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Hi to all,

im havinga question about ignition advance. Because some webers or let me say o lot of them dont have ports for vacum advance there should be something done with the distributor and his wights.
Did someone pplay with the weights?
 

Best regards!

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If you have wights in your distributor... well. I think I'd run away.  Screaming.

 

Seriously, though, the usual routine is to run the tii distributor.

 

You could also tap all 4 intake manifold runners, run tiny hose to a junction, then get an 'averaged' signal 

from there- Alfa did exactly that with the Spica system.

 

t

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The only problem Toby is if you are using manifold vacuum, you have vacuum when the throttle is closed and none when you are on the throttle.  The vacuum advance on the distributor is designed to ADVANCE when it sees vacuum.  If you hook it up this way it will retard when you are accelerating and advance when you get off the throttle (kind of bass-akwards)  The down draft carbs have a vacuum port that sees venturi vacuum so you have vacuum when you are accelerating and none when you are not, the DCOEs do not.  Use a Tii distributor!

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The distributors that have vacuum advance cans on them do have some amount of centrifugal advance (it varies depending on which one you have)

The Tii all centrifugal advance distributors have 28-32 degrees of advance between 900 and 3500 rpm.

The 0231 180 005 and 0231 180 008 (standard US 2002)distributors have the same 28-33 degrees of advance centrifugal but it happens between 700 and 2400 rpm. There is also 8-12 degrees of vacuum advance available based on vacuum supplied by the carburetor.

You can use the standard 2002 distributor without the vacuum advance but you would need to set your timing at full advance (I would use 3000rpm). You would need an adjustable timing light to set it at 34-36 deg BTDC (this will depend on what compression ratio you are running, how good your fuel is, your altitude, how well you have the carburetors adjusted, camshaft, headers, exhaust etc) The major problem will be that all of the advance will come in very quickly and you may have detonation issues at low engine speeds because the 2002 distributor is 8-10 more advanced at 2500 rpm than the Tii distributor. If you just back the timing off you will be 8-10 deg retarded above 3500. You can have a your distributor rebuilt and recurved but by the time you have done that you can almost buy a new centrifugal advance distributor from Ireland.

I know you wanted a simple answer, only problem it's not that simple! Even the Tii distributor might not be the perfect thing for your engine, it's probably better than what you have. It was set up for a very specific compression ratio, camshaft, fuel system, exhaust system etc and BMW spent a lot of time curving it for that engine, your engine MAY or MAY NOT require the same ignition advance profile and no one can tell you exactly what you need unless you find someone that had built EXACTLY the same engine, is running it on the same fuel at the same altitude and had spent hours getting their distributor tuned perfectly.

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Oh, right, Byron, I forgot-

the Alfa system had the taps in the throttle bodies, across the plates at the right place.

 

This does the 'no advance at idle, but high vacuum at small throttle openings' that you would want for

the vacuum advance part of the distributor.

 

I got that corn-fuzed with the ITB Turbo guys who want to know averaged manifold pressure.

 

Sorry,

 

t

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The distributors that have vacuum advance cans on them do have some amount of centrifugal advance (it varies depending on which one you have)

The Tii all centrifugal advance distributors have 28-32 degrees of advance between 900 and 3500 rpm.

The 0231 180 005 and 0231 180 008 (standard US 2002)distributors have the same 28-33 degrees of advance centrifugal but it happens between 700 and 2400 rpm. There is also 8-12 degrees of vacuum advance available based on vacuum supplied by the carburetor.

You can use the standard 2002 distributor without the vacuum advance but you would need to set your timing at full advance (I would use 3000rpm). You would need an adjustable timing light to set it at 34-36 deg BTDC (this will depend on what compression ratio you are running, how good your fuel is, your altitude, how well you have the carburetors adjusted, camshaft, headers, exhaust etc) The major problem will be that all of the advance will come in very quickly and you may have detonation issues at low engine speeds because the 2002 distributor is 8-10 more advanced at 2500 rpm than the Tii distributor. If you just back the timing off you will be 8-10 deg retarded above 3500. You can have a your distributor rebuilt and recurved but by the time you have done that you can almost buy a new centrifugal advance distributor from Ireland.

I know you wanted a simple answer, only problem it's not that simple! Even the Tii distributor might not be the perfect thing for your engine, it's probably better than what you have. It was set up for a very specific compression ratio, camshaft, fuel system, exhaust system etc and BMW spent a lot of time curving it for that engine, your engine MAY or MAY NOT require the same ignition advance profile and no one can tell you exactly what you need unless you find someone that had built EXACTLY the same engine, is running it on the same fuel at the same altitude and had spent hours getting their distributor tuned perfectly.

Im from Europe, so i use normal destributor, i have alpina A1 engine with alpina spec weber dcoe 40. E12 head with pisano top pistons probably 8,5-9 compression ratio. I use naromal gasoline witch is 95 octane.

This is my vacum reading...

2013-06-01-868.jpg

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I'm assuming that is your manifold vacuum at idle? As already mentioned this signature is opposite to that needed to operate a vac advance canister.
Do you have the distributor that came with the Alpina engine? It may be possible to plot the advance curve providing the springs have not work-hardened.
Crank fire ignition is the way to go as it can be mapped to suit either manifold or throttle plate vacuum signature. You could even keep the distributor to take care of the HT plumbing and looking authentic

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The major problem will be that all of the advance will come in very quickly and you may have detonation issues at low engine speeds because the 2002 distributor is 8-10 more advanced at 2500 rpm than the Tii distributor.

I messed with a standard 2002 (vac advance disconnected because of dual DCOEs) for years. At times I had it running ok but low rpm detination was almost always a problem unless I was running Ultra 94. When I finally bent over and bought a tii distributer (no vac advance) all my problems went away. Well worth the money.

John

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