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74 Tii Distributor Vacuum Device question


bergie33
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I'm refreshing my distributor (013 74 tii vacuum retard unit) and I'm questioning the condition of the vacuum device. When I pulled it off, it had bugs and cocoons in it, and the vacuum tube nipple was bent and possibly leaks (see pic below).

 

I have a few questions.  Is there a replacement available for the vacuum device? Is there a way to bench test it? If I am thinking about removing the decel valve, can I get away without the vacuum unit on the distributor? I really don't want to use JB Weld, but if it's my only option... 

20220827_191800.jpg

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3 hours ago, bergie33 said:

I have a few questions.  Is there a replacement available for the vacuum device? Is there a way to bench test it? If I am thinking about removing the decel valve, can I get away without the vacuum unit on the distributor?

 

They do sell new ones, I do believe.  Vacuum advance pods can be flipped over and used as retard pods, but the little nipple will poke up instead of down and you may need to add a new mounting hole or two because their locations vary.  Their timing curves would probably be slightly different. 

 

I probably have a pod like yours that I can send your way.  What is the number stamped into the arm (that attaches to the points plate)?

 

If you're not using the decel valve, I don't think you want to use the pod; but you shouldn't remove it without somehow locking the two point's plates together, or they'll move around and mess up your timing.  It'd be best to leave it attached to the distributor, but not a vacuum source.  In which case, the pod you have should work fine.

 

If you find that your pod is compromised and you want to replace it with one that works, let me know and I'll see if I have one like it.

 

You could also add an advance adjuster to that pod if you're not going to use the vacuum retard feature.  That way you don't have to loosen the distributor clamp.  You just turn the wing nut!

 

IMG_3124.thumb.JPG.b3fbce84860c91ba81aec434debc0dfc.JPG

 

Here are the easy to follow construction instructions. 

 

 https://www.bmw2002faq.com/forums/topic/178062-distributor-mechanical-advance-limiting-screws/?do=findComment&comment=1403854

 

Tom

 

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You might try contacting Advanced Distributors.  I had them rebuild my stock distributor for the 74tii with the vacuum retard and was surprised that when it came back, it had a new vacuum thingy on it.  Jeff from AD recommended that I run it with the vacuum thing disabled (plug off) though.  He said the distributor acts just like a Bosch 008 centrifugal advance distributor used on the earlier tii's (72-73) if you plug off the vacuum retard port.  I'm still running it with the retard in place.  So, I guess, I'm retarded ?

 

 

Edited by JohnS
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On 8/27/2022 at 9:38 PM, Mike Self said:

Presuming it's still connected to the point plate, connect a short length of vacuum hose to the nipple and suck on it; you should feel resistance and see the point plate move.  No resistance= vacuum leak; no point plate movement = stuck advance/retard mechanism.

mike

 

Thanks Mike. I have it all taken apart right now. When it goes back together, there won't be any sticking of the adv/retard mechanism. I sucked on the vacuum port and it seems to function properly and hold vacuum, so maybe it will work just fine.

 

 

On 8/27/2022 at 11:49 PM, '76mintgrün'02 said:

 

I probably have a pod like yours that I can send your way.  What is the number stamped into the arm (that attaches to the points plate)?

 

If you're not using the decel valve, I don't think you want to use the pod; but you shouldn't remove it without somehow locking the two point's plates together, or they'll move around and mess up your timing.  It'd be best to leave it attached to the distributor, but not a vacuum source.  In which case, the pod you have should work fine.

 

 

Thanks for the offer, Tom. Seems mine is holding vacuum. I think once everything is back together I'll probably start with the decel valve connected, get the car running right, then try it without. 

 

 

On 8/28/2022 at 3:05 PM, JohnS said:

You might try contacting Advanced Distributors.  I had them rebuild my stock distributor for the 74tii with the vacuum retard and was surprised that when it came back, it had a new vacuum thingy on it.  Jeff from AD recommended that I run it with the vacuum thing disabled (plug off) though.  He said the distributor acts just like a Bosch 008 centrifugal advance distributor used on the earlier tii's (72-73) if you plug off the vacuum retard port.  I'm still running it with the retard in place.  So, I guess, I'm retarded ?

 

That's great info John. When I get to the point of removing the decel valve, I'll try plugging the vacuum unit.

 

Thanks to all of you for your help. 

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