be here next week. I shouldn't have to rebuild this one...

It would have probably came out to the same price if I just got a transmission from a junkyard. Oh well.

06-06-2019, 06:05 PM
Same with yards around here. Hilltop, which is a big Honda/Acura yard, doesn't even have any older than 1990.

06-15-2019, 06:52 PM
Good news, the motor and transmission I bought a week ago were in good condition. The transmission bolted up and everything is mounted correctly. I'm going to be turning some bushings for the shift fork where the linkage bolts on tomorrow. The rest that's left to do for this swap is to install the pedal assembly, wiring the reverse lights, and neutral safety switch.

Then putting the car back together will be fun : )

06-19-2019, 07:01 PM
The car is mostly all put back together. The automatic driver side axle does not seal up at the transmission. I took the seal off of the old automatic and noticed the ID was smaller than the ID on the manual seal. Now I have to wait around for another CV axle... The first one I ordered months ago didn't even pivot around so I returned it.

Guess this project will be done next week.

06-28-2019, 01:15 PM
Ok well I'm almost done, but now I've got more problems in the way.

First, the starter is not engaging with the flywheel. I'll have to pull it out and see if its popping out, and if it does I'm big time screwed.

Next, the reverse lights are always on, even if the switch is plugged in. At least I got the wiring for the starter correct... maybe. I didn't have access to a multimeter to do further troubleshooting than that.

What I did for the wiring was solder the thick black wires, and the green wires together. This connector was at the automatic shifter.

Its always something isn't it...

06-28-2019, 03:13 PM
There are two wires right next each other in the plug. A yellow and green/black stripe. If your looking at the connector on the side the wires come out, they are the 2nd and 3rd on the bottom row going left to right. Pull those two out and separate them. Everything else gets bound together. Those two are the wires for the reverse lights.
I did the same thing when I swapped mine, reverse lights stayed on.

06-28-2019, 03:20 PM
This is what mine looks like. My reverse light dont work because I have those two wire separated and just never got around to wiring them to the switch on the trans lol

06-29-2019, 09:58 PM
Is there a special MT starter for those like there is for the Accord?

06-30-2019, 09:32 AM
All the bolt patterns are the same, and part numbers on 2 of the starters I have are the same. I will have time to work on this car by Thursday, or I can try to work some time in during the days before that.

06-30-2019, 10:30 AM
All the bolt patterns are the same, and part numbers on 2 of the starters I have are the same.

You might want to double check that. There is a "Mitsuba" and a "Denso" starter. There's a much longer snout on the one. Get the MT starter and you'll probably be good.

07-04-2019, 06:01 PM
I did some measurements on all the starters this morning, which are both for the automatic and manual. They all have the same length "snout." And on top of that, the starter should reach the flywheel when the solenoid activates since the distance from the case to the flywheel was 1.125" (approx). The total length from the starters flange to the tip of the gear is 1.5"-1.6" when activated. I tested the starter out of the car, and it works fine. The wire that activates the solenoid is also hot on starting, so everything is working.

So my real problem is the flywheel from the '83. Its smaller, and the part number for the flywheel on the '84 is different. After taking off the flywheel on the '84 motor I bought, I have a hunch the diameter is larger. It looks a lot different.

What I'm saying is I gotta take everything apart again.


07-04-2019, 06:42 PM
Been there done that

07-11-2019, 10:21 AM
I got the car all put back together a few days ago. Everything works so far. I've got two problems now though. The car had a high idle before doing this swap, and now its even worse, obviously since there isn't a heavy torque converter on there. All 500 vacuum lines are plugged in, so now I have to diagnose this CV cluster fuck. Its too bad the car doesnt get out of reverse at 2500 RPMs... Stay tuned.

07-17-2019, 08:58 AM
Ok, got the idle fixed. All I really had to do was adjust the throttle cable, throttle stopper, and the accelerator petal. The main issue was the pedal. I adjusted it the wrong way. And now the car is great to drive now.

One vacuum line was unplugged in a place that I couldn't see.

I do have a small vacuum leak in a certain area, so I'm going to start replacing some lines later. They are about 35 years old anyways.

08-21-2019, 10:31 AM
Some quick updates:

I've been thinking about ditching the keihin carburetor and going to a mikuni instead. I've been thinking about getting this one here: https://www.amazon.com/Mikuni-RS-Carburetor-RS38-D19-38mm/dp/B00HXJD9QS (EDIT: not a good choice)

Any better options? I've read through a few threads and seen videos with this kind of setup.

Also, I have coilovers on the way from ceika. My current shocks are not that great.

04-15-2020, 02:56 PM
A few months ago I had to move the car out of my garage for an insulation job. Something snapped and my clutch was constantly engaged. Basically I installed a throwout bearing that was too short and it snapped behind the pressure plate.

I didn't work on it for awhile since I had a garage to finish building. I recently did a complete emissions delete and the car has been running better and idles consistently. Also the transmission is rebuilt with a proper throwout bearing installed.


I will leave more info on this in a different post.

04-17-2020, 08:11 PM
Sounds like you're keeping busy. Good work.

05-01-2020, 03:13 PM
So far I haven't ran into any issues with this vacuum delete these past weeks so I will share what I did now. This is the diagram for my carburetor, and it does not have components for AC. I have three of these carburetors, and none of them are the same. I can't guarantee this will work for a different variation.


Everything will be going except for thermo-valve A, the auto choke, the vacuum tank labeled A, and the intake air control diaphragm. The hardest part for me at least was removing the egr tubing since it hadn't been taken off since 1984. The main air jet solenoid valve and inner vent solenoid valve is plugged off, but remains to keep the airbox sealed.

When the emission stuff is removed, the first thing I did was plug off the egr with a plate. As for the new holes in the exhaust and intake manifold I bought some plugs, but I didn't find anything for the larger thread, so a custom bolt was made from the original.

Now remove "air vent cut-off solenoid valve" from the carb. I was able to do this without removing the carbs. Then take the solenoid apart and remove the plunger inside. Doing this will allow the float bowls to constantly vent into the charcoal canister. Plug the smaller hole pictured. Reinstall the solenoid.


Now its time to route new vacuum lines:

-Distributor gets vacuum on both ports
-Power valves get constant vacuum

-Vacuum canister gets constant vacuum, but it will need a check valve so the vents dont flap around at higher rpms

-Line 8 for the intake air control diaphragm needs constant vacuum.

-Route the lines as shown for the auto choke and thermo-valve. This one is a little hard to explain with the diagram.


-Loop lines 22, 23, 24, 25, and plug line 11. These ports have something to do with the air jet controller.


-Take the base of the airbox off and plug off everything except components related to the intake air control diaphragm. Taking this off will also help out while dealing with the power valves.

-Plug off anything from here on out. It would basically be a vacuum leak at this point.

This should cover the basics for the job.

05-01-2020, 04:40 PM
Other news on what I'm doing with this car:

The spare "ES" jdm motor that I got actually turns out to be an ES2 with a CVCC head. Great. Unfortunately I can't use that with a vacuum deleted 2 barrel carb. Good news is I don't have to fix the spark plug threads the last owner screwed up. Its a shame too since after I tore the whole thing apart everything was clean and in really good shape internally. The water jackets were... gross and the water pump was filled with corrosion and rust chunks. No coolant was found in the oil but I won't know the condition of the block until its all cleared out.


On the hunt for a non cvcc head... guess its time to call the junkyards monday morning.

05-01-2020, 07:46 PM
Good work on the vac delete. Best of luck with the head.

05-08-2020, 03:21 PM
Well my mystery JDM motor surprises me every day... I managed to get a used head for an ET2 motor and it does not bolt on because of the oil feed hole is in a different location. The head off the JDM motor has the same head gasket as an A18 which is going to be different from an ET2 block. What a headache. At least I have a spare head for the motor in my car.

So my option as of now is to modify the CVCC head and try to delete it. It sounds pretty dumb... but I'll try tearing it down and see if things can be plugged with press fit pins.

05-11-2020, 06:59 PM

05-29-2020, 04:44 PM
I ended up finding a fuel injected head that will bolt on to the block. So I will just be making a custom intake manifold for the carburetors instead.

07-25-2020, 07:59 PM
Haven't updated in awhile. I finished rebuilding the bottom end. The whole thing would have been re assembled if the last head I got wasn't cracked. I recently got a new one and its out at a machine shop being rebuilt. Getting parts for this motor is tough.

The custom intake I will be making is currently in the works. The plan is to make models of the side I need to mount the carburetors on, and the side that mounts onto the head. So far I've measured the patterns on my work's CMM. Once the model is made we will cut out the profiles and weld up the tubing. It will be awhile before I get there, but when it is done I will show the finished product.