Hi,
I�ve got a problem while rebiulding the vacuum lines on my 1978 250i6.
Looking at the emission diagram the distributor vacuum at carb is near by idle speed solenoid, but my carb don�t have this vacuum port
https://www.carburetion.com/CarbNumber.asp?Number=17058013
The engine is a LD4 Engine, with a non integrated head and i�m pretty shure, that it�s no california version (no smog pump)
So, can you give me a tip, where i put this vacuum line on?
At the monent it�s on the vacuum under the throttle valve under the fuel inlet, but i don�t know if it�s the right place.

I do this becaus the engine loses some zylinder if the rpm comes over idle speed, so i want to exclude that vacuum connection as rootcause. Spark plugs, wires and the complete distributor are new. The idle speed ignition has 8 degree without vacuum, with vacuum i guess ist near 30 degree

Regards
Chris

Personally, I like to use the live manifold vacuum port from under the throttle. You said it loses some cylinder. Do you mean a lose of power? Can you show a pic of your distributor? Is it a new rebuild or a new off the shelf or a OEM unit?

Hi it's a new CARDONE 841697 distributor.
Here are 2 videos of the running engine without load. For me it don't sounds very good but i've never heard another i6 engine, in Germany there are not many US-cars and most of them are v8 engines
https://youtube.com/shorts/50InpIN4pjE?feature=share
https://youtube.com/shorts/NAgJW6iyIOU?feature=share

Right now I'm working through the process of elimination because I don't know which corner to look in first. When I got the truck it was pulling air everywhere because all sorts of hoses were missing and the vacuum ports were all open.
What could also be is that it's the valve train with the hydraulic lifters, but I don't know the technology at all. I had before only old BMW, where you set the valves with a feeler gauge.

It does not sound right. I have found that rebuilt distributors to be trouble. Do you still have the old dist?
When rebuilding, they make them from other distributors. Sometimes piecing together 2 shafts. In doing that, they get the internal timing off between the rotor and cap and pickup coil.
Maybe you should start by finding true top dead center and verify the mark on crank damper matches to timing line.

Hi, thank you for your answers!
I changed the distributor because i thougth it's the cause of the problem. The centrifugal governor is rusted and the shaft seemed a bit worn out. The finger and cap I had replaced before because I noticed when adjusting the ignition that the first cylinder did not always get a pulse.
At one point i thought, it's much easier to change the whole distributor than changing one part after another.
But after the change, the engine ran exactly as before.

The clacking when the engine is running, can this also be the hydros?
I allready tried to adjust the valves by watching this (your?) video:

But i don't know if it's the procedure for a new engine or an engine that allready runs.
For my understanding a hydraulic lifter is completly compressed if the engine is cold, but then with my adjustment the valves would be open a bit all time when the engine is warm. I think i would cause that the engie would stop.

Used engines with original lifters need to be pulled down more than performance units. The OEM lifters like to have around 1 full turn preload.

Ah, okay. All right, I'll adjust them again, perhaps it'll help.
Thank you!

Hi, only as info, i killed my back with another work, so i will take some time till i can look and adjust all your tips.

Hi, i�m only waiting for a seal which i want to replace, then i start to do all you told me. I only have a last question for that. Do i adjust the lifters while the engine is hot or cold? I think �hot� is right, but i want to be shure.
Thanks!

Okay.
Checked if TDC on the balancer is also TDC in the first cylinder - it is.
All valves again adjusted, with warm engine to the point where the push rod has just no more play up / down and then a whole turn on top. With the help of a printed Mercedes star i added 3 marks on to the balancer and also still looked into the spark plug holes that the piston is also up - done.
Then I set the ignition again and made extra points in the 10 degree distance, which is nearly exactly 3cm with the balancer circumference. When revving up I have about 25Grad early ignition at higher rpm. A tachometer to connect, I do not have so i don't know at how much rpm it was.

The engine still sounds like that:
https://youtube.com/shorts/BuZ1bi4eXEc?feature=share

The vacuum for the carb, i addet to the same port as the vacuum choke. Since that it�s a little bit better (as shown in the video).
The only thing left for me to do is to order another carburetor that has all the vacuum hoses in the right place. Or what else can I do?

Having your distributor under full manifold vacuum is way better than ported, so you can keep that.

Have you sorted out your other problems?

LG aus Augsburg - Frank

By "better" I think you mean different.

Does it have a vacuum port above the throttle shaft? Try that one.

No, I mean actually better, unless you are into emission stuff.

Frank