Machine Shop

[flumph]

I dropped off my M20 short block at the machine shop for them to run everything through the parts washer and have everything miced.

Is there anything I should watch out for? Can you guys think of anything I should have checked while it's at the shop that they wouldn't normally check?

[zaq123]

make sure they don't hot tank the block and you should be good. You can ask them to pull the oil gallery plugs too while it's there. This way crap from machining and old crap will get washed out from the gallery

[noid]

I dropped off my M20 short block at the machine shop for them to run everything through the parts washer and have everything miced.

Is there anything I should watch out for? Can you guys think of anything I should have checked while it's at the shop that they wouldn't normally check?

Dont hot tank the block unless you plan to change the auxilary shaft bearings.

Much harder then it sounds (even for your machinist), better to not hot tank the block.

[TobyB]

And those bearings were unobtanium a while back. Are they available again?

t

[zaq123]

And those bearings were unobtanium a while back. Are they available again?

t

$25...looks to be available. Machining it is a different story

[ForcedFirebird]

Still available, the guy I have line bore the main caps does them for me. It' not much different than line boring a block, except it's much smaller. Press bearings in square, while taking note of oil hole location. Then burnish to .001" clearance on the intermediate shaft (shaft diameter is not consistent from engine to engine, which is what confuses people). Any experienced machinist shouldn't have a problem if you tell them the procedure. Some OHV push rod engines use the same process as the m20 for their cam bearings, so it's no really a mystical procedure.

[digger]

I agree I don't get why all the fuss

[ThatOneEuroE30]

What does hot tanking do to the bearings? When i rebuilt my m20 i stuck my block in the parts washer and didn’t have any issues with reassembly. Parts washer and hot tank are different animals though. One is dipped in a mixture of chemicals other is just spraying hot water as it rotates.

[ForcedFirebird]

What does hot tanking do to the bearings? When i rebuilt my m20 i stuck my block in the parts washer and didn’t have any issues with reassembly. Parts washer and hot tank are different animals though. One is dipped in a mixture of chemicals other is just spraying hot water as it rotates.

The soft metals in the bearings will severely oxidize in the tank if the solution made for iron, so they will need replacing in that case.

[flumph]

So I've had my block in the shop for a while now, and everything seems to be fine. It seems that someone put 'i' pistons into their 2.7L block and put an 885 head on it. No big deal though. All the main and rod bearings checked out fine, and the cylinder bores were all within spec. Pistons seem fine. I'm replacing all of the main and rod bearings as well as the piston rings just for good measure (and I mean why not, they're cheap). Also managed to find a set of ARP studs, which are apparently getting kind of scarce in places that stock them. Regrinding and lapping all of the valves as well as surfacing the cylinder head as well.

I made sure to tell them not to tank the block because it will torch the IMS bearings, and he said he would take care of it, but now he keeps using the word "vatting" which worries me a bit.

The thing that has me down though, is that they want $850 to put everything back together into a long block. He says that his guy wanted over $1,000, but that he's giving me a break because I'm having so much other work done. Thing is, I'm kind of out of money to throw at this thing right now, and I have nowhere to keep a fragmented BMW engine until I scrape up a spare grand.

I know it would get done properly and all that fun stuff, but I really have to wonder if it's something that I can do myself. I have all the parts, everything is clean and checked. All the seals and gaskets are new. I've got a torque wrench and a socket set, and I know how to use both of them. All I'm really missing is an engine stand, a hoist to yank the thing out of the trunk of my Jetta (lol), a tube of grease, a weekend, between 6 and 10 beers, and half of a two-car garage. The only thing I might need that I don't have is a ring file and a ring compressor. If I did this, I'd also have a chance to plastigauge everything.

Would it be a foolish undertaking for me to attempt assembling a long block by myself with no prior experience other than general wrenching and several exploratory junkyard trips? I'm reasonably mechanically inclined.

Thoughts?

[ForcedFirebird]

So I've had my block in the shop for a while now, and everything seems to be fine. It seems that someone put 'i' pistons into their 2.7L block and put an 885 head on it.

Are you sure? If one was to put "i" pistons in a 2.7 block, the pistons would be down in the hole by 2mm, and you would have 130mm rods and 81mm crank.

You might have a seta engine - one year only seta pistons that look similar to "i", but have 8.5:1 compression instead of 8.8:1, and the pin height is different to accommodate the cranks throw.

[flumph]

My initial thought was that it was a seta. When I was pulling it at the yard, I was expecting a regular B27, but I was super confused when I saw an 885 head on it after I got the intake mani off. Sure enough, I pulled the head and saw pistons that weren't flat-tops. Furthermore, the car it came out of was an '88 325e, so... I'm not sure what I have here.

It may well be a seta. If that's the case, I'm really glad I'm having it rebuilt. Not too many of them out there. The only thing making me think that it might not be is that the pistons don't have the little chamfer in the dish (seen in the chart on this page). The block was fitted with the crank angle sensor on the flywheel, and a non-toothed harmonic balancer (typical of eta engines).

I'd be happy to post a pic, but I can't figure out how to make photos post on the forum. The piston crown has a small "83.98" engraving for the bore size and then a larger "10". They have two valve relief cuts. I supplied the shop with rings to fit 'i' pistons. I hope this was not an error! If so, does anyone want to buy a fresh set of Goetze piston rings?

Also, after sleeping on it, I'm thinking that it's a good idea to have the shop complete the assembly. I don't have a garage, and I should respect the guys doing the work as professionals and allow them to do the whole job, not just part of it. $850 is a lot of money, but I have a feeling it'll be worth it.

Also, a freshly tanked cylinder head casting is damn near a piece of art...

Edit:
I do have some spare parts that are in decent shape that I could sell off to fund this. I've got two cylinder heads just taking up space, and a really clean set of tail lights. Anyone?

[TobyB]

I don't get why all the fuss

only because the bearing shells themselves disappeared for a while
a number of years back, I think.

t

[ForcedFirebird]

The 1988 325e is a seta. :)

Bad news is, it used eta rings which are thinner than "i" piston rings.

[flumph]

Ok... Long overdue update.

The engine is in and it runs and I've paid the men. The car's back in my hands. It's running with the 'i' rings, what appear to be standard 'i' pistons, late-style main bearings (oil groove only on the upper shell, not both), standard rod bearings, and a crankshaft of unknown stroke. I checked and the pistons do come right up to the deck. They do not fall short, like 'i' pistons would if you fitted them with an 'e' crank.

This leads me to believe that someone swapped in the whole rotating assembly from an 'i' motor, but didn't update the harmonic balancer or transmission so that they could still use the 'e' computer (why they would attempt this, I do not know). This assumption checks out with the fact that the inside of the cylinders were extremely caked with carbon buildup, because the 'e' computer was doing fuel calculations for a 2.7L displacement, while it was in reality a 2.5L.

To further this assumption, I drove it around a little on the street behind the shop, and it was running very rich on the old pre-rebuild tune (that was working well on an engine that I knew to be 2.7L). I even tried setting my AFR tables to 16 at idle (bad idea!), and it never got above 12, even after running VE analyze. This is worsened by 19# Lucas injectors (I plan on returning back to 14# Bosches, since my injector PWM is unnecessarily short). I have some pictures that I can't figure out how to post on here.

But the kicker...

I went through this entire thing for a few reasons.

• blowby gas/steam shooting out dipstick tube (discovered after MS install)
• visible oil mist in engine bay
• oil burning
• gas in the oil
• leaking main seals (both)
• leaking oil pan
• loss of compression on 2 cylinders (1 and 2)
• shuddering under acceleration above 2500 rpm

I thought that the compression problem was causing the shuddering under acceleration above 2500 rpm, and that a new engine would fix this. NOPE! It still does it!! I'm glad I did all this, because now I have a brand new engine, but I'm also really mad at myself for misdiagnosing the actual problem, spending thousands of dollars, and being without my fun car for ~2 months. The center support bearing needed replacement when I got the car in 2016, and I know I have a torn CV boot, so I'm now guessing that my drive shaft U-joint is toasted. Might pull some shafts from a junkyard car and test my luck...

tl;dr: it probably isn't a seta, but an eta block casting with an 'i' rotating assembly and an 885 cylinder head. So, basically an M20B25. Which I'm fine with.

Tonight, I'm going to try changing the fuel calculations in TunerStudio to run with 2.5L displacement and see if my AFR/VE starts to make a little more sense. Also, the new engine sounds wonderful. No more missing, good low, growly exhaust. Sounds like a new car! Just need to sort the software now...

They didn't install my garagistic motor/trans mounts though :rippedoff:. Oh well.