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Discussion Starter · #1 · (Edited)
I've seen this a few times now in some of these European builds , an S38 head on an M30B35 block.

What's the benefit over using a complete S38 engine ? An abundant supply of cheap blocks and bottom ends ?

MI Performance BMW 5 Series E34
Engine
BMW M30/S38 3.5-litre inline six-cylinder, M30B35 block, S38 crankshaft, CP forged pistons, Eagle rods, S38 DOHC cylinder head, custom cams, Comp Turbo CT43-7479 turbocharger, TiAL wastegate, custom exhaust manifold, PPF blow-off valve, front-mounted intercooler, custom intercooler piping, 4.5-inch turbo down pipe, custom 4-inch exhaust system, custom intake, Aeromotive Eliminator Stealth fuel cell, Aeromotive Eliminator fuel pump, Aeromotive fuel pressure regulator, Nuke Performance/PPF fuel rail, Bosch 1600cc injectors, Peterson dry sump, custom billet oil pan, front-mounted intercooler, v-mounted aluminium radiator, 6x MSD coils, Autronic SM4 engine management system
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I would assume its the amount of m30's kicking around. S38 blocks demand a premium, where an M30 block can be had for fairly cheap depending on the source ( junkyard ).
 

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Discussion Starter · #4 ·
I was comparing an S38 and M30 block in the workshop last night and they're almost the same except for some additional oil (?) holes in between the S38 cylinders and some differences with the engine mounts and water jacket casting on the LHS of the block.
 

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is b38 and b36 blocks the same?
No besides the bore and a few other changes the easiest thing visually to see are a few casting differences between the B38 and B36. Pics are borrowed from the web none are mine.

B36 and B35: Notice the oil return casting boss as used on the 745i turbo engines and the number of mounting bosses on the front of the engine block.




B38: Notice the lack of the casting for the oil return as well as fewer engine mount bosses and the thinner looking crank case. Also on the intake side one will say 3.5 and the other 3.8.



-Greg
 

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Differences

I suppose S38 engines have blocks with tighter tolerances which may have an effect on performance and durability. Besides that I think when building up a complete engine, the financial benefit is just marginale but M30 blocks can easily be found.
 

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What is funny is that many in the US think that it impossible to do the m30 plus s38 head combo, but Europe and the rest of the world seems
to have a few of these running around. I suspect tapping the block and adding an oil line is easy enough to do. What is the difference
between the m30b35 crank and s38b35 crank?

I've seen this a few times now in some of these European builds , an S38 head on an M30B35 block.

What's the benefit over using a complete S38 engine ? An abundant supply of cheap blocks and bottom ends ?



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M30 is more common.

I believe the S38B35 is a double row timing chain and the M30 is single chain for sure. This changes the crank and other timing parts.
 

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Hello

I'm new here I just wanted to say this is exactly what I'm trying to do right now, but I can't see ValeraM5s picture. I have a S38 head from a engine that broke (head is okey). But now I'm trying to put the head on a M30B35 block. I know it has been done but I want to know can I run with the M30 pistons? Or do I need to increase the bore and fit S38 pistons?

No one is properly going to answer because this thread is old but its worth a try.
 

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Hello

I'm new here I just wanted to say this is exactly what I'm trying to do right now, but I can't see ValeraM5s picture. I have a S38 head from a engine that broke (head is okey). But now I'm trying to put the head on a M30B35 block. I know it has been done but I want to know can I run with the M30 pistons? Or do I need to increase the bore and fit S38 pistons?

No one is properly going to answer because this thread is old but its worth a try.
I have pics saved locally, and I'll try to dig them up. Regardless, the pics don't show which pistons are being used, and I'm wondering about the same. Concern may be the fact that M30 pistons have only 2 valve slots, where S38 have 4. You may be looking at a potential machining work on the piston crown. Also, I assume that "piano-top" high compression pistons will not be able to fit, without risk of piston to valve contact.

Question for you, what's your plan for the valve train? M30 has a single row timing chain, while S38 has double.

Regards
 

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I have pics saved locally, and I'll try to dig them up. Regardless, the pics don't show which pistons are being used, and I'm wondering about the same. Concern may be the fact that M30 pistons have only 2 valve slots, where S38 have 4. You may be looking at a potential machining work on the piston crown. Also, I assume that "piano-top" high compression pistons will not be able to fit, without risk of piston to valve contact.

Question for you, what's your plan for the valve train? M30 has a single row timing chain, while S38 has double.

Regards
Thanks in advance! Yeah the "piano top" doesn't work. I have tried to put it together, but the valves hit the pistons while I was turning it by hand.

The thing is I have a old S38B36 that blew up (hole in the engine block, connecting rod that gave up), so my thought for the valve train is just that I use the S38B36 crank which has the dual timing gears on it. Then just move over the guide rails.

Best Regards
 

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Thanks in advance! Yeah the "piano top" doesn't work. I have tried to put it together, but the valves hit the pistons while I was turning it by hand.

The thing is I have a old S38B36 that blew up (hole in the engine block, connecting rod that gave up), so my thought for the valve train is just that I use the S38B36 crank which has the dual timing gears on it. Then just move over the guide rails.

Best Regards
I know exactly what kind of a failure you're talking about. Would it be cylinder #5 perhaps? :) That's great re. using the S38 crank, but I'd have it checked by machine shop, for straightness, considering what it went through during engine failure.

I have an extra S38 head with valvetrain, that I'm contemplating on putting on top of my M30B25 turbo project, just for kicks. But I haven't come up with a solution for the timing crankshaft sprocket. Perhaps "degrade" to S38B35 single row timing chain.
 

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I know exactly what kind of a failure you're talking about. Would it be cylinder #5 perhaps? :) That's great re. using the S38 crank, but I'd have it checked by machine shop, for straightness, considering what it went through during engine failure.

I have an extra S38 head with valvetrain, that I'm contemplating on putting on top of my M30B25 turbo project, just for kicks. But I haven't come up with a solution for the timing crankshaft sprocket. Perhaps "degrade" to S38B35 single row timing chain.
It was cylinder #6 actually, I don't know how but it was #6. Yeah checking for straightness is a good idea.

Okey that's a tricky one. I don't know how hard it is to change or get that S38B35 but that is the best idea I could think of also.
 

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It was cylinder #6 actually, I don't know how but it was #6. Yeah checking for straightness is a good idea.

Okey that's a tricky one. I don't know how hard it is to change or get that S38B35 but that is the best idea I could think of also.
Looking at realoem, sprocket is a changeable part, although I'm not sure I know how to take it off the crank, without risking damage (to the crank). So in theory, I could have a custom sprocket manufactured to fit my existing crank, or perhaps a factory unit already fits. I need to do some research...

Edit: or just run a single row chain over the twin row cam sprockets 😆
 
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