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Distributor for 1973 Squareback with Automatic Transmission
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raygreenwood
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PostPosted: Wed Aug 17, 2016 4:31 pm    Post subject: Re: Distributor for 1973 Squareback with Automatic Transmission Reply with quote

blues90 wrote:
I'm having trouble trying to get my head around the trigger cam being in a different position in different years of FI type 3's .

Certainly they have different methods of controlling full load enrichment and yes the base timing is different through the years as was the vacuum and advance curve and the timing will affect the trigger point timing and perhaps that's the entire point .

I thought mainly advance curve and basing timing whether 0 degrees or 7.5 or 5 was based on compression and emissions . I don't see why changing the trigger cam position would be done even though it's related to it being 0 * or 5* .

I have a 72 AF dist for an automatic and an 73 AH . The AF came with a dual vacuum can so @idle even though the timing was set @ 5 * the vacuum retard brought it down to 0* for emissions only the trigger cam is the same for both yet @ idle vacuum @ 0 * it didn't run like crap.


There must be a way to check the trigger cam position compared to rotor position. if I recall one of the mechanical weight pivot pins is what fits in the trigger cam for the position. also to point out that the rotor position on all T-3 engines point to #1 plug wire at the same point when you have the #1 cylinder @ TDC which is 0 *. Also why the dist drive needs to be the proper position not only for clearance sake of the condenser and vacuum can with a carbed engine yet to make sure the trigger points open and close in relation to the camshaft . This is why valve adjustment is critical to fuel injection and this is done the same way on all VW air cooled engines with solid lifters.

Don't FI T-3's have a different cam for a reason.

A T-4 dist may be different and not work in a T-3 . Also to add even if the spec is 5 * BTDC depending on the fuel and engine wear it might ping and all books say adjust to compensate so you might be @ 2 * .

When talking about 0 degree's or 5 degree's base timing I can't see why the trigger cam would require a different position.


Here is why you are not getting it:

Ignition timing is based around performance. You are setting advance and/or retard for spark timing......really....thats all ignition timing is about. As a bare minimum concept....you want spark to happen at TDC when compression is at the highest. However in the real world......for best and most complete combustion efficiency to get the most power. ....you want to start igniting the fuel earlier than TDC....so you can take advantage of the compressing of the space to make better combustion......higher pressure.

Based on that.....guess what....ignition timing is 100% tied to crankshaft and piston position....and advance and retard of ignition timing is a performance based deviation from crank and piston position or timing.. Thats why it makes sense.....that the distributor is driven by...and locked to....the crankshaft.

But......injection timing is keyed to Intake valve timing.......not just TDC on each cylinder. The injectors need to be firing.....in a perfect world....when the intake valves are open....or you waste the primary benefit of fuel injection which is atomization.

See.....the sparkplug is already in the cylinder. Because or advance or retard.....it may fire early or late with reference to TDC of the piston. This may b a plus or minus for performance but it will not affect the spark quality.

When you move the distributor to adjust IGNITION timing.....or a common mistake.... move the distributor to make up for the drive being jnstalled 180° or 90° or 1 or 2 teeth off......even though your timing light shows that you have now moved the distributor far enough to make sure that ignition is once again happening close to TDC on the piston...............what you have changed or corrected is the ignition event with reference to the crank position....because the drive is off.

What you have NOT changed is CAMSHAFT position and valve position.
The injection trigger points timing is only correct...when the distributor body is in the original position that the factory set it.

The trigger points were put in the distributor out of convenience. But the ignition points are allowed movement for advance and retard. The injection triggers are allowed very little lattitude for movement.....because the injection start points are already a difficult compromise with reference to valve open points.

Ray
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raygreenwood
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PostPosted: Wed Aug 17, 2016 5:39 pm    Post subject: Re: Distributor for 1973 Squareback with Automatic Transmission Reply with quote

And....blues90....your thinking is actually on the right track and you have a definite point. Yes....in general since cam and crank are linked....arge movements...like an EXACT 90° or 180°....timing drive change.....will leave the raltionship intact. If your timing of the fistributor body for ignition is then spot on factory.

The real problems. ....are not factory advance levels...and when the distributor drive is installed only 1 or 2 teeth off...and the idle igniton timing setting is not exact.

As I noted....the issue is that more than a few degrees off in either direction disturbs vacuum signature and fuel pressure stability. Ray
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blues90
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PostPosted: Wed Aug 17, 2016 5:40 pm    Post subject: Re: Distributor for 1973 Squareback with Automatic Transmission Reply with quote

Ray I understand all of that . Spark timing is not the trigger timing it is another signal to fire the injectors. Both are affected by dist position yet the trigger points need to be as close as they can be for fuel .

I don't have any older T-3 distributors to compare how different the trigger cam is positioned. If someone did it would be easy enough to set the rotor to #1 and see where the trigger cam is set based on the drilling.

I realize it's not each cylinder TDC and realize 2 injectors fire at the same time.

And you really would not have any sort of good running engine if you were off 1 tooth on the drive that's 30* .

Yet I am talking about say the timing should be 5* BTDC and it pings due to crappy gas we now have so you back it off to 2 * or whatever stops the ping that's a 3* change in the injector timing so even with the proper dist you now have screwed up the injector timing so now what you need to slot the trigger plate ? By the way on the 3 sets of trigger points I have I can move each one at least that much doing nothing to the holes in the trigger hold down .

AS cheap as VW was I can't imagine they would change the trigger cam position in different years yet I can't prove it . One tooth off on the dist drive is 30* so either way it won't run very well if at all unless the drive is set at the close to 60* from case center line and even that is not exact, it's just close. The dist drive dog does not bottom out in the drive notches so one could add another washer and come closer to a true 60* since the drive when dropped in rotates a bit .

To me 0* or 5 * timing does not seem to warrant a new trigger cam position. Seems at 0 * you would want a bit less fuel or it may very well run rich depending on the advance curve . There is so much to consider .

Certainly if I had the wrong dist for the year engine I would want to see how different it was as far as the trigger cam .

Perhaps if anyone here has a few they could check this out . They very well may be set different other wise they would all be the same number . The books only show the vacuum and mechanical curve at dist RPM .


Last edited by blues90 on Wed Aug 17, 2016 6:56 pm; edited 1 time in total
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Donnie strickland
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PostPosted: Wed Aug 17, 2016 5:50 pm    Post subject: Re: Distributor for 1973 Squareback with Automatic Transmission Reply with quote

When I swapped distributors I also swapped my trigger points over, as well as the vacuum canister.
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blues90
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PostPosted: Wed Aug 17, 2016 6:51 pm    Post subject: Re: Distributor for 1973 Squareback with Automatic Transmission Reply with quote

Donnie strickland wrote:
When I swapped distributors I also swapped my trigger points over, as well as the vacuum canister.


Yes you had the proper year dist only a manual instead of for an auto trans .

As far as trigger points go and you got a rebuilt unit . If I recall could be wrong didn't you get a rebuilt complete unit from either Auto zone or one of the online places yet I think the reman company is the same one.

If that's the case I would have used my trigger points simply because they were proven to work and maybe looked better than the rebuilt had.

I was going to do that just to get the vacuum advance yet it was not worth the money mine worked fine.

I have an AH I redid yet since I have a pertronix in mine the AH braided ground strap to the advance plate was different from the AF , instead of it being routed over the vacuum advance arm it was shorter and sat right where I would need to remove it and solder in a new one or change the advance plates over yet the magnet for the pertronix was stuck thought it would break so I just kept the AF and pertronix sent me a new magnetic ring for free.

Perhaps if the OP can measure a few things as trigger cam pin location at say the rotor on and sure it's advance springs snap the rotor all the way or hold it there facing #1 notch and I could try to do the same on the AH I have.
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raygreenwood
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PostPosted: Wed Aug 17, 2016 8:08 pm    Post subject: Re: Distributor for 1973 Squareback with Automatic Transmission Reply with quote

Donnie strickland wrote:
When I swapped distributors I also swapped my trigger points over, as well as the vacuum canister.


Its nice to do if the trigger points are known to be good....no sense in going through all the checking......but my point of what you need to look out for......and mainly if your ignition timing is altered slightly from the ignition timing of the engine that the distributor originally came from....is that the trigger point cams can be in slightly different positioj on each,distributor type.

Ray
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blues90
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PostPosted: Wed Aug 17, 2016 8:16 pm    Post subject: Re: Distributor for 1973 Squareback with Automatic Transmission Reply with quote

raygreenwood wrote:
Donnie strickland wrote:
When I swapped distributors I also swapped my trigger points over, as well as the vacuum canister.


Its nice to do if the trigger points are known to be good....no sense in going through all the checking......but my point of what you need to look out for......and mainly if your ignition timing is altered slightly from the ignition timing of the engine that the distributor originally came from....is that the trigger point cams can be in slightly different positioj on each,distributor type.

Ray


Ok lets toss this in just for whatever it's worth . Someone on this forum bought a rebuilt dist for a T-3 and lets say the body number is correct yet they used a good fit shaft from a different year . Maybe the rebuilder knows , maybe they have no more info than I do . Sure it's reaching yet possible so if it runs fine was it just luck or the owner knows it runs better than it did yet has no way to compare with another like year if it could be much better.
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PostPosted: Wed Aug 17, 2016 10:21 pm    Post subject: Re: Distributor for 1973 Squareback with Automatic Transmission Reply with quote

Wbat doyou consider "runs fine"?

With all lf the niggling tuning issue people have.....its why I keep saying....start paying attention to the details of tuning. ....and very little of it is in any books.

If you have odd idling issues....and off the line performance issues....but the engine "generally" runs fine.......get a real fuel pressure gauge, time the ignition correctly...and check the fuel pressure stability. Most especially if you are using a Pertronix module......which generally FORCES you to alter distributor position....which also forces you to change injection timing position.

And.....if its already off by a few degreez because its not the exact distributor. .....you can have running and tuning problems. Quit just tuning a 40+ year old system by "sorta" installing similar parts.....and realize there are differences in parts and their effect. Ray
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PostPosted: Thu Aug 18, 2016 3:51 am    Post subject: Re: Distributor for 1973 Squareback with Automatic Transmission Reply with quote

raygreenwood wrote:
Donnie strickland wrote:
When I swapped distributors I also swapped my trigger points over, as well as the vacuum canister.


Its nice to do if the trigger points are known to be good....no sense in going through all the checking......but my point of what you need to look out for......and mainly if your ignition timing is altered slightly from the ignition timing of the engine that the distributor originally came from....is that the trigger point cams can be in slightly different positioj on each,distributor type.

Ray


The 69 and 71 cars are both timed at 0 degrees TDC, so I saw no issue; the car runs as well as ever.
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PostPosted: Thu Aug 18, 2016 7:13 am    Post subject: Re: Distributor for 1973 Squareback with Automatic Transmission Reply with quote

Donnie strickland wrote:
raygreenwood wrote:
Donnie strickland wrote:
When I swapped distributors I also swapped my trigger points over, as well as the vacuum canister.


Its nice to do if the trigger points are known to be good....no sense in going through all the checking......but my point of what you need to look out for......and mainly if your ignition timing is altered slightly from the ignition timing of the engine that the distributor originally came from....is that the trigger point cams can be in slightly different positioj on each,distributor type.

Ray


The 69 and 71 cars are both timed at 0 degrees TDC, so I saw no issue; the car runs as well as ever.


Yes......if they are both timed the same.....and since they all use the same factory came....I would bet there is no issue. Ray
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PostPosted: Thu Aug 18, 2016 1:25 pm    Post subject: Re: Distributor for 1973 Squareback with Automatic Transmission Reply with quote

raygreenwood wrote:
Wbat doyou consider "runs fine"?

With all lf the niggling tuning issue people have.....its why I keep saying....start paying attention to the details of tuning. ....and very little of it is in any books.

If you have odd idling issues....and off the line performance issues....but the engine "generally" runs fine.......get a real fuel pressure gauge, time the ignition correctly...and check the fuel pressure stability. Most especially if you are using a Pertronix module......which generally FORCES you to alter distributor position....which also forces you to change injection timing position.

And.....if its already off by a few degreez because its not the exact distributor. .....you can have running and tuning problems. Quit just tuning a 40+ year old system by "sorta" installing similar parts.....and realize there are differences in parts and their effect. Ray


Ray I would consider running fine if the car idles smooth and has no obvious rich or lean issues and a car that picks up speed well and at an even rate.

On the Pertronix . When I installed mine which was long ago 97 I don't recall how much I had to advance the timing from points or retard it. If I recall I had to advance it . At the same time I got the pertronix or close to it I replaced the trigger points with NOS Bosch and since I found I was able to slide the trigger points side to side I moved the trigger points toward the rotation arrow so the trigger points would be advanced a bit.

I ran great , smooth idle and steady vacuum . This was even with the original engine of unknown mileage . I was trying to pass smog and it passed at higher RPM but was high on idle . Once that engine developed a rather loud internal rattle even though it still ran great I rebuilt a 72 automatic case I had sitting here used the same parts and it passed by a hair . It did have better pickup since it had new cylinders and the heads were done . What I found odd and only knew last year was the MPS was a Bosch 0280 100 101 VW # 311 906 051D And not knowing at the time and since it looked new and came off the 72 parts car it ran the same and got the same smog readings as the Bosch 0 280 100 106 vw # 311 906 051E . Externally they looked the same the only external vent was in the center of the single adjustment screw and neither had the full load built in just like all later models with the full load built into the TPS.

So I don't know why the VW D is D unless I read it wrong don't think I did. I say this because D is supposed to have the built in full load enrichment yet on this chart below seems no MPS D existed.

https://www.thesamba.com/vw/gallery/pix/342921.jpg
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PostPosted: Thu Aug 18, 2016 4:29 pm    Post subject: Re: Distributor for 1973 Squareback with Automatic Transmission Reply with quote

blues90 wrote:
raygreenwood wrote:
Wbat doyou consider "runs fine"?

With all lf the niggling tuning issue people have.....its why I keep saying....start paying attention to the details of tuning. ....and very little of it is in any books.

If you have odd idling issues....and off the line performance issues....but the engine "generally" runs fine.......get a real fuel pressure gauge, time the ignition correctly...and check the fuel pressure stability. Most especially if you are using a Pertronix module......which generally FORCES you to alter distributor position....which also forces you to change injection timing position.

And.....if its already off by a few degreez because its not the exact distributor. .....you can have running and tuning problems. Quit just tuning a 40+ year old system by "sorta" installing similar parts.....and realize there are differences in parts and their effect. Ray


Ray I would consider running fine if the car idles smooth and has no obvious rich or lean issues and a car that picks up speed well and at an even rate.

On the Pertronix . When I installed mine which was long ago 97 I don't recall how much I had to advance the timing from points or retard it. If I recall I had to advance it . At the same time I got the pertronix or close to it I replaced the trigger points with NOS Bosch and since I found I was able to slide the trigger points side to side I moved the trigger points toward the rotation arrow so the trigger points would be advanced a bit.

I ran great , smooth idle and steady vacuum . This was even with the original engine of unknown mileage . I was trying to pass smog and it passed at higher RPM but was high on idle . Once that engine developed a rather loud internal rattle even though it still ran great I rebuilt a 72 automatic case I had sitting here used the same parts and it passed by a hair . It did have better pickup since it had new cylinders and the heads were done . What I found odd and only knew last year was the MPS was a Bosch 0280 100 101 VW # 311 906 051D And not knowing at the time and since it looked new and came off the 72 parts car it ran the same and got the same smog readings as the Bosch 0 280 100 106 vw # 311 906 051E . Externally they looked the same the only external vent was in the center of the single adjustment screw and neither had the full load built in just like all later models with the full load built into the TPS.

So I don't know why the VW D is D unless I read it wrong don't think I did. I say this because D is supposed to have the built in full load enrichment yet on this chart below seems no MPS D existed.

https://www.thesamba.com/vw/gallery/pix/342921.jpg



What I was getting at...is that so many VW owners with D-jet especially.....consider their car runs fine....if it idles steady...even with what feels like a very, very slight miss.....or idles too low...but idles fine.....but with a very slight rock to the engine...or seems to idle fine and smells slightly rich......or idles fine but occasionally has a very slight hesitation taking of the line or shifting from one or more gears.

And this is all when its warmed up. They may also be fine with 5-7 seconds of cranking when starting cold or more.....

and with any of this they consider that its running quite fine ....considering.... they qualify that in their mind because its a 40 plus year old car. Wink

Yes....there is a little bit of slack n the trigger plate screw holes that can help. Ray
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PostPosted: Fri Aug 19, 2016 7:59 pm    Post subject: Re: Distributor for 1973 Squareback with Automatic Transmission Reply with quote

Thank you all again for the advice. I'm going to start with the distributor I have and time it to 0 degrees BTDC which is the timing for this distributor and go from there.

Air_Cooled_Nut, it's possible bad engine piston rings are causing rich running. The speedometer has 90,000 miles but as it is only a 5 digit speedometer, this could be 190K miles. I'm starting with the assumption it is 90K and the engine has some life left in it as the seller advertised this as not a project car (http://findclassicars.com/volkswagen/105490-volkswagen-squareback.html). I'm starting by checking the common items that makes these cars run rich (vacuum links, low voltage, fuel pressure, etc.).

If then there isn't any improvement, I'll get a compression tester and check.
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