Need advice from experience for an M42 rebuild

[bmwman91]

I 100% endorse swapping to the 1994-1995 M42 timing case. The deflector sprocket in the original E30 design is crap and a time bomb. It is what did in my original engine.

It is a direct swap using the parts you listed.

The gasket PN was updated to 11141739868. Other than that, everything should be exchangeable between the old & new desgn. Just make sure that the top bolt for the long driver's side guide is 45mm long. When the design was updated, the old rail had a 40mm bolt, and using it with the newer one often leads to stripped threads in the head.

[JonsE30]

so i was researching more on replacing the timing components and i ran across a thread of swapping it to an late m42/m44 timing case?

would this be cheaper than replacing all the original m42 pieces since parts are more avaialble? i also read its more reliable due to deflector vs idle gear?

i found a list of parts needed on m42club:
Lower Timing Chain Case - 11141739699
Gasket, case to block - 11141743032
Deflection Rail - 11311739130
M6x35 Head ScrewsX1 for deflection rail - 07119919824
Bottom deflection rail - 11311734694
M6x25 screws X2 for bottom deflection rail - 07119919926
M6X25 Washers X2 - 07119931044
Gasket set, TC cover - 11141247633

do i leave the upper timing case all original?

[JonsE30]

luckily, i put some pressure on the damper and it has a lot of resistance. so thankfully those are areas i can save money on.

[bmwman91]

The sprockets look good.

For a part produced in early or mid 1990, the damper also looks OK, but it is hard to tell from the photos. With your hands, grip the outer metal toothed ring and use your thumbs to try to separate the inner metal hub. Do this on a few places on the perimeter, from both sides, and keep an eye out for indications that the rubber has cracked. You should not really be able to move anything at all if it is fully intact.

Maybe mine bit the dust because I rev the engine to 7500RPM pretty regularly lol (fully built 2.1L M42).

[JonsE30]

Just dropped off the block (with lower timing case cover and oil pan in tow) at the shop today. I hope the damage won’t drive me off this project.

I got home and checked the condition of my sprockets and they don’t look pointy. I also looked at the vibration damper and it looks like it is still in good condition. I forgot to take a pic of the sprockets in the lower timing case but I’ll inspect that when it comes back.

Here are the pics, tell me what you think:

[bmwman91]

The sprocket thing has been a point of contention in the community. My short answer is that, for the most part, the sprockets should probably last forever.

For a long time it was conventional wisdom among M42 owners that you should always replace the sprockets, and that any sprocket with sharp/pointy teeth was "badly worn." I used to think that was the case as well. After a long conversation with Jim Rowe who owns Metric Mechanic, I stopped thinking that. There were multiple manufacturers of the sprockets, and some simply had sharp teeth rather than square ones. Beyond that, no properly maintained engine would ever have occasion for the chain rollers to come up against the square tips anyway. The chain & teeth simply do not mesh like that.

So unless your sprockets are showing gall marks, pitting, major loss of metal or other major signs of distress, I would just reuse them and save some money.

As for the damper, I'd buy a new one. All of the used ones are old as hell by now. Unless a seller is willing to take a photo of the production date which is molded into the back side of the rubber ring, and that date stamp is from the last <10 years, I would not do it. www.getbmwparts.com is a better place for OEM parts, BTW. ECS, Turner & Pelican used to be good, but they are all now owned by the same not-so-great management company. Very often getbmw has better prices on things, at least for true Genuine BMW, which is the only thing they sell. Not everything matters if it is "Genuine" but I would try to keep all engine bits that way.

[JonsE30]

yikes, thanks for the heads up bmwman91. i'll check the condition of that part when i get home.

i am starting to get nervous about a lot of these parts thats need replacement that are NLA. i did a search on that part number and there are used parts on ebay and ecstuning/tunermotorsports for new but for $500ish.

i even looked for the timing sprockets and those are becoming scarce too. is there any point during a timing rebuild to reuse the sprockets, like can it be inspected and deemed still good or is it a must-replace type part at this stage in the teardown?

[bmwman91]

Yeah, #8 just slides on/off. Part #9 indexes the angular position of both #8 & #6 (and crucially, #1). The immense clamping force from the crank bolt (#4) is what allows all of the torque to be transmitted from the crank to the timing sprocket and the damper/main pulley.

IMO the crank bolt is harder to loosen with the engine out of the car since it is not bolted down, but a decent impact gun should do the trick. I made a crank locking tool which bolts to the #6 hub, but it sort of relies on the car's frame rails to lock against. Getting the bolt back in with the correct torque can be done once the engine is back in, and I can mail you the tool if you need it (looks like USPS is ~$22 each way from here to SoCal).

Also, most torque wrenches do not go up to 224 ft-lbs, and I use a pull force gauge on a breaker bar + pipe at a measured distance to get the proper effective torque.

Lastly, give part #1 a good, close inspection. It comes off easily by removing the 6 x #3 bolts. This is the SINGLE most important part for running the engine since that toothed pattern is how the ECU knows the crank angle & speed. These suckers are all about 30 years old now and the rubber on many is cracking and allowing major wobble of the outer metal toothed part. New ones are almost $500 (ask me how I know lol), which hurts the wallet, but if yours is showing signs of physical failure then I highly recommend buying a new one. I suspect that these parts will become unavailable in the next couple of years. E36 M42 ones will probably be available a bit longer, but you would need to convert to a serpentine belt to use them.

https://www.r3vlimited.com/board/showthread.php?t=429868

[JonsE30]

Need advice from experience for an M42 rebuild

So luckily i called the shop and they said i can leave the oil pan and lower timing cover on when i drop it off however, i know i am going to have to deal with that eventually when i replace the timing components and the timing cover gaskets.

when i take off the crank bolt, i can remove the front lower timing case cover to see all the timing gears, chain and guides. there is an allen bolt for the sprocket on the top , but how do i remove the sprocket (the one that looks like a double gear) at the bottom where the crank bolt is? it looks like this needs to be removed before i can unbolt the inner timing case cover from the block, i dont see a bolt or anything, does it just slide off?

[JonsE30]

Motor is out! With the help of a good friend and my neighbor we got this nugget out. It would have been straightforward but of course I forgot something that was holding it in there. Once we got it out I started removing all the accessories and the transmission to prepare it for drop off at the machine shop....i feel so accomplished! Haha.

Things discovered:

One of the mounting arms of the starter that mounts to the transmission was precisely broken and was attempted to be repaired but it cracked off.

I didn’t know how to take off the lower timing cover. I got as far as removing that piece in front of it, but when I got the front piece off I did it know how to remove that piece that looks like it has 2 gears that is over the crank bolt. So I just removed the chain guides and chain and put the cover back on then that long bolt on for the pulley. It looked like there was a notch for it to go back only one way.

[JonsE30]

Mini update: I had an hour before the wife and kids got home and removed the electrical from the engine. I tried to document and label as much as I can.

[bmwman91]

The oil pump is integrated into the timing case, so if the shop wants the case removed, the oil pump is included there. It is a good idea to check the condition of the rotors anyway, and pack them with assembly lube to avoid pump priming on the first start. You can also check the condition of the oil pressure relief valve bits in the bottom of the timing case.

[JonsE30]

i'll keep that in mind this weekend when i pull it out. i called my shop and they can't get to work on my block for 2 months, so i gotta drop it off and work on other parts of the car, maybe clean up the engine bay during that time.

the shop mentioned i have to strip the block before dropping it off. it looks like i have to remove all the electrical, alternator, water pump, the timing components in the car, mounting arms.

i think he said i can leave the oil pump and pan on, but it looks like the oil pump is mounted to the side of the timing case.

is there a proper sequence, did i miss anything?

thanks in advance

[roguetoaster]

Only other great point would be the cast ear near where the starter would be. Consider the angle you will want to achieve duing the pull, and let that dictate your lift points. Remember that two lift points too near each other will make the engine harder to control coming out.

[JonsE30]

I finally got everything disconnected minus the motor and trans mounts.

Since I’ve never done this before and don’t wanna mess up catastrophically I wanted to check again:

With the head off, I put the head bolts back on to thread the chain through. Which head bolts are the best lifting points? Any other area besides the head bolt I should try to lift from?