S50B30US NA rebuild for track car

[bimmerboy318]

Starting a new thread to ask questions and document the rebuild of an S50B30US motor. The original S50 in my 95 M3 dropped either dropped a valve or spun a rod bearing causing the piston to contact valve. It is still in the car. I had previously refreshed the head and installed updated retainers and keepers.

However, I have a spare S50 motor that I purchased with unknown mileage. Apparently, it was sitting for 6 years and has an E30 swap oil pan on it. It came from a shop that specialized in E30s. Based on how clean everything looks and the condition of the cams, mileage is likely less than 150k. Maybe less than 100k but these motors do not show their age.

Goals... to build a 100% reliable motor with at stock power levels.

I know, I know... most will say just refresh the gaskets and install it. However, I do not want to go through this again. This is a dedicated track car used for DE's. Skill level, I am an instructor (although that doesn't always say much), but I will run in advanced group with open passing (no point-by's required) with any organization that allows it.

On to the pre-build questions and costs.

Here's my summary the hardware with the lowest prices I've found and the respective vendor:

Supertech Spring kit - $646 No Limit Motorsports - Planning to stick with the lowest seat pressure of 67lbs and use the steel retainer version
JE Pistons & Eagle Rods - $1251 CNC Motorsports - Planning to stick with stock 10.5:1 comp ratio. I'm not sure what the cost to reconditioning stock connecting rod would be. But Eagle rods by themselves would cost $550 and I would also use ARP bolts on the stock rods at $172. Makes buying new H-beam rods not much more money.
WPC treated rod bearings - $111 Turner
WPC treated main bearings - $0 Re-used original
INA lifters - $324.48 FCP Euro

Machine shop work:

Bore/hone cylinders
Check polish crank
Balance crank
Line hone crank journals
Assemble short block
Refresh cylinder head and mill gasket surface
Assemble cylinder head (not the cams)

Accessory/ auxiliary items:

S54 dual pick-up oil pump and pan - $600 Ebay
S54 oil pump high flow upgrade by VAC - $699
Vanos rebuild kit - $30 Besian

Notice I did not include deck the block. I doubt it will be needed or recommended but if it is, so be it. I'll include the front timing cover so that gets skimmed as well.

Am I missing anything? Anything anyone would recommend differently? Does the stock harmonic balancer need to be replaced? I didn't include gaskets as those would be replaced no matter what I do with this spare motor. Elring head gasket will be used so long as it works with overbored pistons. Hoping to salvage and sell what's left of the other one to help offset the costs. I'm hoping that once complete I can get a local dyno shop in the Louisville KY area to check my curves and perhaps bump the idle and redline values.

682B866D-8172-4149-BA38-04578712686E by D S, on Flickr

[ScotcH]

Some advice for OP:

- If the main bearings are in good shape, do not line hone to do anything to the caps/crank. Just replace the bearings (or not, if they are not touched ... I've seen 200k bearings that look better than new aftermarket). BMW does a REALLY good job on getting these right.
- Why stick with 10.5:1? You can run 11.5:1 safely on pump gas, and the bump is nice with a good tune.
- Eagle rods are great ... we use them in many race engines, no problems.
- Pistons don't go more that 86.5mm ... more then that you start having HG issues.
- Stock balancer is fine as long as it's in good shape ... no cracks in the rubber
- You can easily bump the redline on this to 7500 rpm with supertech springs.
- Get the Raceland Euro SS copy headers to make the most of the higher RPMs.
- Once you get the budget, a nice set of cams will really complement the build ... especially if you go to 11.5:1 CR
- that is a damn clean engine to start with!

[bimmerboy318]

Some advice for OP:

- If the main bearings are in good shape, do not line hone to do anything to the caps/crank. Just replace the bearings. BMW does a REALLY good job on getting these right.
- Why stick with 10.5:1? You can run 11.5:1 safely on pump gas, and the bump is nice with a good tune.
- Eagle rods are great ... we use them in many race engines, no problems.
- Pistons don't go more that 86.5mm ... more then that you start having HG issues.
- Stock balancer is fine as long as it's in good shape ... no cracks in the rubber
- You can easily bump the redline on this to 7500 rpm with supertech springs.
- Get the Raceland Euro SS copy headers to make the most of the higher RPMs.
- Once you get the budget, a nice set of cams will really complement the build ... especially if you go to 11.5:1 CR
- that is a damn clean engine to start with!

All points noted. Will talk with machine shop on the 11.5:1 ratio as the cost of pistons would be the same.

[GG///M3]

Some advice for OP:

- If the main bearings are in good shape, do not line hone to do anything to the caps/crank. Just replace the bearings (or not, if they are not touched ... I've seen 200k bearings that look better than new aftermarket). BMW does a REALLY good job on getting these right.
- Why stick with 10.5:1? You can run 11.5:1 safely on pump gas, and the bump is nice with a good tune.
- Eagle rods are great ... we use them in many race engines, no problems.
- Pistons don't go more that 86.5mm ... more then that you start having HG issues.
- Stock balancer is fine as long as it's in good shape ... no cracks in the rubber
- You can easily bump the redline on this to 7500 rpm with supertech springs.
- Get the Raceland Euro SS copy headers to make the most of the higher RPMs.
- Once you get the budget, a nice set of cams will really complement the build ... especially if you go to 11.5:1 CR
- that is a damn clean engine to start with!

Knowledge

[bimmerboy318]

- You can easily bump the redline on this to 7500 rpm with supertech springs.

67lbs seat suffice?

[ScotcH]

67lbs seat suffice?

Hmm, not sure. We always use this kit: https://www.supertechperformance.com...lve-spring-kit

[aeronaut]

I went round and round on which supertech springs to install. I think you'd be fine with either. I ended up with the H100DR/BM (lower seat pressure, but higher spring rate). But all the local NASA racers use the ones SchotcH is referencing. I'm not sure what my logic was. lol. And yes, steel retainers.

Other notes:
- Careful of Elring head gaskets, I received THREE head gaskets packaged in elring packaging, but stamped with another manufactuer on the actual gasket! Finally got a real elring from Pelican.
- My lower cam chain tensioner was showing some good wear at 130k (hard) mi.
- for the oil pump chain and cam-cam chain, I used the IWIS motorsports chains. A little heavier duty than OEM BMW.
- I also researched replacing the crank harmonic damper. And agree with ScotcH, no need if it's in good shape, even at higher RPM.
- If you're ever going to remove A/C stuff (if you haven't already), now is the time. Also remove the A/C pulley, and get shorter crank pulley bolts. And remove the compressor bracket.
- Good call on new lifters.
- Good call on S54 pan and pump. I'm just not sure if the VAC pump mod is worth $700. If I had it all over, I'd consider setting idle at 1000rpm, maybe even 1100, and run the stock S54 pump.
- Inspect your steering shaft while you have the engine out. It's just so much easier now.
- Yea definitely consider higher CR pistons, with nice reliefs for the valves in case you ever want to cam the crap out of this engine.

-

[bluptgm3]

The spec for the "400" casting used on S50/S52/M52 is 140mm, min 139.7mm, as I recall, with no machining allowance for S50/S52. That said any head reconditioning can be made up in gasket thickness.

Deck height appears to be 210mm.

Mahle pistons are available in a couple of overbore diameters. I believe Wiesco, JE, and CP also offers pistons.

http://workshop-manuals.com/bmw/


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[bimmerboy318]

Thanks aero. I've been following your build! My thought on the VAC oil pump performance upgrade is that it basically rebuilds the pump. Machined impeller area, new impeller, new shaft, new bolt. Not much else to fail or wear on it. Looks like an ebay dual pick-up oil pump is around $150. So a new S54 pump vs a used one and VAC mods would be about the same. This same thought process goes for the connecting rods.

The "new" motor has the updated 1pc chain tensioner. AC is already gone, the bracket is on the "new" motor still for some reason.

I also read about your IWIS chains and plan to get those. Really need to find a local dyno shop that can tune the stock DME. I read about your less than satisfactory experience with the off the shelf tunes.

[ScotcH]

The spec for the "400" casting used on S50/S52/M52 is 140mm, min 139.7mm, as I recall, with no machining allowance for S50/S52. That said any head reconditioning can be made up in gasket thickness.

Deck height appears to be 210mm.

Mahle pistons are available in a couple of overbore diameters. I believe Wiesco, JE, and CP also offers pistons.

http://workshop-manuals.com/bmw/


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Yeah, spec is no machining, but you can easily take 10-15 thou off the head without issues ... though it if needs 10 or more, I'd be worried about a previous overheat. The block usually does not need anything. And with custom pistons, you can get deeper valve pockets (I would definitely do that for future cams!)

Also great points from aeronaut! I forgot about the Elring BS... I think they own VR now, so yeah, you get VR gaskets I'd definitely ask they place you're ordering from to actually look at the gasket.

[bluptgm3]

My thought on the VAC oil pump performance upgrade is that it basically rebuilds the pump. Machined impeller area, new impeller, new shaft, new bolt. Looks like an ebay dual pick-up oil pan is around $150. So a new S54 pump vs a used one and VAC mods would be about the same.

The S54 requires less volume than the S50, solid lifters vs hydraulic lifters.
The VAC S54 oil pump modification adds volume. Same oil volume as the S50 (M50/M52/S50/S52), machining of the S54 pump casing to accept the M/S5X internals.


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[bimmerboy318]

Now my head is spinning reading all these threads. Do I need to replace the valves themselves as well? Is that a definite weak point?

[ScotcH]

Now my head is spinning reading all these threads. Do I need to replace the valves themselves as well? Is that a definite weak point?

It is not a weak point ... plenty of OE valves in race engines.

[aeronaut]

^That. Not from direct experience like ScotcH has, but only from asking a lot of questions when I had my head off last time. Not 1 single engine builder or racer said I needed new valves. Ok, maybe VAC did, but you know. lol.

[bimmerboy318]

Feel slighty swindled. After measuring with calipers (not micrometer), it seems my exhaust cam is in fact an S50 with 9.7mm lift but the intake is a regular M50 with only 9mm lift. Also found that the timing is kinda strange compared to the last S50 head I pulled. Not sure what’s more cost effective, buying a pair of new Schricks and selling the S50 exhaust, or trying to buy just the S50 intake cam.

Intake cam is on the right and should be rounder than the exhaust from what I’ve learned. Live and learn I suppose. I’ll contact the seller an d,Ayer he has an S50 intake he’ll swap with me.

B5D982D1-695F-498D-B20D-686560D23961 by D S, on Flickr

94162CAB-C366-436C-9876-81203A394F58 by D S, on Flickr

09F28F79-325F-4BF1-8907-A7EBE8F9EDE8 by D S, on Flickr

[aeronaut]

Not sure what's going on here, but a few thoughts:
- Can you measure lift with just calipers? Lift depends on the center bore of the cam, and the radius of the contact area, and then the lift. I think.
- No part numbers?
- Your cams don't appear to be at the correct location for timing.

I have a set of S50 cams I can make any caliper measurement on to compare, if that'll help.

[bimmerboy318]

Not sure what's going on here, but a few thoughts:
- Can you measure lift with just calipers? Lift depends on the center bore of the cam, and the radius of the contact area, and then the lift. I think.
- No part numbers?
- Your cams don't appear to be at the correct location for timing.

I have a set of S50 cams I can make any caliper measurement on to compare, if that'll help.

Thanks! I watched a YouTube vid that said measure the middle round diameter which was 38mm for both cams. Then measure the length which was 47.6 on exh and 47mm on intake. The difference being 9.6 exh and 9mm intake. S50 spec is 9.7 and 10.2. M50 spec is 9 and 9.

[ScotcH]

What happened to your old cams? Toast? Schricks, or Cat cams are a nice upgrade for sure, but you'll need a tune to take full advantage ... you won't get much money for the single s50 cam (like $150 maybe?). If the cams are wrong, are you sure you got an s50 bottom end?

Your timing is definitely off ... you need to redo that in any case. Start at the beginning setting your exhaust cam to be square when crank is at TDC, and make sure you have tension on the chain when you lock it down. When you install the vanos, make absolutely sure it only rotates enough to mesh the gears and no, otherwise your intake cam will be off.

[bimmerboy318]

I got this motor as a spare. I don’t think it was run before I got it. It came from an e30 specialist shop that retired. It has an e30 conversion oil pan. I’d bet that they assembled the motor, and it sat waiting to be installed. Over time, other cars broke down and they robbed parts off it. It has a brand new Stewart water pump that doesn’t look like it ever got wet. Maybe they “timed” the cams for more power or something?

The old cams are still in the bad motor in the car. I wanted to take this down some to see what it might need. Taking your advice, I may not completely rebuild the bottom. Leave crank and mains in place and just replace rod bearings. Rebuild top half with upgradeD stuff. Re-gasket everything and go. The money on pistons/rods would offset the cam purchase.

[aeronaut]

For the record, here are some S50 cam intake and exhaust measurements, and markings on S50 intake cam.
(Didn't include "E" or "BMW" stamp)

S50CamMeasurements.jpg
S50IntkMarkings-3.jpg
S50IntkMarkings-4.jpg
S50IntkMarkings-5.jpg
S50IntkMarkings-6.jpg

[bimmerboy318]

Well, here’s what I was greeted with when I pulled the head off. No saving the bottom from the machine shop.

cyl 1 has a slight score most could live with.
cyl 2 had a deeper score in the same spot.
cyl 3 had water or coolant in it that turned into a rusty paste. After a little clean up with paper towels and WD40. The cylinder wall had a rust spot that you could feel texture.

I checked the head for flatness with a long level and I don’t think it’s warped beyond .004”. But who knows really.

Can someone confirm these are BMW pistons? If so, then this is an S50 for sure. If not, it could be an M50 bored out to an S50 spec. However, the little ID placard on the block tells me it started life as a 3.0L.

The little carbon present came off pretty easy which leads me to believe that the motor is actually low mileage. Just rode hard and literally put up wet!

197B6B3A-D467-452F-8A10-788DBD8DA352 by D S, on Flickr

46955DDB-8111-439C-844A-E302A531744A by D S, on Flickr

96971B48-64DD-46C3-895D-6BFF7889CE0B by D S, on Flickr

F11A5231-4D82-4E4B-8C2C-F1E2991CEB6E by D S, on Flickr

DA62BA61-DF43-4965-888F-B588E69EE1C1 by D S, on Flickr

[Def]

At the very VERY minimum I'd whirly bird hone that and toss in new rings and hope it cleans up enough that blowby won't be horrible.

But honestly, it probably needs a slight overbore, and at that point, might as well go higher CR pistons etc... then you start to question if it's worth it.

[GG///M3]

I have a set of s52 cams if you want to go that route

[ScotcH]

s50 is a nice rod ratio, so if you do keep going, I'd bore it out to 86.5mm, CP/JE 11.5:1 CR pistons, and those s52 cams from GG. Would be a nice reliable pump gas engine. Put some Supertech springs in, and rev to 7600 all day long.

[bluptgm3]

I would move to a better flowing head pipe - OE OBDII, Jet Hot (if you can find them), Turner Shorties, or eBay-what-ever.


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