Swap or Rebuild for Z4M Track car

[TAL2GK]

I bought my beautiful Z4M as a track car from Bring a Trailer in 2019 largely because receipts showed Rod Bearing replacement had already been done. One day into my first HPDE session of the year at Road Atlanta and it became obvious that something was wrong. A little investigation by my new friends at Euroenvy Autowerks revealed that the previous owner that did the rod bearings did so with full knowledge that one of the bearings had spun. The shop in Texas that did the work recalled the car and the conversation with the owner who said “just do it anyway, i’m selling it.”

So here’s hoping a giant pile of bad karma is coming his way.

Meanwhile, here’s where I am. I’m weighing my very expensive options of replacing the engine or rebuilding it with a stroker kit. One option i’m seriously considering, but the cost and complexity are daunting, is going with a 2JZ swap. I’ve seen the videos and followed every page of the build thread on here. The problem is the cost of the 2JZ is going sky-high. So much that pure cost is greater than a stroker-kit rebuild.

Another option is to cut my losses and sell the car with a damaged engine. I’d rather not do that because I love the car and also because I just sunk a ton of money on JRZ RS Pro 3 suspension and AP Racing BBK. Each of these has exactly 1 day of HPDE on them, so they are brand new!

So any advice or experience is welcome here. I’ll plan to update with what’s done and how it changes the handling and performance.

[wdb]

First of all report the issue to BaT. They probably can't make you whole but they can prevent the dweeb from doing the same thing to someone else.

Next up is just a WAG on my part, but the stroker option sounds like the most fun. I guess I'd want to be sure that nothing else was wrecked internally from the spun bearing before I went too far down that rabbit hole.

Good luck and pleasepleaseplease update us if you decide to keep the car and do something cool with it.

[bwright657]

I would go for the rebuild and stroke on the current engine. Since you're in Charlotte, I would recommend calling Schall Motorsports in Spartanburg, SC about doing the rebuild. Marcus does great work and is the go to guy around here for S54 engines. He's done all the servicing including a VANOS rebuild on my Z4MC.

[TAL2GK]

Here’s the rebuild part list with stroker kit. (May not need all these parts, but won’t know for sure until it’s fully opened up.) Leaning this direction vs. FI with rebuild even though power likely won’t be equal. After this experience I need my power with a strong dose of reliability.

VAC VAC MOTORSPORTS PREMIUM STROKER KIT, BMW S54, 3.4L - 10.5:1, 85MM, ARROW PRECISION RODS
REI Timing Cover Gasket
REI Timing Cover Gasket
VAC VAC MOTORSPORTS PERFORMANCE MULTI LAYERED STEEL HEAD GASKET, BMW S54 ARP Head Stud Kit - S54
OES Cylinder Head Gasket Set - DOES NOT INCLUDE HEAD GASKET
OES Crankshaft Seal Kit
CFW Crankshaft Seal - Front
LMO Motor Oil 10W-60 RaceTec 5 Liter
LMO Motor Oil 10W-60 RaceTec 1 Liter
MAH Oil Filter Kit w/ O-Ring
OES Coolant/Antifreeze 1 Gallon (Blue)
BEISAN VANOS SEALS REPAIR KIT
BEISAN EXHAUST UPPER CHAIN
BEISAN REBUILT VANOS SOLENOID PACK - $150 CORE
OES VVT Oil Control Valve Fi - Filter
OES Oil Cooler Seal
OES ORING - VANOS FILTER
OES VVT Housing Seal Plate
OES Timing Chain Guide Rail - Left
OES Timing Guide Rail - Right - Lower
OES Timing Chain Guide Rail
INA Timing Chain Tensioner
ELR Seal Ring - Copper - Aluminum
OES Gasket Ring
OES Gasket Ring
OES ORING
OES Multi Purpose O-Ring
LANG S54 CAM GEAR BOLT KIT
OES Oil Pick-up Tube Gasket
OES Oil Pump Chain Tensioner
TURNER DRILLED OIL PUMP NUT
OEA Flywheel Bolt
NGK Spark Plug DCPR8EKP NGK
ARP MAIN STUD KIT S54
OES MAIN BEARING SET
HPENGINES CYLINDER HEAD RESURFACE AND REBUILD

[Ryan13]

Can’t speak to a swap, but I would rebuild. Unfortunately a rebuild could cost 40%-50% of the car’s value of it’s done correctly. It will be much more if done incorrectly. At least you didn’t punch a hole in the side of the block. Definitely don’t run it, at all, even to show off your new engine “sounds” to the shop…it’s spun, that’s not going to change, no one needs to confirm it.

I’m in the market for another car if you go that route. I need a parts car to feed the other ones.

Good luck with your decision. Truly sucks having someone hide and pass off a car/engine that has had damage. Perhaps if you post the link to the auction, we can figure out the previous owner.

[TAL2GK]

I know the previous owner, as he also listed the car on here. It would appear the underhandedness was done by the owner HE bought it from.

https://bringatrailer.com/listing/20...z4-m-coupe-12/

So, now that i’m in full rebuild mode, what else should be done for performance? I’m looking hard at headers and a tune, but could be talked into cams or others. Especially stuff that’s easiest with the engine out already. Researching threads now, but welcome your direct input.

[Michael9218]

Why not replace the motor with another used motor?
Building a stroker motor sounds sexy, but it’s a deep rabbit hole. For a track day car it’s not worth it. The guys running strokers in club racing expect to rebuild frequently. Gets very expensive.
If you want more performance, remove weight from the car. Gut it and buy a trailer. Still cheaper than a stroker build…

[Ryan13]

Good decision on the rebuild…you’ll know what you have. Make sure the machine shop uses a torque plate when they bore…not everyone does. Have the crank balanced, fluxed, and polished. My crank had been previously ground down to accept wider bearings by Lang, so you could have that done if you trust the local shop. King bearings if you go that route. You could upgrade the rods to remove some internal weight (not positive everything included in the stroker build). Cams leave alone, in my opinion. Headers are a nice upgrade to go with all the other stuff you are already doing.

May as well rebuild the diff and put a 3.91 in…that will feel magical for track work.

I have a SC on mine, but now you get into cooling upgrades…oil, water, intercooler, holes in the hood for air flow, remove AC, etc.

Build it and bring it to the track and let’s see it run some laps.

[TAL2GK]

Originally Posted by Michael9218

Why not replace the motor with another used motor?
Building a stroker motor sounds sexy, but it’s a deep rabbit hole. For a track day car it’s not worth it. The guys running strokers in club racing expect to rebuild frequently. Gets very expensive.
If you want more performance, remove weight from the car. Gut it and buy a trailer. Still cheaper than a stroker build…

I just purchased a sweet Trailex enclosed trailer last year and was in the process of upgrading handling when the motor gave up the ghost. The rabbit hole is what i’m trying to avoid, as gutting and safety improvements are vital next steps for me and we’re supposed to be happening with the money now allocated for rebuild and upgrades. Aside from initial cost of stroker kit, what rabbit holes should I be on the lookout for?

[TAL2GK]

Originally Posted by Ryan13

May as well rebuild the diff and put a 3.91 in…that will feel magical for track work.

I’ve received similar guidance offline. Doesn’t a higher gear ratio sacrifice top end speed?

[Michael9218]

Originally Posted by TAL2GK

I just purchased a sweet Trailex enclosed trailer last year and was in the process of upgrading handling when the motor gave up the ghost. The rabbit hole is what i’m trying to avoid, as gutting and safety improvements are vital next steps for me and we’re supposed to be happening with the money now allocated for rebuild and upgrades. Aside from initial cost of stroker kit, what rabbit holes should I be on the lookout for?

Aside from the inevitable “while you’re in there” cost over runs, more power means more stress (and more heat to dissipate). I would expect a shorter life from the motor. Make sure you use a good tuner.

The car will be faster and more enjoyable to drive on track with less weight versus putting money into more power. The stock S54 is plenty of motor for a light track car. Less weight also improves handling and braking. Win, win, win.
My Z4MC weighs 2,600 with a modest 335 hp at the wheel (exhaust and a tune from Severn). 1:33.9 at Road Atlanta.

Power is one the last things you should be looking for.
1. Weight
2. Chassis (bearings/bushings, suspension, setup)
3. Tires (if you aren’t running a sticky DOT slick than don’t waste your money on power)
4. Aero (more grip)
5. Power

[Michael9218]

Originally Posted by TAL2GK

I’ve received similar guidance offline. Doesn’t a higher gear ratio sacrifice top end speed?

Poor mans supercharger.

Ideally, for a track car, you want to set the gear ratio so you hit redline in top gear at your fastest straight away. In other words, you want the lowest gearing you can get away with for power delivery.

With a 5 speed behind an S54, this will be 4.10 gears with 275 sized tire (25.5” diameter). Although you don’t need to have a 5 speed as the stock 6 speed has the same 1:1 5th gear as the 5 speed. But the 5 speed is 20 pounds lighter…

[TAL2GK]

Originally Posted by Michael9218

Power is one the last things you should be looking for.
1. Weight
2. Chassis (bearings/bushings, suspension, setup)
3. Tires (if you aren’t running a sticky DOT slick than don’t waste your money on power)
4. Aero (more grip)
5. Power

Oh, I agree with the priority and I didnt intend to chase power this early in the build, but then a rebuild hit me and if parts need to be replaced anyway it’s hard not to spend now for what would be bigger dollars later when the engine is back in.

[Vanne]

Id say Mick's advise is spot on. bloke knows his shit, ive borrowed from him many a time. Rabbit hole is there even if you cant/dont wanna see it. Good luck with whatever choices you make, one thing is for certain, you'll learn from it.

enjoy the build.

[TAL2GK]

I’m happy to take Mick’s advise. His build thread is epic! Maybe I should just trailer my car 4 hours down the road and drop it off in his garage with a briefcase full of money and let him do his thing all over again.

[bananabun]

Sorry to hear that you're dealing with this.

In case you do replace the car, consider my track car for sale. It might suit your needs just fine, and you can always throw your JRZs and AP kit on it along with pretty much anything else. Mine isn't as pretty as yours, but I'll eat the cost of detailing it and at least you know that the motor won't blow lol

https://www.zpost.com/forums/showthread.php?t=1839476

https://docs.google.com/spreadsheets...tUaBem9ZI/edit

Just to note - I can sell it to you without the MCS, and save you some more $$ so you can drop in the JRZs.

[F360C]

Sorry to hear about the engine problems! I agree with some of the other on this thread and say just pop a new motor in there with some bullet proofing. Easiest solution to get you back on track and enjoying those new parts.

How bad is the engine damage though? Can you not rebuild your current engine to stock specs or even a light NA build? I have always been interested by the Lang Racing solution to the bearing issue by widening the journals along with a set of light weight pistons/rods. They can even fix the crank too. https://store.langracing.com/s54-rod...-modification/

Maybe even bore it to 87.5 to make the car effectively a 3.3 liter (think this i the route I will go). I have seen a couple of these 3.3 builds and they interest me because you get a tiny bit more displacement without the inherent issues of the stroker. Steve Dinan actually even sells a 3.3L kit on his website. https://carbahnautoworks.com/product...e-rebuild-kit/

Also what AP racing kit are you running? I am looking at picking up their CP8350/325 kit and it looks to be the one you're running.

[dre99gsx]

Why I swapped mine out years ago - not a fan of BMW engine longevity.

2JZ swap is easy, but making the whole set up last for track abuse is a whole 'nother ballgame. If you plan on making more power with whatever you choose, be prepared to upgrade/fix many other things you did not have intention on doing. Heat will end up being your biggest problem.

I've been forced to install trans and diff coolers, just to give you a glimpse. If you go 2JZ-NA with ITBs, that would be a sweet long lasting setup. No need to buy a $4900 JDM imported engine, you can just source parts as needed. You can even go 2JZ-GE route (non turbo) for a fraction of the cost.

Even ACR Viper manual states if owner drives more than 25minutes on track, they are encourage to add coolers as well. Go figure...

[filtercoffee]

> How bad is the engine damage though?

+1, this would be the determining factor for me.

Sounds like a stroker would accelerate rod bearing wear due to higher piston velocities, especially if you spend time at high rpms.

Oop, this thread is a month old, which direction did you go OP?

[ANILE8]

Really a low blow about your motor, I hope the Taliban rape that dog's mother for what he did. Most on here would not even think about doing anything like that if they were selling their vehicle, let alone going through with it!

I like strokers. I drove one hard on the street and drag raced it for over a decade without one issue, but not on the S54 platform.

So, I wouldn't say a good stroker kit is inherently more unreliable than the factory combo if the rods and crank are sized correctly. It is all about the machining, how it is screwed together and the tune.

Love your coilovers, not many on here go for them which is a pity. Start a new thread with some pics.

If I was in your position with a stuffed S54, I would consider the 3.4L stroker kit from Lang Racing or go a full on N/A LSX swap if $ were not a problem.

For a dedicated track car, whichever direction you decide to go, I would get a Samsonas sequential box before I spent big bucks on the motor. But if you can afford both, why not.