Installing a SR20DET Lightweight Flywheel and Clutch into the CA18DET.

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Background

Even with the abundance of OEM parts available for the CA18DET, there seems to be a very striking lack of affordable lightweight flywheels. Clutchmasters and Spec make several clutch kits for this motor but for the time being there really isn’t a true, US market, bolt in replacement flywheel. Of course, there is always the occasional JUN lightweight flywheels that pops up on ebay costing anywhere from $500 to $800. Or you can go through an importer and pay even more and wait one to two months for your flywheel. When it is all said and done, the former just isn’t an option and in the spirit of CA18DET tuning, I am going to show you how to dig into the Nissan parts bin and come out with more flywheel and clutch choices than you will ever need.

All CA18DET guys know that our motor is the bastard child of Nissan motor swaps. Sure, it’s short stroke and iron block can handle a ton of abuse but when it comes down to it, the SR20DET is the mainstream swap. But feel neglected no more because it just so happens that SR20DET flywheels bolt directly to the CA18DET crank. What this means is that with a few adjustments to the bellhousing of the CA18DET, you can go from a handful of clutch and flywheel choices to dozens.

Getting started

First things first, you will need to gather all of the items necessary to complete the swap. You will need a SR20DET clutch and flywheel. I chose the Fidanza nine pound flywheel and Exedy clutch. You will also need some sort of grinding tool to modifiy the bellhousing. Finally, a gear reduction starter (the hoodless one) from a 1986 Nissan 200sx is necessary because the factory CA18DET starter will hit the SR20DET flywheel in a bad way.
Image showing the lightweight fidanza flywheel from a SR20DET before installion on the CA18DET.

You can order the Fidanza 9lb flywheel and Exedy clutch as a kit that includes new throwout bearing, alignment tool and pilot bushing.

Removing the transmission

The method herein is the way 99% of people perform clutch swaps in their garage. It is a dirty and difficult process. The average garage mechanic does not have access to expensive lifts so read through this next section carefully and exercise extreme caution when removing the transmission. There is a very real risk of falling transmissions and heads colliding so be careful.

Also note that replacing the clutch and flywheel is a walk in the park before you have installed the motor so if possible, this is a great mod to be made when you first get your motorset.

For those who have already installed their motor, first place your car on jack stands and then drain the oil from the transmission.

Image showing the drain plug on the underside of the CA18DET transmission.

The transmission plug is on the underside of the transmission and can be removed using the 1/2″ breaker bar if it is stuck.

Remove the driveshaft by disconnecting the front shaft from the rear shaft and then remove the bearing cap. (If the shaft is spinning, engage the parking brake) Swing the rear shaft downward and then pull the front shaft towards the rear and it will slide out of the transmission.

Image showing the driveshaft of a Nissan 240sx.
Disconnect the front and rear shaft from each other and then remove the bearing cap.

The front half of the driveshaft removed from a Nissan 240sx.
This image shows the front shaft removed and the rear shaft tilted downwards.

Proceed to the interior of the car, unscrew the shift knob and then remove the molded plastic cover from the center console. (it pops off) Now remove the 4 x 10mm bolts from the shift knob upper cover and lift the cover off of the knob. Next, remove the lower cover to expose the shift knob assembly. Note the snap ring at the base. You will need to use a pair of snap ring or needle nose pliers to compress this spring and then pull the shifter assembly out of the transmission. Stuff a shop towel in the exposed hole to prevent debris from entering.

Next, walk to the front of the car and remove the starter. The starter is located on the passenger’s side below the intake manifold. First disconnect its two electrical wires and then remove the two long 14mm bolts. Once these bolts are out, pull the starter from the engine bay.

In an alternating pattern, unbolt all of the bolts that connect the bellhousing to the motor using a 14mm wrench. For instance, after removing a bolt from the left side, remove one from the right. This will ensure that everything stays straight.

Disconnect the electrical leads from the transmission to the engine harness and unbolt the clutch slave cylinder from the side of the transmission. Place a jack under the oil pan in front of the front crossmember. This will ensure that the motor makes no wild movements once the transmission is out and will also be used to angle the motor back when removing the transmission. (pad the jack with foam or a towel to prevent any denting of the oil pan) With the jack in place, go under the car and using another jack, support the transmission and then unbolt the transmission brace from the underbody. Finally, with an extra set of hands work the transmission out of the motor by slowly raising the front jack to tilt the motor back while lowering the transmission jack; all while pulling backwards and making sure the transmission does not drop. If it sounds difficult and dangerous, that is because it is. So take your time and be patient here.

(Note: If the transmission will not budge backwards, use a flathead screwdriver or pry bar to get the bellhousing to separate from the motor.)

Remove the heavy flywheel and stock clutch

Insert the alignment pin that came with your new clutch into the factory clutch and pilot bushing and then remove the 6 x 12mm bolts that hold the pressure plate to the flywheel. Once the pressure plate is off, remove the alignment tool and the clutch will come off with it. Use an impact wrench with a 17mm socket to remove the 8 flywheel bolts. Pull back on the flywheel and it will slide off of the crankshaft. (Now is a good time to replace your rear oil seal.)

Prepare the bellhousing

In order for the SR20DET flywheel to spin freely in the bellhousing, the two humps on the inside need to be ground down. An angle grinder will make quick work of these humps. Just make sure to cover the input shaft in the bellhousing to prevent metal debris from working its way where it shouldn’t. Additionally, it is a good idea to go ahead and loosely assemble the new flywheel, clutch and cover so that you can test fit the flywheel and verify that it spins freely in the housing with no interference.

Image showing the two bumps that need to be ground down on the CA18DET

The two humps that need to be ground down are circled in red. It is a good idea to test the flywheel for clearance before you finish grinding to make sure that you took enough material off.

The bell housing of the ca18det ground down to accept a sr20det flywheel.

After grinding, the outline of the bump is still there but it is now relatively flat and no longer interferes with the SR20DET flywheel.

Image of the sr20det fidanza flywheel and exedy clutch combo assembled.

The new flywheel and clutch should be loosely assembled so that the fit can be tested.

The assembled sr20det flywheel test fit in the ca18det bellhousing.

This is the new assembly pressed on to the input shaft to test for clearance. Spin the flywheel and make sure that nothing rubs in the housing.

A little more grinding

Depending on which flywheel you choose, there may or may not be an alignment pin hole on the back of the flywheel that lines up with the little pin on the back of your crankshaft. If there is no hole, grind the pin off of the crankshaft taking care not to damage the shaft. Once the pin is ground down, clean the area to remove any metal debris that was created.

The flywheel pin needs to be removed from the back of the ca18det crankshaft.

This is the pin ground down before cleaning. Remember that oil seal I was talking about, it’s only a five dollar part, replace it.

Clearance the flywheel: VERY IMPORTANT

Depending on your flywheel, there is a risk that the flywheel bolts will bottom out in the crankshaft once tightened. This means that the bolts have tightened down all the way but there is still space between the flywheel and its mating surface on the crank. This is a scenario that is very easy to miss and if it goes unnoticed, will result in a loose, vibrating flywheel that will destroy the drive-ability of your car before ruining your crankshaft. To avoid this scenario, place the old flywheel and the new flywheel side by side and place one flywheel bolt through each. Check that the amount of bolt protruding at the back of the new flywheel is the same length and no longer than the run out on the stock flywheel. If the bolt protrudes more on the rear of the new flywheel, place washers on the bolt until the lengths match. (in effect, making the new flywheel match the thickness of the old) So if you find a length difference, you will need to pad the 8 bolts with the appropriate number of washers when installing the new flywheel. (Alternately, you can purchase new bolts at the parts store in the appropriate lengths.)

Install the flywheel

With everything clean place the new flywheel on the crankshaft using the 8 flywheel bolts previously removed. (and the washers if you need them) Use an alternating pattern and an impact wrench to tighten these bolts. Also, you should use locktite on these bolts. Take care not to overtighten.

Now insert the alignment tool into the clutch disk and place the tool through the center of the flywheel and ensure that the clutch disk is contacting the flywheel’s mating surface. Place the clutch pressure place over the clutch disk and tighten the pressure plate to the flywheel using an alternating pattern.

(Note: The Fidanza flywheel is an aluminum unit and as such, the threaded pressure plate holes strip very easily. To avoid this I tightened mine to 15ft-lbs using a little bit of locktite on each bolt to ensure that they do not back out. Also, the CA18DET flywheel uses only 6 bolts to attach the pressure plate whereas the SR20DET uses 9. Just use your 6 bolts in holes that are across from each other on the flywheel. (i.e. each 1/3 of your new flywheel will have 2 bolts instead of the 3 it could accept.))

Aligning the clutch on the ca18det.

The alignment tool inserted through the clutch disk and into the flywheel. The clutch disk should make contact with the flywheel.

The pressure plate attached to the flywheel

The pressure plate attached to the flywheel.

Additional transmission prep

If you haven’t done so already, go ahead and blow out the bellhousing with an air compressor. Do this before removing the covering you put on the input shaft. Once you are satisfied that all of the metal is out, take a wet rag and wipe everything to grab any metal the compressor may have missed. Then pull the transmission fork from the bellhousing by pulling the throwout bearing off of the input shaft. Remove the old bearing from the sleeve using a bearing puller from the autoparts store. I couldn’t find mine so I used a vice and mallet to pop the old bearing off of the sleeve.

The clutch fork and throwout bearing.

Clutch fork, throwout bearing and the two retaining springs.

Using a table clamp to remove the old throwout bearing

I didn’t have my puller so I used a table mounted clamp and tapped the bearing off of the sleeve.

You can press the new throwout bearing onto the sleeve with the clamp but you must be very careful not to damage the bearing. Make sure the new bearing spins freely once it is installed. Conversely, if you have the puller tool, mount a wooden block under the sleeve and then use the 3 arms of the puller, placed on the edge of the new bearing to pull the new bearing onto the sleeve. Once done, coat the input shaft in lithium grease and place the clutch fork and throwout bearing back on the input shaft using the two clips.

Reinstalling the transmission

Reinstalling the transmission is done in the reverse order of the removal. Go slow and make sure that you have a helper to assist in guiding the transmission back on the motor. Take care to align the input shaft inside the pilot bushing in the crankshaft and do not tighten things down if the assembly starts to bind and turn crooked. If this happens, something is not aligned properly so back the transmission out and start the alignment over. Once the transmission slides into place, begin to reinstall the transmission bolts using an alternating pattern to 33ft-lbs. Once everything is reattached, install the new starter, connect all of your electrical connections, attach the slave cylinder, reinstall the driveshaft and refill your transmission fluid before reinstalling the shifter. Finally, triple check your mounts and anything you may have loosened during this install and then crank up your car. Follow the break in instruction that came with your clutch and if you need to adjust your clutch, refer to the clutch section in the FSM.

(Note: You can refill the transmission fluid through the shifter hole before the shifter is reinstalled. The gearbox holds 2.4 liters of fluid. I use Mobil 1 75w-90 gear oil.)

The new starter, 1986 Nissan 200sx gear reduction starter.

The new starter from a 1986 Nissan 200sx and the factory CA18DET starter. The new starter is a hoodless design and will not interfere with the SR20DET flywheel.

The new starter from a 1986 Nissan 200sx installed on the ca18det.

The new starter installed.

By 240am

Chris Simmons is a race car driver, instructor, business owner and all around gearhead. His passion for motorsport started in the drifting community over 10 years ago and progressed into wheel to wheel racing of all kinds. When off track Chris can be found training and working on a myriad of projects. After a hiatus from writing, he is back to share his passion, knowledge and experience in regard to motorsports on and off the track.

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