Engine ID Help - 72' Bav

davidwmontgomery

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Hey guys,

New to the forums,

I have a 72' Bavaria, and I'm having trouble id'ing the engine. I can about confused after an oil change, and the filter not fitting. The Filter was a tad too big diameter wise, and the oil filter housing in a bolt in from the top (which I like anyways.)

Here are some pics. I tried getting the engine code off the Crankcase, but its worn down pretty good, and I can't make out the numbers. I did get the head code, stamped on the driver side of the head, below the valve cover, above the manifold. Its 12500199.

Anyways, here are the pics of my engine bay and where I "think" the code is:







 

davidwmontgomery

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I also have some questions about the carbs. I was trying to find the source to my issue about my nose diving RPM's. I think its Ignition, but I'm not going to rule out Vacuum leaks either. I noticed what looked like exhaust coming out from under my air filter housing. I noticed that it was very loose on the carbs, and when I took it off I noticed a few things. One, on the rear carb, the pin thats supposed to hold the filter housing to it has been stripped on the carb side (so I need a new one). Im not all too knowledgable with these, so heres a pic. Is this right?



Also, i have an entire wiring harness not hooked up to anything. I know that I have the voltage regulator that is attached to the alternator, so the older one is not hooked up, but then there are a few more wires. Two of the wires attach to the rear carb, and there are two more similar looking wires that don't have a place to attach to the front carb.
 

Stevehose

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Exhaust looking smoke is likely the oil blow by coming out of the hole in the center of the valve cover, is this normally connected to your air cleaner housing with a hose like it should be?

Loose air cleaner housing will not cause vacuum leaks.

Show us pics of what is different about the fornt carb electrical connections. There should also be an electric choke connection there also just like the rear carb.

Change your fuel hoses asap including the one down the firewall to the metal pipe. They look ready to burst.

There are 2 vacuum connections on each Zenith, one on either side, make sure they are capped if not hooked to the distributor for advance/retard.

After cleaing it with brake cleaner, put a piece of paper on the VIN pad above the starter and trace it with a pencil so you can read it.

I also have some questions about the carbs. I was trying to find the source to my issue about my nose diving RPM's. I think its Ignition, but I'm not going to rule out Vacuum leaks either. I noticed what looked like exhaust coming out from under my air filter housing. I noticed that it was very loose on the carbs, and when I took it off I noticed a few things. One, on the rear carb, the pin thats supposed to hold the filter housing to it has been stripped on the carb side (so I need a new one). Im not all too knowledgable with these, so heres a pic. Is this right?



Also, i have an entire wiring harness not hooked up to anything. I know that I have the voltage regulator that is attached to the alternator, so the older one is not hooked up, but then there are a few more wires. Two of the wires attach to the rear carb, and there are two more similar looking wires that don't have a place to attach to the front carb.
 

davidwmontgomery

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I have a hose connected to it, but not sure if there needs to be a clamp. Again, the housing was very loosely on there, I could shake it easily, and from the driver side, could see the housing lift up from the rear carb.

I plan on getting all the hoses changed here soon (not a daily driver) so I'll go ahead and make the fuel hoses priority.

Im not too familiar with these carbs, so here are some more detailed pics of them:

Here is a look driver side of both:


Here is the front Carb: Notice, no connections:


Here is the firewall side carb, notice connections on rear side and something bolted to the driver side, whereas a epty hole on the front one:


Here is the relay that the wiring harness comes from:


and here are the cables. Many more in this car have fallen apart. Sad. If I had the knowhow/money/time I'd just get a new wiring harness for her:
 

davidwmontgomery

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From Engine Help to Carb Help.

So, to add to the mystery, Im comparing my Haynes Manual to what I see, and Form what I can tell, it looks like I have two totally different Carbs, but similar. Here is where someone tied wire around the Throttle Lever...


Here is the rear Carb's Choke Unit:


And here is the Forward Carb's Choke Unit:


Notice, no wires connected.

All strange, since it runs, and ran well for a while.

Oh so strange.
 

davidwmontgomery

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Not sure if its keeping it form opening, or keeping it open. There is a throttle linkage on the other side of the carb, and they seem to be linked... Wouldn't make much sense for me to be able to make my 12 mile commute to work and it run properly if they weren't. Then again, Im a Carb noob.
 

Stevehose

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looks like it is keeping your secondary barrel from opening. I'd have them rebuilt. Maybe some of the Florida guys here can chime in for a local pro. Or you can buy a used set off someone here.
 

davidwmontgomery

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Well, I just snagged another Carb off eBay for $145. I also just realized that one carb has the Mixture Bypass System and the other does not....

o_0

Big thanks to bavbob for PMing me to give me some help over the phone.
 

HB Chris

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Your front carb is missing the rectangular auxiliary cold start device and if choke wires aren't connected they won't work properly. Not all Zeniths have that aux device but the carb needs a bolt to block the hole. That relay is for the cold start system, most wires will be Green. They should also hook up to temp sensor under front carb.
 

61porsche

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nosediving

is another symtom of your engine is not getting spark or the fuel mixture is going off.

First, check your points- looking for dwell. A bog could mean your points need adjusted. Over time, your timing goes retarded or out of range and the engine lurches as the spark goes away just as if you turned off the key. Slow down at it catches again- there you go.. Easy and doesn't cost you much. Then tmake sure your timing is right. Might help to know at what rpm it happens as there are three basic functions of the carbs.

The exhaust coming from the air cleaner- might be that original egr valve located below the fuel pump. It hooks into the exhaust manifold and each carbs. great idea that didn't work. Rare to see one actually. Remove it as it's not likely working, leaking, or something worse like a big honking vacuum leak. Cut off the SS at the manifold, cap, or simply hook the two together with vacuum hose. But then you have to cap that pesky exhaust manifold too.

Other's comments are sage advice. You're missing parts. You're chokes need wired. But by god they're working somehow in the picture.( water) You're choke plates are a little open and should be about 1/8" closed. Small adjustment, maybe better starting. That's for later.

Secondaries vacuum box- have one, need two. Looks like that's why one's wired closed.

Second cause of nosedive is carb out of balance. Soulnds simple. Each carb doing the same thing at the same time. If one isn't, bog. Usually rich. Pull your spark plugs and look for the dark side and go looking at that carb. The other carb with the secondary box could just be opening when you stomp on it and just cause an over rich condition and imbalance.

Go slow when you're learning. Zeniths have made many a man criy Weber. Just remember Mercedes used them too so it can't be all that bad.

You can repair the carb top with the stripped stud. or use blue locktite if you're in a pinch.

Happy trails.
 

davidwmontgomery

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is another symtom of your engine is not getting spark or the fuel mixture is going off.

First, check your points- looking for dwell. A bog could mean your points need adjusted. Over time, your timing goes retarded or out of range and the engine lurches as the spark goes away just as if you turned off the key. Slow down at it catches again- there you go.. Easy and doesn't cost you much. Then tmake sure your timing is right. Might help to know at what rpm it happens as there are three basic functions of the carbs.

The exhaust coming from the air cleaner- might be that original egr valve located below the fuel pump. It hooks into the exhaust manifold and each carbs. great idea that didn't work. Rare to see one actually. Remove it as it's not likely working, leaking, or something worse like a big honking vacuum leak. Cut off the SS at the manifold, cap, or simply hook the two together with vacuum hose. But then you have to cap that pesky exhaust manifold too.

Other's comments are sage advice. You're missing parts. You're chokes need wired. But by god they're working somehow in the picture.( water) You're choke plates are a little open and should be about 1/8" closed. Small adjustment, maybe better starting. That's for later.

Secondaries vacuum box- have one, need two. Looks like that's why one's wired closed.

Second cause of nosedive is carb out of balance. Soulnds simple. Each carb doing the same thing at the same time. If one isn't, bog. Usually rich. Pull your spark plugs and look for the dark side and go looking at that carb. The other carb with the secondary box could just be opening when you stomp on it and just cause an over rich condition and imbalance.

Go slow when you're learning. Zeniths have made many a man criy Weber. Just remember Mercedes used them too so it can't be all that bad.

You can repair the carb top with the stripped stud. or use blue locktite if you're in a pinch.

Happy trails.
Yes, it nosedives and gets rough, and at first I thought it was ignition. All of the spark plugs were pretty fouled when I changed them a few weeks ago. Mainly the rear 3 plugs. (side note one (second from front) had oil around the threads, which leads me to piston ring.) She misses spark for like a second, then goes back up to idle. Usually around 3k or a little under. Being an automatic, it doesn't get much higher. :.(

To rectify the different carbs, I went ahead and found a matching Zenith 35/40 on eBay and Im going to replace the rear one with it. Then use any parts from the rear one to give to the front, like the Thermostat Valve.

So I can just delete the EGR Valve? I think the smoke was coming from either the EGR or the head cover (burning oil) into the carb filter cover, and then leaking out under the bad seal to the rear carb. (most likely). Which caused me to uncover this strangeness.

Thanks, guys! You've all been a great help!
 
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