S38 Head bolt onto M30?

[Robin-535im]

Assuming the intake and exhaust are carried over, can an S38 head be bolted onto an M30 short block?

[BillionPa]

thats a really interesting question.

would you be putting the intake and throttle bodies on there too if it did?

[Robin-535im]

thats a really interesting question.

would you be putting the intake and throttle bodies on there too if it did?

A guy can dream, right? :) in theory... you'd have to use the m5 in/out because the inlet/outlet ports are double wide from the twin valves.

[angrypancake]

i've often wondered this myself. bump.

[rob101]

i've often wondered this myself. bump.
+1 bumpo

[The Bigfella]

So - assuming you made it work (I believe the block is different - something to do with the oil system) - the first time you gave it a rev in order to use the performance, a conrod would come out the side of the block.

[angrypancake]

the s38 in and of itself is just a bored m30, is it not? if the transmission from an m5 works with an m30 engine, then it seems like the head would bolt onto an m30, with minor mods

[The Bigfella]

I believe the limiting factor in relation to the rev limit is the big-end bolts - which, I gather are different.

[The Bigfella]

Just looking at realoem, the block is $1800 or so for a 535 and $4,100 for an M5 - connecting rods about $840 vs $2,800 - bigend bolts $5.80 vs $14.00 each. crankshaft is $1040 vs $2940. This doesn't necessarily mean they are different - but I wouldn't bet on them being the same.

[Brandon J]

The coolant and oil passages are different. Look at pictures of the head gasket to see.

[BillionPa]

damn!

[genphreak]

Just looking at realoem, the block is $1800 or so for a 535 and $4,100 for an M5 - connecting rods about $840 vs $2,800 - bigend bolts $5.80 vs $14.00 each. crankshaft is $1040 vs $2940. This doesn't necessarily mean they are different - but I wouldn't bet on them being the same.Er, M5 is all forged. Stock M30 I don't think uses forged pistons but the crank and rods are not forged... AFAIK- please don't take this as gospel... its hear say

M5 is forged comps all the way through, its how it gets a higher rev limit. I'd also expect that the tolerances are much closer.. am also very interested. Given that the M30B35 block is the same block as the turboded M102/M106 745 M30-style motor, surely its up to the job- and perhaps the oil plumbing is acceptable if you don't run it to redline too often, or keep your limit within normal M30 levels. Surely the turbo one is all forged too ;)

Oh if this is possible one would need S38/M88 headers as the exhaust ports are all different- spacing maybe not but the stud pattern and sizes are.

We definately need more info on this subject, surely someone has done it!

:) Nick

[winfred]

looks like one of those things that if you don't have them side by side it's impossible to tell

[Jon K]

Also, an S38 head is a 24v head. An M30 is a 12v head. The pistons in the M30 are cut to clear 12 valves coming down.

Here is the M50, see the cuts in the piston for valve clearance:

http://blowneuroz.com/newmotor/8.jpg

[Robin-535im]

So - assuming you made it work (I believe the block is different - something to do with the oil system) - the first time you gave it a rev in order to use the performance, a conrod would come out the side of the block.
You've got one of each I see... how 'bout running out and swapping the heads real quick?

:)

Seriously - one would build up a new bottom end with beefier m30 parts.

Brandon's comment on the HG makes sense...

Sneaking suspision is that it *is* possible if you overcome enough hurdles, but by the time that's done you'll have spent more time and money that you could have just bought an m5 in the first place.

I imagine people would have done it before if it were cost effective... still, throttle bodies and those curly-q m5 exhausts really light my fire.

[Jon K]

Yeah I tend to agree - by time you get the S38 head to fit an M30 block, make the oil/water work, clear the pistons, etc., you might as well buy an S38.

[The Bigfella]

Yeah I tend to agree - by time you get the S38 head to fit an M30 block, make the oil/water work, clear the pistons, etc., you might as well buy an S38.

That's what led to my M5 purchase. I got the 535i to replace my son's E21 (we couldn't locate a new exhaust manifold - and at 520,000 km .......) I drove the 535 and said "hmmm - this'd be nice with 50% more go ........."

[MPD47]

the s38 in and of itself is just a bored m30, is it not? if the transmission from an m5 works with an m30 engine, then it seems like the head would bolt onto an m30, with minor mods
No, the S38 is based on the M30, but the castings are different.


We definately need more info on this subject, surely someone has done it!

Little late on this topic, however, It can be done. I can tell you that, as I've got an S38 and an M30 side by side in my garage, completely torn down. HOWEVER, you'll need to machine the M30 block for oil returns, by the time you do the machining to get it to fit, you could've purchased an S38 block. They are remarkably similar. Honestly it's just a couple extra passages from being able to fit, the M30 headgasket even has them cut into it. We were quite curious about this as well until we took a close look. Here's some photos:

S38
http://www.mturck.com/S38B36/S38.jpg
M30
http://www.mturck.com/S38B36/m30.jpg
http://www.mturck.com/S38B36/DSCF5798.jpg

I have photos of the heads for comparison too, but I seem to have misplaced them, worst case I'll go shoot some new ones. Yes Jon, I finally got headwork for it.

So in recap, yes, it could work, but NO it doesnt just bolt up and work without machining to the block.

[jrobbo]

The M30 and S38 blocks are almost identical, the only differences AFAIK are: 1) The S38 has been bored a little, and
2) The S38 head has an extra oil drain at the back of Cyl #6, and this gets routed via a pipe into an extra oil return machined into the block underneath the Cyl #6 exhaust port. From what I can see, there's no reason why that return can't be routed directly into the sump.

Take a look at the following pic:

http://www.jrobbo.com/M5/Head11.jpg

to see the extra oil return machined into the block.

As Ian points out though, the pistons, rods and crank a also very different, your engine won't last very long if you try to run the S38 top end on the M30 bottom end. When you buy an S38 block from BMW, it comes with a matched and balanced set of pistons and rods. That explains part of the price difference, and the rest is just price gouging by BMW.

John

[MPD47]

There are a few structural differences too, along with the oil and coolant passage differences in the decks as I pointed out above you.

[jrobbo]

Yeah, I saw the photos that you posted after I posed my note, thanks for the extra info. What, specifically, are the few structural differences that you speak of? I was under the impression that there were no structural differences in the block.

Back in the late 90's, my S38 block developed cracks so I rebuilt the engine (which is where the above photo came from). While I was looking around for options, I came across one of the well known US engine builders that was rebuilding S38 motors, and using modified M30 blocks to save some $$$$, but I can't remember who it was now, it's been 8 long years since then.

John

[MPD47]

Pretty sure some of the bracing around the base of the block is SLIGHTLY different. I could be mistaken, I'll grab some photos next week when I'm back in the garage from all angles so people can see the differences.