S52 Rebuild Progress

[hotballs]

Great thread! I have a few questions.

How did you know which size main and rod bearings to buy? I understand once you replace them you torque them down with plastigauge to check the tolerance but I don't get how you know which size to get.

What rings did you use? Were you able to run the stock pistons again no problem? OEM rings seems to be a lot of money.

[MyE30]

@kendogg thanks for the vid!

Great thread! I have a few questions.

How did you know which size main and rod bearings to buy? I understand once you replace them you torque them down with plastigauge to check the tolerance but I don't get how you know which size to get.

What rings did you use? Were you able to run the stock pistons again no problem? OEM rings seems to be a lot of money.

hotballs, the crank and the block are color coded. There are paint markings on the crankshaft balance weights that correspond with color for the main cap bearings and there are paint markings in the block to tell you what color bearings go in the block. However, according to the manual when you replace the bearings in the block you use all yellow bearings and follow the colors on the crank for the main caps. For the rods, the paint markings on the rods are no longer followed. you just get the corresponding blue and red bearings for the grind stage crank that is in your block (standard, size 1, size 2), which is marked on the first balance weight. This will give you a good starting point. I also used a micrometer to verify that I had a standard size crank as well. The manual lists the thickness of all the bearings so if you measure the outer diameter of the crank journal and the inner diameter of the main cap and block you can determine the size bearings you will need based on the desired oil clearance.

I used Grant piston rings. I've heard mixed reviews about Grant and Hastings. However, I believe some of those reviews could have been due to installer error being that Hastings and Grant use the same material for the compression ring (steel). After contacting Grant, Hastings, and Top Seal I decided to go with Grant because they were the most willing to answer my questions even going as far as to call me back to answer questions that the tech had to research.

Yes, I used the original pistons from the motor. They all miced well within tolerance and all weighed the same down to 0.001 grams. So they were good in my book. I just had the piston skirts coated with PC9 dry lubricant. I've had a lot of success with is coating in the past with track Honda motors that saw 9000 rpm for 20-25 mins at a time.

I hope that answers your questions.

[hotballs]

Very thorough. Thank you. Is the coating something you did yourself? Is it just a spray can?

I'm going to rebuild the bottom end of my s52. Just getting as much info as possible.

Did you measure the axial play of the crank?

Can you list all the special tools you used? Things people wouldn't normally have in the toolbox.

Seems like 25% of this rebuild is going to be spent just on tools. I understand someone qualified could do it for me, it's just an interest I want to learn and get into.

[hotballs]

Another question about the piston rings.

So there are 5 rings per piston? The compression ring up top the middle ring and then 3 for the oil ring?

Do you have to put each one of those rings 1 at a time into the bores and measure each one with a feeler gauge?

[MyE30]

I sent the piston off to get coated. There is a special process.

I did not measure the axial play beforehand because I was replacing the thrust bearings anyway. Usually, if the thrust bearings are bad or if the crank journal is bad then you'll have problems. With new thrust bearings the crank had very minimal axial play.

Really the required "special tools" would be dependent on what you already have in your toolbox. The only tool I had to purchase was for a kit for setting the timing on M/S5X motors. I believe it was only 110 shipped on ebay. There is a company on ebay that sells copies of special BMW specific tools for a fairly good price. Alternatively, that tool set can be rented for about $35+shipping after you get your deposit back. Also, if you don't have a piston ring compressor that can be borrowed from most auto parts stores for free after return and the torque angle gauge is about $25 from summit racing (at least it was when i bought it 10+ years ago).

[MyE30]

Another question about the piston rings.

So there are 5 rings per piston? The compression ring up top the middle ring and then 3 for the oil ring?

Do you have to put each one of those rings 1 at a time into the bores and measure each one with a feeler gauge?

Yes, yes, and correct.

[hotballs]

Awesome, you're in socal who did the machining work? Did you fire it up yet?

[MyE30]

The place that balanced the rotating assembly and did the head work is called San Diego Engine Balancing. With a name like that hopefully they know a thing or two about rotating assemblies.

Yes, the car is up and running I just haven't got around to sorting through/resizing/uploading the pictures to post yet and I want to keep all in order. This whole copious documentation thing is fairly new to me. Normally, I like to provide short and sweet write-ups but rebuilding S5X motors don't seem to be documented much so I figured I'd try to empower others who were on the fence about it.

[atldohc]

great thread i may have to do the same to my s52 eventually. are the wrist pins floating or did you have to press them back into the pistons?

[S62]

Do you mind telling me how much you spent on this rebuild? The S52 in my M3 is starting to drink oil and I'm just surveying my options right now.

[MyE30]

great thread i may have to do the same to my s52 eventually. are the wrist pins floating or did you have to press them back into the pistons?

The piston wrist pins are the floating type.

Do you mind telling me how much you spent on this rebuild? The S52 in my M3 is starting to drink oil and I'm just surveying my options right now.

I spent about 3000 rebuilding the engine (replaced nearly everything that was a wear item) and about 1000 on the transmission (new clutch, flywheel, shift detent/5th/reverse service, seals and other wear items).

I would say 90-95% of all the parts I bought were BMW parts. So you could cut the cost way down if you went with OE manufactured parts. Here are a few examples: I paid about 500 for all of the rotating assembly bearings, I believe a set of Glyco main and rod bearings come out to be half that. The BMW chain tensioner is about 1/3 more than the same part from INA (INA makes them for BMW). The BMW head gasket set and bottom end gasket set cost me about 500 total and their aftermarket counterparts cost about 250 total.

If I could do it all over again I wouldn't change my decision about the BMW bearings but there are more than a few parts I would purchase OE manufactured.

[jph]

Quick question since you encountered this on your build I'm sure. I cleaned my pistons and rods really well in by letting them soak in Berryman carb cleaner for about 30 min and then put them into an ultrasonic tank for about 35 min. They all came out clean as a whistle. I removed the wrist pin clips from both side of one of the pistons but I am not able to push the wrist pin out either side. It's almost as if it has been press fit in there. Everything was lubed with WD-40 to prevent corrosion on the rods so I feel like lack of lubrication is not the issue here. How did you go about getting the pins out?

Oh yeah, one more question. I noticed some skirt wear on both skirts of all 6 pistons. It's a light scuffing of the surface and the horizontal machine marks on the piston are still visible. There are some spots with vertical scoring, but nothing too deep. I can't catch a fingernail on them but I can "feel" them there and obviously see them. Did you have this issue too? I concluded it was piston slap from a wall clearance that may have been on the high side of factory spec. I plan to get the block honed and will also be sending the pistons off for the PC9 and TBC coatings so the skirts should be taken care of. If the bores need to be opened up a bit for some reason I will be using OEM .2mm overbore pistons so this will all be moot.

Any advice or shared experiences would be helpful!

[Blackthorn]

Bumping the dead

Hey i know im bumping an old post but id love to see how this finished up. im fixing to gear up on my s52 refresh and this post has been illuminating.