72 300sel 4.5 fuel injecion problems

i recently replaced the the rubber lines that go from my main metal "trunk line" to the fuel injectors on my 72 300sel 4.5 because they were leaking fuel. before my car was runing rough on idle and after the change it still runs rough at idle.. but on light acceleration it sounds like it is missing and the acceleration is choppy for lack of a better word and there is some hesitation. also during hard acceleration the choppiness goes away and it sounds fine... but some black smoke is blown out the tailpipes. i know there is a blown seal around the drivers side manifold (anyone know where i can get a new one?) and i just replaced the org. exhaust system witha SS one from manifold back. I am thinking that there is multiple problems and am seeking advice on how to fix them and what they are. i am in desperate need of help i leave for college soon and need her to make the 5 hour drive. thanks again and this site is a lifesaver.
jon

[cth350]

Which seal "around" the manifold? There is a big asbestos/metal ring connecting the manifold to the system and 4 small metal/asbestos plates between the manifold and the head. Sometimes these last guys are just metal plates.

A good muffler shop or foriegn autoparts store will have them. If not, you can always get these guys (parts shop) to sell them to you. Last I looked they were like 3-5$ each.

Also, those nuts holding the manifold to the head are special, deformable nuts. If you remove them, throw them away and buy new ones. They are 8mm and avaiable from the same sources with the gaskets. The hard part, is if you have to replace the two long studs on that side. They are not common at that length. Be sure to replace the washers behind those nuts too. If they're not there, then the last guy just threw them away. They are simple 8mm flat washers.

Now, if you discover a crack in the cast iron manifold, you will have to replace it.

You do NOT want to drive around with a leak at the export ports of the head. It lets Oxygen in where it shouldn't be and the extra combustion raises the temp around the valves and that leads to valve guide failure. My very first 280se 4.5 only cost me 500$ because the PO didn't fix a cracked manifold. Two guides dropped. My 2nd DIY valve job fixed it right up. Just the thing to do before heading to school, right?

-CTH

PS. For extra credit, take the manifold to somebody local that does "powder treatment". They should have a special compound that will survive high manifold tempratures. They will sandblast the manifold and then coat it.

The seal around the manifold and the head is well... nonexistant. I do not think there is a crack, but the manifold is rusted pretty bad.
The current problem, besides that of course, is that under load, eg when i shift into drive, my engine really bogs down. it idles fine. When i lightly accelerate you can hear the engine miss and almost stall... pressing down on the accelerator more pulls it through and it runs ok for a bit. while driving at higher speeds and consequently having to give it more gas the engine sounds like it is misfiring and backfiring. The blown seal around the manifold makes a clicking sound normally, but now it is silent and sporaticly makes the clicking noise. I replaced the rubber fuel lines going to the fuel injectors the other day and it is entirely possible that something fell down into one of the injectors. also it is right after i replaced the lines that i started having all these problems, before that it ran fine.
there is also a rubber hose that runs off of the drivers side head cover at 90degrees to a something that has a whole lot of lines running into it and i was wondering what that was and what its purpose it. that hose also has a small tear in it which i think is not serious but since i don't know what it is i can't say so let me know if you have any idea what i am talkign about... sorry for being vague.

I am still learning about the fuel systems of cars so i need help. Any and all info is much appriciated. thanks

[cth350]

From valve cover to manifold is a PVC vent hose. It's no big deal for it to be broken, but add it to the list of parts to replace.

From the intake throat to that same block is a metal hose with rubber joints (or a whole rubber hose) that funnels the fresh air that will be used for idle.

The block that these hoses connect to is where the cold start injector lives (wired from the top with a fuel line), the idle air screw (big mother screw at the front), and the temp sensors (wired w/o fuel).

It's all in the engine manual. You really, really want that book.

-CTH