DIY: M30 Engine Rebuild - '77 530i

[Funf Dreisig]

I'm deep into the rebuild of my '77 530i's M30 engine. The engine has low milage (75k) but has also had two long periods of no use. After the last one, I discovered that the head was cracked which allowed water into the #3&4 cylinders leaving large pits in the cylinder walls. Even though it wasn't the most economical solution, I decided to go with Metric Mechanic's 92mm pistons (3mm over bore) and a new AMS head. I had the block over bored 3mm (89-92mm) and line honed.

These photos show the block before/after painting. Yes, one of those Shiners has been opened ;)

-- Funf Dreisig

[Funf Dreisig]

These photos show the results of Dremel wire brushing the main caps, rods and interior of the block. The periods of disuse had left behind a crusty varnish/rust coating on all of the internal steel parts which was only obvious once the oil was completely removed. Scrubbing these parts with Varsol, soaking them in Berryman's B9 (48hrs) and then scrubbing them with Berryman's B12 didn't even phase this varnish/rust crust. So I ended up Dremel wire brushing the interior of the block, main caps and rods:( The picture of the main cap shows the varnish/rust crust on the left and the result of Dremel wire brushing on the right.

The next step is to put the crank back where it belongs and check the main and rod bearing tolerances. FWIW I mic'd the crank in January and expect that the tolerances will be at the ragged edge of being over spec. using standard size main & rod bearings.

If there is interest, I will continue posting notes and pictures of my progress assembling what will be a 3.2 liter M30 engine. I'd appreciate any advise you may want to offer on how to do a better job.

-- Funf Dreisig

[JoeCinVa]

I don't have any advice to offer but would like to add a vote to you continuing with progress and pictures.

[Funf Dreisig]

I don't have any advice to offer but would like to add a vote to you continuing with progress and pictures. Thanks for the interest.

The next step was to detail the crank and do a final inspection of all the crank journals. I've attached an overall view and close ups of two rod journals. The first one shows the indelible result of a stupid error -- I didn't cover the rod bolts with tubing when removing this piston and the sharp threads clipped the crank on the way past leaving a nice nick in the journal:( The other one is the #6 rod journal which shows a wavy banding in the finish. I've mic'd the crank twice to insure consistent measurements, Both times this journal measured .001" out of spec. Although .001" doesn't sound like much, it is a large percentage of the overall radial play tolerance on the rods -- .0011 - .0027". Based simply on mic'ing the crank, the #6 rod should have a radial play of around .0035" and the other 5 rods should be around .0025". Having one rod out of six this far out of spec is simply not good. So I will need to 'fix' this before final assembly.

FWIW this rod journal was probably damaged when the oil pump failed a few years ago. I noticed the oil light had not gone out as a backed out of the driveway after start up one AM. The engine only ran that way for a few minutes but every _second_ counts when you have little or no oil pressure. The #6 rod is at the furthest point away from the oil pump. Hence most vulnerable to oil pressure loss, oil contaminants, etc.

-- Funf Dreisig

[Funf Dreisig]

I finally reached a serious milestone -- I began assembling the engine! You know, the part of the project where you get to turn the nuts/bolts clockwise ;)

Well, technically this session wasn't actually 'assembly'. But I did get turn a few bolts clockwise and use the torque wrenches, while checking the main bearing tolerances:) The good news is that they were all nearly identical. The bad news is that they are all out of spec. This took me by surprise since the mic work I had done on the crank shows that it is in spec and the bearings were new std size bearings. So the problem must be somewhere else.

I've attached pics of the crank in its proper place and some of the Plastigage(tm) measurements during this 'dry assembly' session (#4 main closeups and group photos with PG-1 and PR-1). BTW the BMW Repair Manual specifies using Platigage PG-1 the check these 'overal'l radial bearing play tolerances. But as you can see the mains were out of the PG-1 (green) range (i.e. over .003). So I switched to PR-1(red) to get a rough feel for how far.

FWIW Plastigage is an inexpensive way to verify whether things are "OK" during a 'dry assembly'. In this case it told me that these bearings have very little or no taper but the 'overall' radial play is roughly .0035" (between .003" and .004") which is at least .001" out of spec. But once it showed me this 'overall' problem, Plastigage couldn't tell me exactly how far out of spec the mains are or where the problem is. For example, is this 'overall' .0001" error due to the crank, bearings and/or bearing bores being out of round or is it due to one (or more) of these components being out of spec.(all 360degrees)? And OBTW which component(s) is(are) the culprit(s)?

- Funf Dreisig

BTW The images are in reverse order, I tried twice to upload them in the correct order without any luck.

[Jetfire]

Ouch. Be careful there with the clearances. IIRC, you can run into oil pressure issues if you're running a thousandth of an inch too wide.

I'd also be a little wary of your crank. Again, it doesn't take much before the journal fails to maintain oil pressure. Visibly speaking, my crank journal was certainly in worse shape than yours, but I'm not sure what an acceptable amount of wear really is. The ideal is to have a mirror-smooth finish and I can't say with certainty that your crank will hold up if the journals aren't that smooth.

Do you have any technical resources (book, human, or otherwise) at your disposal with experience on acceptable tolerances? The BMW manual is telling you that you're somewhat out of spect, but how dangerous is that in real life? It's definitely MUCH better to find a replacement crank right now, rather than deal with failing bearings after the engine has been assembled and installed.

[Funf Dreisig]

Ouch. Be careful there with the clearances. IIRC, you can run into oil pressure issues if you're running a thousandth of an inch too wide.

I'd also be a little wary of your crank. Again, it doesn't take much before the journal fails to maintain oil pressure. Visibly speaking, my crank journal was certainly in worse shape than yours, but I'm not sure what an acceptable amount of wear really is. The ideal is to have a mirror-smooth finish and I can't say with certainty that your crank will hold up if the journals aren't that smooth.

Do you have any technical resources (book, human, or otherwise) at your disposal with experience on acceptable tolerances? The BMW manual is telling you that you're somewhat out of spect, but how dangerous is that in real life? It's definitely MUCH better to find a replacement crank right now, rather than deal with failing bearings after the engine has been assembled and installed.Thanks for the comments and advice.

The oil pressure issue is a big concern that is driving me to find a solution to the .0035" mains tolerances. The 'condition' of the #6 rod journal is also a worry. As you say, it's much better to deal with these issues now rather than after the engine is assembled and installed:)

BTW my posts have been lagging behind the actual engine work since there had not been much dialog. For example, I've already broken out the dial bore gauges and determined that the biggest culprit in the main tolerances is the main bores. They ended up .0008-.0012 over '0' spec when the block was line honed. Luckily BMW does sell a set of slightly oversize main bearings for the 'blue' crank/block combination. These are .0004" thicker that the more commonly available 'standard' bearings for the 'red' crank/block combination. This should compensate for .0008" (2 bearings @ .004"), bringing the .0035" tolerance back just into spec at .0027". Even if I end up getting a replacement crank, I'll need these 'blue' bearings to compensate for the main bores.

FWIW I discovered the Bimmerfest forums via Google link to one of your threads about rebuilding your M3 engine:) I'm sure I've read every one of your engine rebuilding posts at least twice gleaning tips, tricks and general info. Which brings me to your question about local resources. One of the great paradoxes of the asynchronous communication of the Internet is that, it is often much quicker/easier to find useful info, help, etc on the Internet than around the corner. Yes, even when you live in a major metropolitan area and belong to the local BMW CCA chapter for over 20 yrs. The phone book stinks compared to Google and you've got to make a lot of phone calls, attend a lot of chapter meetings, etc. to make the necessary local connections.

Please keep commenting. I need the info and suggestions to keep from messing up big time.

-- Funf Dreisig

My engine rebuilding helper got bored with all those micrometer/ dial bore gauge settings and feel asleep reading the specs:)

[Jetfire]

:) I'm glad to be of service. What use is gaining knowledge if you don't want to share it?

I was going to suggest oversize (or is that undersize? I never got the hang of that terminology) bearings for your crank. If your block was prepared correctly, those will be perfect for your situation (even if you get a replacement crank). As for connecting rods, be sure to check for roundness on the big end. If they've been pounded out, most machine shops have the ability to make them round again. Typically a very small amount of material is machined at the mating surface between the rod and the cap, then the ID is machined back into round. If you only have a marginal clearance issue there, this should be a good fix. Cleaning your rods was a good first step. Don't forget to label them by cylinder.

I got most of my technical help from the E30 M3 SIG, which is a subset of the BMWCCA. I can't remember which others SIGs exist, but perhaps there is one that would be in line with what you need. Another possibility is to try talking to some of the better known shops out there, like Don Fields, Korman, etc. They may be able to refer you to someone who can help. You may want to check out www.koalamotorsport.com; they publish a CD that exclusively covers E30 M3 repair, and they offer a few other titles for other models.

[Funf Dreisig]

:) I'm glad to be of service. What use is gaining knowledge if you don't want to share it?Exactly. It was your threads, with good quality pictures attached, that caused me to start posting my own rebuild notes and pics in this 5 series DYI forum.

As for connecting rods, be sure to check for roundness on the big end.... Don't forget to label them by cylinder.I've dial bore gauged the rods and they are probably OK (i.e. bore dia, and roundness). This engine was low mileage (75k) and I've put every mile on it:) So I'm going to stick with these rods as is. BUT I am going to swap the #3 & #6 rod. I couldn't believe it, but the #3 rod is perfectly on '0' spec for diameter. (yes I did measure it three times to make sure I wasn't fantasizing again ;) ) This makes it .0004" smaller than all of the others. So when mated to the #6 undersize journal it will 'fix' roughly half of the tolerance problem. I've ordered a pair of 'blue' rod bearing that are supposed to be smaller in diameter than std bearings. SO if everything works out I will be able to compensate for the #6 rod journal being undersized without having to grind the crank.

I got most of my technical help from the E30 M3 SIG, which is a subset of the BMWCCA. ... Korman... www.koalamotorsport.com...I've become pretty active on the BMWCCA www.firstfives.org E12 SIG. This is a very active and helpful group. I really appreciate this high quality E12 resource.

I bought my 92mm pistons, bearings etc from the Metric Mechanic. Jim Rowe (the MM) has been absolutely wonderful with phone advice and tips. I spent 45min on the phone with him today, talking through my main bearing clearance measurements and possible solutions. Those high ticket forged pistons are getting less and less expensive every day:)

Thanks for the link I'll check it out.

-- Funf Dreisig

[Funf Dreisig]

Before I ordered a full set of 'blue' std main bearings and the 'blue' std rod bearings for the #6 rod, I decided to follow jetfire's advise:) and get a 2nd opinion on the condition of my crankshaft and have it 'micro-polished'. The machine shop did a very nice job on the journals. They look great and mic out just as before. I took detailed pictures of each journal in three different positions to 'blue print' the crank with both pictures and mic measurements.

I've attached a picture of the crank after I mic'd it and before/after pictures of the worst journal -- the #6 rod. You can still barely see the wavy band pattern (if you know what to look for) but I'm happy as it is. I'd rather not lose any more clearance on this rod journal trying to get it better.

-- Funf Dreisig
Sorry the order of the photos got wonked up again:( They are #6 rod journal before, crank, #6 rod journal after micro polishing.

BTW is there some trick to controlling the order of the pics? FWIW I add them to the attachments dialog in the order I want them displayed but they seem to come out randomly.

[Jetfire]

Much better. :) Did the machinist seem to have confidence in the condition of your crankshaft?

[Funf Dreisig]

Much better. :) Did the machinist seem to have confidence in the condition of your crankshaft?Yes he checked it out pretty well and of course micro-polished the journals. He was only concerned about the #6 rod journal _diameter_ which I told him I had a fix for. Just swapping the #3 and #6 rod will bring it back just in spec but I expect the 'blue' bearings to bring it back well within tolerance. We'll see when the bearings get here:)

BTW thanks for the advice. I'm going to feel a lot better putting this baby back together knowing that a good machinist who looks a cranks all day every day (instead of once every 20-30 years) thinks it looks good to go:)

-- Funf Dreisig

[Funf Dreisig]

I'm in the final stage of prep-ing my 92mm bored M30 engine for the bottom end assembly. I mic'd all the journals after the crank returned from the machine shop for a 2nd opinion on its condition and a micro-polish of all the journals. The micro-polishing left the journals ODs essentially unchanged. So I've ordered the std 'blue' main bearings (.0004' thicker to compensate for line honing the main bores). And I will use the nearly perfect ID #3 rod to compensate for the .0004" undersized #6 rod journal OD. This should give me roughly .0025" clearance on all the bearings (mains & rods). I'll be starting the bottom end assembly as soon as the bearings arrive some time next week. But I still have the opportunity to do a better job based on the skill, knowledge and experience of helpful folks on this forum.

Any bottom end engine assembly suggestions/advice/tips?
What common errors should engine assemblers avoid?
What would you do differently the next time?

TIA - Funf Dreisig

[Jetfire]

Of course, take your time. That's the most important part.

Some machine shops don't do a great job of cleaning out the passages in your block after doing their work. Most small-block Chevy books will tell you to take some pipe cleaners or gun barrel cleaning kits through the holes until they come out clean. My machinist told me that the block was put through their bath both before and after honing, so I skipped that step and so far I'm doing fine. I've heard of some disastrous failures from missing this step, though.

Don't forget to use assembly lube. Be generous with the stuff; until you build up oil pressure in the engine, there will be nothing else to prevent your crank from rubbing against the bearings. Remember - the side of the bearing that touches the block or the rod is installed dry, the side that touches the crank is lubed.

Be sure to remove as much dust and other scrap material from the surfaces where the bearings meet the block/rod. I used brake cleaner to clean and dry all of those parts prior to installation.

Check and re-check the torque you apply to the fasteners. I almost left my main bolts torqued at just 25 ft-lbs because I had missed the part about angle torquing another 50 degrees! That would NOT have been good.

IIRC, both the rods and the pistons face a certain direction in the engine. If you didn't take photos during the teardown, consult with someone to determine the way to tell the proper orientation.

Be careful when knocking the newly ringed pistons into the block. Use PLENTY of oil -- just drench the damn thing. This will make your ring compressor somewhat slippery, so watch out there. I have two lovely scars from slips that occurred while working those pistons in there. A common issue is that the ring compressor will let a ring slip out between the bottom edge and the top of the block, so watch for that. When everything is lined up, the piston will almost get sucked right in. Watch out for that -- I have a nice scar on the inside of my left wrist from when that caught me unaware.

From now on, whenever you're not working on the engine, cover it with a trash bag or something similar. Make every effort to keep the dust outta there.

Sounds like a lot, but it's really quite simple. Again, take your time, and if something doesn't seem right to you, stop. You will find that you can usually use more effort than you think is safe, but there are some things you absolutely shouldn't force.

[Funf Dreisig]

Thanks again for your advice. It's always good to hear for someone who been down the same path recently:)

... I almost left my main bolts torqued at just 25 ft-lbs because I had missed the part about angle torquing another 50 degrees!.... Where did you find the angle torquing specs for the mains and rods? The BMW repair manual I'm using only lists standard torque specs (e.g. ft/lbs not degrees). FWIW I understand the concept but I don't know where to find the angle torque specs. Did you use an angle gauge or just estimate it while using a standard torque wrench?

BTW I'm guessing that there are nearly as many "assembly lubes" as engine assemblers;) Which assembly lube did you use?

Lastly, did you 'wind your rings on' or use piston ring pliers?

TIA - Funf Dreisig

[Jetfire]

Thanks again for your advice. It's always good to hear for someone who been down the same path recently:)

Where did you find the angle torquing specs for the mains and rods? The BMW repair manual I'm using only lists standard torque specs (e.g. ft/lbs not degrees). FWIW I understand the concept but I don't know where to find the angle torque specs. Did you use an angle gauge or just estimate it while using a standard torque wrench?

BTW I'm guessing that there are nearly as many "assembly lubes" as engine assemblers;) Which assembly lube did you use?

Lastly, did you 'wind your rings on' or use piston ring pliers?

TIA - Funf Dreisig
The Koala manual that I used for most of my work had angle torque specs. Only the rod, main, and head bolts use angle torques, though, and I believe that some of those specs were supplanted with traditional ft-lb specs in some instances. Double check, but you should be fine as long as the torque specs for those fasteners are sufficiently high (eg, not just 25 ft-lbs).

I bought a torque angle meter. The one I used is made by Lisle, and it basically looks like a small dial gauge with socket attachment points. I think it cost me around $35, which is a lot of money for what it is...but it worked.

I just picked out an assembly lube from the local parts store. Don't remember the brand name at the moment, but it was black and reminded me a bit of ointment in consistency. People will talk for hours on the merits of having various things in or out of their assembly lubes, but I didn't want to go mail order for something like that.

Piston rings -- I used pliers. Nothing special, just ones from the local store again (as well as the ring compressor). I think they cost me all of $10, and they came in pretty handy. Doing just four x3 rings on my engine by hand would have been pretty time consuming, and I'd just as well get a tool for the 18 you have to do. :)

[Funf Dreisig]

The special order 'blue' rod bearing shells for the #6 rod arrived yesterday. These are the 11 24 1 284 551 "BEARING SHELL BLUE 48,00MM(0)" that were used in various models of BMWs including 1502-2002Tii, 5' E28, 6' E24 and 7' E23. BMW says this bearing shell replaces the NLA 11 24 1 258 429 which was a 47.975mm (.001 oversize from 48.00mm) rod bearing shells for my E12 ('77 530i).

I was more than a little skeptical about this 'replacement'. I was even more skeptical whenI read the part number stamped in the bearing shell 11 24 1 284 550/551. This would indicate that the same bearing is now being used for the 'red' and 'blue' engines BUT>>>

After installing two of these dudes in my 'perfect' rod, I was astonished (and very glad/relieved) to see that the .0030 tolerance had been reduced to .0019! Which is pretty close to .0010 better than .0030;) And now nicely in the middle of the spec tolerance range of .0009-.0027.

So, now I'm ordering five more of these dudes, because the other five rods are running .0025-.0027 (just in spec) using the std bearings. I plan to use one 'std' and one 'blue' bearing shell on each rod. This should reduce the tolerances on the other rods by only .0005" and bring them to .0020-.0022" tolerance.

-- Funf Dreisig

[Jetfire]

Uh...the math adds up, but is this a common practice? I've never heard of mixing bearing shells before, but I am admittedly new to the game.

[Funf Dreisig]

Uh...the math adds up, but is this a common practice? I've never heard of mixing bearing shells before, but I am admittedly new to the game. I got this idea from Jim Rowe the Metric Mechanic. He says that this is fairly commonly done to 'fix' tolerances that are only marginally out (e.g. .0005"). It's common practice enough that I read elsewhere that there is even a 'recommended procedure' to place the thicker shell in the rod cap (IIRC).

Edit: Well I didn't remember correctly:( The thick shell goes on the rod side, not the cap, on connecting rod bearings. BUT the thick shell goes in the main cap, not the block, on main bearings. See http://engineparts.com/motorhead/techstuff/bearinginstall.html for more info.

-- Funf Dreisig

[Funf Dreisig]

The full set of 'blue' main bearing shells arrived this AM. These are part #s 11 21 1 261 042 & 11 21 1 261 034 for the "blue" engine/crank combination. Each shell is supposed to be .0004" thicker than the standard 'red' bearing shell to fit the slightly larger main bores in a 'blue' block.

I checked the radial play on my worst and an average main bore (#1 & #3). First, I double checked the radial play (using a dial gauge zeroed on the mic'd journal diameter) with std shells installed, then with the 'blue' shells. The 'blue' shells had exactly .0008" less radial play :) This will bring 4 of the 7 mains from .0035" just into spec @ .0027". Unfortunately, my worst main bore (#1) is still .0005" out of spec @ .0032". The #2 and #7 will be just barely out of spec @ .0029".

I'll probably just live with this and begin assembling the engine. But I'm still considering shaving the main caps .0005" to bring the #1 into spec. I'm assuming that I need to shave all of the caps to keep the bore aligned but wonder if this is necessary since it is such a small amount (.0005").

Has anyone had any experience (good or bad) with shaving main caps to tighten up the radial play?

-- Funf Dreisig

[Jetfire]

The full set of 'blue' main bearing shells arrived this AM. These are part #s 11 21 1 261 042 & 11 21 1 261 034 for the "blue" engine/crank combination. Each shell is supposed to be .0004" thicker than the standard 'red' bearing shell to fit the slightly larger main bores in a 'blue' block.

I checked the radial play on my worst and an average main bore (#1 & #3). First, I double checked the radial play (using a dial gauge zeroed on the mic'd journal diameter) with std shells installed, then with the 'blue' shells. The 'blue' shells had exactly .0008" less radial play :) This will bring 4 of the 7 mains from .0035" just into spec @ .0027". Unfortunately, my worst main bore (#1) is still .0005" out of spec @ .0032". The #2 and #7 will be just barely out of spec @ .0029".

I'll probably just live with this and begin assembling the engine. But I'm still considering shaving the main caps .0005" to bring the #1 into spec. I'm assuming that I need to shave all of the caps to keep the bore aligned but wonder if this is necessary since it is such a small amount (.0005").

Has anyone had any experience (good or bad) with shaving main caps to tighten up the radial play?

-- Funf Dreisig
Rather than go to the machinist with my own requests, I just brought the block and crank and asked him to check and machine the parts back into spec. The main caps are certainly machinable, and it's not a bad idea for you to get that done.

[Funf Dreisig]

Thanks again for you advice Jetfire.

I should have made my query more clear. I was (and still am) interested in the experiences of people who have used a plate of glass and 240-400 grit wet/dry sand paper to manually shave their main caps to tighten up main bearing radial play as much as .0005".

FWIW I have I spent most of the afternoon with a torque wrench or dial bore gauge in my hands :) double checking the main bores in more positions (e.g. 10:00, 12:00, 2:00; front and back) after cycling the main bolts several times. It turns out that the worst bore is only the front half of the #1 main. It is still .0007" over the max for a 'blue' main bore (.0008') but the back half is only .0003" over the max 'blue' spec. The other mains average within spec for a 'blue' block with the next worst single measurement being .0004 over spec.

Since the main journals are all in spec for a 'blue' crank (and almost identical), I plan to just use the 'blue' bearing shells to compensate for the average over bore on the mains and 'live with' the taper on the #1 main.

-- Funf Dreisig