my new engine M30B30

[deQuincey]

now that many of our fellows are preparing new overpowered engines for their coupes, i am still keeping myself stock

here is then a project to be completed little by little, no rush, just enjoying the road as much as the finish...

it is the pending job on my car, to prepare an engine from zero, nut and bolt, there is no need for this, as my actual engine was recently rebuilt and runs smooth and beautifully, but i didn´t perform the task by myslef,

so i was thinking of this as a challenge, an entertainment and a hobby,..and finally when completed, cover the openings and keep it warm and dry for the future, or place it in a stand in the middle of the diningroom, who knows ? ;-)

i had a complete engine, from a 1975 CS, at hand, the owner had long ago decided that there was no use for it as far as the carriage was badly rotten and long ago found its way to the scrapeyard,

the block is in very good condition, but i wanted a newer head (>83), with proper water passages, so i hunt a 1277358 head from an e24 or e28, fortunately i have a proper camshaft in my stock,...



here is the dirty block, yes, it is dirty, but sometimes is better to have a dirty part, than a badly reworked one, i have checked all the threads, and aluminum covers, they are all ok, we have meassured the cylinders, and they are within admissible deviations, there is no need to machine them, but anyway i have decided to go to new pistons, so i must go for +0,25

as there is a little time now for preparation of the block and head, and time for buying or finding parts, some questions will arise and thus i will be asking for help, help that i will highly appreciate...

 

[deQuincey]

first question: timing chain single or double ?

here is an odd question, but probably important to decide which way to go:

my actual engine (a 1971 block) has double timming chain, this means that the pulley that belongs to the camshaft, and the one that belongs to the crankshaft are double

see it in this picture: (double timing chain)





but the new engine that i want to rebuild by myself (a 1975 block) has a single timing chain, consequently the pulleys at the cam and crankshafts are single too

can anyone explain why ? and moreover what is better ? or stronger ?

i have checked that it is really possible to convert crank and camshafts to double pulleys, subsequently moving onto double timing belt, but is there really a need for it ?

regards

 

[Nicad]

I think you will enjoy this project DQ. Once disassembled, send the block out to be boiled clean. That is step 1. Step 2 is to get an engine stand. No answers from me on the cam chain differences.

 

[deQuincey]

I think you will enjoy this project DQ. Once disassembled, send the block out to be boiled clean. That is step 1. Step 2 is to get an engine stand. No answers from me on the cam chain differences.

nicad, yes, thank you, the block is already disassembled and clean now, and the engine stand is not with me yet but i will get it soon

i am now in the process of buying the pistons (at +0,25) and the new valves, which are the first parts needed for doing the machining job

additionally i found a guy capable of doing the tricky job of producing a hole for the mechanical fuel pump, see what i mean:

1975 head: central 8mm hole, and two M8 studs




1985 head: (not easy to make the 8mm hole as that M6 stud is already there, we will use a bushing)

 

[deQuincey]

BTW, anyone on the single/double timming chain question ?

 

[sfdon]

When I began using slotted cam gears to set crank/cam timing I asked whether there was a chance that the cam gear bolts would slip in the slots- the number I heard was there is only 8 pounds of torque on the cam bolts at 4000 rpm.
Probably why they discontinued the double row chain and the locking tabs.
I hope this helps!

 

[deQuincey]

When I began using slotted cam gears to set crank/cam timing I asked whether there was a chance that the cam gear bolts would slip in the slots- the number I heard was there is only 8 pounds of torque on the cam bolts at 4000 rpm.
Probably why they discontinued the double row chain and the locking tabs.
I hope this helps!

thank you very much

certainly that answer can help, so in your opinion the single row chain is an upgrade, or lets say a safety issue ?

sounds strange, probably i can not interpretate this correctly but a double line of teeth seemed as an extra safety to me, probably i am wrong...:roll:

 

[sfdon]

Double has to be better but they decided it wasn't needed is the best I can figure.

 

[DerSchwede]

Double has to be better but they decided it wasn't needed is the best I can figure.

Yep, the double cam chain is only a plus on high-output engines like tripple-carbed or other +85hp per 1000cc mods. Even the Alpina B10 engine came with a single row cam chain with 261hp / 3430cc.

 

[deQuincey]

Yep, the double cam chain is only a plus on high-output engines like tripple-carbed or other +85hp per 1000cc mods. Even the Alpina B10 engine came with a single row cam chain with 261hp / 3430cc.

thanks, very accurate
funny, because i received my actual engine like it is with that double chain, and mine is a stock carbed 3.0

 

[deQuincey]

another question as i am finding that my donnor new engine is a continuous source of surprises

this was supposed to be an M30 engine for zenith carbs, but i just found that the engine block has the leters 3.3/3.5 writen on the admision lateral in big figures

i have investigated a bit, and the differences that i found between the 630, 633, and 635 cars that might use this block are,

both 630 and 633 might use the same nominal diameter value pistons, as far as i have analised the difference between 633 and 630 is that the cranckshaft of the 633 gives an extra displacement

then the 635 has not only that extra displacement but enlarged diameter pistons

my problem is that i need to build a 3.0 engine, and i do not know what block and bits i have for building it, i mean i can easily check the cylinder diameter to know if i can use it, the diameter must be around 89mm

the problem comes on how to asses that the cranckshaft is ok for a 3.0CS, can anyone help, are they any marks as they are on the camshaft ? any correct reference that differenciate the displacement, any dimension to check ?

regards

 

[DerSchwede]

Hi DeQ,
Please check the engine No engraved above the starter. That might help to figure out what kind of engine you have.

 

[deQuincey]

Hi DeQ,
Please check the engine No engraved above the starter. That might help to figure out what kind of engine you have.

yes, thank you, i am not close to it, but i recall checking that the 3.0 figures are definitely on it, when i saw that i relaxed myself thinking that it was the right engine, my doubts came when i saw the 3.3/3.5 written in the lateral

what i do not remember also is what else is written on that row that you mentioned above the starter, i barely recall an "A", i will check it on monday

remark, this engine was on a CS car equipped with zeniths, and as far as i know, zeniths can only feed up to a 3liter engine, so i may assume that no other transformation was made, i explain, my assumption is that when for whatever reason the block was changed, pistons were kept, and cranckshft too, this i do have to check

BTW check your PMs !

 

[Nicad]

I built a 3.3 that ran on Zeniths about 25 years ago. It came about by accident. I bought a motor from a 733 that had caught fire thinking I would rebuild it and drop it in my Bavaria. When I took it apart I found that the cylinders were completely rust pitted due to sitting with water. So then I decided to use the crankshaft and put it in my 3.0 Block, thinking the extra displacement would be all gain. Once I was at the final assembly stages I found out the crankshaft would not fit the 3.0 block and hit the sides of it. So, I decided to try grinding away material to make it fit. Eventually I ground right through to an oil Galley. With no options but to continue, I made a threaded piece to repair the damage I had caused. It seemed to hold up OK.. Once the engine was together and running, it never was a gem of an engine. It was rather dull in terms of power band. I had a noted local BMW specialist enlarge some carb jets on his suggestion and it ran OK, but certainly never felt like a sparkling engine.

 

[JFENG]

I don't think so

When a block fails, it's most often due to a catastrophic failure (rod breaks, main bearing fails and seizes the rod, etc). So when you need a new block, you usually need new pistons and rods (and crank). To be honest with you, I've never heard of anyone replacing on the block but reusing the original pistons and/or crank.

No reason Zeniths can't be used on bigger engines, they will pass more gas and air for a given rpm if there is more manifold vacuum (because of bigger displacement). The absolute manifold vacuum will be higher at high rpm and large throttle opening than for a smaller engine, so max potential power will not be available. In this way, the car will restrict performance, but it should be able to provide a reasonably acceptable F/A mixture on an engine that 10% or 20% larger..

 

[DerSchwede]

You can get enough air through one Zenith carb to feed ca 130 hp - as used in Opel KAD 2.8 in the late 60ies. That will require other jets and venturis though. The E3 3.3L used two Zeniths to produce 190 hp and 300 Nm, only with other air jets, main jets, pump jets and idle jets... the aux venturis were the same (24/30)

 

[deQuincey]

some little preparation, the banjo bolts on the oil spread rail inside the cyl head are known for their ability to unbolt and cause terrible issues there,

so i prepared the bolts of the new engine this way, in order to prevent the unbolting action i want to place a securing cable around, so i need to make a hole in the hexagonal head:





done, easy and convinient

 

[deQuincey]

identification of engine bits

finally i have been able to check the engine and its elements carefully, and this is the result,


engine block,
i made a mistake, the big figures are 3.0/3.3
near the bellhousing, in the rear side of the engine you can read:
30 A 4. 80
in the lateral, ref. 1259525

i assume that the engine is a replacement engine made in 1980, for some reason the whole thing was replaced with a short engine, cos the head is from 1980 too, but the front covers are marked 1975

as to the cranckshaft, it is marked:
GK45
12500420, the books say that corresponds to 2800 till 3.0 cars with a lift of 80mm (i.e. 3.3 should have reference 12594790, which means a lift of 86mm)

here an odd thing:

i measured the lift, and it is 84mm, not 80mm

on the other side cylinders had not been regrinded if i believe the expert opinion of the workshop, but pistons happen to be 89,2mm in diameter instead of 88.9mm

i was puzzled, because 89,2 is the first oversize of pistons when speaking about the 3.0 engine

....then i found a solution:

89.2 is the nominal value for the 3.0 CSL engine !
moreover the 84mm lift is the nominal value of the CSL engine !
so this seems to be a 3.15 engine !!!

does that mean that i have been touched with the fortune of finding a CSL engine ? i can not find any information about this with the engine block reference 1259525, anyone can assist ?

moreover the "piano" shape in top of the pistons is usually 5,6mm high when compared with the flat top, but in the pistons that i have removed from this engine that heigh is only 3,5mm, what for sure gives a little more frre volume, thus probably less compression ....

anyone can explain this ?

regards

 

[sfdon]

BMW routinely sent out engines with oversized pistons- I did a csi last month with 89.47 from the factory. Not such a gift really, if you have damaged bores you will need custom pistons.
I believe they had a lot of extra CSL engines they needed to get rid of.

 

[DerSchwede]

Hi DeQ,
the std piston was 88.97mm and then there were 89.02, 89.22 and 89.47. The combination of any of these with an 84mm crank will produce an engine with the same capacity as a Bat-CSL engine. That one having higher piano-top pistons (9.5:1) due to its D-jetronic configuration. The 84mm crank however was also used in the M90, used in all 3.5 between 78 and 81.

Check the markings on the inside of the pistons, those numbers will give you the answer which engine they were made for.