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1973 Alfa Romeo Berlina 2000
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Happy Holidays All - I hope many of you are reading this as a small break from hanging out with your families or working in your own garages. I am working on a few posts in different areas. My primary focus this winter is on replacing the majority of rubber bushings in my suspension, and I'll build a post on that later. In the back of my head, I know that I have a bigger problem (or at least I think it is...) related to my engine, and I am concerned that my novice abilities are not up to the challenge. I have no Alfa mechanics nearby, so would like to troubleshoot and solve myself. Of course, some help from the Alfa BB would be much appreciated! A few have already offered to help (Thank you!) but I thought sharing my problem for the Alfa BB world to see might be the best benefit for all.

I'll start at the end. Just before my Berlina was pulled into the garage for the winter, to be placed up on jack stands for all the bushing work, I took her for a final spin. She had been having some engine issues, but I need a last spin.
  • 1973 Berlina 2 liter with ~96,000 miles. Unsure whether it's turned over.
  • Converted to Webers prior to my ownership.
  • She idles between 800-1000 rpm once warm.
  • Around 3000-4000 rpm in any gear, the engine begins to miss, or something... I am not experienced enough to describe it correctly. The car lurches or jerks slightly. Something is definitely not right.
  • If I let off the gas, I can get where I am going, but she's not happy....
  • Under 3000, she sounds OK....
This problem has slowly developed over the last year. So let's go back to the beginning and I will try to highlight what may be important pieces of evidence.
  1. Purchased a well-cared (I trust the previous owner and he seemed to know the car well) for Berlina in July of 2020 and drove 1300 miles home. No engine trouble, but some blue grey/blue smoke seen towards the end of the trip on downhills when letting off gas.
  2. Driving that summer was great! Car pulled well. Grey/blue smoke seen both under hard acceleration and on downhills, but car ran well!
  3. Black sort of sticky soot comes from the exhaust. Not terrible, but enough that I clean it off the rear driver's side 2-3 times a year. If you stick your finger in the end of the exhaust, there's a fair bit of this black soot.
  4. Burns about 1 qt of oil every 400-500 miles.
  5. I use ethanol free fuel. The original owner swore by Chevron Techron fuel additive. I used this for awhile, but was convinced by my local mechanic to switch to Marvel Mystery Oil. I have also run without either at times... I'm not sure if either additive helps.
  6. Switched from Castrol GTX 20W-50 to Valvoline VR-1 20W-50 (Again at the recommendation of my local mechanic (He's very good, but more of a German car guy... Doesn't really like Alfas, but he's all I've got.)
  7. Drove the car 2 hours to an expert in York. Car ran great on the way down (75-80 mph the whole way!). In York, we identified all the bushing work that needed to be done. Expert took the car for a spin, and was only really concerned about the suspension bushing work that needed to be done. Really, beyond knowing that rings and valves were probably needing some work at some point, the engine was still running well...and then...
  8. On the drive home from York, we were cruising along at the same 70-80 mph and having a great conversation... and then I felt a little skip or hesitation, so small that I am not even sure my co-pilot noticed. But I think everyone know that feeling..like... ohhh, what was that?... Please let me get home and off the highway... There were a few more of these small skips, but we made it home fine.
  9. Once home, I replaced the cam cover gasket to solve a small oil leak. At the same time, I made a very small tightening of the timing chain and checked the cam/valve clearances. I also replaced the front fuel filter, the rear look nearly brand new. All this seemed to go well.. clearances were acceptable and car ran alright although...
  10. The skipping/missing/lurchy behavior started to become more noticeable when accelerating hard in 4th... sort of solved by shifting down to 3rd...
  11. Based on all of this, I've checked the spark plugs a number of times. They do not look too fouled, but I did clean them and even tried to index them correctly. This did not help.
  12. This brings us to today... she was really unhappy during my last drive this summer. I would not trust her on a drive outside of town, and I know can't take her on the beautiful winding roads of central PA in this condition...
OK...Here are the thoughts and advice I've had so far:
  1. Your valves or rings are worn, leading to burning oil and grey/blue smoke.
  2. Your car is running too rich.
  3. You should check fuel pressure.
  4. Your carburetors need adjustment.
Once I get the suspension completed... Where do I start? I fear this may be an impossible question and simply demonstrates my ignorance. I'm patient though, and willing to work on this... I hope I can get a bit of help here.

And because I know everyone likes them... Here is a pic or two of the engine bay.
Motor vehicle Hood Automotive design Automotive exterior Vehicle

Motor vehicle Vehicle Automotive exterior Gas Nut
 

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'66 Sprint GT, '67 Duetto, '70 BMW 2800CS
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OK...Here are the thoughts and advice I've had so far:
  1. Your valves or rings are worn, leading to burning oil and grey/blue smoke.
  2. Your car is running too rich.
  3. You should check fuel pressure.
  4. Your carburetors need adjustment.
Burt:

Let me begin by saying that it's impossible to diagnose a car over the internet. Your issue could be spark, fuel, or compression. The four suggestions you listed (duplicated above) are good, and probably contain the solution. Commenting on each:

1) Yes, your rings and valve guides probably are worn, resulting in the high oil use. But that alone wouldn't cause a miss between 3,000 and 4,000 rpm. However, it would foul the sparkplugs, though fouled plugs wouldn't only cause problems between 3,000 and 4,000 rpm.

2) Your Webers may be jetted too rich. Or the jetting issue may be more subtle: the 3,000 to 4,000 rpm range is where the Webers transition from the idle to the main circuit. Incorrect jetting can cause a stumble in that transition.

3) Fuel pressure seems less likely. But, what sort of a fuel pump and pressure regulator were installed with the Weber conversion? I see an aftermarket fuel regulator in your first photo - where is it set?

4) Yea. See #2.

Two other ideas:

- Whoever did the Weber conversion took the shortcut of retaining the Spica manifold and using adapters. The seals between the adapters and carburetors used with that set-up are prone to leakage. You may have a vacuum leak.

- How fresh are your spark plug wires? Old wires tend to miss at high rpm or under load, which corresponds to your "more noticeable when accelerating hard in 4th" symptom. Replacing the cap, rotor, points, wires and plugs isn't expensive, and might be a good idea if their ages are unknown.
 

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Just a wild guess but...
that is not a good pressure regulator, I would replace with one that has an internal filter. Like Filter King...
what fuel pump is installed? This sounds like the pump is going south and cannot keep up with fuel demand
you can check the fuel pressure but really need to install a gage to check what happens when running the car on the road
 

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Start with basics. How is compression, how much oil does it burn, make sure plugs, ignition are good. Make sure advance works. Make sure cam timing and tappets and valve clearances are OK. Once you've done that then try to narrow down possible causes. This is a ton of symptoms to pore through.
Andrew
 

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Another thought... the electronic ignition may be starting to head south, causing an occasional miss. Regardless of compression, oil burning, engine should still run, not miss. Plug wires are certainly a possibility and easy to replace. However, I still like the fuel pump. Had the exact same symptoms on an MG and it was the fuel pump.
 

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Here's a quick and easy test. Since your description indicates that the "miss" occurs when the engine is at full temperature, start the engine and bring it to full operating temperature. Set the car in a dark garage at night. The darker the better. Attach a hose to carry the exhaust gasses outside. Close garage door. Garage needs to as dark as possible. To achieve this I have used a heavy tarp to cover the engine compartment, and me, together. It's easier with a helper; start engine, open hood, and hold revs at 4k. Position yourself on the intake side and look at the distributor cap and the ignition secondary (spark plug) wires and spark plugs. Look carefully for arching-sparking along the top of the dizzy cap, and ignition wires. With a wood stick, gently move ignition wires a bit; especially any that are resting against the engine, or any ground. If no arching or sparking is found, there may still be an ignition problem with the primary side. Or a fuel delivery problem. Good luck, Burt.
 

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'66 Sprint GT, '67 Duetto, '70 BMW 2800CS
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Another thought... the electronic ignition may be starting to head south, causing an occasional miss.
Yup. Another item to add to your list of possible suspects. I spotted that vintage capacitive discharge ignition box in the first photo. Those Delta Mark 10B's were state of the art back in the 1970's, but any still surviving today are going to be pretty well-used. Capacitors may have dried out, connectors oxidized, etc.
 

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'66 Sprint GT, '67 Duetto, '70 BMW 2800CS
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The Delta Mark Ten has a red button that only needs to be clicked to go back to standard ignition.
Yes, a testimony to how confident the designers were in their product's reliability.

Still, the "red button test" assumes that the contacts behind that button aren't the core problem. It also assumes that your points are properly gapped.
 

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Based on all of this I would simply go back to points. They always work, or can be made to. Electronic ignition can leave you at any time, with no recourse. I like the Bosch dizzy with Bosch points. Put one in my car and it was night and day vs the 123 which stopped advancing. 18 degrees total advance just doesn't make it.
 

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I use points or Marelliplex. Have never been stranded but now that I say it I'm probably asking for it. Points can be dealt with on the side of the road in most instances. Easy to check for spark with simple tools.
Andrew
 

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1973 Alfa Romeo Berlina 2000
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Discussion Starter · #13 ·
As always... Thank you so much to the Alfa BB community for your valuable feedback. I am keeping this all and will act on it when I can. At the moment, the car is not going anywhere as I work on the bushings... Again... I want you all to know how much I appreciate your help!... Honestly, buying my 1st Alfa has been made better because I see many of you here on a regular basis.

Happy Holidays!
Burt
 

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Based on all of this I would simply go back to points. They always work, or can be made to.
I use a Delta Mark Ten... works great so far, and the red button is there. As Jay said, it goes back to the day when we didn't trust electronics or microprocessors enough to let them rule the world. And now, 5G is there, have faith!

Seriously, I had this sort of symptoms when leaving home for the 2012 convention. Alfa stayed home, turned out to be broken rings on a 95,000 miles engine.
 

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'66 Sprint GT, '67 Duetto, '70 BMW 2800CS
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I use a Delta Mark Ten... works great so far
Yea - those things were pretty simple (by today's standards) and built like tanks. The point to Burt isn't that we're telling him to run out and junk that Delta Mark Ten, but that he should add it to the list of things to check. Frankly, I think it has a low likelihood of being the problem, but anything is possible.
 
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