S38b35 vs S38b36 Cylinder Head

[downforce22]

I found an e30 with an s38 swap and bought it but I knew it wasn't quite running right. I did some maintenance and that helped but it still wasn't running as good as an s38b35 so I did some tests.

Compression and leakdown test pointed to a burnt valve. I proceeded to get the head off the engine and found that was it. But we also found hairline cracks in it as well. So I am searching for a new b36 head and wondering what the differences are between the b35 and b36.

Mooseheadm5 said this. Anything anybody else has to add?

The heads are very similar. The intermediate housing (cam housing) is the same for all S38s. The lower part of the head with the chambers is different for each. I believe that the ports are different sizes in each head (largest is B38, smallest is B35) and I know there are other small differences, like a sensor fitting in the front of the B36 and B38 heads, etc. but the basic design is the same for all (since they have to bolt to essentially the same block on the bottom and intermediate housing on top.)

Questions

• Are the ports different?
  
  Are the combustion chambers different?
  
  Would there be a drawback to using the b35 head? A benefit?

Here are some picture of the damage and one of the car in question.







Thread on r3vlimited about it.

http://www.r3vlimited.com/board/showthread.php?t=356570

[downforce22]

Anybody?

I found another head and upon investigation there is a crack in this one as well as it needs 0.010" of decking to be flat.

Is it normal for the s38 heads to crack? I am not sure I want to chance it on another head only to find another crack..

What do you guys think? Is this usable?

[Randomg]

The answer to your original questions:
The intake ports are different, I think the only difference is the little lip on the b35 is removed on the b36, so it looks more like an oval.
I don't believe the combustion chambers are different.
Not sure on the last one, there might be different mounting points for the hardware that goes on the outside of the head.


When I rebuilt mine, I had a few cracks. Paul B told me that it wasn't common for them to crack unless they overheated, and kept inquiring on what I had done to get it to crack that bad (I think it was running the engine for a few miles with NO coolant) but I want to say a guy at VAC said "that's pretty common" when I mentioned head cracks. I'd go with Paul's answer though. He charged me roughly $100 to fix each crack, I wouldn't put it back on with any cracks when finding the right place can get it done for a few hundred dollars. (Cut them out, fill them in, and straighten the head).

[downforce22]

The answer to your original questions:
The intake ports are different, I think the only difference is the little lip on the b35 is removed on the b36, so it looks more like an oval.
I don't believe the combustion chambers are different.
Not sure on the last one, there might be different mounting points for the hardware that goes on the outside of the head.


When I rebuilt mine, I had a few cracks. Paul B told me that it wasn't common for them to crack unless they overheated, and kept inquiring on what I had done to get it to crack that bad (I think it was running the engine for a few miles with NO coolant) but I want to say a guy at VAC said "that's pretty common" when I mentioned head cracks. I'd go with Paul's answer though. He charged me roughly $100 to fix each crack, I wouldn't put it back on with any cracks when finding the right place can get it done for a few hundred dollars. (Cut them out, fill them in, and straighten the head).

Thanks for the heads up. I would think the cam tray would be the same and the cams were the main difference as well as the intake and possibly exhaust ports. I found a b35 head that I could use but I want to make sure it will work for my application and won't leave untapped potential in the engine. Are the intake and exhaust valves the same?

I guess I will start scouring realoem.com for specific valvetrain components.

[Randomg]

Realoem has them as the same for both engines.

[downforce22]

Thanks Randomg, I found that also. I found this sheet from metric mechanic which basically claims the b35 and b36 are only different in stroke, intake port diameter, Cam duration, and exhaust tube diameter. This ignores the differences in AFM/ MAF and the intake/plenum/ throttle body, strictly speaking of the engine components.

http://www.metricmechanic.com/pdf/M5-M6 ... -Chart.pdf

[downforce22]

It looks like cracks in the s38 head are not all that uncommon.

I found this thread with detailed pictures showing how to repair the s38 head. It is very intensive with respect to welding and machining. I am leaning toward using the s38b35 head that I found and potentially porting it to match a b36 head +2 mm.

Full thread here, I may upload and backup the pictures so they do not get removed.

http://www.e34m5.de/board/showthread.ph ... S-M5/page2

[downforce22]

Does anybody have any experience with s38 heads from VAC?

https://store.vacmotorsports.com/vac--- ... p1291.aspx

What about their stage 1-3 head rebuilds?

https://store.vacmotorsports.com/vac--- ... hread=True

[downforce22]

Does the s38b38 head differ and/or bolt on to the s38b36 block?

I found two documents with information on the two engines. Basically, I am thinking, if I have to buy a head from BMW, maybe I could run the b38 head with larger diameter intake ports, intake valves, and exhaust valves. I couldn't run b38 cams without changing the bottom end, but it should give me airflow for my altitude deprived engine.

Any thoughts? it would be +1.5 mm intake valve diameter and +0.5 mm exhaust valve diameter.

Is it possible?

http://www.asean-aerospace.com/BMW%20E3 ... %20Doc.pdf

http://www.asean-aerospace.com/BMW%20E3 ... alInfo.pdf

[Randomg]

Realoem is your friend...

The 36 and 38 have the same head, same cams, same valves, same rods (which are also shared with the b35 I believe). The crank and rod bearings are different, and everything I've read says that the b38 rod bearings don't hold up nearly as well as the b36 or b38.

Also, there are s38 heads around, and they're all very similar (the b35 to b36/38 change in port and valve sizes the only thing I'm aware of). I wouldn't buy a new one for the price BMW sells them for.

[downforce22]

Realoem is your friend...

The 36 and 38 have the same head, same cams, same valves, same rods (which are also shared with the b35 I believe). The crank and rod bearings are different, and everything I've read says that the b38 rod bearings don't hold up nearly as well as the b36 or b38.

Also, there are s38 heads around, and they're all very similar (the b35 to b36/38 change in port and valve sizes the only thing I'm aware of). I wouldn't buy a new one for the price BMW sells them for.

I think you mistyped there. The valve diamteres are definitely not the same between the s38b36 and s38b38. Look at the differences in the documents I linked in my last post.

As far as s38 heads, the only ones I have found are either cracked or have damaged valve seats. If you know where I can find a good condition head aside from BMW, please let me know. I guess that's the problem when looking for a head on an engine with only 1,678 produced in the North American Market.

For b35 heads, only 1,767 M6's were sold in the NA market, and only 1,340 M5's...

[Randomg]

You're right, I did a cross reference on the b38 valves and saw it was in the m5 touring, which I thought was the b36, my mistake.

The cheapest dealer source I use (there might be some insider guy here who can get it cheaper) has a b36 head at ~3000k without any valves, guides, springs, etc.

I paid Paul Burke 2 years ago for a B35 head refresh with stainless valve option (38mm/33mm) $1699.00 + $100 a crack (so it was about $2200).

Do what you want with your money I guess.