M30 B35

[turbodan]

I would recommend new rockers and shafts, or the rockers and shafts from the engine the cam came out of. They wear together, so if you use a broken in cam and broken in rockers from different cars you will probably wear the cam and rockers out quickly. Same deal if you mix the rockers up on the same cam. If you don't use the old ones on the same lobes its the same problem.

Ideally, you should buy a new b35 cam, rockers and shafts. You can feel the difference between all used parts and all new parts. Might as well do it right. And it would be too easy not to throw a performance chip in there at the same time.

[BAVARIANUT]

do you need to reprogram the chip for the b35 cam? can I go with the stock ecu?

[marks]

so how does the b35 create 211 when the older m30 is at 180. cams??

I don't know, just what someone in this forum told me.

Is that number incorrect?

[turbodan]

so how does the b35 create 211 when the older m30 is at 180. cams??

I don't know, just what someone in this forum told me.

Is that number incorrect?

Its close. They were factory rated at 208.

[Mike W.]

If only someone had swapped a b35 cam into a b34 motor, and dynoed the results. I bet thats most of it.

I will allow I haven't personally, but with only 4 degrees difference, 260 to 264, I doubt it would amount to much at all.

I think a bump in compression, bigger intake valves, bigger and better shaped intake ports and intake manifold and better flowing exhaust manifolds would be most of it.

I would recommend new rockers and shafts, or the rockers and shafts from the engine the cam came out of. They wear together, so if you use a broken in cam and broken in rockers from different cars you will probably wear the cam and rockers out quickly. Same deal if you mix the rockers up on the same cam. If you don't use the old ones on the same lobes its the same problem.

Uh, I've put over 100K on two different M30's I've rebuilt mixing and matching cams, rockers and shafts, all used, without any problems. Good used parts don't wear out good used parts prematurely. Bad, or excessively worn parts do. So, if they're in good shape, don't worry about them.

I don't know, just what someone in this forum told me.

Is that number incorrect?


Its close. They were factory rated at 208.

It was probably me. It seems like I've seen both numbers in print and even if I'm imagining things, 3HP isn't anything to worry about, ~30HP is.

[turbodan]

I guess I've had bad luck with used rockers. I could be wrong, but I was under the impression that BMW's M20 and M30 cams were case hardened. So the thought of breaking in more than one rocker on each lobe seemed risky with that in mind. I didn't say it was a horrible idea or that you can't do it, just that I would recommend new parts instead.

The B35 cam has more than just 4 degrees of duration. Its a completely different profile, as shown on the following chart from the archives:



It looks more aggressive than the Hartge 292 cam, with more lift and similar timing and just a little less overlap. I really think the difference is significant to make most of the difference. Especially looking at the very low overlap B34 cam. I really don't think a 1mm increase on the intake valve, mild port changes and different manifolds made the majority of the difference considering such a vastly different cam profile.

[Mike W.]

Sorry if I came off a little strong.

Interesting shot of the cam profiles, I'm going to have to study it a bit more, is it the one Divender came up with a while ago? I think I've mic'd out B34 and B35 cams and came up with them having the same lift, unlike what it appears in the shot. I'd also like to see the later L-jet cam in there, it was a nominal 260 like B34's, but I think it had more lift. The cams are hardened, but I'm not sure just how hard. The rocker pads are quite hard though, but they have a much harder life than the cam.

Good info, but I'm still going to have to disagree with your conclusions, I think compression coupled with better breathing made much more of the difference.

[Rich Euro M5]

There are two of us in Houston running stock M30B34 engines with the B35 cam. Jimmy G. was the first to do the swap based on Devinder's cam profiles. He was favorably impressed with the change in perfromance. When the HG failed on my DD, I swapped in the rebuilt head from my deceased 533i. During the cleanup of the head prior to installation some pitting was found on a couple of cam lobes. Since the cam needed to be replaced, I too installed a B35 cam based on Devinder's data and Jimmy's positive experience. I don't have dyno info, however the butt dyno indicates there was an increase in power. My 535i now pulls very strongly right up to the redline. It's been my experience that the torque output of the B34 engine starts to roll over and decrease between 5000 -5500 RPM.

IMO, the B35 camshaft provides a positive improvement in performance.

Rich

[cgraff]

I guess I've had bad luck with used rockers. I could be wrong, but I was under the impression that BMW's M20 and M30 cams were case hardened. So the thought of breaking in more than one rocker on each lobe seemed risky with that in mind. I didn't say it was a horrible idea or that you can't do it, just that I would recommend new parts instead.

The B35 cam has more than just 4 degrees of duration. Its a completely different profile, as shown on the following chart from the archives:



It looks more aggressive than the Hartge 292 cam, with more lift and similar timing and just a little less overlap. I really think the difference is significant to make most of the difference. Especially looking at the very low overlap B34 cam. I really don't think a 1mm increase on the intake valve, mild port changes and different manifolds made the majority of the difference considering such a vastly different cam profile.

Where is the info on how these were mic'd? cscoupe.org?

Just FYI, but the high compression B34 had the SAME CAM as the 'world' B35.

PNs:

E28 M/535i:
11311287606 (high comp)
11311707151 (low comp)
11319058576 (addt'l hardened, high comp)

E34 535i:
11319058576 (addt'l hardened)
11311287606 (std)

[BAVARIANUT]

what about slapping a b35 head with all the stock components on a b34 block? possible? Any electronic issues?

[Brad D.]

The head replacement should be a direct swap, however, both exhaust and intake mani ports will be undersize relative to the ports in the head.

[Rich Euro M5]

And the engine's CR will drop by about 1/2 a point.

Rich

[BAVARIANUT]

And the engine's CR will drop by about 1/2 a point.

Rich

the compression ratio you mean? So that would equat to less torque and less stress on the headgasket, etc.?

so the complete head intake and exhaust manifolds off of any b35 will swap right in and match with the throttle body and exhaust downpipes from the b34? Will it work with the current b34 ecu? cold start injection? any sensor ports different? Coolant connections? You think D'silva can make a chip to optimise this mod?
i think that this, instead of doing the complete motor swap seems more practical since theres less work involved and you get the assurance of having a fresh headgasket. unless your bottom end is shot too.
I like the compatibility between BMW parts. It makes it easier to make a frakenproject. It feels good to have a BMW alittle more special than most others, without paying a fortune. thanks for all the feedback. I love the fact that I can customize my bimmer with quality BMW parts without the custom part pricing that comes attached with such a mod, typically...

[M635CSi]

And the engine's CR will drop by about 1/2 a point.

Rich

the compression ratio you mean? So that would equat to less torque and less stress on the headgasket, etc.?

It’s a mechanical ratio but isn't the actual compression ratio which should be considered to vary slightly with engine speed and load. What this means is that cylinder pressure not "compression ratio" dictates torque. It is sometimes possible to reduce the mechanical ratio ("CR") while at the same time increasing cylinder pressure.

so the complete head intake and exhaust manifolds off of any b35 will swap right in and match with the...

It seems like a cool swap but on the euro engines I'm wondering if it might be a good idea to install the B35 pistons as well.

[Brad D.]

Since it doesn't sound like you want to do the entire b35 swap, I don't think just the head will benefit you all that much. My guess is that while you make some more power from the more aggressive cam, you are taking a hit in CR which won't help power or economy. I would probably swap the b35 cam into your b34 head to keep your current CR and you will have no issues with ports matching. While it probably won't make as much power power as a full b35 setup it'll probably be better than just the b35 head on a b34 block.

[BAVARIANUT]

And the engine's CR will drop by about 1/2 a point.

Rich

the compression ratio you mean? So that would equat to less torque and less stress on the headgasket, etc.?

It’s a mechanical ratio but isn't the actual compression ratio which should be considered to vary slightly with engine speed and load. What this means is that cylinder pressure not "compression ratio" dictates torque. It is sometimes possible to reduce the mechanical ratio ("CR") while at the same time increasing cylinder pressure.

so the complete head intake and exhaust manifolds off of any b35 will swap right in and match with the...

It seems like a cool swap but on the euro engines I'm wondering if it might be a good idea to install the B35 pistons as well.

so a reduction in CR means, less power? 1/2 point would equat to what exactly. Mechanical compression stands for what? whats wrong with the b34 pistons? euro engines? but i thought the b35 head flows better, why would putting a b35 head be less beneficial than just putting the b35 cam on the b34 head? you starting to confuse me with the mechanical compression, I've never heard of it? Is the b35 head shorter in height or something? what influences the mechanical compression??

[BAVARIANUT]

How is the b35 block different or better? Pistons, crank, what?

[Brad D.]

IIRC the b35 head's combustion chambers are 10cc larger and the b35 pistons have a different shape than the "piano top" b34 pistons which is what is responsible for the raised compression. Mechanical or static compression ratio is (total cylinder volume + clearance volume)/clearance volume. When you put the larger cc b35 combustion chamber on the b34 block you reduce your compression, I don't know by exactly how much, but I have read that it is lower than a stock b34. Any time your static compression is reduced you are compromising VE(volumetric effeciency, or you cylinders ability to fill) which affects power and fuel economy. I don't know if you can go as far as equate a point of CR to a finite amount of horsepower but dropping the CR typically isn't what you want to do unless you are running considerable amounts of boost on pump gas and you don't care about off boost response. I raised the compression in my turbo nissan to 9:1 from 8.5:1 and I still run 18psi with no detonation.
Yes, the b35 head and manifolds flow better and the head is better in almost every way, but if you are wanting a street driven NA engine, putting the b35 head with b34 manifolds which will now have a lower than stock CR, is probably not what you want.

[alpinass]

at 9:1 CR, 208h.p. - 230ft lbs of torque. Lots of torque. I have a 1985 Euro M30b34 10:1 - 218h.p.-229ft lbs torque that will run with a 059 ECU. I am going to do a full rebuild - Stage II P&P, mild cam, new seals, rockers and 50% stiffer springs.
It will be UP for grabs soon. It should be good for 240h.p.

[Rich Euro M5]

Mechanical compression stands for what?

Basically it's a value calculated by making physical measurements of such things as the head's combustion chamber volume, the small volumetric space between the piston and cylinder walls above the top compression ring, etc. Once you have the data you can then calculate the Compression Ratio "CR".

The B35 head on the B34 bottom end is a good solution for a turbo engine because of the slight drop in CR. So if FI is in your future plans this swap might make sense, particularly if your HG needs replacement. However if you don't have FI in your future plans, I'd stay with the B34 head and install a B35 cam as already suggested.

Rich

[Azure]

When you put the larger cc b35 combustion chamber on the b34 block you reduce your compression, I don't know by exactly how much, but I have read that it is lower than a stock b34.

From what I recall, it's about a half a point. Yielding a CR in the vicinity of about 7.5:1.

[BAVARIANUT]

thanks, so I don't plan on FI, but if I were todo the b35 head, I wuold include the manifolds. But looks like the b34 head is a better option for me. What about adding the higher flowing intake and exhaust manifolds? Any room for improvement from the b34? I would probably need to get a chip for the higher flowing manifolds? i s there realy that much a diiference from the b34 manifolds? will they match up with the b34 downpipes and throttle body?

[BAVARIANUT]

thanks, so I don't plan on FI, but if I were todo the b35 head, I wuold include the manifolds. But looks like the b34 head is a better option for me. What about adding the higher flowing intake and exhaust manifolds? Any room for improvement from the b34? I would probably need to get a chip for the higher flowing manifolds? i s there realy that much a diiference from the b34 manifolds? will they match up with the b34 downpipes and throttle body?

what about manifolds? can I slap them on the b34 head with the cam for some extra ponies. how much better are they, is it not worth it to throw them in?

[Rich Euro M5]

thanks, so I don't plan on FI, but if I were todo the b35 head, I wuold include the manifolds. But looks like the b34 head is a better option for me. What about adding the higher flowing intake and exhaust manifolds? Any room for improvement from the b34? I would probably need to get a chip for the higher flowing manifolds? i s there realy that much a diiference from the b34 manifolds? will they match up with the b34 downpipes and throttle body?

what about manifolds? can I slap them on the b34 head with the cam for some extra ponies. how much better are they, is it not worth it to throw them in?

It won't do you any good unless you port the B34 head to match the B35 intake ports.

Rich

[BAVARIANUT]

thanks, so I don't plan on FI, but if I were todo the b35 head, I wuold include the manifolds. But looks like the b34 head is a better option for me. What about adding the higher flowing intake and exhaust manifolds? Any room for improvement from the b34? I would probably need to get a chip for the higher flowing manifolds? i s there realy that much a diiference from the b34 manifolds? will they match up with the b34 downpipes and throttle body?

what about manifolds? can I slap them on the b34 head with the cam for some extra ponies. how much better are they, is it not worth it to throw them in?

It won't do you any good unless you port the B34 head to match the B35 intake ports.

Rich

can a shop port the head properly, is it expensive? Is it worth it?

[turbodan]

When you get into swapping intakes you really need to address the fuel injection too. While it may not be radically different, it can cause problems during closed loop operation. If you go for a B35 cam and intake, you might as well go for the B35 injection too. It might be a stretch for the B34 hardware.

[Brad D.]

This is not meant to be dorogatory in any way, but I recommend that if you don't need to mess with the head or internal engine parts, don't. I'tll probably wind up being more trouble and expense than its worth with more downtime on your car than you want. Just chip your car the way it is and get a lower ratio LSD and enjoy the car. Down the road, as you learn more and plan everything out, get an entire b35 engine inlcuding electronics and do the complete swap, not piecemeal it together with results that will probably less spectacular than a stock complete b35 swap.

[spinedocab]

the b35 pistons have a different shape than the "piano top" b34 pistons which is what is responsible for the raised compression

FWIW, the standard North American b34 or the "green" euro motors do NOT have "piano top" pistons. These motors have flat domed pistons. The piano-tops are found in the high compression (10:1) "dirty" euro motor, and the raised section of the piston (which resembles a piano) is what raises the compression ratio.

And I am thinking of a b35 swap myself. I think the approximately 30 hp and associated torque in non-trivial. Definitely a bit of work to get done, including the harness and ECU change, but very possibly worth it.

My .02

Andrew

[Brad D.]

Thanks for the clarification spinedocab. Either way, for the original posters info, the 10cc increase in combustion chamber size on the b35 head will still lower the comp if he drops the whole head on his b34 block.
I would do my b35 swap over again in a heartbeat. I needed to replace or rebuild the engine and I felt it was just the right choice. The electronics make the car so much smoother. It idles better, starts better, gets better gas mileage and the overall package transforms the car. I ran the b35 off of the original Motronic 1.0(059 DME) and it was marginal at best. I say if you are going to do it, go all the way.

[spinedocab]

I agree, if I do it I'll certainly change the harness and the ECU. Eliminates the cold start injector, and all the later enhancements resulting in improved driveability.

AB