cylinder head swap

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Lock
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Re: cylinder head swap

Post by Lock » Sat Jul 20, 2019 4:28 pm

Mike W. wrote:
Sun Jul 14, 2019 1:15 pm
Not to worry, just bolt it on up.

You do have the right cam in there or adapter nut, correct?
Hey Mike I am going to put Motronic EFI on my b28 engine and optionally the e34/b35 upper timing cover and distributor. Will this fit my b28 head with adapters and parts, or is it camshaft-specific?

If not I'll just keep the original distributor in place and disable the advance, but I was planning on the newer distributor setup.
1979 528i 5-speed conversion G260/6

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Mike W.
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Re: cylinder head swap

Post by Mike W. » Sun Jul 21, 2019 12:30 pm

Motronic will work with an older head, but needs a motronic cam which can be installed in an older head. The nose of the cam where the adapter for the distributor rotor attaches is different.

Ironically there is an adapter where you can use a motronic cam for a conventional distributor, but not the other way around. You should be able to actually use the conventional distributor to just distribute spark and have motronic control timing although I've never seen it done.
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter

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Re: cylinder head swap

Post by Lock » Sun Jul 21, 2019 1:20 pm

Thanks Mike, good to know. I'll try using the original distributor, might need to modify the arm for the wide advance angle the Motronic arm has. That way I don't need to remove the timing gear or swap the valve cover.

I've read of people putting our distributor on Motronic engines, so sounds like I can keep it on a B28 engine. I'll make a build post when I install the Motronic.
1979 528i 5-speed conversion G260/6

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Re: cylinder head swap

Post by Mike W. » Sun Jul 21, 2019 2:56 pm

I don't think you would need to modify the rotor, but you would need it to be timed "about right" Motronic curves are more complex than a conventional distributor, but as long as it's close I think it would be ok. I would retain the centrifugal advance in the distributor which should very roughly correspond to the M advance, but not use any vacuum control on it. Or you could keep the distributor in it's entirety, but use M just for fueling and idle control.

Are you talking M1.0 or M1.1/1.3? The latter is actually an easier swap, you don't need a motronic flywheel and bellhousing.
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter

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Re: cylinder head swap

Post by Lock » Thu Jul 25, 2019 12:00 am

I was thinking that too, leave the centrifugal advance to keep the rotor 'near' the correct point.
It is Motronic 1.3 from a 1990 e34 b35, not sure how close the fuel/ignition maps will be stock to a '79 2.8l, but I'm going to find out soon. I'll probably use the 3.5 manifold (injectors won't swap), and maybe get a Miller WAR chip to adjust if it runs poorly.
1979 528i 5-speed conversion G260/6

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Re: cylinder head swap

Post by Mike W. » Thu Jul 25, 2019 12:01 pm

Later injectors can be used in early manifolds. IIRC you can put the small and large seals on the later ones by changing the pintle cap but will have to use the late fuel rail and rig up mounting brackets for it. But the clips hold the injectors in place anyway and even at 3 bar the amount of pressure fuel is putting on pushing the injectors off isn't all that great.
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter

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Re: cylinder head swap

Post by CabbageFumes » Sun Aug 25, 2019 2:46 am

Lock wrote:
Thu Jul 25, 2019 12:00 am
I was thinking that too, leave the centrifugal advance to keep the rotor 'near' the correct point.
Let me stop you right there.
Don't allow any advance from the distributor if using Motronic 1.#, because that's the DME's job. Motronic needs a stable point to advance/retard timing from, not a moving target.Take whatever dizzy you plan to use, gut it, spot weld the shafts so they don't move independently. Set the crank at TDC and center the rotor on the notch in the dizzy body to line up with cylinder #1 and lock it down.
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Re: cylinder head swap

Post by Lock » Sun Aug 25, 2019 11:39 pm

In my instance it's okay - I'm using the Motronic 1.3 sensor wheel for timing, not the L-jet dizzy. All it will be doing is distributing the spark to the correct cylinder, as the 1.3 Motronic dizzy does. My only issue is that the L-Jet dizzy has a small rotor arm and contact surface, and if I disable the rotor arm centrifugal advance, then if Motronic advanced ignition to say 20btdc the rotor would still be at 0btdc and the contacts are so small that the arm might be too far away from point at the time, or at worst would be closer to the previous cylinder.
The Motronic dizzy has a very wide arm surface and is physically bigger for this reason, whereas the L-Jet dizzy (with an arm that's designed to follow the timing in tandem) is a lot smaller and wasn't designed for this.
This isn't perfect or accurate, it's just meant to ensure the arm is at least 'generally' in the same area. If it fails, I'll try something else.
I was planning on putting the Motronic valve cover, upper timing cover and dizzy in, but it doesn't fit the key in the cam and so far I haven't found an adapter because rational people in my situation just get another engine, or a new car.
Also sorry Sharky1980 I didn't mean to hijack your post.
1979 528i 5-speed conversion G260/6

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Re: cylinder head swap

Post by CabbageFumes » Sat Sep 14, 2019 12:38 am

Lock wrote:
Sun Aug 25, 2019 11:39 pm
...it doesn't fit the key in the cam and so far I haven't found an adapter Because it doesn't exist.
Fiver 12/73
Fiver 06/87
Sixteen-O-Two-er 11/69
i3 8/14

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