1974 tii Distributor

[LHCTii]

The 1974 tii's had a vacuum retard diaphragm on the distributor, I have heard if you disconnect the vacuum hose  and cap the port, the 1974 distributor has the same advance curve as the earlier centrifugal only distributors. If I knew someone with a SUN machine the question would be easily answered, but, alas they are mostly gone, can anyone chime in on this? 

Thanks, Doug  

['76mintgrün'02]

3 hours ago, LHCTii said:

The 1974 tii's had a vacuum retard diaphragm on the distributor, I have heard if you disconnect the vacuum hose  and cap the port, the 1974 distributor has the same advance curve as the earlier centrifugal only distributors.

 

 That's interesting.  I have examples of both distributors in the shop, an early Tii 0231 151 008 and the '74 Tii 0231 180 013.  I also have a SUN machine on the bench.  The thing is, that machine will tell us what they are, but not what they were. 

 

The curves in the factory service manual have the advance/retard curves on separate charts, so comparing the mechanical curves between those two distributors should answer your question.  My book is from '73, so it won't answer your question, but I'll peek at the one in the articles section of the FAQ.

 

I'd also like to peek inside the 180 013 distributor, to see if the mechanical advance parts are the same as on the 151008.  It seems like they would be, if they are meant to deliver the same curve.  I have a 151 008 in pieces right now, so that comparison will be easy enough.

 

Tom

[LHCTii]

The base plate will be different, hopefully the advance mechanism is the same. The Sun machine , I think, will show where the advance starts and completes, i don't think it will show total advance. A newer timing light will show total advance. 

['76mintgrün'02]

Both the sun and a variable light will allow you to plot the advance curve.  The timing light will give you the total advance number, based on how you set the timing.

 

It is pretty funny how much variation there is between the weights, springs, center posts and things.  I will be surprised if many, if any, overlap between the two models.  I agree though, it'd be cool if they did share parts. 

 

I have two 151 008 units with center post problems.  One with very nice cam lobes, but worn on the inside and the other with slightly worn lobes, but the bore is fine.  The funny thing is, both are 151 008 distributors, but the top of the shaft inside the center post is different between them.  After forty-some years, it's hard telling what is original.  Someone could have mix/matched parts at some point.  They numbered the bits and I've taken some notes so it will be easier to spot things that aren't original.

 

Do you have a 74Tii, with the 0231180013 distributor?  Do you have a variable timing light?  If so, have you put the curve on a graph?

Have you opened up your distributor?

[LHCTii]

Actually i have two 1974 tii's but I do not have a variable timing light, i don't know anyone close by with a Sun machine.

['76mintgrün'02]

I recommend the Innova 5568

 

['76mintgrün'02]

I opened up a 0231 180 013 distributor and the guts are different.  The weights and springs are lighter and the lobes on the center post are smaller.

 

The mechanical curves may be similar between the '74 and '73 distributors, but I don't think they were the same.  Otherwise, why bother changing the weights/springs/center post?

 

I did not bother plotting the curve on the Sun machine, because the existing curve won't reflect the original.  Look at the worn pins and slots in the weights and you'll see why.  The springs also wear thin where they rub on the center post lobes and that weakens them.

 

People often say that all of the distributor curves are in the service manual, but the one on this site is very similar to my '73 version, in terms of which models it shows in graph form.  I would love to see a source for graphs of each distributor model.  

 

The '74 uses "backwards" points and according to the service manual, the dwell setting is higher for that model as well @ 66-69 degrees.  Any idea why?

 

Tom

[visionaut]

I’ve never seen mentioned that disabling the vacuum advance/retard on any such 02 dizzy will yield an advance curve thats the same as a full-mechanical only 02 dizzy. Seems wishful-thinking to me.

 

Tom - aren’t the backwards points related to using vacuum to retard vs advance the timing?

 

Tom-too

['76mintgrün'02]

3 minutes ago, visionaut said:

Tom - aren’t the backwards points related to using vacuum to retard vs advance the timing?

 

Yes, the points would be in the way for the pin that the retard pod uses.

 

EDIT- my "why?" question was about the dwell difference.

Edited June 18, 2020 by '76mintgrün'02

[LHCTii]

Very interesting and very telling, thanks for the detective work, question now answered. It would be interesting to know how the 74 curve looks without vacuum attached. Thanks

[visionaut]

38 minutes ago, '76mintgrün'02 said:

EDIT- my "why?" question was about the dwell difference.

The difference in dwell is possibly due to the ‘backward’ positioning of the points.  The points might not lie the same distance from the dizzy cam as they do in their ‘normal’ location. Thus different dwell angle...

 

I know you can measure to verify...

 

Tom-too

[JohnS]

On 6/17/2020 at 2:24 PM, LHCTii said:

The 1974 tii's had a vacuum retard diaphragm on the distributor, I have heard if you disconnect the vacuum hose  and cap the port, the 1974 distributor has the same advance curve as the earlier centrifugal only distributors. If I knew someone with a SUN machine the question would be easily answered, but, alas they are mostly gone, can anyone chime in on this? 

Thanks, Doug  

I had a 74tii stock distributor rebuilt by Advanced Distributors.  The owner Jeff Schlemmer told me the same thing.  He said the advance curve was similar/same as the earlier tii 008 distributors.  Maybe that's after he does his magic on it.  Don't know.  He suggested that I cap off the vacuum retard on mine.  I haven't installed the rebuilt unit yet.  I'm running another stock 74tii distributor with the vacuum retard and all of the stock air hoses still there.  It runs great so I haven't messed with it.

['76mintgrün'02]

1 hour ago, JohnS said:

Maybe that's after he does his magic on it.

 

How did Jeff tell you to set your timing with the rebuilt unit?

 

The couple of rebuilt ones I have seen both came with instructions to set the timing at idle to 14-16 degrees btdc, which is a lot higher than the manual calls for.  (one was for a '73 Tii and the other for a 2002 Ti).  IIRC, the curve did not move from that setting until up around 1800 rpm, or so.

 

Tom

[JohnS]

19 hours ago, '76mintgrün'02 said:

 

How did Jeff tell you to set your timing with the rebuilt unit?

 

I just checked.

For the 74tii distributor he said:  "Try 14 degrees BTDC at idle no vacuum".

For the 008 from my 73tii he said: "Try 14 degrees BTDC at idle."

 

Both are using points.

Edited June 19, 2020 by JohnS