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Old 05-17-2013, 11:42 PM   #1
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Default m42 to m44 conversion

I have a 318i with a blown M42 OBD1 engine, I found a good M44 engine and tranny with half the miles. I want to install this and figure the best approach is to convert this back to OBD1 with all the manifold and sensor parts etc from the original.
I've looked and posted on other sites and am getting mixed responses anywhere from just plug it in, (Which I know won't work) to it can't be done which I also know not to be true.
Problem is I can't find anyone who has actually done it and can give me a list of the things that need to be done or what to watch out for.
I've also seen some information on converting from OBD2 to OBD1 which in essence is exactly the same as what I'm trying to do. I have access to all the parts from either system OBD1 or 2 but would prefer to put the effort in converting this engine to OBD1.
Any help or insight would be greatly appreciated.
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Old 05-18-2013, 03:36 AM   #2
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M42 is 1.8L and M44 is 1.9L so minor mechanical difference but largely the same motors.
Sorry I can't offer any specific advice but if converting the 4 cyl motors is anything like converting the 6 cylinder motors everything needed to do the OBD conversion is simple swap of sensors, wire harness and ECU (etc).

Maybe you are the pioneer for this conversion, just tackle it and keep us posted.
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Old 05-22-2013, 06:23 PM   #3
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Default M42 to M44 Conversion Success

It took 3 days of research and step by step but I can tell you an M42 to M44 conversion is absolutely possible. It isn't for the faint of heart but it can be done, having a full M42 engine to work from is a must but here are the things that need to be changed over. M44 cam sprockets need to be replaced with the M42 cam sprockets along with replacing of the front cam gear cover. This allows you to use the old cam sensor from the ODB1. Make sure you top dead center the engine and mark the spot on the timing chain that the cam sprocket ARROW points to. Put the M42 sprocket in exactly the same spot. Tie wrapping the gears to the chain when taking them off will help ensure you don't slip which takes you down a completely different path of having to set the timing of the cams. M44 Single temp sensor vs M42 dual temp sensors. This was straight forward if you have the plug off the M44, the color coding of the wires is exactly the same for the two as it is for the single sensor, properly spliced to the matching color, covered with heat shrink tubing and then cover off the entire harness section again and you can plug the dual sensors into the single M44 sensor. Changing over the manifold is easy but you need the lower intake manifold Y support off the M42 engine, the M44 is different and won't fit. Power steering pump mount bracket and pump are also different and need to be changed over unless you want to change over the power steering lines at the same time, changing the pump and bracket was allot easier. When you make this change you will need to use the M42 drive belt as the power steering pump pulley is smaller in diameter and the belt is about 2 inches shorter than the M44. The valve cover breather hose that connects to the intake needs to be modified if your using the hose off the M44, my M42 didn't have a hose to compare to but the M44 hose needed a 1/2 inch elbow and about 1 1/2 extension to properly fit to the manifold. Same with the water hose that comes off the back of the manifold on the M44, the M42 comes off the side of the head and it won't reach to the back and the one off the back has a different size outlet at the manifold end. I used a 1/4 nipple adapter and spliced on a piece of tubing that fit the manifold, it was quite tight on the nipple but it won't leak. Exhaust, just bolt it up, no issues. Biggest challenge was finding out where and how to mount the Crank Sensor bracket, after numerous attempts at patterning I finally found one that I think will work, its out being machined right now. In the mean time curiosity was killing me, I needed to know if it was going to start so I tie wrapped the crank sensor to the AC bracket roughly where it belongs and it fired right up. My new M44 hybrid. If anyone is going to attempt this and has any questions please don't hesitate to ask. Randy
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Old 05-23-2013, 12:18 AM   #4
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I haven't done this myself, but from what I've heard the motors are nearly identical. You could switch the earliest M42 with the last M44 - just a few parts interchanged.

I'm glad you posted the belt drive accessory changes - that's good info.

Many parts were upgraded along the way - the later M44 chain guides, tensioner and lower rear timing case (eliminates the problematic idler wheel) are a good idea for all M4x motor rebuilds.

I'm wondering why didn't you just swap the front lower chain case? The M44 lower front case has no provision for the crank sensor, of course. I thought they were a direct swap?
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Old 05-23-2013, 02:33 AM   #5
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The version of the M42 that was in my car has the Crank Sensor mount part of the block, not the lower timing case cover, I wish. I ended up having to remove the lower cover during the process when I dropped a razor blade down the tiiming chain opening, that whole process including cleanup probably cost me a couple hours, on the plus side I'm pretty sure there won't be any oil leaks from that area.
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