cylinder head compatibility

30csl

30csl

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I think an M30 head post 1982 will work. My '73 CSi has a 1986 head. The original head had 2 cracks at the exhaust valves from over heating.

Also recommend getting a triple core radiator, and say good bye to cooling problems.
 
Hi Adawil, I have the 9 blade fan and a good radiator so am going to try the later head with that first. My car got hot once due to an air lock but the head has been skimmed a few times so I want more peace of mind with the later head.

Thanks!
 
Andrew,

The best head for an M30 motor is from the last models that used the M30 motor.
A 1991 535i had a head they call a B35. It has bigger valves and nice combustion chamber and better intake ports. The problem is this head on a older block will have less compression. Guys that use this head usually have higher compression pistons.
This is what I did with my 3.5 in my coupe. Higher compression pistons and the B35 head.
I have a good head called the b34 that would work for you.

Gary
 
m5bb said:
Andrew,

The best head for an M30 motor is from the last models that used the M30 motor.
A 1991 535i had a head they call a B35. It has bigger valves and nice combustion chamber and better intake ports. The problem is this head on a older block will have less compression. Guys that use this head usually have higher compression pistons.
This is what I did with my 3.5 in my coupe. Higher compression pistons and the B35 head.
I have a good head called the b34 that would work for you.

Gary
Click to expand...

+1

It is not as simple as directly swapping the cylinder head. The deck height needs to be measured/understood, head gasket thickness, "squish area", cylinder head combustion chamber volume measured - in short, the compression ratio variables need to be well understood when mixing/matching blocks and heads. Our M30's (as I suspect most are well aware) had cylinder head casting issues. Many heads have been replaced over time, some using heads manufactured by a Spanish company "AMC" - which have a good reputation despite external casting roughness. In short, there is a fair amount of research to do before simply swapping cylinder heads.

...I'm learning too!
 
My car still has its original head which I suspect is cracked but wont know until I remove it - either way I want the better waterways. Is an M30 B30 head from 1988 compatible or would it give lower compression as guided above? This really is the weak spot on these cars mechanically! Thanks all.
 
adawil2002 said:
I think an M30 head post 1982 will work. My '73 CSi has a 1986 head. The original head had 2 cracks at the exhaust valves from over heating.

Also recommend getting a triple core radiator, and say good bye to cooling problems.
Click to expand...

No need for a triple core. Just move to Vermont!
 
In the UK there are not a whole load of days requiring any cores at all once not in traffic!
 
Hi all, Does anyone have a rule of yhimb on which b number head is best? As Gary points out above there are compression considerations. For a stock bottom end there must be a head of choice? Is a b30 head from 88 a good choice?
 
Just bumping up this thread - looks like I need an M30 b30 but these seem quite rare on eBay for example. What years did this head run from? Am I looking for an e12 530 or e24 630? Thanks for the help, Rohan
 
30csl said:
Just bumping up this thread - looks like I need an M30 b30 but these seem quite rare on eBay for example. What years did this head run from? Am I looking for an e12 530 or e24 630? Thanks for the help, Rohan
Click to expand...

i have a spare, but ready to plug and play head, it came out from a e24 630
i recall it was from 1985
i can check in detail
 
e32 730 or e34 530. Likely not to find the e12/e24 3 litre in the UK.
I don't know what the head differences are (I can only compare to m90 or m30b35 heads) but I do have a 1978 m30b25 head that I intend to scrap (and block)
JP

edited, you are in luck, just checked on realoem and the head I have (111 212 622 41) was used on the e23 730 (76-79) and e24 630 (75-79). It came off a running car that I stripped the engine from (e12). The valves are still in, I think some of the rockers may be missing. I don't sell many of these old parts (John!), you are quite welcome to it for nothing.
 
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Hi guys,

Jesus - that is the head I want and may well be in touch. Hoping to visit that factory near you before next summer! Thank you.

John, that is very kind. Just the job too as i plan to swap over valves sprongs etc. Does it have the less crack prone waterways do you know or is it still mated to the block? Where in the UK are you?

Thanks,

Rohan
 
A couple thoughts.

There is a good FAQ on m30 cylinder heads at this site. http://www.firstfives.org

My understanding is a 1981 or later head or one of the AMC heads will offer the best construction of coolant passages to resist heat related cracking.

Don't think any compression related head geometry changes until get to the final m30b35 version.

But if you have an original head - correct model year ID cast into head for your car - give careful consideration to keeping/reparing what you've got. Especially for CSLs guys in US seem to be looking hard to find a year correct head for originality sake.

Paul
 
Hey Paul, yes this is the original head and i plan to get it tested and if ok cleaned up but I am a bit sick of how fragile they are!

Thanks,

Rohan
 
Rohan, Maybe your comment suggests a good strategy. When you need to do head work, put on a newer head, but preserve the original. That is If, like you, one is lucky and has the original head.
 
So i got the deck height of my old cylinder head checked and its 128.3mm pre a skim versus min i found of 128.6mm. If a skim take 0.25 off im 0.6mm under. Am i looking at a thicker gasket? Any thoughts welcome!
 
30csl said:
So i got the deck height of my old cylinder head checked and its 128.3mm pre a skim versus min i found of 128.6mm. If a skim take 0.25 off im 0.6mm under. Am i looking at a thicker gasket? Any thoughts welcome!
Click to expand...

i have been told: "not recommended" but there was in fact a thicker gasket, yes i recall something like 3mm against 1,5mm for the standard one, i do have an old goetze catalog at home

but if you will be keeping matching numbers (matching date in fact) this way it might be worth a try, at least i would do,...

nevertheless in extreme cases there are other problems:

warpage affects all the head, so camshaft will be forced in the ends when compared to the centre

valves will have to seat in an oval seat not perfectly circular

check it hollistically ;-)
 
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A good skim is 5 thousands not twenty five thousands. Over 5 thousandths is warped or damaged
Heads come (let's keep this in inches - machine shops in the states stare at people who want things done in mm)
A new head is 5.079 inches
Minimum size is 5.063 inches
Do the math- you can cut a head .016 inches.

The extra thick head gasket is .011 extra
Your current head is 5.051
Do the math and you are at the minimum with the thicker gasket with NO more machining.
All the numbers add until you say you still need to still get your head skimmed and then nothing works at all.
 
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