Rebuilding a BMW intake: S52 to M50 manifold conversion, day 5

Coming to you live from my parents garage in this 7 part series, are the chronicled adventures my dad and myself had converting an S52 intake manifold to the larger M50 intake manifold.

At last, we found a stud earlier this week!!

I was at my friend Gary’s shop earlier in the week and we were chatting and low and behold, he had a “junk” M50 engine sitting there in pieces. He had all of the studs there so he let me grab a couple, wahoo!

With the new stud, I was able to put the valve cover back on and finish the valve cover gasket replacement, whoohoo!

At last, one part of the car was finished, now onto to the throttle and intake.

With the manifold back on and most things connected, we still had one problem. The 2 major mounts on the manifold were not aligning anywhere near close the car mounts.

Back to our spare sheet metal, we “manufactured” some new mounts, which worked out pretty well.

But now with the manifold mounted and most hoses connected, we realized a few hoses would not fit. Luckily we had some extra tubing we picked up and we cut a few pieces to make it fit. One particular one that was a bit odd was the idler control valve hose—we took a brand new OEM hose, cut off part of it, extended it, and then reattached it. Although a bit odd, this worked out really well, since otherwise it would not have fit at all because of the new mounting points.

To improve the seal between the M50 manifold and the throttle—one of the most common places to have a vacuum leak in this conversion, we applied some gasket sealer to both gaskets (replaced both gaskets with brand new ones too).

Next up was remounting the air temp sensor. The KO directions called for a 1/8” hole but it turned out 1/4” was the magic number to remount the air temperature sensor in the rubber boot.

After that, we carefully drilled out the metal mounting points in the fuel rail so we could reposition it and attach it.

We then changed the two rubber gaskets in the oil dipstick and finished putting things back together, wahooo!

Turning the car on, it indeed was idling rough as expected. This smoothed out after a couple of minutes. Driving it around was a bit rough, again as expected, since the DME has to recalibrate itself because of the extra airflow. The check engine light should come on and last for about 24-48 hours before it goes away as well.

However, after driving on the highway back home this evening from my parents, things did not smooth out and I’m seeing misfires on every single cylinder, with the O2 sensors going crazy.

Maybe this will pan out tomorrow… or maybe we’re not even close to being finished yet, doh!

In the mean time, check out all the parts I didn’t end up using. Most of these were left overs from the S52 intake manifold and then some were extras because we made new mounts that actually fit :-)

Tips from Day 5:

• Print diagrams from RealOEM.com
• Take before pictures and lots of them as you take things apart if you haven't done this before