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N62 Z3 Part 31: The End of the Beginning & Beginning of the 4.8 era

Well, after driving the car more it seems the smoking out of the exhaust did not fully resolve and cylinder 7 spark plug was always oily and 8 was oily, although less so than 7. I decided to investigate deeper in the engine as I had a hunch about what was going on. And unfortunately, that hunch was right.


I had read a few posts over the years and seen a few documented cases of scored cylinders in the N62 which can cause excessive crankcase pressure and smoking. Cylinder 8 had cylinder wall scoring, as pictured below:



But cylinder 7 was even worse. On one side, you can see deep scoring and it looks like the coating of some sort is being scraped off. I'm not entirely sure what happened, or why, it never overheated (in my ownership, anyways) and oddly enough, it still runs pretty well - it juts smokes a little bit, but consistently.


But the opposite side of cylinder 7 was a whole different story. Not even sure what I'm looking at here, but I know for sure it isn't good:



So cosmetics are on hold and a 4.8 engine will be going in soon. I am currently focusing on emptying my storage unit as I am sick of paying monthly rent over there - but as soon as that's done, this will be my priority.



I write this blog as sort of a stream of conciousness, and update the posts continuously as things progress - moving to a new post when it's become too lengthy. So if the tense seems off here or there, that is why. At some point I plan on cleaning it up for clarity but, as of this update (which is a couple weeks after the last update) I wanted to update as the storage unit is finally emptied.


When I closed up the shop, all the stuff had to go somewhere; thus renting the storage unit. And then more and more stuff got moved in there from my house as time went on, some came out - but certainly more went in. A year and a half ago - it looked like this. Literally floor to ceiling with... stuff. You can't even see all the way back in this picture as it was taken at night and I was using my headlights to look inside. Some of it was valuable, some only valuable to me and frankly just some absolute junk.



This was earlier today. A lot of it got thrown out or donated. Some if it got sold. The rest got moved into the house I now own, with ample storage space (thanks in part to the shed I built in the backyard and the shelves I built in the garage).



The feeling of looking back on my empty shop was a very negative one. It wasn't a decision I wanted to make and it felt like it was taken from me. Looking back on it though, it was one of the best things to have happened to me. After closing the shop a regular customer told me to apply the company he worked at as they needed people and I've been there since then and honestly I absolutely love what I do. More than that though and to the point of the build, it's really great to have wrenching be a fun hobby again, instead of a job.


I had long believed that if you do what you love you never work a day in your life. My current experience has re-contextualized this a bit though. If you love your job, you never feel the burden of work. If your job is your hobby, you don't have hobbies - you have a job. I now feel this is an important distinction.

Anyways, the point of all of this is to say that while I looked back at my empty shop with a heavy heart, I look at this empty storage unit feeling very grateful and with a huge appreciation for where I am. Emptying this storage unit feels like I am finally closing that chapter of my life and I am really excited for what is next.


And what is next is, of course, rebuilding a 4.8 N62


I found a 4.8 locally for sale and was allowed to look inside with my borescope. Cylinder 1 had an oily plug and looked like this inside:



~Many months later~


I looked at that last engine in June and finally, in October, found another 4.8 locally to buy. It came discounted due to a damaged oil pan which I will re-use from the current engine


I wasn't thrilled with how it looked on the pallet. It was covered in oil on bank 1 especially and was resting on the bank 2 valve cover. I wanted to inspect the bores before even leaving but wasn't able to do so - I had to get home to meet someone and I wouldn't have been able to look at bank 2 anyways due to how it was sitting. So I loaded it up and went home

Once I got it home and got time to work on it, I got the plugs out which looked great. Very optimistic at this point!

I went through each cylinder inspecting the bores and this was the worst I found. Combined with the clean spark plugs I think this engine has a clean bill of health!

I cleaned it up a bit and was pretty happy with the condition. The engine came from California, I think in transit an adjacent engine fell into it and spilled some oil on it. The oil that came out of this engine was a nice amber color. The oil on bank 1 was pretty dark and gross looking

After cleaning the fresh oil off the engine block appears to be in remarkably good condition. No signs of baked on old oil leaks!

There is *some* annoying stuff I need to deal with. The fuel rail is 4.8 specific and it is damaged. The valve covers are also both damaged, but I should be able to use the good ones off my 4.4; though that will require a different ventilation hose (which is fine, I hate the look of the hose with integrated CCV currently on this engine). Almost every sensor visible on the outside of the engine is also damaged, but I think they should mostly all interchange with the 4.4 stuff. The oil pan is also slightly damaged, but that was disclosed before I bought the engine.


Next up I'm going to take the valve covers off and take a peek inside.



I also went to mockup the M62/S62 headers but literally *all* of the exhaust studs are the opposite of how I need them (at least on bank 1... I think bank 1 might have one exhaust port that matches what I need). I'm going to have to devise some sort of jig to drill the new studs straight. I think I'm going to use a piece of wood and drill out where the current studs are - then drill where the new studs need to go and use some brake line in those holes to force the drill bit straight. Once the jig is set up, I'll use a little spray paint to mark where the new hole needs to be drilled, whack the center with a punch then use the current exhaust studs to hold the whole jig in place while I drill...


There is one point of concern with this - the technical literature says:

The early E65 745i *does* have a 4.4 specific oil pan part number. But, between 09/03 and 10/03, the oil pan part number changed to one that fits 4.4 and 4.8 N62's (11137519491 vs 11137589687). My engine came from an E60, and all production months of E60 used the 687 oil pan, which is listed to fit 4.4 and 4.8... Also of relevance, the 4.4i had a steel lower pan which BMW says accompanied the change to the deeper oil pan.

I also can't find *any* evidence of a cast aluminum lower pan, even in old E65 diagrams


So I don't think this will be an issue - but it's something that has been in the back of my mind for quite awhile. It'll be nice to find a solid answer on this soon enough


I have also already bought an oil cooler, and will customize stock E65 lines to fit. I think I'll mount it behind the kidney grills, but not sure yet Looks really great under the valve covers too. Might even have the newer style valve stem seals already... I'll be replacing them anyways, but that would be a good sign that the previous owner cared about and took care of the engine

I took the intake manifold off and compared to a spare "DIVA" style N62 intake (used on the 4.4i and E53 4.8is)

They look almost the same... but do seem to measure a little differently

They are both about 32mm width-wise, but the DISA style 4.8 intake is about 56mm length-wise compared to 53mm for the DIVA 4.4 intake. I'm still uncertain which intake I want to run, as I am a little hesitant to use the 4.8 even if it seems to have slightly larger intake ports, because it is a two-stage intake with sliding sleeves, instead of the continuously variable length of the DIVA


I'm going to try to do some more accurate measuring before making a decision. At this point I'm not entirely convinced the 4.8 is meaningly larger


I removed some other accessories as well and am very happy overall with the condition of the engine. All the cleaning I've done is using a paper towl to wipe off some of the oil that spilled on it during transit


Making good progress on the engine removal. Took maybe an hour to get it stripped this far

I do have a few things I want to upgrade or do a little differently on the reinstallation process. Some things I did sort of "temporarily" on the front end because I was so eager to get it driving once I got to that stage. I also need to relocate the power steering cooler because I'm going to put the oil cooler in the area that the cooler is mounted currently. I also think I'll upgrade the p/s cooler to one with a bit better capacity/cooling ability - I don't plan on tracking it necessarily but I also don't want to be in a situation down the road where I want to autocross it or something and back out because of worrying about something like overheating p/s fluid...


I also have one thing that has really, really bothered me since finishing the swap - and that is this dumb bracket. In hindsight, I should have mounted it off the timing cover of the engine. It was really dumb spending the amount of time I did on shaving the engine bay, then welding this dumb bracket on to make it all look ugly. So I'm going to shave this off, fix the indent for the reservoir and repaint both sides of the engine bay from the shock towers forward. Because I'll be doing a little more bodywork, I also want to touchup the radiator core support. It's such a focal point of the engine bay and it's not really up to my standards. It's not horrible, but it could be better...

The next day the parts arrived!

Included in that shipment was a new antennae seal, so for the Z3'ers following along at home here's a little trick on how to get that installed properly. If you don't have a long bolt in the correct size, use a tap to create one

Remove the remnants of the old seal

Then install the bolt and set the new bushing in place

Install the new bushing onto the antennae assembly itself first. Pull on the bolt while pushing the bushing down

Then push the bushing down into place. Use a little lubricant as needed

Remove bolt then install antennae

Done! Easy, no faffing around in the trunk, no hassle and no headache - done all from the outside of the car

Back to the V8 swap! I don't know why I decided to focus on this now, but I decided to fabricate a holder for the power steering reservoir. I wanted it about here

I used some brackets I had in my spares box and spent a little time welding this together. It's really sturdy, but I'm not sure how it will look when everything is installed. If it's too ugly, I'll build a jig off of this and make something nicer

Location is pretty much perfect, I didn't want to move it too far because I didn't want to make a new supply line. I also didn't want it too close to the engine, these things always leak and I didn't want it leaking all over the alternator. This seemed like a reasonable compromise

Then I removed the engine

Old meet new...

Feels like so long ago (it's currently October 12, 2024)

I heard some people say they remove the eccentric cam assembly to do the valve seals easier so I took that off. This picture also shows the exhaust cam off because I decided to go ahead and take the head off

FWIW if you did want to take the eccentric cam assembly out, I think you could use a marker or paint pen to mark the chain where it meets the intake cam, wedge something between the exhaust cam sprocket and the head to keep it from slipping on that side and then a ziptie on the other side to something to keep it from slipping off the crankshaft. In theory, if you reinstalled the intake cam at the alignment mark then timing would still be correct. I decided I will not be doing this on my new engine rebuild though, I'll just do the seals the same way I did last time

Got the head off to take a look inside

It looks bad from here too

The sections that look "raised" here are actually flush with the bore material, they look raised because the surrounding material is worn away

I am still not sure how this wear occurred to be honest. The smooth area on either side of the damaged section makes me think the piston skirt may have been rubbing against the cylinder wall, possibly due to overheating causing the piston to expand too much. Really not sure



The next day I took the piston out and confirmed my suspicions - the skirt was definitely scraping the wall there

What is odd too, is pretty much every piston exhibited some signs of contact, some more than others

I think what happened is the engine overheated and all of the piston skirts started dragging against the cylinder walls. On most it wasn't bad enough to damage the cylinder wall dramatically, but cylinder 7 - maybe because it was the hottest, or maybe for... who knows why - started gouging into the cylinder. This certainly made some sort of scary noise, at which point I presume the previous owner shut it off. Then they removed the engine and sold it to me, lol


It is annoying that this happened. But there is a silver lining because I had always planned on putting a 4.8 in there but at some point along the line I convinced myself I was ok with the 4.4 ...now that this happened, 4.8 was the only option. An extra ~30hp and ~50 N-m of torque and maybe even a bit more if I manage to get the M62 headers to fit!


I think that's about the end of the diagnostics on the 4.4... and this is getting a bit long, so let's separate the 4.8 rebuild portion into it's own post

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