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But Mad North-Northwest
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Okay, so it's running good with the non BMW AFM then? Sounds like you found your problem.

Tracks being worn is a common problem. It's possible to shift the copper arms forwards or backwards a little so they ride on a fresh section of track. If you search the BB or web there are details on this.

Unfortunately a restrictor won't fix the ported vacuum issue. The later distributor needs no vacuum at idle: adding a restrictor to plenum vacuum won't do that (there's very little actual flow here so the size of the port doesn't really matter, just how much vacuum it's connected to).

The problem with your setup as I understand it is that if you tune your static timing to 7 BTDC (or whatever the spec is) with the vacuum hose disconnected per the manual, as soon as you reconnect the hose you're going to have like 19 degrees BTDC idle advance, which is way too much. Alternatively if you set your static timing with the hose connected, as soon as you pull away vacuum is going to drop and you're going to retard the timing.

No idea how much of a running problem this will cause in practice, but it's not really a great thing either way. So it's possible this is contributing to some of your running issues. I guess as a test you could just temporarily disable the vacuum advance: plug the hose, set static timing to spec, and see if it runs better.
 

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I thought the problem would be the AFM after the experience I had with the one on the 75. I'm glad you tried it and got it working.
 

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Discussion Starter #83
I was worried about changing the AFM as the connector has some home made qualities to it. There is still the bunny hopping and aside from less smoke, there is no real change....

My theory with the restrictor was to even out any fluctuations that I thought might occur if vacuum is erratic at low load. Guess not.

I guess I am left to compare parts with what's on the black car, that one has the only throttle housing with the vacuum port in the correct position, that I have, and maybe try that housing. Assuming it is that kind of distributor. I am pretty sure it won't start now if I disconnect the vacuum hose and if I set it to spec then I am back to where I started. Or do you have something else in mind? Or should I set timing with hose connected? Haven't tried that yet.
 

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But Mad North-Northwest
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Sorry if I wasn't clear. If you really have the advance distributor, then there's basically no way to set it up properly with plenum vacuum. If it's a 3L, it's supposed to be timed to 7 deg BTDC at idle (verify this with your manual as it's from memory). If you set the static timing at 7 with the hose disconnected and then connect the hose it's going to be at like 19 BTDC at idle (7 deg static + 12 deg vacuum advance). This may be why you haven't been able to time it to the factory settings and get it to start.

If you time it to 7 BTDC with the hose hooked up to plenum vacuum it'll start and idle fine, but once you're off idle your timing curve will be all messed up.

Here is what I would do:

1) Disconnect and plug the distributor vacuum hose and time the car to 7 BTDC. Does it start and run okay-ish with the hose off? If not, I think you've got some other problem besides the distributor
2) Hook up a small hand vacuum pump to the distributor (I use a Mityvac brand, you guys probably have something similar). Watch the timing with a timing light as you pump vacuum at idle. 500 mbar of vacuum should advance the timing ~12 degrees if you have the later style distributor

I'm not an expert and I could be wrong, but if you have the advance-type distributor I'm pretty sure you're going to need one of the later-style throttle bodies with port vacuum to get the advance to work properly. There should be no vacuum on that line with the throttle closed, and then you should get vacuum as you open the throttle plate.

Maybe someone else has better ideas than me, though. Or maybe I'm misunderstanding something about your setup.
 

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Perhaps a photo of the throttle body and plenum would help us see what you have.
 

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Discussion Starter #86
I just had it confirmed that I do indeed have the wrong distributor. On this one the magnet turns counter clockwise on vacuum, in the black car it turns clockwise. If this is advance or retard I don't know.

Now, I do have one clockwise distributor but it has too much play in the axle. Unless the bearings can be replaced that one is out. Next is the throttle housing, now I want one with the port on the top side if I am to use this distributor. I have several but the have the Milano/75 linkage. I have one with the correct linkage but instead of a tube at the port there is what appears to be a solid pin. Does it never end???

Tomorrow will tell...


Edited for pics of throttles
 

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But Mad North-Northwest
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Rotor goes clockwise, so the one that moves the magnetic pickup counter-clockwise should be the one with vacuum advance.
 

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Discussion Starter #88
Done! Almost.

Now picking up vacuum from upstream of the throttle, the car at last appears to be running properly. What was looking like a solid pin was just a plugged tube and cutting a few millimeters of was the easiest solution. Idle is a little high and there is still a hint of the stalling tendency when stepping of the gas, I'll have to look into that but for now I can see myself being happy with this car.

Also I will be refitting the larger AFM to see what happens.

This turned out to be quite the ride. Thank you everyone, especially you Gubi for your elaborations regarding vacuum advance.
 

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Discussion Starter #90
Missed me?:grin2:

After two years in a barn this car has now had its original (?) vacuum-less distributor refitted and is running fairly well, once I understood how to set it up. It does smoke a bit on startup and on acceleration. What is left is that thing about legality. It is not quite street legal with this engine, but it could be. [insert long winded explanation about local registration regulations] I have therefore sourced parts from a 3.0 75/America/Milano necessary to complete the process, cat, cable harness, oxygen probe, ignition boxes. All is well, then it strikes me. This car has C&B S2 cams.

Is this usually a problem with cat and oxy probe? I recall having read about issues with emissions with these cams, and indeed it is dirty as it is but those numbers are not relevant for a -84 car. Going forward however, the rules for the donor car would apply.

Do you have a 3.0 L-jetronic with cat and C&B S2 cams? What kind of CO, HC numbers do you get?
 
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