Author Topic: BMW engine questions (Read 4648 times)

michael27 · « **on:** March 18, 2012, 04:26:19 PM »

Hi I have a 1991 BMW 318is that I bought off a guy that wrecked it. I completely restored it from the ground up. The car only has 75,000 miles on it, but the motor blew up recently. I have worked on a lot of American v8's and these European motors confuse me. I really love the light weight car and great engine power for a small engine so I am looking at doing an engine swap. How do I know what my motor is? I'm guessing its an e30 but I see all this stuff about m42? Can someone help me with all the information I need, thanks!

DesktopDave · « **Reply #1 on:** March 18, 2012, 07:33:59 PM »

You have the last year of e30 coupe. It came with the M42 motor. The convertible e30 went on for a few more years. There was an earlier e30 318i ('84-85) but it has the earlier SOHC M10 motor. You can swap a bunch of motors (including a smallblock)...the bigger inline six from the '93-'95 325i and 525i (called an M50) makes a good swap too. BMW typically keeps developing the motor, just gives it updated names so it's easier to deal with.

So "E30" describes the chassis. All BMWs have those nicknames, since there are so many variations of motors installed in each model. As far as donors, you'd be looking for 91-93 3-series (e30 chassis) and the 90-96 3-series (e36 chassis). The M42 was also in the 318Ti and the Z3...both are based on the e36.

Here's an example. I have an '81 633CSi. It's an E24 with an M30B32 motor. The B32 means displacement (it's actually a 3.2L I6, confusingly). There are about six versions of the M30 "big six" including a few turbos...those names make sure you get the right parts.

Clear as mud, right?

rob_e30 · « **Reply #2 on:** March 18, 2012, 07:35:36 PM »

The 91 318 came with the M42 engine. What exactly failed on your engine? Blew Up covers a lot of ground. It's hard to destroy the bottom end on these, but if the timing chain tensioner failed you likely bent many valves.

michael27 · « **Reply #3 on:** March 19, 2012, 12:30:14 PM »

Thats what happened. The tensioner went and the chain jumped a link and bent everything in the top end. Like you said bottom end is perfect, looks like new.

Gabs · « **Reply #4 on:** March 19, 2012, 12:57:20 PM »

Not that I doubt you Dave, But I don't think the Z3 used the M42. Even though its engine variants are basically one in the same, I believe the Z3 used a 1.8L M43 in early days and later used the 1.9L M44, and of course the 6 cylinders. When it comes down to it though, not much difference between the M43/M44 and M42.

Michael27, as mentioned above, you should have an M42B18 motor. When I hear the engine "Blew up" I cringe and have a mental image of a Bright red oil lamp, rapid destruction of front case, rails and roller parts everywhere. We can only hope its something to a lesser extent.

Well since your considering a swap anyway, I would pull the valve cover and top timing case and take a quick look. Even with just the Valve cover off, you should be able to check and see if the cams are badly out of line. Check the cam squares on the rear end of the cams to make sure they are parallel, with the Engine at Top Dead Center, you should be able to lay a ruler flat across the squares. Another indicator, although Im not 100% sure this is accurate, your cam arrows should be roughly parallel.

Sorry couldn't find a suitable picture of the cam squares.
Also someone please correct me, if my cam alignment clues are inaccurate. I wasn't 100% sure on my tips, its been a year or two since I�ve been under my own valve cover.

Gabs · « **Reply #5 on:** March 19, 2012, 01:02:37 PM »

While I was replying, you replied Michael. I suppose you can disregard my last.
Though I would search locally for an M42 out of a E30 chasis vehicle and I believe you could even swap an M42 from a E36 Chasis Vehicle. As well I'm sure an M44 would also be a good plausible swap, though I'd look further into that.

Also if you do swap, you could part out the good parts of your engine on this forum

Hopefully you can a find a good swap locally.

DesktopDave · « **Reply #6 on:** March 19, 2012, 02:06:06 PM »

Quote from: gabskee;111217

Not that I doubt you Dave, But I don't think the Z3 used the M42. Even though its engine variants are basically one in the same, I believe the Z3 used a 1.8L M43 in early days and later used the 1.9L M44, and of course the 6 cylinders. When it comes down to it though, not much difference between the M43/M44 and M42.

Looks like you're right. My mistake! Good catch...I'd assumed that the Z3 came out before '96.

michael27 · « **Reply #7 on:** March 19, 2012, 03:22:54 PM »

Quote from: gabskee;111218

While I was replying, you replied Michael. I suppose you can disregard my last.
Though I would search locally for an M42 out of a E30 chasis vehicle and I believe you could even swap an M42 from a E36 Chasis Vehicle. As well I'm sure an M44 would also be a good plausible swap, though I'd look further into that.

Also if you do swap, you could part out the good parts of your engine on this forum
Hopefully you can a find a good swap locally.

I tore everything apart and the cams were off badly the chain was destroyed. Everything on the top end will need replaced. I looking at stuff to rebuild mine but it won't be cheap thats for sure. If anyone has suggestions on where to find stuff to rebuild my motor I will look into that seeing finding a good motor is hard.