Cylinder head questions

[Gransin]

My car when I bought had been sitting in a garage for 15 years, but it ran and I've driven some with it before the restoration and now afterwards, and with some I mean some hundreds of meters, not kilometers. The seller of the car stated that the head was practically new and had been renovated before it was put in the garage, and since it ran great with no noices we believed it. Everything seemed fine until we checked the dipstick when it came back from the paint shop a week ago and found cream, not oil on the dipstick.

So we hoped for a blown headgasket, but we weren't that lucky.

Here is the specs of the engine (as much as I know about it):
Block: 3liters and vin-number confirms it comes from a BMW e3 3.0. Bore 89.0mm
Head: 2.8 cast -73.

I've been thinking about this over the last 4 years while restoring the car, if this is a possible combination? Is there any advantage of putting a 2.8 head on a 3.0 block?

Here is a couple of pictures of the pistons when we removed the head, what I'm sure about is, as you can see, the intake valve had a date with the piston. What I'm not sure about is, if it might be from earlier in this engines life? Because there has been no noices and I can't see anything on the intake valve suggesting there has been contact. All 6 pistons have the same mark from the intake valve.

And, are these the original pistons for a 3.0 from an BMW e3?





Head 2.8 cast -73



Head was cracked at several places, not much to do about it, but here is a couple of pictures if anyone wants to look at the misery.

Cylinder number 4:



Also in cylinder number 4:



Cylinder number 3:



Cheers,

 

[Sven]

These look like high compression pistons which were not stock in the 3.0. If the head and top of the block were milled during a previous r&r, then the clearance between piston top and valve will have gotten smaller - hence contact.

 

[Markos]

From what I have read (here), the early heads were notorious for cracking, so the cracked head could have happened regardless of the clearance issues. The high compression pistons are referred to as "piano top" pistons for obvious reasons. They came on the 2.8 (thanks Chris), the 3.0 CSI, the 2002tii, the euro M30B34, and several other cars. I thought that I had read that the B32 (which had high compression) also had piano tops, but I have seen pictures with conflicting information. See the image below with 3.2 on it though. I would measure the cylinder bore to start. If you google "BMW piano top" you'll see some images of the different pistons. Some were taller than others, those look pretty short. Others can chime in with info as I'm not terribly familiar with this stuff. As far as I know, the heads are all the same, and I think the cams were all 272 so all things should be equal on the cylinder head. Like Sven I would guess that some decking took place.

I'll edit this thread for accuracy if anyone has additional info.

Presumably a 3.0 piston. I haven't found any pics of a CSI piston and I haven't removed my head yet on my parts car:

Presumably a euro M30B34 piston:

2002tii piston:

2.8 per Chris. This certainly wouldn't fit in a 3.0 block

 

[nashvillecat]

The many cylinder head cracks pictured are unusual for an M30 cylinder head -- including earlier castings.

I believe it has been pointed out in other threads that the major difference between earlier and later heads is water jacket design, including thickness, so that the newer versions are not as open as the earlier versions.

IMHO, the newer heads offer more protection from overheating but are not essential for most pre '74 M30 engines. Some later (post '74) North American Market M30 engines were fitted with extra emission controls that tended to function better with increased engine operating (exhaust) temperatures. See the exhaust gas reactors below. These were the precursors to catalytic converters and clearly introduced significantly higher temperatures to the cylinder heads. In order to avoid related warranty and reliability problems, the factory beefed up its cylinder head design. Again, this "extra" protection is nice but unnecessary for an early M30 engine with a well maintained cooling system -- that operates in the blue. Although I once collected a few new cylinder head spares, fortunately, I never had to use them and they were donated to other causes. As an aside, many M30 engines seemed to be magnets for neglected cooling system maintenance, so that the early design water jackets showed advanced signs of corrosion. In turn, the same serious neglect might make the same cylinder head less able to resist high temperature engine operation and more prone to overheating. Any renewed head design would be an improvement over a significantly corroded head. As it happens, newer water jacket design also included different coolant port sizes that emulate most cylinder head gaskets - so that coolant flow is proportionally restricted for some cylinders. In theory, this design maintains even temperatures for each combustion chamber, but the head gasket seems to serve the same function. More on cracking and overheating http://www.firstfives.org/faq/cylinder_head/cylinder_head_faq.htm

Returning to Gransin's case study, so many cracks indicate metal failure caused by overheating and/or an engine stressed beyond its design limits. Overheating can be a question of degrees, so that there is mild and not-so-mild variants. There are obviously limits to temperature endurance and the number of (over)heat cycles before the metallurgical stresses begin to show. This is particularly true for an aluminum alloy head. Repeated removal and replacement of a spark plug on a hot engine can both strip threads and cause cracking. A plug that is the wrong heat range can also affect cylinder head integrity after many years of heat cycling -- as can a plug that is too loose, over torqued or cross threaded. Likewise, valves transmit some of their heat to the combustion chamber valve seats. If a valve or valves were deformed due to even slight impact with a piston, it/they will likely no longer seal properly against the valve seat/s. The valve’s ability to transfer combustion heat to the valve seat is also impaired. Presto - cracking occurs. Another possibility might even be a machine shop that did a poor job when installing the valve seats so that unnecessary stress was created in the surrounding metal.

The M30 is an interference engine so that its valve timing must be maintained to avoid valve-piston interference. The double row chain in your picture ordinarily prevents such an occurrence. However, an engine that is poorly assembled (or modified) with altered valve timing can suffer from such damage on the first run. As has been pointed out, interference can also occur when: the stock cylinder head has been excessively milled or, a head gasket is too thin or, the piston crown is altered or, the piston stroke is lengthened. Even on a meticulously constructed, stock engine, there is a reason for that tachometer’s red line, the placement of which, is often governed by valve train design. Missing a shift at speed can easily push an engine far beyond its valve springs' capacity to retract the valve/s -- and -- oops, (it or they) may kiss the corresponding piston crown/s.

Having not viewed a 2.8 liter cylinder head in a long time for direct comparison with a 3.0L casting, I am unclear regarding the exact differences between the two heads, and any obvious advantage between the two. It may be that the internal exhaust and intake passages are slightly different, but other than that, I do not think the head is automatically incompatible with a 3 liter block and vaguely recall seeing one or two such matings. A quick check with Realoem seems to bear this out, although that does not explain why there would be different casting numbers. Without much thought, the other major difference might be each head's ability to accommodate various piston crown designs, but I cannot recall, offhand, a difference in combustion chamber shape or area between the two heads. Instead, I thought the displacement and compression ratios were primarily a function of piston displacement (bore and stroke).

In summary, you may have acquired an engine that was a mishmash of well-worn parts. Even the best rebuilt cylinder head can quickly succumb to metal fatigue when severely overheated or pushed beyond reasonable limits. Also consider that a crack or cracks may not always prevent an engine from running - especially if the cracks become practically non-existent when the metal expands with elevated engine temperature. At some point, something has to give and usually does. This might explain why you did not notice any unusual engine noise when running the 100-meter dash.

Best of luck.

older style head with large water jacket ports




newer style head with smaller water jacket ports

 

[HB Chris]

I think Don would say you can use a 2800 head on a 3.0 but not the other way around, due to the bore. Maybe I have that backwards!

 

[Peter Coomaraswamy]

Well, in either case I think you're looking at a rebuild, I'm sure there are a few good engines in your area so you have your work cut out for you. As far as being "practically new" before being stored I'll keep that line in mind before buying my next used e9 Good luck Gransin at least the engine is easier to fix than rust.

 

[sfdon]

It's the bore that counts.
Can't put a small bore headgasket on a bigger bore block

 

[Gransin]

Wow, thank you all! That was much information!

I'm running late for work, but a short question. I'm planning swapping in a B35 later after getting the car registered with this 3.0 engine.
So I might be driving with this 3.0 say a summer or two before tossing it, do you consider the marks on the pistons to be too big to not replace them or take them out to inspect?
My thinking is to source a new 3.0 head (already found one) and just cross my fingers it will work for a while.

Your input is helping alot, thanks again.

Cheers,

 

[sfdon]

Just get a head that is dated 1983-88
3.3 or 3.5
Not a b35

 

[Gransin]

Don,

Thanks for your input.
The head I found is from a carburated e23 730, model year not confirmed yet. Is this a no go? And if so, why?

Cheers,

 

[sfdon]

Heads from 1983 and on rarely have problems
Earlier heads crack
Just use a head from 1983 -1988
From the Wiki
Emissions equipment such as EGR (Exhaust Gas Recirculation) and an air pump were used on the 530i, along with modified exhaust manifolds called Thermal Reactors. The latter caused several engine problems including burned exhaust valves and overheating, often resulting in warped or cracked cylinder heads.

A separate defect in the 530i cylinder head design prompted a lawsuit against BMW. As a result, in 1980 BMW offered replacement cylinder heads for owners whose cylinder heads had cracked, even if the warranty on the car had expired.

 

[nashvillecat]

I would expect the E23 head would work. For reasons offered above, a later style head is better than an earlier style, but I would not hesitate to use the earlier style if it were in good shape.

I vaguely recall head gasket sets with 2.8L different 3.0L labeling, indicating slightly different gasket sizes, per sfdon's post. A quick search indicated some retailers treat one gasket set as being compatible with both engine sizes, so they may (now) be the same. See e.g., ElringKlinger 11121730223. How this differs from 11121730226, is unclear.

If the 2.8L and 3.0L cylinder heads are virtually identical and interchangeable, setting aside typical production/manufacturing dates, is there a significant purpose for the different size markings, or is this merely vestigial for an earlier production run?

 

[autowerks]

I think you should check your piston rings, if the rings are stock you have to replace your pistons too, otherwise you burn lots of oil

 

[Gransin]

Heads from 1983 and on rarely have problems
Earlier heads crack
Just use a head from 1983 -1988

Okay, yes I've heard that earlier heads are more fragile, I just wanted to check if there might be anything else than that preventing me from using a 3.0 head.
Carburetor/Injection heads are the same part, correct? Exept the opening for the fuelpump.

I would expect the E23 head would work. For reasons offered above, a later style head is better than an earlier style, but I would not hesitate to use the earlier style if it were in good shape.

I vaguely recall head gasket sets with 2.8L different 3.0L labeling, indicating slightly different gasket sizes, per sfdon's post. A quick search indicated some retailers treat one gasket set as being compatible with both engine sizes, so they may (now) be the same. See e.g., ElringKlinger 11121730223. How this differs from 11121730226, is unclear.

Yes, this was my thinking also.
If this were the engine I was planning to use for the foreseeable future, I would not hesitate to do a complete rebuild and put all the right parts in the engine. Now would certainly be the time.
But considering that I will start rebuilding my B35 as soon as the car is driveable, this seems like a big waste of money as I mostly only need this engine to pass registration (does not have to pass any smog test).

I think you should check your piston rings, if the rings are stock you have to replace your pistons too, otherwise you burn lots of oil

Yes, but I can't say there has been any indication at all that the engine burns oil so far, the exhaust gases smells exactly as they should and zero blue smoke, so if nobody thinks the marks on the pistons are alarming, I probably won't remove them now.

And thank you all, this brings me alot more confidence putting it back together.

Cheers,

 

[Ohmess]

Just one other comment. In the picture of your pistons, there appears to be antifreeze in the cylinders. I was told by a mechanic friend of mine that ethelyne glycol can corrode the material in the piston rings causing them to stick to the cylinder walls. Thus, a car that sits with antifreeze in the cylinders for a long period of time will have compression problems when reassembled.

I'm no expert, but I would suggest you ask this question of someone who is.

 

[Gransin]

Just one other comment. In the picture of your pistons, there appears to be antifreeze in the cylinders. I was told by a mechanic friend of mine that ethelyne glycol can corrode the material in the piston rings causing them to stick to the cylinder walls. Thus, a car that sits with antifreeze in the cylinders for a long period of time will have compression problems when reassembled.

I'm no expert, but I would suggest you ask this question of someone who is.

That might very well be true, the antifreeze in the cylinders you can see on the pictures is there because we lifted the head just moments before, and there was still some antifreeze left in the cooling channels which went down into the cylinders when we lifted the head. It is cleaned out now!

My guess is that the cracks in the head are old cracks that were there before the car was stored away for 15 years (or maybe the reason?) Over the 15 years it stood in the garage the cracks may have been filled up with whatever collects in the cracks, old antifreeze and whatnot, and after a couple of small driving sessions and heat cycles the cracks started leaking badly again. This could explain why there wasn't any (notably) leaks before. This last time we moved it on and off the trailer we noticed alot more white smoke from the exhaust, but we didn't make anything of it right then.

Cheers,

 

[Bwana]

Slight hijack: NVCat, what's the story on that huge oil filter extension sticking out of the side of the engine? Is that stock and why is it there?

 

[Markos]

Slight hijack: NVCat, what's the story on that huge oil filter extension sticking out of the side of the engine? Is that stock and why is it there?

That is a late model M30 filter housing. I brought it up in the oil change tricks thread. I'm going to snag one from the local pick and pull before I change the oil in my project car. Need to see how it woulds with tripples.

 

[restart]

Wow, thank you all! That was much information!

I'm running late for work, but a short question. I'm planning swapping in a B35 later after getting the car registered with this 3.0 engine.
So I might be driving with this 3.0 say a summer or two before tossing it, do you consider the marks on the pistons to be too big to not replace them or take them out to inspect?
My thinking is to source a new 3.0 head (already found one) and just cross my fingers it will work for a while.

Your input is helping alot, thanks again.

Cheers,

By no means an expert, afaik the divot in the top of the piston should just have the edges taken off to reduce the possibility of a hot spot and you should be goodto go. YMMV and wiser minds will chime in.

 

[Gerrit]

"If the 2.8L and 3.0L cylinder heads are virtually identical and interchangeable, setting aside typical production/manufacturing dates, is there a significant purpose for the different size markings, or is this merely vestigial for an earlier production run?"

>That is correct, the early -199 M30 heads were made over time from 5 molds marked in roman numbers I, II, III, IV, V the first mold being made at a time there were only 2.8L engines so a "I" marked head always carry the marking 2.8 regardless of the date of manufacture. The 2.8 marking is a carry over without relevance to its application.

Gerrit