Bought M42 - Winter refresh coming - what to look for/replace

[irish44j]

Recently picked up an M42 (with most of the parts, etc) from a local member to swap into my early 318 (M10). He pulled the engine to do an M20 (turbo) swap, and said that the engine runs fine. He's on here and no reason he would lie since he lives like 1/2 a mile from me, lol. I don't see anything suggesting any problems on the outside, other than typical gunkiness.

Anyhow, I plan to refresh the engine this winter and then swap it in. So looking for a basic list of things worth checking and/or replacing while the engine is on a stand and not in the car. This thing has alot more going on than my simple M10, lol.

Keep in mind this is for the rallycross beater, so I'm not doing a full rebuild and am not going for anything more than stock-ish power.

Should I bother pulling the head if there' s no evidence of HG issues?
I'll probably do the water pump.
How can I check if the timing chain tensioner is the "updated" one?

Other suggestions on things worth replacing on a well-used M42 are welcome....spark plug gaskets, sensors, hoses, etc?

thx
Josh

[bmwman91]

The timing assembly is the real weak point in the motor. It is overly-complex and is starting to become prone to failure without proper maintenance. Just replace the tensioner. They are $40 and take 5 minutes to swap. Letting one go to save $40 is almost guaranteed to lead to very expensive and lengthy repairs.

I would pull the timing case covers and closely inspect all of the guides and sprockets. The cam gears should have blunt ends on the teeth; if they are sharp points, they need replacement or the chain could jump. The crank sprocket is made with sharp teeth, so it is harder to tell how worn it is. Your best bet is to open it up and take good pictures, and post them in here for comment. M42Club.com is also a huge resource and has a lot of people that have learned about the M42's weak points the hard way (myself included).

Also drop the lower oil pan and look for debris and bolts. Yes, bolts. There are some in the upper oil pan that loosen and fall into the lower pan. This is a major risk because the ones that fall out are near the oil pickup, and when that part of the gasket is not compressed it can implode and your oil pump sucks air.

Good luck, have fun! The M42 is a great motor when properly maintained!

[irish44j]

thanks, now you're making me a bit nervous about the swap lol.....M10 is basically indestructible. Ah well.

[roguetoaster]

Don't sweat it too much, just do the basic checks as you would on any other new to you car and you will be good to go. Essentially, if it's not leaking coolant or oil and there is nothing that looks too bad under the timing case you are good to go. If you end up needing M42 timing components or items, & don't mind used parts (perfect for a rally-X beater IMHO) PM me.

[bmwman91]

roguetoaster,

I generally agree with you that one can tell a lot about the motor from super basic inspections. The timing case has become a real weak point on these motors though, with people dubiously maintaining them due to the cost of parts and labor, so it is well worth it to dig into the M42 I think. It is relatively easy to prevent a repair that requires $500 in parts and 12 hours of your own labor.

[roguetoaster]

Agreed that the timing chain/tensioner system is the weak point of the engine, outside of the crank bearings. I was not attempting to discourage irish44j from opening at least the top chain case, and the lower pan for inspection, don't forget to check the upper pan bolts tightness BTW. As far as the tensioner goes, buy a NEW one of course.

Other things I missed before:

It's probably not necessary to pull the head unless you have a crapped out profile gasket.
Replace the spark plug well gaskets, the valve cover thats on there ought to be fine.
Probably do the mess under the intake mod if not done already. Check the intake boot as well.
What is your target budget for slightly refreshing the engine before it goes in?

On another note irish44j's M10 318 rally-X build continues to be an awesome read!

[willworkfore30s]

Change the rear main seal while its out of the car.

[MF DOOM]

Listen to him^^ its a cheap seal and is easy to install.

[irish44j]

Agreed that the timing chain/tensioner system is the weak point of the engine, outside of the crank bearings. I was not attempting to discourage irish44j from opening at least the top chain case, and the lower pan for inspection, don't forget to check the upper pan bolts tightness BTW. As far as the tensioner goes, buy a NEW one of course.

Other things I missed before:

It's probably not necessary to pull the head unless you have a crapped out profile gasket.
Replace the spark plug well gaskets, the valve cover thats on there ought to be fine.
Probably do the mess under the intake mod if not done already. Check the intake boot as well.
What is your target budget for slightly refreshing the engine before it goes in?

On another note irish44j's M10 318 rally-X build continues to be an awesome read!

thanks :) Now if just included some first-place finishes, lol. Hence why an M42 is going in there.

I don't really have a target budget per se (I have all winter, with my "winter job" at a ski shop providing car money that I don't have in the summer), but I'm certainly not trying to do anything particularly trick. I'm fine with stock power (or stock-ish), I just want to make sure it's reliable since it's not a short drive back from rallycrosses and I plan to do some farther from home int he future.

Feel free to make suggestions if there's something worthwhile that might cost a bit more. I just sold my excellent JDM Enkeis for the WRX, so now I have some play money for the e30 :)

roguetoaster,

I generally agree with you that one can tell a lot about the motor from super basic inspections. The timing case has become a real weak point on these motors though, with people dubiously maintaining them due to the cost of parts and labor, so it is well worth it to dig into the M42 I think. It is relatively easy to prevent a repair that requires $500 in parts and 12 hours of your own labor.

Yeah, timing case is definitely high on the list, along with water pump and all the hoses, for sure.

Change the rear main seal while its out of the car.

Listen to him^^ its a cheap seal and is easy to install.

yep, that's definitely in the plans


also, what is this "mod to get rid of the mess of hoses" thing? ANyone have a link to the thread?

[Simon S]

some additional reading in this thread..

also, what is this "mod to get rid of the mess of hoses" thing? ANyone have a link to the thread?

dude - just run an advanced search for "mess" in thread titles of the m42 section..

[roguetoaster]

As far as mess under the intake links, r3v, r3v & M42Club.

Just wondered about the budget, most rallycrossers I know tend to be super, shall we say "budget oriented." As you have probably divined by now there is not much cheap power to be had in a N/A M42 outside of the regular chip & exhaust routine.

[irish44j]

As far as mess under the intake links, r3v, r3v & M42Club.

Just wondered about the budget, most rallycrossers I know tend to be super, shall we say "budget oriented." As you have probably divined by now there is not much cheap power to be had in a N/A M42 outside of the regular chip & exhaust routine.

I am budget oriented to an extent, but not to the extent of the other e30s running locally in rallycross, which run in stock/prepared classes. I'm in modified so have a lot of leeway with things (like....swapping my M10 for an M42). I enjoy working on and building the car almost as much as driving/racing it, so my budget includes constant projects, even if small.

I'm not real concerned with power. I'm sitting in 2nd place in class for the season right now with an M10, and just want the extra grunt to get me up to the power levels of the RX-7's I"m running against (which an M42 will, for the most part, do). That should be sufficient to get me gunning for the top spot since I'm a few hundred lbs lighter than the RX's I'm pretty sure. There's only so much traction to be had in RWD rallycrossing, so there's a point where "more power" won't help much. In this car I consider that point to be about 150hp or so, honestly.

I'm fine making near-stock power, I just want the engine to be as bulletproof as possible, basically. I also want to do some trackdays with the car, so again, reliability is the main factor. If I could pull of gains in the 10-20hp range without reducing reliability, that would be worth it if it's not too pricey. not going to do FI or internals because....this is a $1000 car :)

some additional reading in this thread..

dude - just run an advanced search for "mess" in thread titles of the m42 section..

yeah, I found it about 2 seconds after I posted the question, and then got wrapped up in the thread and forgot to delete my post, sorry ;)

[irish44j]

one thing is for sure: I'll be doing the cam sprockets

[roguetoaster]

I don't know how far into the minor tear down you are, but pointy cam sprockets almost always equals doing the entire timing assembly. I have two very reasonable cam sprockets, an upper guide, a lower guide, a tensioner rail (passenger side one) as well as a good crank sprocket if you end up wanting used bits.

Did anyone mention checking crank end play, if not it's worth it.

Stock M42 power is just perfect for rallycross anyway. At least the initial cost of an M42 is low. Perhaps this has been mentioned in your other thread, but what differential ratio are you going to use with the M42?

[bmwm42]

Fuck those are pointy I'm more than positive those guides are shit along with the chain