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Extreme Engine Tech: Building a BMW S52 – Part 1: The Short Block

by Nick Betz

There comes a time in a project build when you just have to throw everything out the window and rewrite your storyboard. Over the years we’ve been bolting on parts to Project E36 323is and not seeing the gains we were looking for. Sure it’s been fun but it’s time to make some real power. We had plans for an M50 manifold swap paired with M3 cams, bigger air meter, headers and throttle body but as the old adage goes, there’s no replacement for displacement, so that’s where our journey has taken us.  

If you’re not a BMW fan boy then some of these engine designations might be a little confusing, so here’s a quick primer on what we’re working with. The E36 3-Series BMW’s of the 90’s came with a couple engine configurations, but we’re just going to focus on the 6 cylinder OBD II options; the M52/S52 for the 96-99 models. Here’s where it gets even more confusing, the non-M car engines were designated as the M52 while the M-badged cars got the S52 designation.  One would think the M models would get the “M” engines and the standard models would get the “S” but those crazy Bavarians saw it the other way around. 

 
Our stock internal 2.5L M52, factory rated at 168hp/181 lb/ft torque… With the upgrades we’ve done; Intake and Software, Corsa Exhaust with M3 mid pipe, we’ve seen an increase of 10hp and 12 lb/ft torque totaling 150whp and 150 lb/ft torque, which all came from the exhaust upgrade… Yawn. 

Our 2.5L M52 was the smaller of the two 6-cylinder base variants available, while the 328 came with a 2.8L M52 rated at 190hp and 210 lb/ft of torque. The M52 in our Project 323is came from the factory with 168 hp and 181 lb/ft torque, which is enough to make it a fun car but nothing worth bragging about. When compared to the 3.2L S52 in the M3, 240hp and 240 lb/ft from the factory, there is definitely a big power gap. 

Here’s the crazy part of the M52/S52 family of engines, they all use the same iron block and aluminum head. Yes, you read that correctly; the S52 block from the M3 is the same iron block that’s in any of the 6-cylinder 3-Series models, as well as the same aluminum head. So what makes the S52 so much different? Well, they increased the bore from 84mm to 86.4mm and the stroke from 75mm (84mm for the 2.8L) to 89.6mm, giving it 3.2L of displacement. The M3 head gets more aggressive and hollow cam shafts and a different set of valve springs, but the castings are identical. We used this modularity to our advantage. 

Swapping S52 engines into non-M E36s has been happening for years. This isn’t ground breaking work we’re doing, but, with the help of Pure Performance we’re hoping to end up with something different from what the BMW factory intended.

 

We found this nice example of an S52 swapped E30 BMW on Bimmerforums.com, it belongs to a user by the name of CosmoE36.  

Our first step in this journey was to get our hands on the parts unique to the S52, which are mainly the crank and cams. After searching the forums for these parts, we came across a full S52 motor that had a blown head gasket due to an overheating incident. We were able to pick up the whole engine for $600 minus the head casting, as it had a crack in one of the combustion chambers. This turned out to be a great deal since we only needed the crank, cams and cam trays.

 

Our used S52 block had some scoring in the cylinders due to the overheating incident so it quickly got sent to the recycle bin. In order to make everything go smoothly, Pure Performance offered up a block in trade for our soon-to-be-homeless M52. Before we got started the block was sent out to get bored, honed and Magnafluxed. 
 
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Comments
B.Holmstrom
B.Holmstromlink
Wednesday, May 20, 2015 1:47 AM
I wish You could share the full story directly! This was very interesting!!
M-P
M-Plink
Wednesday, May 20, 2015 5:36 AM
Awesome build Nick! Definitely looking forward to what kind of power you can eek out of that thing with the high compression pistons.
blackdbl0si
blackdbl0silink
Wednesday, May 20, 2015 5:42 AM
It's always amazing how simplified engine assembly looks on a TV show or in an article like this. What doesn't come across to the reader is the amount of time and small details that go into making everything right. Checking the ring gaps, how you stack the rings on a piston, making sure everything is clean and lubed. All of these little things mean one engine will run happily for years with no issues, but skip or miss one and you end up tearing down and replacing everything a month later. Nice article guys, looking forward to the next one.
MDR
MDRlink
Wednesday, May 20, 2015 6:51 AM
It's amazing how many people don't know about the oil pump nut, then track their cars a lot, and then it's bottom end rebuild time. It was one of the first things I did when I started tracking my E36 M3. I also did the Z3 reinforced oil pickup tube and oil pan baffling.

Is this a track car build or a street machine? I guess I'm a little surprised you didn't go with an S54 oil pan/pickup setup. But it is a bit pricey.

Also what is everyone's opinion of painting the inside of the block with something like Glyptal?
M-P
M-Plink
Wednesday, May 20, 2015 7:01 AM
@ MDR | When I used to prep/build engines at a Fiat/Abarth race shop I was asked to completely sand down all rough cast surfaces and apply Glyptal to any internal surfaces of the engine that didn't need to remain bare. I'll be honest that I never saw the benefits of it since we didn't build any engines without it, but the owner of the shop swore by it for its oil shedding abilities.
Sootfoot
Sootfootlink
Wednesday, May 20, 2015 7:19 AM
Great article Nick! Your Kojima-Fu was particularly strong. While we're in there LOL...
Pablo Mazlumian
Pablo Mazlumianlink
Wednesday, May 20, 2015 8:09 AM
I assume with the RPM capability you have now (at least on the bottom end so far), reaching a cool 300+whp NA shouldn't be a too much a prob. That is going to be one fun car!
Nick B
Nick Blink
Wednesday, May 20, 2015 9:14 AM
@B.Holstrom - If we did everything at once it would be a VERY long article, probably hitting 20+ pages. I'm planning on getting Part 2 out within a few weeks to keep it moving, then part 3 and 4.

@MP - Thanks! I think you'll be pleasantly surprised by the final power numbers, especially on the stock cams.

@black - Assembly of a short block really isn't that difficult, it's all about good machine work and then as you said, just making sure everything is cleaned and lubed.

@MDR - It's a street car that occasionaly sees track time, it might compete in a few time attack events soon. The S54 oiling system would of been nice but I do have a budget... and it's not unlimited lol.

@sootfoot - when you work with him everyday something do rub off.

@Pablo - the bottom end is built to handle some high RPM's for upgrades planned much later down the road. Right now we're staying stock cams so that means hydro lifters so we're keeping the rev limit/power band below 7400. 300whp could happen later down the road but we're pretty happy with the whp we got out of it so far... you'll have to wait to find out.

Protodad
Protodadlink
Wednesday, May 20, 2015 10:09 AM
No matter how many times I see it I am always fascinated with engine builds. Any chance MotoIQ might do a technical article on doing a full engine rebuild (what to measure, etc.)? The internet is filled to the brim with either articles that don't actually show the details or are just flat out wrong when it comes to engine building.
Scott Helmer
Scott Helmerlink
Wednesday, May 20, 2015 12:12 PM
Great build so far, and I LOVE the attention paid to this block, but I have what may sound like an odd question: what kind of piston to wall clearances and ring gaps are you running?

When I learned to install pistons with that style of ring compressor, we use a spray lubricant on the walls, ring compressor, and (optionally) the sides of the pistons, no hard banging required, just a fair amount of pressure from your thumbs, and it worked a treat. I'm not sure yet of how it affects racing coated pistons, but that's the current factory recommended method for OEM engine rebuilding, and it's not exactly like OEM's use particularly loose tolerances these days.
Supercharged111
Supercharged111link
Friday, May 22, 2015 8:53 AM
I giggled at one down, 5 to go. Real motors have 8 lungs! Merica! :)

Cool build though, jumping a whole liter should give it a good kick. You porting the head, too?
Mipe
Mipelink
Friday, May 22, 2015 9:37 AM
The build seems cool but what's up with all this hype? It seems like you are a sales rep trying to sell the parts going into the engine. This isn't what I was used to from MotoIq...
Nick B
Nick Blink
Friday, May 22, 2015 10:02 AM
@Mipe - can't please everyone all the time. When we editorialize products we want to talk about the features, benefits, pro's and con's. This is how we've always done things. For example, if we just say "Here's a Mahle piston at 11.3:1 compression" then we'll get questions asking "what's on the side skirt?" "why is it grey" etc... If we don't include all the benefits and features is it really worth reading? Wouldn't have too much substance if we did it that way. Yes companies sell off the benefits and features of their product so there is some cross-correlation but that's not the reason we do it. We just want to make sure the reader is informed of these things so if they were in the market for these types of products they could at least compare different manufacturers.
CTK
CTKlink
Saturday, May 23, 2015 6:55 PM
Definitely curious to see what you guys get out of this engine.

My dream Bimmer project is still a Z3 shoe with a VQ35 though.
buzzboy
buzzboylink
Monday, May 25, 2015 9:14 PM
It's very cool to see an S52 build up. My 332ti's at 100k and I hope feverishly that it has no big trouble for another 100k. I like engine building but doing something this new still freaks me out a bit. I'll stick to building pushrod engines for a bit longer.
Nick B
Nick Blink
Tuesday, May 26, 2015 8:51 AM
@buzzboy - The original M52 in Project E36 323is came out at 190K and it was in great shape, you should easily get another 100K out of your engine if you take care of it. Also, if you can build a push-rod engine you can do an OHC engine... don't be afraid, just do it!

@CTK - by Z3 shoe I'm assuming you mean the Z3M coupe? That would be an odd couple mating the VQ to it. Has it been done? I think an S54 would be a great candidate for that chassis but to each his own.
Duncan
Duncanlink
Monday, September 28, 2015 6:44 PM
@Nick B Can you share the part numbers for the King bearings you used?
Nick B
Nick Blink
Tuesday, September 29, 2015 12:56 PM
@Duncan:
Main bearings - MB7039XP
Rod Bearings - CR6640XP
Duncan
Duncanlink
Friday, October 16, 2015 5:31 AM
Thanks!
jason 8ch
jason 8chlink
Tuesday, November 10, 2015 4:04 PM
What was the size of the ARP piston "funnel" you used for the 86.6 mm Mahle pistons? I am using the same bore Mahle pistons but in a 9.0:1 compression ratio and would love to use this method for piston installation. Thanks!
jason 8ch
jason 8chlink
Tuesday, November 10, 2015 4:11 PM
Is there a reason why you used Total Seal rings instead of the rings supplied with the Mahle pistons? VAC Motorsports did the file fitting of my rings to the bores and contacted me saying the rings were sized for the 87 mm bore pistons. When I contacted Mahle to get the correct rings sent out they told me that both the 86.6 and 87 mm bores used the same ring sets and that they had to be filed down the additional .4 mm to work with the pistons we have. I thought this was odd and VAC had their doubts but supposedly everything worked out fine. They did mention using Total Seal rings but I asked them to try their hand at fitting the Mahles first and if that didn't work we could go the TS route. I plan to check the ring gaps before final assembly just to be safe. Just wondering what your reasoning was behind not using the Mahle rings. Thanks again!
buzzboy
buzzboylink
Wednesday, December 28, 2016 10:16 AM
Still waiting on part 2!
Nick B
Nick Blink
Sunday, January 01, 2017 6:16 AM
@buzzboy - you'be been waiting? It's been published for a while now:http://www.motoiq.com/MagazineArticles/ID/3889/Extreme-Engine-Tech-Building-a-BMW-S52--Part-2-The-Cylinder-Head.aspx
buzzboy
buzzboylink
Tuesday, January 03, 2017 7:38 AM
Thanks Nick, I don't know why i couldn't find a part 2.
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