Looking for an engine builder who’s a fan of the factory design*

[IamFODI]

It’s… not quite engine rebuild time, but the odometer has me wanting to start feeling out options.

If and when, I’d like to go one of two routes, neither of which seems popular among rebuilders:

1. 100% factory, indistinguishable from what BMW would do, or
2. Same as above, but with lighter internals and no other changes.

Obvious choice for #1 would be a factory reman, but it looks like those are NLA. Someone please correct me if I'm wrong on that.

Most aftermarket rebuilds seem to focus on increasing power and/or durability. Makes sense, but I need neither of those.

I also generally distrust “OEM+” upgrades for reasons that probably aren’t worth getting into. The only possible exception – maybe – would be if it's possible to have lighter rods and pistons with no other modifications and no side-effects on how the engine operates. (I'm assuming that's a big "if")

If I can't have a lighter rotating assembly without other changes, then what I'd want is a truly plug-and-play clone of the original. Yes, all the way down to the rod bearings and magnesium valve covers and plastic VANOS caps and all that.

Either way, I'd like to be able to talk with a builder who at least understands the difference between durability and longevity. That's another thing that seems rare.

Am I unicorn hunting here, or can y'all recommend a shop or two that might be worth talking with?

[Bimmer Barney]

Probably not any reputable shops. Don’t forget they’re putting their name in the build and it’s a skilled craft. Most take pride in their assembly and some things, like oem bearings and plastic vanos covers, likely won’t make the cut.

Also depending on the need for rebuild, you may be forced to bore the cylinders.

[///M Power-Belgium]

Originally Posted by IamFODI

It’s… not quite engine rebuild time, but the odometer has me wanting to start feeling out options.

If and when, I’d like to go one of two routes, neither of which seems popular among rebuilders:

1. 100% factory, indistinguishable from what BMW would do, or
2. Same as above, but with lighter internals and no other changes.

Obvious choice for #1 would be a factory reman, but it looks like those are NLA. Someone please correct me if I'm wrong on that.

Most aftermarket rebuilds seem to focus on increasing power and/or durability. Makes sense, but I need neither of those.

I also generally distrust “OEM+” upgrades for reasons that probably aren’t worth getting into. The only possible exception – maybe – would be if it's possible to have lighter rods and pistons with no other modifications and no side-effects on how the engine operates. (I'm assuming that's a big "if")

If I can't have a lighter rotating assembly without other changes, then what I'd want is a truly plug-and-play clone of the original. Yes, all the way down to the rod bearings and magnesium valve covers and plastic VANOS caps and all that.

Either way, I'd like to be able to talk with a builder who at least understands the difference between durability and longevity. That's another thing that seems rare.

Am I unicorn hunting here, or can y'all recommend a shop or two that might be worth talking with?

Think , this is the place to be => https://www.m3post.com/forums/showthread.php?t=1504062

[Chrisyphus]

So option 2 is almost exactly what we call a "better than stock" rebuild. I give Peter a hard time over it because calling Carillo H beams and Mahle Power Pack pistons "better than stock" is a bit of an understatement.

I hear you, though, and it is a real concern: you don't want built motor problems on a car you want to be able to drive as much as you want without feeling guilty for wasting a potentially short life cycle. This is a critical consideration when weighing the pros and cons of something like a built motor, which we have to explain to many of our customers... "No, you cannot have a forced induction fully forged S65 with 2618 alloy pistons that will also last as many miles as a stock rotating assembly while also supporting 800 wheel horsepower. There are necessary trade-offs when going to such a high-strength alloy regarding increased clearances that will reduce the lifecycle of the engine."

4032, however, is a different story. It still expands more than stock-cast pistons, but not as much as 2618. With good maintenance and a touch of mechanical sympathy for a cold motor, you can expect 100k+ miles out of a motor built with Mahle Power Packs and appropriate tolerances.

Our rotating assembly loses a total of 800 grams across all the pistons and rods vs. stock. It can tolerate a significantly higher power level than stock and is remanufactured to a tighter tolerance than OEM BMW remanufactured engines. But you do not have to live the racecar life of constantly monitoring your motor because your bottom end is built to handle 1000+bhp while only making slightly higher than stock power.

We do not offer stock rebuild options for any of the engines we do because the cost simply isn't worth it for our customers or ourselves. If keeping the OE rotating assembly is your absolute highest priority, the best route would be to have new rod and main bearings installed in your motor without removing the rods/pistons themselves, and having your heads rebuilt with new OEM components- these are hard to get, so I would recomend Carbahn valve springs (theyre only SLIGHTLY stiffer than OEM) and re-using the stock valves etc. (assuming they are in good, serviceable condition). Then all new components everywhere else- VANOS hubs, solenoids, timing kit, new OEM magnesium valve covers (so you can have at least a few years before they start to leak), etc.

The cost of all of this will approach the cost of our better-than-stock option, while not being better than the better-than-stock option in any material way, because youve done nothing to address the wear on your original pistons and cylinder walls, they will likely have a shorter life at this point than our Power pack solution. You can get OEM pistons in the first oversize (+0.007") if seven thou is enough to clean up any scoring on your cylinder walls (honestly, 50/50 if it will), and you can do a completely new OEM rotating assembly. But the wholesale cost of the OEM piston (I just looked out of curiosity) is $900 per piston, and the rods are $340 each. So, you'll have spent $9,900 on rods and pistons before the first machine turns on. Additionally, the OEM oversized pistons are backordered across the board, with no ETA.

Our Carillo/Powerpack rotating assembly is a $3,900 cost and represents a genuine improvement in lightness, durability, and power. Albeit with a slightly reduced lifecycle due to the nature of forged internals. I think a 100K+ mile life expectancy is quite solid, especially considering that if at say, 120k miles the motor starts showing signs of wear, it could be refreshed with a new set of pistons, new bearings, and a fresh hone (rather than buying all new components), you can double the life at a dramatically reduced cost.

Additionally, there are more options with our rotating assemblies- a .5 increase in compression paired with a good set of cams and other supporting mods will get you in the 410+ wheel horsepower range, which I recognize is not your goal, but if that power comes at no cost of engine life, drivability, or anything along those lines, why not? This power level with our most basic rotating assembly will have no net effect on the engine's lifecycle.

As I said, there are a million ways to approach this- I just strongly advise against buying a used motor off eBay and hoping for the best when the day comes. We've bought six S65s in the last month, and of all of these, advertised as "healthy and ready to run with replaced rod bearings," only 2 actually had the RBs done, and of all the motors, only one did not have some issue that represented an impending catastrophic failure- not an issue for us as the work we do to them will correct nearly all of these issues except for the one with a scored crank. To say buying a used motor is a gamble is overly optimistic about the subject.


Sorry for rambling... Ive been off the forum too long lol.

[omgzirra_exe]

i did 80k miles on a 4.4 stroker i daily and track often before i lost compression in cyl 8. I still haven't had the chance to inspect the walls on Cyl 8, but my guess is the Alusil silicon crystals are non existent.

so you can def get 100k+ miles if you're lucky.

if you let the car sit for too long in between usage you might have more of a problem tbh lol.

Can def recommend Chris/Partee Racing.

[nick3753]

I’m curious, at what mileage does one start thinking about an “engine rebuild”?

[BenFenner]

Originally Posted by Chrisyphus

Our rotating assembly loses a total of 800 grams across all the pistons and rods vs. stock.

Are you removing mass from the crankshaft counterweights to go along with that?
If so, are you knife-edging them, or?

[omgzirra_exe]

Originally Posted by nick3753

I’m curious, at what mileage does one start thinking about an “engine rebuild”?

For a built race engine, and honestly stroker motors fall into this category at this point, mileage really is not the metric anymore.

Realistically you go by engine hours. But most of us still street drive the cars, so it ends up being a mix of both rather than strictly one or the other.

For example in a typical year I do about 8k miles of normal driving, plus maybe 5 track events if I am lucky. Each event is around 2 hours of track time and about a 400 mile round trip.

On paper that does not sound like much, but the engine definitely does not live like an 8k mile street car. With the sustained load and heat from track time it ends up feeling closer to something like 15k miles worth of real wear.

So getting 80K miles was damn near best scenario and not a waste of 16k at the time of build lmao.

[Chrisyphus]

Originally Posted by BenFenner

Are you removing mass from the crankshaft counterweights to go along with that?
If so, are you knife-edging them, or?

We do remove weight to achieve balance with the lighter rotating assembly. We balance all of our motors to </= 1gram.

We do not knife edge. Significant testing across countless engines has proven that it’s not worth the effort because the process typically throws the crank miles out of balance, which requires adding in new heavy metal cylinders into the crank to regain the lost weight, then removing more weight to bring it all back into spec, all for what has been an immeasurable difference in performance in our testing.

[Chrisyphus]

Originally Posted by nick3753

I’m curious, at what mileage does one start thinking about an “engine rebuild”?

Zirra hit the nail on the head. This is a wildly subjective topic where in order to give a remotely reasonable answer, you’d have to know the entirety of the car’s history to an impossible degree.

We have an engine in the shop that spun a main bearing at 60k miles with 20k miles on the rod bearings, in the best condition I’ve ever seen a used motor (aside from the spun main bearing obviously) which came out of a car that had a perfect maintenance history and is a single owner car, which is also nearly flawless. On the other hand, we recently received a running core that (and I’m not at all joking here) had the drain pan on the oil plug welded shut because the owner had stripped the threads. 190k miles of obscene neglect lol.

My M3 has 180 on the clock now? Maybe more… I don’t pay attention to it. I daily drive it from my house next to VIR to the shop, approximately 30 minutes each way, and there’s not a single time I drive the car where it doesn’t see 8000+ RPM. Last year I did 8 track days with it, full send the whole time. Original motor. Mine too was a meticulously maintained single owner car before I bought it at 150ish thousand miles. At our last track day in October, my brother’s m3 with 200k miles seized up on the back straight as he passed bitch. Scattering pistons across the track. Kitty litter is expensive lol.



My point being, there doesn’t seem to be a simple recipe for success. We’ve identified a major issue regarding the oiling system that is a symptom of a handful of causal factors. We’ve not done enough testing to speak to it definitively, so I cannot go into specifics on it at the moment, but simply doing rod bearings is entirely insufficient. All of the blown motors we’ve received in the last 2 years have had front main bearings welded to the crank and aftermarket rod bearings in pristine condition (except for 1/5, typically). This could be survivorship bias, or it could be a pattern. Once we complete more research, we’ll likely put out a paper on the topic outlining everything we’ve found, how we came to our conclusions, and what the ultimate solution is.

[IamFODI]

Originally Posted by Chrisyphus

I hear you, though, and it is a real concern: you don't want built motor problems on a car you want to be able to drive as much as you want without feeling guilty for wasting a potentially short life cycle.

Pretty much.

Here’s how I’d put it:

In my decision matrix for this car, more-than-stock durability and more-than-stock power are weighted at zero. So, no amount of added durability or power over stock could offset even minor downsides for me – and it does seem like there are downsides to even the best non-OE rebuilds out there right now.

I do value the hell out of throttle response, so a lighter rotating assembly and less internal friction might ease the pain, depending on the details. But even then, the game still centers on minimizing downsides.

Does that make sense?

Originally Posted by Chrisyphus

Sorry for rambling... Ive been off the forum too long lol.

Don't be silly. Really appreciate you weighing in, especially with that level of detail.

Originally Posted by omgzirra_exe

i did 80k miles on a 4.4 stroker i daily and track often before i lost compression in cyl 8. I still haven't had the chance to inspect the walls on Cyl 8, but my guess is the Alusil silicon crystals are non existent.

so you can def get 100k+ miles if you're lucky.

if you let the car sit for too long in between usage you might have more of a problem tbh lol.

Can def recommend Chris/Partee Racing.

Nice. Thanks.

Any opinion on how long is too long to sit between drives?

Curious about your experience with Partee. Will PM you at some point.

Originally Posted by nick3753

I’m curious, at what mileage does one start thinking about an “engine rebuild”?

Again, speaking only for myself: I’m at 174k.

I’ve seen/heard Steve Dinan suggest that the design life of M engines is ~150k miles. My completely unscientific sense is that that feels about right. Like, I feel like I’ve seen these engines run past that mileage, but not often far past it. I feel like it's best to assume I'm on borrowed time and start learning now so that I'm ready when the time comes.

[RichardC300]

What are some of the actual downsides of a rebuilt engine, specifically a “better-than-stock”, street-driven engine? Assuming a street-friendly, pump-gas tune… Increased oil consumption? Increased maintenance frequency for some parts/services? I’m currently looking for an M3 and planning for the worst case scenario of a blown engine, and I’m someone that would be interested in the above mentioned engine in that case.

[IamFODI]

Originally Posted by RichardC300

What are some of the actual downsides of a rebuilt engine, specifically a “better-than-stock”, street-driven engine? Assuming a street-friendly, pump-gas tune… Increased oil consumption? Increased maintenance frequency for some parts/services? I’m currently looking for an M3 and planning for the worst case scenario of a blown engine, and I’m someone that would be interested in the above mentioned engine in that case.

The big one IMO is forged pistons. Everyone uses these, and that's for a variety of good reasons. Downsides are more blowby and wear, especially when cold – so shorter oil change intervals, shorter rebuild intervals, and more need to drive gently until everything's warmed up. Also more oil consumption and noise when cold, if you care about those.

Some builds slightly increase compression (e.g. when they use Mahle POWERPAK pistons) and displacement (cylinder bores often need that much machining). Those introduce variables that might affect your margins for error in fuel octane, fuel quality, cooling, cat life, and maintenance. You should always be on your game with fuel quality, cooling, and maintenance anyway, but less margin is less margin.

Then there's the potential for little unknowns that won't matter to most customers but might add up over many tens of thousands of miles assuming the big stuff (tune, fuel, boost, abuse, etc.) doesn't kill your engine first. Aftermarket rebuilds make changes that have the potential to affect a bunch of obscure crap (combustion dynamics, material resonance properties, etc.) that can in turn affect oil change intervals, longevity, etc. Competent people and companies can do good guesswork about how those will pan out in reality, but there's no way to know for sure without at least an OEM-level engine development cycle. BMW of course did that for the S65, and then they followed it up with abusive real-world testing and validation. As we all know, even that arguably wasn't enough. But it's miles beyond what any aftermarket company is ever going to do. It's insanely involved, eye-wateringly expensive, and probably not a game changer for most customers.

None of this is unique to the S65, by the way. It's pretty standard stuff when looking at an aftermarket solution.

[omgzirra_exe]

Originally Posted by IamFODI

Pretty much.

Here’s how I’d put it:

In my decision matrix for this car, more-than-stock durability and more-than-stock power are weighted at zero. So, no amount of added durability or power over stock could offset even minor downsides for me – and it does seem like there are downsides to even the best non-OE rebuilds out there right now.

I do value the hell out of throttle response, so a lighter rotating assembly and less internal friction might ease the pain, depending on the details. But even then, the game still centers on minimizing downsides.

Does that make sense?



Don't be silly. Really appreciate you weighing in, especially with that level of detail.



Nice. Thanks.

Any opinion on how long is too long to sit between drives?

Curious about your experience with Partee. Will PM you at some point.



Again, speaking only for myself: I’m at 174k.

I’ve seen/heard Steve Dinan suggest that the design life of M engines is ~150k miles. My completely unscientific sense is that that feels about right. Like, I feel like I’ve seen these engines run past that mileage, but not often far past it. I feel like it's best to assume I'm on borrowed time and start learning now so that I'm ready when the time comes.

I daily drive mine, so the engine is always getting heat cycles. That keeps the seals from drying out and helps maintain a proper oil film on the internal parts.

That said, I don’t have any hard data to back this up. It’s just what I’ve seen over time.

What I do know is that cars that sit for long periods tend to develop more issues. When they’re not driven, oil drains off internal components, seals can dry out, and condensation can build up. In my experience, those cars often end up with more problems than higher-mileage cars that are driven regularly.

Honestly, I’ve seen more low-mile S65 cars with issues than higher-mile ones that are consistently driven.

If it were me, I’d aim for at least one real drive per week. Not just a cold start and idle in the driveway, but a proper 40–50+ mile drive where everything gets fully up to temperature. That keeps oil circulating, burns off moisture, and generally keeps the engine happier.

Again, just speaking from experience, not engineering data.

[Thumbie]

Originally Posted by IamFODI

Am I unicorn hunting here?

So in other words, you are looking to rebuild your engine to be EQUAL OR BETTER in terms of performance (power, throttle response), but WITHOUT sacrificing reliability or daily drivability?

If so, not a unicorn. because that is what I want too lol. I suppose you would call that "OEM+" and I think it's possible. Given how old these engines are now, rebuilding with all OEM feels silly, like there has to better parts out now, right?.

[omgzirra_exe]

Originally Posted by Thumbie

So in other words, you are looking to rebuild your engine to be EQUAL OR BETTER in terms of performance (power, throttle response), but WITHOUT sacrificing reliability or daily drivability?

If so, not a unicorn. because that is what I want too lol. I suppose you would call that "OEM+" and I think it's possible. Given how old these engines are now, rebuilding with all OEM feels silly, like there has to better parts out now, right?.

OEM length Arrow rods or any brand with a .5 compression bump via Pistons would do wonders.

assuming you rebuild the motor before you have to decide on boring it.

[IamFODI]

Originally Posted by Thumbie

So in other words, you are looking to rebuild your engine to be EQUAL OR BETTER in terms of performance (power, throttle response), but WITHOUT sacrificing reliability or daily drivability?

If so, not a unicorn. because that is what I want too lol. I suppose you would call that "OEM+" and I think it's possible. Given how old these engines are now, rebuilding with all OEM feels silly, like there has to better parts out now, right?.

Haha, cheers man
Yeah, technology sure has moved on since the 2000s when this engine was developed. That means there's plenty of stuff out there that could make this engine better in any way a person might want.

The thing is, there's a gap between "could" and "verifiably and repeatably does". It's not hard to cross that gap for power and durability. Crossing it for longevity requires f*cking around and finding out on a scale that no one other than BMW has ever tried or will ever try. The resources involved are eye-watering.

That's why, in practice, prioritizing longevity usually means defaulting to OE or OE-like solutions (e.g.cast pistons and one-time-use rod bolts). It's not that there isn't modern tech that could do better; there surely is. It's that implementing and validating those solutions requires incentives and resources that the aftermarket just doesn't have.

And it seems like the only thing unsexier than longevity is defaulting to OE or OE-like solutions. So, the aftermarket has even less incentive to do that, and finding a builder who'll die on that hill is hard. That's what I meant by "unicorn".

[omgzirra_exe]

Originally Posted by IamFODI

Haha, cheers man
Yeah, technology sure has moved on since the 2000s when this engine was developed. That means there's plenty of stuff out there that could make this engine better in any way a person might want.

The thing is, there's a gap between "could" and "verifiably and repeatably does". It's not hard to cross that gap for power and durability. Crossing it for longevity requires f*cking around and finding out on a scale that no one other than BMW has ever tried or will ever try. The resources involved are eye-watering.

That's why, in practice, prioritizing longevity usually means defaulting to OE or OE-like solutions (e.g.cast pistons and one-time-use rod bolts). It's not that there isn't modern tech that could do better; there surely is. It's that implementing and validating those solutions requires incentives and resources that the aftermarket just doesn't have.

And it seems like the only thing unsexier than longevity is defaulting to OE or OE-like solutions. So, the aftermarket has even less incentive to do that, and finding a builder who'll die on that hill is hard. That's what I meant by "unicorn".

Unfortunately, OEM isn’t always the clear answer.

For example, I bought a brand-new factory 2JZ-GTE short block assembled by Toyota. OEM rods, OEM pistons, factory fresh. And I still have to tear it down and check clearances just to be sure everything is actually right. That’s another $1,000 just for peace of mind.

At that point, what did I really gain from going OEM?

My original thought was to leave it untouched for longevity’s sake. Don’t mess with it. But in reality, I probably should have just pulled the 2JZ-GE short block that was already in my car and sent it out to be measured, machined, and blueprinted.

It would’ve cost about the same, maybe slightly more, than buying a factory short block and then paying to verify it anyway.

So I’m starting to think there really isn’t a clean “OEM vs OEM-like” solution. If longevity is the goal, the smarter move might be rebuilding the engine properly before you’re forced into an overbore. Once you overbore, you’re into new pistons and you risk compromising the cylinder walls if the Alusil surface isn’t handled perfectly.

Rebuild it early and you can keep the OEM pistons, refresh the rings, upgrade to stronger rods, and preserve the factory cylinder integrity.

Then, if you want make it "durable", cryo-treat the block, WPC treat the parts that would see friction, even the piston rings, upgraded main bearings, rod bearings, and use 625+ hardware where it matters. It might sound excessive, but it addresses weak points up front instead of reacting later.

That’s just my theory from building my 2JZ-GE, which is now basically a GTE-spec bottom end with a GE head. I’m not claiming it’s the definitive answer, just that “default to OEM” isn’t as simple as it sounds once you’re actually in it.

[IamFODI]

So here are my top 4 options right now, in no particular order, along with some commentary. Putting them here to record my thinking, offer some ideas to anyone else who might share my priorities (hopefully I've understood and summarized everything correctly!), and hold my thoughts up to the scrutiny of the community.


1. Full OE-spec rebuild

- Result would be exactly what I'm after

- So far, it’s hard to find someone who’ll do it the way I’d want it

- Highest sticker price, largely because factory internals are hugely expensive as Chrisyphus pointed out

- …Or they would be if they were even available, which some might not be, as Chrisyphus also pointed out

- Lowest probability that my block would be suitable, or that I could find a suitable block in the wild, because the cylinder bores need to be in great shape (they can only be machined so much before they're too big for stock pistons)


2. Partee "Better than Stock," Budget Version

- Requires a slight overbore right off the bat, so less need for a pristine core block

- Least expensive sticker price

- Forged piston problems, though not the worst (4032 alloy)

- Slight CR increase, which I’m a bit nervous about – I'd really rather not get a tune (trying to open up as few cans of worms as possible), and I don't like the idea of having narrower safety margins


3. Partee "Better than Stock," High End Version

- Can get stock CR (pistons are custom either way)

- Forged piston problems are worse than with option #2 (2618 alloy)

- Best feature set for reduced weight & friction – though apparently that includes DLC, which may introduce another unknown (DLCs have specific needs WRT lubricant formulation)

- Requires the biggest overbore, so maximum flexibility on the starting condition of the bores

- Sticker price comparable to the full OE option


4. Carbahn 4.2L

- Same upsides and downsides as Partee’s High End option

- Sticker price between those of the two Partee options – but 2x the core charge, and who knows how much I'd get back on a high-mile engine

- 2 year warranty

- Other side of the country (vs. Partee, which is ~6 hrs away)


Does this all make sense? Anyone think I’ve missed or misunderstood anything here?

[omgzirra_exe]

you won't really need a tune with a slight bump in CR. you don't even need a tune for a 4.2L or a 4.4L.

although it'll give you the full potential. on top of that you live in an area were 93OCT is readily available vs in SoCal where we have to use 91OCT and most people don't invest enough to run Full E85. so you'll be fine there.

the 4.6L yes for sure you will need a re-map.

[spammysammich]

Can confirm Dinan 4.2 ran well enough on stock tune to break in the cams and get the first few heat and drive cycles done. I was impressed how well the cylinders turned out having seen the state of the core going out to them.

[IamFODI]

Thanks, guys.

Power-wise, all I really care about is that I don't end up with less than stock. That seems unlikely, so I'm assuming I'm fine on that front.

I mainly want to avoid a situation where

1. The DME is constantly trying to run "normally," knocking, and then compensating; and/or

2. Combustion quality ends up subpar, because that can shorten oil life and cat lifespan.

I guess if either of those happens, it'll be visible somehow (basic logging for #1, oil analysis for #2), and I can... get a tune. I'd rather not open that can of worms if I can avoid it, but it's far from the worst outcome. OTOH, if the downsides of 2618 alloy forged pistons turn out to be significant in my use, there's no easy way around that.

I guess I did list my choices roughly in order of preference after all! 😬