m42 timing guide cracked

[red318is]

I was fixing a leaking timing case on my m42, and I noticed the passenger side guide has lots of cracks in it. Also, timing sprockets have a bit of wear on them. Engine has 160k on it. I priced out components and found that doing a refresher would cost me over $1000, and cam sprockets are no longer able to be found. So my question is what do you guys think for options?

new components and reuse worn sprockets? $1066
new m42 engine?
something used?
swap in a different engine? maybe, dare I say it, Japanese?


I'm really just curious if these engines are worth putting this kind of money into, at this mileage, and where in the world I can find cam sprockets?!

Also, not looking to spend a lot, or make a ton of hp. I just want a runner.

[red318is]

and the pic

[bmwman91]

Wow, yeah that is an original guide which was later updated, as indicated by the metal housing. Later ones were all rubber+plastic.

So for the cam sprockets, a very common misconception is that sharp sprocket teeth are a big sign of wear. That is 100% NOT true though, as there were multiple suppliers, with some being square-tipped and some being sharp. The main thing to be looking for is galling on the faces that mesh with the chain rollers, chipping anywhere on the edges and missing/worn material at the root of the teeth that would change the profile (causing the teeth profiles go "down and in" rather than just "down"). Get some more pics of those sprockets and maybe we can figure that out. It is hard to tell if they are messed up in your pic, or if it is just from shrinking the image. Honestly, you could probably find some clean used ones and use those. A properly lubricated and tensioned timing system should really not produce wear on the sprockets, and an engine builder that I respect says that he can't see these ever wearing out as long as the engine has oil flowing.

Anyway, if that guide is original, I am more than willing to bet that everything else in there is too and it absolutely needs an overhaul in that case. I know it is expensive...even 15 years ago when I did the same overhaul, the parts came out to like $600 (not including the deflector sprocket). Yeah it is costly, but these are nearly 30 year old cars, many of which were not maintained very rigorously over their lifetimes. A $1000 parts bill sucks, but it is for stuff that you won't need to touch again for 200K miles and NOT doing it makes the thing a time bomb. You could buy a used M42, but it would probably also need a timing overhaul. The timing chain system is one of two major weak points on the E30 version of the M42 (the other being the half-shell crank thrust bearing)

If and when you do get the parts in be sure to let us know. There are some simple but essential steps to getting the crank & cams timed properly, which are more than just lining up the visual markers.

One thing you can consider is swapping in a used 1994-1995 M42 timing case since it eliminated the costly and failure-prone deflector sprocket in favor of another plastic guide. This is a totally optional idea. However it is not a simple task and requires sliding the new timing case + profile gasket in under the overhang of the head while jacking it upward to get the oil pump onto the crank snout...a real pain and possible to have the inner profile gasket leak if it catches. You could also just pull the head and get it cleaned up which would actually make the timing case swap a hell of a lot easier. BUT, I only mention this since it might save you a little money if you are thinking about replacing that deflector sprocket. A timing case overhaul is a pretty simple procedure, but this swap makes it into a complex one.

[red318is]

I was absolutely going to replace the idler sprocket, or swap cases and upgrade to the new style, but you are correct in that it will be a lot more work. I will take more pics tonight. Thanks for the help!

[bmwman91]

Sounds good. The idler sprocket has caused a few total failures of M42 engines, myself included. However I am not sure if it is actually commonplace since people with cars that run fine don't post about it! But, there have been enough instances of the pulley itself failing, or the boss that it bolts to snapping off of the timing case that I would swap any M42 I owned to the later version. My current engine has an M44 case to get the 10% higher flowing oil pump, but you need a machined adapter to hold the crank position sensor.

[red318is]

[red318is]

pics as promised

[bmwman91]

Hmm, well they do have a little wear, but they are not terrible. If some better looking ones came up on eBay I would probably get those. These should be fine if you can't find better ones.

[red318is]

after doing more research I'm starting to lean more to doing a 3S-GE swap. seems like I would get more out of it for the money. It's nice having a clean e30 but at this point it has become an extreme money pit.

[bmwman91]

Ha yeah I know the feeling. An internally stock M42 isn't exactly a screamer, although it has its moments. If your goal is to make the thing faster then engine swaps are usually a better bang for the buck. I opted to build out a 2.1L M42 and it is a lot of fun, but it also cost a lot more than a swap!

[red318is]

yes I know, that was my other consideration but it would have been a 2.0 m42. Still, I've been driving with this engine for 12 years so maybe a change is due.