Why does my 74 have a vacuum advanced distributor

[buckweber]

Good Afternoon,

 

The car is an 1974 TII,    I believe it was used as a parts car by a previous owner.   Somewhere along the road I believe I heard the distributor was out of a 1969 model.

 

I will re-read all of the responses.   I appreciate them all.

 

Question:  Does the BB indicate a specific advance.   IE: 25 Degrees.

 

The manual indicate a 1974 TII is to be timed to 25 Advance at 2400 RPM.    To get a baseline before I get the proper timing light does this mean i set the idle at 2400 RPM and then should see the BB???

[buckweber]

To Confirm:  The  distributor in the car  has centrifugal and vacuum advance

['76mintgrün'02]

36 minutes ago, buckweber said:

Question:  Does the BB indicate a specific advance.   IE: 25 Degrees.

 

The manual indicate a 1974 TII is to be timed to 25 Advance at 2400 RPM.    To get a baseline before I get the proper timing light does this mean i set the idle at 2400 RPM and then should see the BB???

 

Yes, the BB is 25* btdc.

 

Yes, standard procedure is to disconnect the vacuum pod and rev the engine to 2400 rpm and align the BB to the edge of the hole in the bell housing.  That prescription is for the stock distributor though, so it may not give the proper advance at the rest of the rpm range.  In this case, I would not reconnect the pod, but simply cap the vacuum source.  No need to cap the nipple on the pod... except to keep bugs out.

 

Of course you need to set the dwell within spec before setting the advance.

[buckweber]

Is there a job aid on how to set dwell.

note: I disconnected the vacuum and set timing to 25 degrees at 1400 RPM. Car is running Better than it ever has. I will reset to 25 degrees at 2400 and report results


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['76mintgrün'02]

3 minutes ago, buckweber said:

Is there a job aid on how to set dwell.

 

do you have a dwell meter?

 

 

[jimk]

 

Section 10.  If dwell is in spec, leave It alone because retiming is required after futzing with the points.

[buckweber]

I will be getting timing light / dwell meter. Not sure how to actually hook up the dwell meter to check dwell. If it is off, hoe is dwell adjusted. By the points gap?


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[buckweber]

I will be getting timing light / dwell meter. Not sure how to actually hook up the dwell meter to check dwell. If it is off, hoe is dwell adjusted. By the points gap?


Sent from my iPhone using Tapatalk

['76mintgrün'02]

yup, dwell is essentially a means of measuring/defining the points gap, as the number of degrees of shaft rotation that the points stay closed.

 

the information Jimk posted above will walk you through it.

 

they even tell you how to set the gap/dwell, using the meter and spinning the engine with the starter motor, to make the adjustment; then put the cap back on and you're done.

 

 Otherwise, it is set the gap, replace the cap, fire it up and measure.  Repeat.

 

Haynes makes a decent manual for basic tune up procedures.

[jimk]

2 hours ago, buckweber said:

 

I will be getting timing light / dwell meter

 

With the dwell meter, if you are adjusting/installing/did not mess with the points yet, you can simply hook up the meter and start the car for a reading.

['76mintgrün'02]

There is a '74 tii distributor for sale on eBay right now.  (nmna)

http://www.ebay.com/itm/Bosch-Distributor-0231180013-BMW-2002-E10-Tii-/162678453182?hash=item25e06433be:g:GRsAAOSw0h9ZsWEK&vxp=mtr 

 

Depending on what you learn about the curve/condition of the one you have, this may be one to consider.  Hard telling what condition it is in, internally, but it looks nice and clean.

 

It also has a pertronix unit installed, which eliminates the points/condenser and the need to adjust the dwell.

(a new pertronix ignitor costs more than the buy-it-now price of this distributor)

 

I'll bet there is a good chance that you'd be the only bidder at the opening price.  Once a bid is placed, the BIN option goes away; so you may as well start low and see what happens.  Assuming you are even interested  

[John76]

The eBay offering does indeed have a vacuum retard....not advance.

['76mintgrün'02]

... which you might as well disconnect, unless the rest of the 'control system/emissions package' is intact.

 

The big question is the condition of the centrifugal advance mechanism.

This early style is funny, the way the weights rub on the side of the puny little springs.

 

The gear retaining pin looks original, so I doubt it has been refurbished.

 

[buckweber]

I changed the AutoLite plugs to the recommended, new wires, cleaned up distributor,removed vacuum line and timed it to 25 Degrees at 1400 RPM.   It is running good.  Best yet.  

 

I am going to set the timing to 25 degrees at 2400 RPM as recommended to see if it gets any better.

 

May get a Pertronix in it or purchase the distributor on eBay.

 

Thanks again to all for the help.    I was getting ready to push it of a cliff.    Push it because I couldn't drive it off.

['76mintgrün'02]

well, it sounds like you are making progress.

 

With your new timing light, you will be able to assess the curve from the distributor you have now.

 

I would not buy a Pertronix for it, until you know this curve will work for you.

 

If you do shop for a Pertronix Ignitor, make sure to get the one that works with your particular distributor model.  They do vary.

 

Timing to the BB is just setting the advance at **** rpm and too much advance at other rpms may be a problem.

 

Once you get familiar with the variable advance timing light, you will be able to make an informed decision as to how to proceed.

 

The advance needs of a tii are much different than those of a carbed engine.

Just ask this guy!