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**roguetoaster** · 11-03-2019, 08:32 PM

Well, that's unfortunate, but the lack of exhaust gas in the coolant or coolant in the oil really bodes well for a relatively quick fix. However, I'd still dig in to the failure mode a bit more before yanking the head, even though it's not exactly a difficult task mechanically. Maybe start with a borescope/endoscope to check out the cylinders in question? If you do remove the head you'll need to pick your poison as to how you plan to clean the block surface as it's going to be a mess if there was a cross cylinder failure. Plugs look on the rich side of normal, with more deposits than I am used to seeing.

**bmwman91** · 11-03-2019, 09:07 PM

Yeah, I am trying to figure out how to proceed with additional diagnosis without jumping right into pulling the head. I have a cheap USB endoscope that I can try to get a look at the piston crowns with, and I can pull the manifolds to verify that the valves are closing. Still, 0PSI on adjacent cylinders and being able to detect air passing between them seems reasonably conclusive. I have no experience with this particular failure...what sort of carnage am I looking at with an inter-cylinder blow out? Could chunks of metal gasket have broken off and damaged a cylinder wall or valve? My bet for what damaged the thing is the totally bad ignition timing when the crank damper wheel failed. It did a fair amount of pinging for 10-20 seconds.

Plugs being rich is expected since I was doing a lot of tuning earlier in the year, and the car was running pig-rich for a while. But yes, the deposits on #3 & #4 are a little odd and I am not sure what the build-up is.

Got any pro-tips for how to minimize the amount of coolant and oil mess that I get when I pull the head? Last time I did it, I got a lot of coolant spillage even after draining it. It was a mess, and I don't want my cats getting at it (although I could push it out into the drive way for removal and then push it back in).

**roguetoaster** · 11-04-2019, 06:51 AM

Yes, absolutely, metal bits could have come off, but then again this isn't exactly a race engine built to the nth degree, so who knows.

As to minimizing mess, the coolant isn't too big of a deal as you can always drain first, refill with water and drain again. As to oil, the cam tray area really holds a lot of oil, so at best you might be able to bungee a skirt of rags to the block.

**bmwman91** · 11-04-2019, 09:20 AM

OK, well fingers are crossed that it's just a straightforward HG failure with no collateral damage. It's good that it was #2 & #3 since their compression & exhaust strokes coincide, so they never really had an opportunity to build much compression and ignite the mix...one would just push most of its air/fuel mix out the other's exhaust.

And yeah, pile-o-rags it is to deal with the oil. Pushing the car out to the driveway to drain the coolant is doable, and running a hose through the system seems like the fastest way to get the coolant out so that the cats won't find anything to drink when it is back in the garage.

I'll see about yanking the valve cover this evening to poke around up there for any signs of distress. In a couple of days I should have a rigid/controllable endoscope so that I can look up at the valves and HG interface from the spark plug holes. Even though I am 99% sure that the head is coming off no matter what, it'll likely be a few days before I hear back from Metric Mechanic about updated cams, so I'll leave the head on the car until I know if I am getting it machined locally or shipping it to them.

**bmwman91** · 11-04-2019, 11:13 PM

I got a little bit of prep done after work today. Mainly, I wanted to completely drain the coolant using the block drain so that there would be an absolute minimum of coolant left in the head. It makes a bit of a mess when you pull it off! I am being extra careful because the repair will be done in my garage, where my cats have access. Coolant is EXTREMELY toxic to cats, who like its taste and smell, and it causes an agonizing death. Anyway, I carefully drained it from the radiator first, and then got the rest out from the block drain using a funnel with a hose under the outlet. There was minimal spillage from there, and I just rolled the car back out into the driveway to hose things down. It'll sit there to dry for a day or two since I have limited time during the week, and it gets dark earlier now with the time change and all (I do not like Daylight Savings Time). I am sure my neighbors are used to seeing me manually pushing the car around in the driveway by now lol.

As a part of getting the funnel under the block drain, I removed the exhaust header. It is super easy to do if you remove the right side engine mount arm (support the engine with a jack). It slides right out the front...as long as you do NOT have A/C installed. If you do have A/C, then you either need to remove the compressor, or the sway bar (and even then I am not sure if it would go out the back).

The coolant did not quite look right. I'd say that combustion gases were definitely making their way into places that they did not belong. This coolant is less than a thousand miles old!

A good amount of debris came out with it, after using the block drain. The dark stuff was almost all magnetic, and I am guessing that this is burned head gasket material.

There was also this bit of paper material in there. I'd guess that it is not from this failure since it does not look burned. Maybe it is just crap from a past gasket that I scraped.

There was a little bit of an indication of trouble (maybe) at cylinder #3's exhaust port. I am guessing that some of the large detonations that occurred in the exhaust when the crank damper was failing had damaged the gasket. It would explain why I thought that the car was making more exhaust noise than usual.

That is it for today. Next steps in the immediate future will be to re-run a compression test after re-charging the battery fully, and using a better compression test kit. It irks me a little than cylinders 1 & 4 were reading low with the loaner compression gauge, and I can't imagine that all four cylinders went out together. Besides, if they were totally shot, I wouldn't think that the engine would run on 2 cylinders at all, let alone enough to get me the last mile home. After the compression test, I will start stripping the rest of the stuff off of the head in preparation for its removal.

**digger** · 11-05-2019, 02:18 PM

there are a lot of dodgey comp testers out there. people say its consistency across cylinders that matters but the absolute numbers means something as well.

are you using any kind of additive in the fuel like octane booster or cleaning agent? none of those flecks on the plugs looked like alumnium did they?

good news is if/when head comes off it means there's scope for some tinkering.....

**bmwman91** · 11-05-2019, 02:27 PM

No additives at all. And no, I do not believe that any of the contamination on the plugs was aluminum, although I can't really test to be certain. What would aluminum on the plugs indicate to you?

And yeah, possible tinkering. I was on the phone with MM earlier. While it might not really be something I have budgeted for, it sounds like they have vastly improved upon the ultralight rods and pistons that they use. The stuff in there now is about half the mass of stock, and their latest and greatest stuff is nearly 40% lighter than what is in there now. That would be some real tinkering lol...ship the engine back out there and have the moving bits in the bottom end lightened up even further. It'll all depend on what I find when I get in there. MM thought that seeing low compression on cylinders 1 & 4 could also be a sign that there are bigger issues, like burned valves or shot rings, but considering that the thing will still run on those cylinders, well enough to limp home, and the failure occurred under light-load in 5th gear put-putting around town, I am hoping (living in denial?) that it's just a crappy tester and maybe fuel-washed walls. The valve timing is, as far as I can tell, just fine since the M42 makes distinctive noises when valves meet pistons. Since cylinders 2 & 3 registered as ZERO on the gauge, I think it might well be the gauge since I'd expect at least a few PSI from cranking with just a hole in the HG.

**digger** · 11-05-2019, 03:16 PM

Originally posted by bmwman91 View Post

No additives at all. And no, I do not believe that any of the contamination on the plugs was aluminum, although I can't really test to be certain. What would aluminum on the plugs indicate to you?

And yeah, possible tinkering. I was on the phone with MM earlier. While it might not really be something I have budgeted for, it sounds like they have vastly improved upon the ultralight rods and pistons that they use. The stuff in there now is about half the mass of stock, and their latest and greatest stuff is nearly 40% lighter than what is in there now. That would be some real tinkering lol...ship the engine back out there and have the moving bits in the bottom end lightened up even further. It'll all depend on what I find when I get in there. MM thought that seeing low compression on cylinders 1 & 4 could also be a sign that there are bigger issues, like burned valves or shot rings, but considering that the thing will still run on those cylinders, well enough to limp home, and the failure occurred under light-load in 5th gear put-putting around town, I am hoping (living in denial?) that it's just a crappy tester and maybe fuel-washed walls. The valve timing is, as far as I can tell, just fine since the M42 makes distinctive noises when valves meet pistons. Since cylinders 2 & 3 registered as ZERO on the gauge, I think it might well be the gauge since I'd expect at least a few PSI from cranking with just a hole in the HG.

Detonation can cause piston material to deposited on the plug sometimes but is probably unlikely.

Don’t you have the 2.1 rally? Like ~300g piston and ~500g rod? You aren’t going to make big savings on that and any savings will give minimal tangible effect as the durability is probably already well in excess of what you need and any change in mass moment of inertia is a small part of the total system inertia.

IMO You want to focus on breathing mods, not reduction of mass.

Yes, a zero reading is an indicator of a rather large hole.

**bmwman91** · 11-05-2019, 08:59 PM

Yeah, 2.1L rally from Metric Mechanic. They have been cooking up some pretty crazy stuff in the piston & rod department in the last 7 years: pistons at 195g vs. the 310g in there now, rods at ~350g vs 500g in there now. Obviously MM is going to try to sell these things pretty hard since they are a business, but if it does end up being the case that I need bottom-end work, I might go that route. We'll see...it wouldn't be cheap for the kind of returns I'd see, and an MM engine is already high on the $/HP chart.

As far as breathing mods, I have thought a bit about that. I like the mid-range power that it makes now and don't want to end up taking a big hit there. I'd need some input from some experienced builders to determine the right amount of porting to do in the head, and what could be done with the exhaust and intake while keeping a balanced torque curve. I know that the conventional wisdom is that opening things up "is bad for low-end", but I have also seen a number of engines not have that be the case after a proper tune. People who actually spend the time to learn the science and engineering behind optimizing air flow must roll their eyes at such statements. I know enough to know I don't know enough to make flow modification decisions myself and expect good results! I always wanted to go super technical on engine operation and optimization, but my technical hobbies and career all sort of veered away from cars over the last decade and I probably won't have the time to try to become proficient in that area any time soon, as much as I really would like to.

**digger** · 11-06-2019, 01:46 AM

what happened to some posts?

Their recent M20 piston stuff is 245g so another 50g off is huge when the physical size is about the same and id be worried about putting that in an engine without them having test mules that have done 60,000 miles. The fancy slipper design light weight pistons have a tendency to crack when they get light especially with lightweight wrist pins. The combustion loads are quite a bit higher than the inertia loads so I don’t see huge gains in durability with overly light parts, seems like mostly risk. It’s not a race engine that gets torn down often.

some ideas from me
- a tri-y style header with about 24" primaries 1.5" diameter would be a good fit
- a catcams http://www.catcams.com/products/cams...nguage=english with cam centrelines much tighter than what MM recommend
- cylinder head depends what it flows, what the cross sectional areas are and resulting velocities are as to how efficient what you have.
- ITB seem to work well.

i'd probably get a good core and find a specialist to do some head work new cams etc

**bmwman91** · 11-06-2019, 12:10 PM

The auto-moderation seems to flag a post as SPAM if it is edited multiple times or (maybe?) has certain words).

Yes, that was one thing that gave me pause. The ultra-ultra light stuff they are just coming out with has not seen a tremendous number of miles yet, and given my increasing desire to not have to mess with this engine much more, I am largely tempted to keep the bottom end as-is if it is not damaged. And yes, durability is probably not going to increase so significantly that I ever notice since even stock heavy stuff can go for half a million miles in many cases. MM's logic is that reducing the reciprocating mass frees up a fair bit of kinetic energy, particularly at higher RPM, to be put into the drivetrain instead of accelerating piston/rod assemblies. Technically it makes sense, but there's the big question of just how worth the money it is. The thing already revs like a crazy animal, and for the (I assume) $5K+ it would cost to ship + rebuild the bottom end, I could probably do all of the stuff you suggest while leaving the already built bottom end alone.

- Sssquid mentioned another 2.1L M42 that he tuned had a higher flowing header, and that it made a noticeable improvement in performance. I'll see if I can track down specifics.
- Interesting about the cams. It looks (from your build thread) that you have used some MM stuff int he past. Is it your experience that they are being conservative with their cam profiles? Also, what is your take on their surface turbulence valves?
- The head is MM's usual moderately opened-up one, which as far as I can tell is a reasonably conservative porting. This area, specifically, is where I would need to sit down with a competent shop and discuss what all could / should be done to keep a balanced torque curve while allowing for better flow & gas dynamics.
- ITBs. There are a couple of bolt-on options that I know of (dBilas, RHD), so that would be easy enough, logistically. I have heard that the dBilas setup is not terribly well optimized for the M42, which is why RHD developed a well engineered kit.

Agreed about the spare head. If I am going to do any amount of head work, it would best be done with a clean original one.

If you don't mind sharing some guidance once I know for sure what broke, and how far down the rabbit hole I want to go with this, then maybe I could rekindle my desire to get from ~95HP/L to over 100.

**digger** · 11-06-2019, 04:10 PM

Some food for thought

Mass/Inertia

I look at it like this, if you want to reduce the inertia of the engine to make it rev quicker you target the biggest inertia which will be flywheel so if you don’t have a RHD lightweight FW then you are not picking the lowest hanging fruit so going nuts on the other stuff is not the best approach.
After the FW probably the crank (excluding the clutch pressure plate) is the next big ticket item and the big end weight of the rod. I wouldn’t be targeting the big end weight too much because the metal around that helps keep the big end tunnel round under load to keep the bearing lubricated properly.
Without question the best way to make the engine rev faster under load is make more torque/power. The lighter inertia helps in first gear and a bit in 2^nd. In 3^rd the effect is essentially negligible.

Header

The header does need to be big but it needs to align with the ports and transition smoothly and the smaller the pipe the more it matters. The length is important as runners in the 18” range tune in at too high of an rpm to be useful on a street engine. i haven’t done much modeling of 4-1 or 4-2-1 system to give too much insight other than 4-2-1 on a V8 seems to be better for rpm we are dealing with here.

MM Engines

The underlying philosophy behind what seems like most of their engines is a bias towards fuel economy, emission and smooth idle by limiting what they do on the exhaust side and with cam timing (lobe centerlines). For a street engine it’s certainly a balancing act but IMO they are too far to the left for most.
A high performance engine must use the exhaust side to do the following

Have enough “time-area” to exhaust/evacuate the cylinder sufficiently such that the cylinder pressure reduces as low as possible prior to the induction starting;
Pull additional depression on the cylinder to support 1) and get the inlet charge moving before the piston starts moving;
Have the exhaust valve to open as late as possible to extract all the energy yet still have sufficient time area to achieve 1).

Failure to achieve that causes reversion at the start of the induction stroke and the engine will never make good VE (i.e. good torque per capacity “ft/L”) irrespective of how good the inlet side is.

Cams

The cam lobe profiles MM use are pretty aggressive which is good, by aggressive I mean

the duration numbers at high lift are good;
the lift is reasonably good so the area under the lift curve is good; and
they don't use excessive duration.

Some negatives

The exhaust duration is pretty conservative which is ok if the engine has a good efficient exhaust system but if you are using a stock-ish setup then this costs mid to topend power.
The lobe centrelines they use are designed for fuel economy and emission, as such they are very wide which limits overlap and the engines ability to do 2) and 3) does not occur either. It’s the exact opposite of what you want for WOT performance specifically bottom end to mid range.

Head

For the ST on back of valves, it seems that the angles on the valve seat, backcut and margin are sufficient enough to shear the fuel adequately. Unless I see A-B tests confirming that kind of stuff then in my mind it’s still just theory. My thoughts are there might be merit in textured surfaces but the scale and shape are important and it probably needs to be smaller scale (finer grooves/texture etc) to actually work.
To make more power often you need to open the restrictive parts of the head up, without knowing stock M42 head details it could be oversized already from the factory as many early 4V are, so the porting approach is different. If One thing for sure is if you open the head up the flow should increase accordingly and the flow divided by area (average velocity) should increase otherwise the engine will be a dog.
Good cylinder head specialist will be able to improve I’m sure. The issue is finding someone.

**bmwman91** · 11-06-2019, 08:31 PM

Wow, thanks for the primer on that stuff, the explanations are good and clear.

Mass/Inertia
Yes, the low-hanging fruit is mostly claimed. The pistons & rods are already significantly lighter than stock, so changes there would be marginal. The crank is the 88mm M47 one, so it's a necessary mass increase that I am sure more than makes up for itself. I have MM's lightweight flywheel in there now. It's an M20 FW turned down to ~11.5lbs. More importantly, almost all of the mass was removed from that thick part of the cross section near the OD, so the polar moment of inertia was greatly reduced, which is what counts. The M20 PP & clutch offset that a bit since they are 228mm vs the M42's 215mm. Anyway, it looks like mine is 8lbs less than stock, but 4lbs heavier than the RHD one, with even more mass removed from the OD on the RHD one. The RHD one is so (relatively) cheap that I might consider it, especially if I end up pulling the engine to do the head and clean everything up nicely (or get the block re-decked).

Header
I'd believe that the stock 4-2-1 M42 header might be a bit under-size for the 2.1L. Again, Sssquid mentioned that he tuned a 2.1L with a larger custom header that responded well to it. I am seeing if he can track down some details. It's a bolt-on, so this is highest on my list since it's an hour to install once I am confident that a competent design is on deck. Sssquid could probably work up a new tune for me pretty easily (he and I have been collaborating on M42/Motronic 1.7 stuff for a couple of years now).

MM Engines
This makes sense. Given their prices and who I assume their target market is mostly comprised of, I can see them shooting for getting the best performance possible after making sure that idle, MPG and in-traffic behavior are nice and predictable. I have no idea what their race engines are like, but the "rally"/street engine I have fits your summary pretty well. It's more pleasant to drive as a DD than the stock M42 while also being a good deal faster. 195bhp from a 2.1L seems fair enough. You are way better informed on this than me...is getting above 100HP/L no longer a really big deal on a built NA street engine without major concessions to MPG and reliability?

Cams
It Cat Cams can work up a better profile for this engine that basically makes things better all over the powerband, I am up for giving them a call. These are bolt-ons for the most part, and I am sure I can get a good tune to go with them.

My preference is not to take a hit to fuel economy though...the car has been getting 18-22MPG since I put the engine in 7 years ago. I've been over every part of the fuel & control system in the car and replaced basically everything, so it isn't from that. The drivetrain is basically brand new, and the parking brake is correctly adjusted. Anyway, I assume it's just how the built engine runs. If this is an indication that something is very wrong, then I'm all ears.

Head
Yeah, I'd need to do some leg work to find a trusted, competent head specialist. I am not sure how many are in the region, but I believe that there are at least a couple. My inner OCD tendency is to want to do head + cams + exhaust all together and have them designed for one another. The realistic side of me figures that the exhaust & cams can be done individually to get things flowing better, and then if I do end up getting head work done, maybe the whole system together would be 90% as good as it would have been had it all been designed together. As far as I can tell, the big factor here is getting the fuel & ignition re-tuned to take advantage of the new system dynamics.

==================================================

I got a look into the cylinders with the borescope this afternoon. I noted multiple HG failures, and I assume that cylinder 3 was the source of the problem. Both cylinders 2 & 4 showed HG ruptures protruding into them, so there must have been a heck of a misfire in #3 at some point. Back when the crank damper went out, I was driving through my neighborhood under light load. The misfires occurred when limping it the last quarter mile home and while troubleshooting in the driveway, so no high RPM operation was occurring at the time. That makes me think that I may have made a mistake (or multiple) when installing the HG in 2013, and that whatever flaws there were in the assembly were made worse by the low-load detonations and then it finally gave up the ghost this last weekend. I'd bet that the inter-cylinder leaks have been there for a while as pin-holes, which would partially explain the bad gas mileage. My increasingly-poor idle and increase in engine/exhaust noise over the last few months could have been the leaks opening up further. Considering none of the external visual and electrical tests I did at any point came up with a cause, this seems plausible as a root cause.

Here are borescope shots of everything. I don't see any immediately obvious indications of trouble beyond the multiple HG failure sites. Despite my best efforts to vacuum all debris out and away from the plug holes, crap still made its way in, so I am not bothering with any compression tests and just going straight to pulling the head. Turning the crank with a wrench also aligns with what I can see. Cylinder 1 has the expected compression/resistance, cylinder 4 has a little resistance and there is none from 2 & 3. Basically, I am sort of surprised that it was running at all.

EDIT: Now that I look closer, #1 might have also been leaking with #2. Not enough to rupture, but there is a suspicious amount of carbon buildup. Anyway, the period of time in 2013 when I did the HG was not a good point in life on multiple fronts, and I was ready to sell the E30 just to be rid of it. I was stressed, sleep deprived and rushing the repair despite it being my first time doing it. If I really did that poor of a job, then I am glad it failed enough to be obvious so that I can take my time and do it properly this time. I almost don't want to post these pictures because it's embarrassing to believe that I may have done it so poorly!

Cylinder 1

Cylinder 2

Cylinder 3

Cylinder 4

**roguetoaster** · 11-06-2019, 08:58 PM

Gnarly, but not beyond salvation by any means. If you don't already have the IM off I'd be curious if you has a seal failure or crack at number three. Alternately, you may have damage in the number three injector loom, or maybe just a clog at the injector as a single cylinder massive over lean condition does not seem likely to be a management issue, but rather a physical failure.

Neat borescope, wish mine were aimable in that way. Model details if not egregiously expensive?

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M42 Head Gasket Blown, Project Thread

M42 Head Gasket Blown, Project Thread

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