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Vacuum Lines and Webers: Help/better Understanding

4K views 25 replies 9 participants last post by  terrylewisac 
#1 ·
I found some thing interesting today that I never noticed before ( if I did I must have said well it's running fine leave it alone) But it now has me very curios.
1, the advance hose off the distributor is going to the tree ( 73 with both advance and retard ports)
2, the retard hose off the distributor goes no where
3, the advance port on the carb WEBER 32/36 is going straight down to the tee
All the research I've been doing has led me to believe that this is incorrect.
From my research I am to believe the following
1, the advance hose from distributor should go to the carb advance port
2 the retard hose from the distributor should go to the tree
3 then the last nipple on the tree should go to the little port on the valve cover ( which I don't have and is wide open)and I'm not fond of the air breather turning black because of this).
So if the advance from the distributor goes to the tree and then the carb advance was attached to said tree is there technically no advance or retard?
Thank you in advance for your thoughts and help
 
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#2 ·
I've been dealing with some of these same issues recently on the 69. In our case the vacuum advance isn't holding vacuum. No's 1 and 2 are correct, and there are several threads out there that recommend plugging the retard port. One thing you didn't mention was the brake booster hose that should be coming off the bottom of the tree.
 
#3 ·
AH Yes I did forget.
yes the brake booster hose goes right to the very front of the tree
In my case that hose is new as well as the brake booster and master cylinder from ogts
 
#4 ·
Search and Yee shall find...

 
#10 ·
Ok Thank you.
I did observe the breaker plates moving while I was tinkering before I put the hand pump on to see how well it holds and how long.
So I feel a little better there.
I looked a little closer at the tree because I thought there were 4 ports (not including the booster hose) on it and there are 3 on the tree and underneath of it was a metal tube screwed to the manifold and It appears to be pinched off.
I am assuming this would have been for an automatic trans? Just seems weird for it to be there when this is a standard.
So if I have everything connected the way it should now including the retard , Then I would have one port left over that's not used that I just plug.
 
#12 ·
so once I get brave enough to start learning to time this little bugger I have a manometer I use for a/c stuff, if I use it to get data on vacuum while I'm playing with timing where do I hook it up at or tee it into?
 
#13 ·
Hook up to full manifold vacuum port at the bottom of the carb below the throttle plates (the vacuum line goes to the retard canister). The port in the middle of the carb which hooks to the advance canister is ported vacuum and should be at or close to 0" at warm idle. Personally, I can't get it to 0" unless I drop the rpm's down to 650 and then the engine idles like a tractor so I still have some diagnosing to perform.
Your advance diaphragm seems OK; mine dropped from 15" to 10" in 10 seconds, and from 10" to 5" in 30 seconds. By comparison the retard canister held steady vacuum for about a minute; I didn't test it any longer.
 
#14 ·
Just to update my dilemma's
I have rerouted and hooked up all my vacuum lines as they (should be)
Now the fast idle on start up no longer works?
Which is in turn leaning me towards putting it back the way it was before.
I tried on 3 different days with motor completely cold, initial start to get gas to carb then one press of pedal I hear choke plates set then it starts but no fast idle at all.
I'm thinking it's something with the retard port to the tree?
My fast idle always worked until now.
 
#16 ·
Humm thanks Kyler, Maybe just coincidental it stopped working after the change?
I did accidentally touch the choke wire/lead to the choke base when I forgot to hook it back up
It sparked quickly then I tested to make sure I still had 12 volts to it incase it was long enough to blow the fuse But it was still getting voltage.
I have not messed with the fast idle screw since I first got the car and it's been fine until now?
 
#18 ·
Thank you Lindsay,
I tried it again today and no go so I'll have to look into why this is happening.
Does anyone know the ohms value for the electric choke cold?
Or would that even be worth checking?
 
#19 ·
Installled 32 36 DGEV carburetor approx. 1980.
Never checked ohms for electric choke.

Refer to attachment. Loosen three (3) adjustment screws at choke ring.
When you rotate choke housing, top sheet metal plate will open and close.
Ensure plate is verticle (straight up) when vehicle is warmed up.
Product Toy Gas Machine Nut


See the screw to the right of the choke element in this picture? It's above the brass vacuum tube. That's the fast idle speed adjustment.
Motor vehicle Gas Auto part Nut Machine
 
#20 ·
I would recommend plugging the retard port and connecting the advance port to manifold vacuum. Then setup your timing again. In a crude way, consider port vacuum an indicator or throttle position and manifold vacuum as an indicator of load. Port vacuum is always supposed to be zero when the throttle is closed. Manifold vacuum will be different depending on is the car at idle or did the engine just come off of full throttle. These two scenarios should have different vacuum readings. I would not want to retard the ignition with manifold advance when you let off the throttle. That would mean spark happens closer to TDC when the engine could be at high RPMs, and you want the exact opposite. I could be wrong here of course.
 
#21 ·
There’s nothing wrong with vacuum retard working when you close the throttle plates at high rpm. It’s like 4° of difference. Remember when you lightly touch the throttle at 4000rpm you are advancing 22-28° in a split second. Let off the throttle again and you drop that 22-28° again just due to 18-24° vacuum advance + 4° retard
The vacuum retard just makes for a more complete and cleaner burn at idle and off throttle. It can be kept or deleted and you’ll never notice the difference except for a slightly faster idle speed after deleting.

I strongly disagree with moving ported advance to the manifold. I’ve undone this on several cars I’ve helped people tune up. It seems like on every classic car people decide to hook up advance to the manifold. All it does is make the car hard to start and/or virtually guarantee it’s timed incorrectly.

What I see the most is that people end up with is 0° static timing + 18-24° of vacuum advance at idle and a portion of that during cranking which makes the car harder to start. This also makes cars run pretty hot at idle and really makes for an interesting throttle transition from a stop in my experience.

What I see the rest of the time is that static timing gets set to around 10° retarded because the car was timed by ear and the 10° retard compensated for most of the excess vacuum advance. Downside is these people get awful top end performance because they get less than 25° advance at WOT.

The common thread with the half dozen people I’ve helped out that had there advance on the manifold is that the car was much better after switching back to ported.
 
#22 · (Edited)
Just an update while I watch paint dry and wait on a couple parts.
Got a chance to play with it again and couldn't get things to do what I wanted.
I got out the carb and choke spray to test for some vac leaks
To my surprise, as soon as I started spraying around the intake at the head Guess what happened?

Also got the fast idol working again I must of somehow deactivated it through all the things I was doing
But I do want to start it cold again tomorrow and see if it stays activated.
 
#23 ·
Now having a chance to reflect on the new symptoms from can't get timing right to mushy brake pedal and 2 days ago interesting enough engine idol would change if I hit the brakes repeatedly a few times and higher idol after I switched to the electronic ignition and the list goes on.
It would now make sense to me that most if not all of this is due to the vacuum leak/leaks I wasn't aware I had
Funny (to me anyway) That I found the nuts to the carb to heat shield/manifold were a little loose so I tightened them and thought ok that would make sense( possible vacuum leak).
I was right there at the problem the whole time but thought no way is it where it is.
My thinking here is correct?
 
#24 ·
As I have said many times: It's always a vacuum leak. Back when I had a normal GT with a 32/36, that I drove for 225K miles over 18 years, it was always a vacuum leak that would cause trouble. 1/8th of a turn to the 6 manifold bolts and good as new. If you have an old oem brake booster, toss it and get yourself a spiffy new Honda big brake booster.

Those darn vac leaks will have you chasing rabbits everywhere but where they are.
 
#25 ·
Yep on opels it’s always a vacuum leak (or a clogged idle jet for me).

I wonder why Opels are so darn sensitive to vacuum leaks. I’ve had nearly imperceptible vacuum leaks that couldn’t be found with carb cleaner cause havoc numerous times.
 
#26 ·
I was not thinking leaks at all, In fact when I hit that area with the cleaner and idle went way down I was still in disbelief
No that was a coincidence, until the third time and exact same response at the exact same place
I guess that's it's revenge for leaving outside ( covered) for a week while I straightened out the garage.
The irony is when I did bring it in to start on the ignition redo I didn't start it to bring it in I just pushed it in.
Had I started it I'm sure this would have been noticed almost right away.
 
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