Putting an M42 back together...checklist

[bmwpower]

I'm finally getting ready to put my engine back together from an overheated state.  I'm looking for some things to look out for and check/replace while I'm in there.  Head is new, so I'm good there.  Block is in the car.  So far I've come up with:

- chain tensioner - use new M44 chain tensioner or a new M42 tensioner?
- oil check valve - E36 Bentley says I need to put this back...I don't seem to have one.  Is there one of this engine between the head and the block?  IS the E36 Bentley talking about E36s only?
- guide and timing gears - these look close to new, so I'm not going to replace them.
- get rid of those stinking web of coolant hoses - I'm convinced I don't need them and can consolidate things here
- yank the block out? - if I want to do the oil pan gasket, should I just pull the block out, too?  That way I can replace the rear crank seal, too.

Anything else I should do now or replace?

[strad]

I don't think you can even buy the M42 tensioner anymore.  I'm running the M44 tensioner and it's fine so far.  

As for yanking the block to replace seals, are they leaking?  If so, go ahead and replace them however you think it's easiest.  If not, leave them alone.

[Wise Old Dog]

Is your new head a rebuild? Make sure that if the head was shaved, that you compensate with a thicker gasket. This eliminates running too high of a compression ratio and/or valve clearance problems. I don't think the e30 had the oil check valve, there was some discussion about that previously. You can tidy up the hoses by eliminating the throttle body heater and associated hoses. You only need 2 hose runs, The ICV and crankcase vent. Plus whatever you decide to do with the TB heater hose. e30 m42 re-plumbed his with Samco silicone hoses. Cost him about $100, but it looks good, and should be trouble free for a long time. Don't forget to replace the seal on the plastic outlet pipe, maybe the pipe also. Some people have had them crack from age. Did you check the block for damage from the overheat? I would at least check the top for straitness. The oil pan can be removed easily without pulling the block. Good idea to do it if you have never had it off. Just to check for loose bolts inside, and to remove your oil pick-up bolts, loctite, and reinstall. M44 tensioner is all you can buy, works fine.

[bmwpower]

Is your new head a rebuild? Make sure that if the head was shaved, that you compensate with a thicker gasket. This eliminates running too high of a compression ratio and/or valve clearance problems. I don't think the e30 had the oil check valve, there was some discussion about that previously. You can tidy up the hoses by eliminating the throttle body heater and associated hoses. You only need 2 hose runs, The ICV and crankcase vent. Plus whatever you decide to do with the TB heater hose. e30 m42 re-plumbed his with Samco silicone hoses. Cost him about $100, but it looks good, and should be trouble free for a long time. Don't forget to replace the seal on the plastic outlet pipe, maybe the pipe also. Some people have had them crack from age. Did you check the block for damage from the overheat? I would at least check the top for straitness. The oil pan can be removed easily without pulling the block. Good idea to do it if you have never had it off. Just to check for loose bolts inside, and to remove your oil pick-up bolts, loctite, and reinstall. M44 tensioner is all you can buy, works fine.

Yes, head was rebuilt.  Block is straight.  Head was shaved, but not sure how much.  What are the limits for getting a thicker gasket?  I've done other heads where the shaving was minimal so a different thickness headgasket was not needed.

Who sells the Samco hoses?

For pulling the oil pan, do I just loosen the tranny mounts, undo the engine mounts and lift the front of the block up?  Might be best to do it now before the head is on.  I guess I can forgo pulling the block.  I can always pull the tranny later.  I don't think the rear crank seal is leaking.  I just tend to go overboard with restoration and do much more than I really need to cause I'm right there or al least 1/2 wy there.

[2002maniac]

chain tensioner - There is only one part# available.  The M44 tensioner superceded the M42 part
oil check valve - E36 Only
guide and timing gears - if they look fine, dont worry about it. (I would at least replace the chain though)
get rid of those stinking web of coolant hoses - good idea
yank the block out? - I wouldnt.  Raise the motor a few inches so you have some room between the subfrane and the motor.  There are a few bolts hidden inside the bellhousing.  I wouldnt worry about the rear main.  getting the block mated up to the tranny again will be a PITA.

[2002maniac]

Dont worry about getting a thicker HG.  More compression is a good thing and timing isnt an issue because it can be adjusted at the cam gears.  As long as your machinist didnt face the head past tolerance you'll be fine.

[bmwpower]

chain tensioner - There is only one part# available.  The M44 tensioner superceded the M42 part
oil check valve - E36 Only
guide and timing gears - if they look fine, dont worry about it. (I would at least replace the chain though)
get rid of those stinking web of coolant hoses - good idea
yank the block out? - I wouldnt.  Raise the motor a few inches so you have some room between the subfrane and the motor.  There are a few bolts hidden inside the bellhousing.  I wouldnt worry about the rear main.  getting the block mated up to the tranny again will be a PITA.

There doesn't seem to be "a few inches" of room.  The tranny will hit the tunnel before I get that high.  Lemme lift it up again and take a look.  I'm pretty sure it's like 1/2 inch - that's it.



Yea I can get my hand between the trans and the tunnel...that's it.

[Esprit Aviation]

chain tensioner - There is only one part# available.  The M44 tensioner superceded the M42 part
oil check valve - E36 Only
guide and timing gears - if they look fine, dont worry about it. (I would at least replace the chain though)
get rid of those stinking web of coolant hoses - good idea
yank the block out? - I wouldnt.  Raise the motor a few inches so you have some room between the subfrane and the motor.  There are a few bolts hidden inside the bellhousing.  I wouldnt worry about the rear main.  getting the block mated up to the tranny again will be a PITA.

How is the tensioner different between the M42 and M44?

After dissasembly, I found what looks like a .22 LR bullet on the floor, I suspect this is the oil check valve. Our engine is out of an E30. Since the head and block are @ the machine shop I don't know where it is supposed to go. What would be the benefit of having one or leaving it out?

Does anyone have a diagram of the hoses that can be eliminated?

Thank you in advance for your time.

[bmwpower]

How is the tensioner different between the M42 and M44?

After dissasembly, I found what looks like a .22 LR bullet on the floor, I suspect this is the oil check valve. Our engine is out of an E30. Since the head and block are @ the machine shop I don't know where it is supposed to go. What would be the benefit of having one or leaving it out?

Does anyone have a diagram of the hoses that can be eliminated?

Thank you in advance for your time.

http://www.m42club.com/forums/showthread.php?t=2742&highlight=coolant+hoses

Are you sure the engine is from an E30??  Everything I've read on here is pointing to the fact that it's NOT on the E30's, only E36's.  You'd better check casting #'s/dates to make sure.

[Ricer Ennemi]

Dont worry about getting a thicker HG.  More compression is a good thing and timing isnt an issue because it can be adjusted at the cam gears.  As long as your machinist didnt face the head past TOLERANCE you'll be fine.

Anybody know how much U can shave with stock pistons?
What compression will it give me too?