The Ultimate Motor Swap
INDEX
THIS IS STILL IN DRAFT FORM: AUGUST 2010
1. History and reasoning for swap
2. Purchase of motor
3. Refresh of motor
A. Receiving and InspectionB. Disassembly and checkingC. Refreshing components and parts4. Installation
1. History and reasoning for swap
The S38 B38 was BMW’s ultimate evolution of their traditional ‘big-six’ motor. It was the largest stock offering, with the latest head design, and most ‘hot rodding’ done to it. Our goal, our theory, for this build was to install this motor into an E28 “as BMW would have done it from the factory.” What does this mean? It means using as many stock components as possible and making all of the features and options work between the E28 and S38 B38.
There are a multitude of other options available. People can simply buy a stock S38 B35 and install it in the E28 – like the US M5. Or an M88/3. Or an S38B36 from the E34. And even if you go with a S38 B35, you can get it tricked out by just about anyone who knows a thing or two about BMW motors (e.g. Korman). You might have the same or more power than a stock B38, but we wanted to go with a car that looks as stock as possible – and that means no custom fabrication – or as little as possible.
Again, if we wanted the most power, we probably could have gone with the ultimate Dinan motor, their 3.9 liter powerhouse. But it wouldn’t have been consistent with our goal, and it’d have been far more expensive. Now, before we begin, we should discuss costs.
The one really enticing option is to start with a S38 B35, and hot-rod it with a full rebuild. If we outsource that, it’d probably be between $12,000-$14,000 (you can ask Korman how much their rebuilds go for). But taking that example, a Korman Stage 2 rebuilt 3.6 liter would be around $15,000, give or take, and give you 373 bhp according to their website. Add to that about $3,000 for the core motor, and then another $4,000 to $6,000 to install the motor into an E28 (e.g. coolant system, A/C, exhaust, etc), and you’re talking about something well north of $20,000. But, you do get a 2 year warranty from Korman – which is a good piece of mind.
So how much is an S38 B38? A good one with under 100k miles is probably $6,000, plus shipping from Europe. You’re talking $7,000 just to get the motor. Then there’s about $3,000 to refresh the long-block (timing chain components, new rod end bearings, intake rebuild – but no rebuild of the head or head gasket), and then approximately something north of $7,000 to install it (e.g. coolant system, A/C, exhaust, wiring, engine mounts, etc). So a ‘good’ S38 B38 installation starts around $17,000 in terms of cost. But what about a S38 B38 that’s questionable? You might be able to get one for $4,000 after shipping, but you’ll need to spend at least $12,000 to do a ‘stock rebuild’ and the same $7,000 for installation – so you’re still looking at a total cost north of $20,000.
These are all estimates – your costs may vary depending on what you decide to keep as is, replace, or rebuild. But we’re assuming that you’re going to want to replace as many components as possible to ensure reliable performance. As low-mileage S38 B38s become less available, it might be a necessity to get one and rebuild it. But suffice it to say, any way you look at it, it won’t be inexpensive.
When purchasing an S38 B38 there are a few things that you want to keep in mind. First off you want to learn as much about this motor as you can before you buy one. There are certain items on this motor which are not the most reliable and they are not easy to find. First item that must be considered is the condition and mileage of these motors. The 3.8L has a bad habit of destroying connecting rod big end bearings. These usually need to be replaced every 60k miles. Also the condition of the cooling system is very important. These motors can and do overheat the number 1 and number 6 cylinders.
2. Purchase of Motor
Here is a short list of items that will need to purchased with the motor. Obviously you want to get a complete long block. But the following items from the 3.8L need to be purchased with the motor. You will need to have the harmonic damper and accessory pulleys. You will need to have the intake and throttle bodies and the associated equipment. You will also need to have the MAF and the wiring harness with DME and you can purchase the alternator. You will need the coolant tubes with the motor along with the thermostat housing.
Now onto the non-3.8L parts that will be needed. You need to have E28/E24 M5/M6 engine mounting arms. You need an M30/M88/(E28/E24 S38) oil pan and oil pump. You need the accessory brackets from an M30/M88/(E28/E24 S38). You need an M88/S38 oil filter canister and mouting block. You will need an E28 M5 coolant overflow tank and an E28 535i radiator. The details of the hoses and other items will come later. Lastly you will need to purchase some adaptors (Koala motorsports) for the engine mounting brackets.
3. Refresh of motor
A. Receiving and InspectionIn this section we will discuss the items that need to be addressed in a typical refresh. We will also discuss some of the changes that will be made and some of the touches we put on this motor. To start with, when you take delivery of your motor you want to inspect it for damaged parts from shipping snd probably do a leak down test to ensure the motor is in good health.
Here are some pictures of the motor when it was received. Needless to say I was not impressed with the packaging.
Now at this point I really want to make sure that safety comes first. The only way to do any work on the motor safely at this point is to put it on an engine stand.
In these pictures I had taken the motor off of the pallet and was inspecting the underside, along with doing taking pictures of how things are assembled. I cannot stress enough how important it is to take these pictures. These will help you put the motor back together correctly considering to work you are about to undertake.
What cannot be easily seen is that the oil pan is cracked. I am not sure this came as a result of the shipping reopening a weld that was used to repair a crack before or if this was caused by the accident. The good news is that I never planned to use the oil pan so the damage would have no effect on the project.
Now that the engine is on the stand. I took some more reference photos. As shown in the first round of pictures I have already removed the power steering pump, AC compressor, passenger side engine mount, header heat sheild and flywheel and clutch assembly.
After this I decided to remove the coils and the spark plugs. This allowed me to do the leak down test on the motor. I also removed the headers which I took some pictures of. I knew I was not going to be reusing these because of the fact they must be modified to fit in the car, M88/3 headers bolt on, and I am not using the air pump system. Lastly I decided to remove the starter and alternator.
The next step was to see inside the beast. I really wanted to get a sense of what the internals looked like, so I pulled the valve cover to expose the cams. I was plesantly surprised with what I found. The cams looked great and everything looked really clean.
I then pulled the oil filter housing off. I knew that I wanted to use the M88/3 or S38 B35 oil filter housing so the E28 US M5 oil cooler that I had in my car would bolt up. I also knew that the driver's side engine mount would need to change so that was removed.
I followed this up with some reference photos before further disassembly.
I then proceeded to remove the thermostat housing and coolant cross tube. What I then noticed was that it seems the timing chain tensioner was leaking and causing the front of the motor to get covered in oil.
I decided that the next thing to do was to remove the air pump equipment. I was dead set on not wanting to use this when I put the motor in the car, but I decided I needed to remove it carefully just in case.
Because of the leaking tensioner I decided it would be good to pull the oil pan. What I found was again very pleasing. The bottom of the pan looked clean. The inside of the bottom end also looked great.
I took some reference pictures of the underside of the intake as there is a lot of plumbing under there. I also took some more bottom end photos.
At this point I decided that it was important for me to remove the intake plenum. This would get a very large item out of the way and the work on refurbishing it along with the valve and coil covers could start.
When removing the plenum I also removed the oil separator valve and support bracket. I removed the oil separator valve from the plenum and found the inside to be quite dirty and also wanted to replace the rubber mounts at the bottom. Replacing the rubber mounts proved to be the wrong decision. The rubber mounts we stuck in the bottom of the separator. I tried in vain to remove them, but ended up causing so much damage to the separator I had to replace it.
Now I also split the plenum to make sure that the vacuum acutated flap that is in the center of the plenum was working smoothly. This also allows easier access to refurbishing the plenum.We decided when refurbishing the plenum and the valve cover that we wanted to go with something that looked as close to factory as possible. In order to do this, we had three pieces that we needed to refresh. The valve cover is actually two pieces - the aluminum portion and the inlay that is (we think) Magnesium. We wanted the inlay to match the intake plenum as closely as possible as it is a near-crinkle coat finish. Also there were some gouge marks on the intake from shipping damage. For the valve cover, we were able to get that powder coated. Now, powder coating aluminum is tricky, but doable. The results speak for themselves.
As for the inlay and intake plenum, these were first stripped of that horrible purple paint. Then cleaned thoroughly. And we used a semi-gloss black engine enamel paint to be able to sustain the high temperatures. The problem with this paint is that it's very prone to chipping. And we also added a clear enamel as the final layer. This retains the crinkle finish in the aluminum / magnesium, and gives the closest factory finish. The painting was a long process making sure everything was masked off appropriately and that the paint was given sufficient time to dry.
I hate to say this but at this point in the build I am almost sure that I continued to take pictures but for some reason I can't seem to locate them so the rest of the disassembly will just be text. I will do the best I can at describing what was done.
Now my attention moved to the bottom end. First I removed both accessory brackets from the motor. I then remove the accessory pulley and the harmonic damper. The harmonic damper is held on with 4 Torx head bolts that must be replaced. When reinstalling them they also require torque plus angle tightening which is critical to get right.
Once the damper was out of the way I moved my attention to the oil pump. I decided that I wanted to use the E28/E24 oil pan so that I could ensure the proper fitment in the car. I verified this would work by cross referencing the oil pan gasket, which is the same for both motors. The next item that had to be verified oil pump. The B38 oil pump will not fit in the E28/E24 oil pan so I was lucky enough to be able to use an old M88/3 oil pump to verify the fitment. Everything worked great.
I then removed the old B38 oil pump which exposed the bottom end.
C. Refreshing components and partsAfter the oil pump was removed I turned to the rod end bearings. I knew the motor had 67k miles on it, which is generally considered low mileage, but unfortunately the B38 requires rod end bearings at this mileage if they are driven hard. Since I was already in there I decided to replace them. This was not a big deal especially since the mileage on the motor was so low. I was able to use OE bearings as the wear on the journals was insignificant. One key point is that the rod end bolts need to be replaced and are tightened to torque plus angle. Also make sure to use assembly lubricant when reassembling the bearings. This will help prevent scoring and spinning a bearing when doing the initial start-up of the motor.
Now I moved my attention to the timing chain and tensioner. I decided that since I was in the motor I would replace the tensioners, guides, and chains. To do this I first had to pull the water pump off and should be replaced anyway. Now that the water pump is out of the way you can get access to all of the lower cover bolts. I then set the crank and cams to TDC and removed the tensioner. Now if you read the factory manual it states that you must remove the head to ensure that you get a good seal between the head and the front lower cover. I have never had to remove the head, I have just been very careful when removing the lower cover not to damage the head gasket. This worked and I was able to get access to the lower portion of the chain.
I then pulled the cam gear covers off and unbolted the gears and the upper chain guide. This allowed me to drop the chain down out of the top of the head. I had to remove the chain guide on the intake side of the motor which was fairly easy. I then had to remove the tensioner guide. This was very difficult. The tensioner guide is a two piece item. The top section in the head is easy to remove. The lower section is much harder to remove. The part is on a stud at the bottom of the block and the top is located in the head. There is not enough clearance in the head to pull this out. I found a way to get this part out by brut force.Once all the timing chain equipement was removed, I started the reinstallation. The most difficult part of this was the lower tensioner guide. I was able to get everything reinstalled and tightened to spec. I decided to use the S50 tensioner upgrade as I have seen problems with the old style tensioners. I then verified the chains were set right by rotating the motor by hand and verifying all the timing marks. This is critical because the worst thing you could do is be off 1 tooth. I also installed the oil pump chain and tensioner.
A. Removal of old motor and engine bay preparation
i. Heat shield from E28 M5
Once the old motor and transmission is removed, we prepared the mounting tabs and studs for the heat shield on the passenger side frame rail. The E28 M5 comes with a heat shield here, and it's relatively simple to mock up the heat shield with the studs. We used studs that came with a flat plate from McMaster, and epoxied them to the frame rail.
We suggest installing the heat shield because of the heat that the exhaust headers will generate. Protecting the AC lines and brake lines is critical in this area.
ii. Battery and all that rewiring
You need to do this here
iii. Radiator core support and coolant pipes
When we were test fitting the motor, we found that the radiator to coolant pipe clearance was very tight to the radiator. In fact, it was hitting the radiator side tank. The radiator core support has a flange that we bent back in order to pull the radiator closer to the core support. This helped, but only marginally.
In addition, we later modified the coolant pipes so that the supply bib comes from the top, not in front and to the side. Doing this allowed us to have clearance of about 1/2 to 5/8 of an inch to the radiator with the radiator in its original position.
In addition, the coolant pipe that goes to the lower rad hose only has about 1/4 to 3/8 of an inch clearance to the side of the frame rail. This is acceptable, given the amount of movement side-to-side that this motor has. The bigger concern is the front/back movement.
iv. Removal of engine bay brackets to clear intake
The intake plenum clears most of the engine bay, however the rubber elbow hose is a very tight fit. In fact, it is basically pressing up against the power steering reservoir and the hard line that runs from the booster, along the side of the reservoir, and down to pump. In the long-term, this hard line will need to be replaced with a custom one. But we were able to use the mounting clamp in reverse to effectively pull the hard hose down and away from the rubber intake elbow. Doing this allowed us enough clearance to be able to push the elbow onto the intake plenum.
In addition, we had to remove the bracket that used to hold the 535i's coolant expansion tank. This is necessary to do since the MAF and intake elbow sit in its location.
v. Heater valve movement and bracket adjustment
The intake plenum will not clear the heater valve the way it is currently mounted on a 535i. There are two things that need to happen to clear this. First, the heater valve bracket has to be moved to the M5's position, and it then has to be bent backwards towards the firewall. Currently if you look at it from the side, it is shaped like a "Z", with it initially coming down, then going forward and down at an angle, and then down again. You have to bend it so that it goes backwards and down at an angle. By doing these two things, you move the heater valve over to the driver side about 1/2 to 3/4 of an inch, and further towards the firewall another 1/2 to 3/4 of an inch.
vi. Fabrication of expansion tank mount, use of E28 M5 expansion tank
B. Engine Installation
Here we just need a description of step-by-step what we did and the install pictures.
C. Other Considerations
i. Coolant system and hoses needed to interface to E28 chassis
ii. PS hoses and clearance to reservoir tank, adjustment
iii. Removal of airpump and AC bracket
iv. 140 amp alternator
v. Oil cooler lines
vi. AC line (custom) and use of B38 compressor
D. Wiring considerations
i. Removal of air pump
ii. Wiring loom – removal of superfluous wiring
The wiring harness was modified in 3 ways.
First we had to cut off the X20 plug, and then wire the right engine wiring harness side plugs to the C101 connector on the side of the E28 fuse box. The E34 loom isn't long enough to reach across the back side of the engine and then down the inner fender, so we cut off a spare C101 connector with approximately 24" of wires to be able to lengthen the wiring harness to reach the fuse box. The pin outs are located in the next section.
Second, we pulled out the wires having to do with the A/C control, and routed them from the ECU to down the passenger side inner fender. These are explained in the following section.
Third, we pulled out 4 wires having that used to go to the X20 plug on the E34, and routed them through the hole in the firewall to the C103 connector in the cabin near the ECU above the glove box. The pin outs are described in the section below.
We did not change the way in which the cruise control worked. It still works like the E28 way. Although we had to use an E24 M6 cruise cable to have the extra length needed to reach the throttle lever on the intake. Also, the main ground strap was moved to
!!!!!!!!!!!!!NEED TO FINISH THIS!!!!!!!!!!!!!!!
We also had to use a XXXX PN for the coolant temp sensor in the cluster to work correctly.iii. X20 to C101 plug connections
Here we should just list our pin outs from the xls sheet.
iv. Diagnostic plug wiring (same except needs power)
Here we should just explain what we did to make the Diag plug work.
v. AC wiring
Here we should just list our pin outs and what we're doing from the xls sheet.
vi. C103 connector
Here we should just list our pin outs and what we're doing from the xls sheet. Including the fact that you do not wire up the DWA signal for the OBC, and that you need the vehicle speed input to the DME.
5. Final Product
And now we have the final product:
Our second start ever of the motor was captured on video.
insert link here.......
There is still a lot of work remaining. We have built a custom exhaust for the car, that will need to be installed and the headers will need to be modified. An alternative is to purchase the Euro M5 exhaust system and install it - however you will sacrifice some top end power because that system can, at best, flow around 300-320 bhp (stock euro motor making 286 bhp), out of the twin 2.0 inch system. The 3.8 will be a little bit strangled. Ideally you'd want to bump up to at least a twin 2.25 inch system, of similar design to the stock US M5 (i.e. X-pipe, cat, resonator, and muffler).
Now all we have to do is drive the requisite 1200 miles for break in, change the oil, and enjoy!
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