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SBL74
Samba Member
Joined: November 25, 2013
Posts: 125
Location: Treasure Island, FL
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 Posted: Sun Aug 22, 2021 12:13 pm Post subject: Help with Vacuum Hose Routing |
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This might could be posted elsewhere because my 1974 Thing has a transplanted engine. It is supposed to be a duel ported 1600. It has a 34PICT3 carb, and a DVDA distributor.
I notice that the PO connected the rear port of the distributor diaphragm housing to a port below the carb at an intake manifold port. The port that I think it is supposed to go to is on the left side of the carb near the air control screw. It is blocked off. The front port on the diaphragm housing of the distributor is connected to the rear-facing port, which I think is correct.
I have a flat spot just as the pedal is pressed which I want to troubleshoot but I want to make sure that these 2 vacuum hoses are correctly connected.
Steve |
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74 Thing
Samba Member
Joined: September 02, 2004
Posts: 7390
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| Posted: Sun Aug 22, 2021 1:24 pm Post subject: Re: HELP WITH VACUUM HOSE ROUTING |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50338
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| Posted: Sun Aug 22, 2021 5:08 pm Post subject: Re: Help with Vacuum Hose Routing |
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| You need to check that your retard can holds vacuum. If it does not, all hooking it up does is create a vacuum leak. The retard nipple is the larger sized one and points towards the distributor body. |
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michaelhiggins
Samba Member
Joined: January 09, 2020
Posts: 2
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| Posted: Sun Aug 22, 2021 6:29 pm Post subject: Re: Help with Vacuum Hose Routing |
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| Have any idea where I can get a new vacuum can or diaphragm for a DVDA? |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50338
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| Posted: Sun Aug 22, 2021 7:05 pm Post subject: Re: Help with Vacuum Hose Routing |
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| michaelhiggins wrote: |
| Have any idea where I can get a new vacuum can or diaphragm for a DVDA? |
They are hard to find, I got a NOS one for my 1.9L Vanagon through Ebay from some source in eastern Europe.
If you don't have to meet smog, you can easily run without one by doing the pop rivet mod to your throttle plate. |
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waxhead
Samba Member
Joined: January 19, 2004
Posts: 946
Location: Philly 'burbs
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| Posted: Thu Aug 26, 2021 6:51 pm Post subject: Re: Help with Vacuum Hose Routing |
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| Wildthings wrote: |
| If you don't have to meet smog, you can easily run without one by doing the pop rivet mod to your throttle plate. |
Could you please elaborate on this mod?
_________________
Mike B. |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50338
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| Posted: Thu Aug 26, 2021 7:18 pm Post subject: Re: Help with Vacuum Hose Routing |
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| waxhead wrote: |
| Wildthings wrote: |
| If you don't have to meet smog, you can easily run without one by doing the pop rivet mod to your throttle plate. |
Could you please elaborate on this mod? |
I can't say it better than it has already been said, so search "pop rivet" and "carb*" and see what you can find. |
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ncpi
Samba Member
Joined: May 10, 2020
Posts: 208
Location: TN & FL
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| Posted: Sat Aug 28, 2021 5:54 am Post subject: Re: Help with Vacuum Hose Routing |
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| SBL74 wrote: |
This might could be posted elsewhere because my 1974 Thing has a transplanted engine. It is supposed to be a duel ported 1600. It has a 34PICT3 carb, and a DVDA distributor.
I notice that the PO connected the rear port of the distributor diaphragm housing to a port below the carb at an intake manifold port. The port that I think it is supposed to go to is on the left side of the carb near the air control screw. It is blocked off. The front port on the diaphragm housing of the distributor is connected to the rear-facing port, which I think is correct.
I have a flat spot just as the pedal is pressed which I want to troubleshoot but I want to make sure that these 2 vacuum hoses are correctly connected.
Steve |
Steve,
I am a fellow TI resident, I PM'd you.
The folks here helped me with the correct connections... see my thread here:
https://www.thesamba.com/vw/forum/viewtopic.php?t=756646&highlight=
However, I found that my DVDA dizzy didn't hold vacuum at either side of the cannister. You can suck on either side, if it holds and the plate moves its probably OK to use. If the retard port (facing front of car) of the dizzy doesn't hold vacuum but the advance port works you can plug the Carb retard line and it will operate OK...but timing should be set to 5 deg BTDC at idle. If there are vacuum leaks, it will never idle/run correctly.
I sent my original dizzy to Bill at sparxworks and went to a 009 Dizzy to hold me over. Sparxworks did a great job, but its at my engine builder for installation on a newly rebuilt engine. |
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SBL74
Samba Member
Joined: November 25, 2013
Posts: 125
Location: Treasure Island, FL
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| Posted: Thu Sep 02, 2021 7:05 pm Post subject: Re: Help with Vacuum Hose Routing |
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Wildthings :
I believe that you are incorrect, and for the sake of others that might read this thread:
The larger port and hose comes off the BACK of the 34PICT3. And it goes to the retard port on the distributor can which is pointing to the FRONT of the car. |
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SBL74
Samba Member
Joined: November 25, 2013
Posts: 125
Location: Treasure Island, FL
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| Posted: Thu Sep 02, 2021 7:26 pm Post subject: Re: Help with Vacuum Hose Routing |
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Here is the picture of what I believe is the incorrect vac hose routing. Note the port under the carb, in the intake neck (or whatever it is called). There is more vacuum there at idle than when connected to the correct one, which is located on the carb body on the left side. So at 3500 RPM there was the correct advance, but, at idle it was not correct. So, this is why it ran and idled rough I assume.
It is better now, after I moved the hose to the correct port, fixed the choke (it was turned so far that it was open all the way), retimed it, adjusted mixture and idle.
But still, I have a little flat spot around 1500 RPM (essentially just off of idle). I have checked dwell and it is 26 on 8-cyl scale (=52 4-cyl), so I will let that be. With all hoses connected, idles at 5 deg, and at 3500 = 36 deg. Pulling the retard line and plugging the carb port changes the timing at idle but still have the flat spot.
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50338
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| Posted: Thu Sep 02, 2021 7:59 pm Post subject: Re: Help with Vacuum Hose Routing |
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With the hoses on the distributor can both removed and plugged you want to see 30°+/- BTDC at 3800+ rpms.
Verify that the accelerator pump is working and that the nozzle is in place and spraying when the throttle is pumped. |
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SBL74
Samba Member
Joined: November 25, 2013
Posts: 125
Location: Treasure Island, FL
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| Posted: Thu Sep 02, 2021 9:08 pm Post subject: Re: Help with Vacuum Hose Routing |
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And 36 deg with the hoses connected, which is what needs to be checked in the final analysis. I will check accelerator pump. If that was screwed up, wouldn't I have poor performance during aggressive acceleration through the gears?
In assume everyone agrees that the PO had the vac hose on the wrong port, right ? |
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ncpi
Samba Member
Joined: May 10, 2020
Posts: 208
Location: TN & FL
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| Posted: Fri Sep 03, 2021 5:19 am Post subject: Re: Help with Vacuum Hose Routing |
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| SBL74 wrote: |
And 36 deg with the hoses connected, which is what needs to be checked in the final analysis. I will check accelerator pump. If that was screwed up, wouldn't I have poor performance during aggressive acceleration through the gears?
In assume everyone agrees that the PO had the vac hose on the wrong port, right ? |
Reading your last post, it sounds like you have it correct now but without retard connected. Which is fine if you plug the rear port midway up the carb. BUT, don't forget step #4 below,
They were wrong as you suspected. Here's the process I would use (when I say front, I mean Front of car):
1. With the distributor cap and rotor removed, take each hose going to the distributor and suck on it watching the plate the points are mounted on. When you apply vacuum, you should be able to hold vacuum on each line and the plate should move slightly. If you can't hold vacuum, the canister is bad. The port to the dizzy rear (facing away from the dizzy itself) is Advance, it needs to hold vacuum. The port on the dizzy front (facing the dizzy) is Retard. If that leaks, its workable but you will set the timing different AND you can't hook it up to the carb.
If neither port holds vacuum, you need a new canister or the dizzy rebuilt. I have used Sparxworks, Bill is great, but there are a couple others too.
Assuming the Advance Port holds vacuum:
2. Connect the Advance dizzy port to the brass fitting on the side of the carb (in your pic its behind the spring).
If the Retard port holds vacuum:
3. Connect the Retard port on the dizzy to the brass tube midway up the carb pointing to the rear. You will set timing at Idle to 7.5 deg ATDC
If the Retard port leaks:
3. Disconnect the hose (set it aside for when you get a good DVDA dizzy) and plug the brass tube midway up the carb pointing to the rear. In this case you will set Idle timing to 5 deg BTDC
4. Plug the vacuum port on the intake manifold (where your vacuum hose was connected when you got the car).
Now you should be able to set Idle and Idle mixture (but set the point gap/ dwell first). Check total Advance, it should be about 32-36 deg at 3000. You can actually set that point and let the Idle advance fall where it may.
...Bill |
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SBL74
Samba Member
Joined: November 25, 2013
Posts: 125
Location: Treasure Island, FL
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| Posted: Fri Sep 03, 2021 10:05 pm Post subject: Re: Help with Vacuum Hose Routing |
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Thanks for confirmation that the vac lines were not connected correctly by the PO. I plugged that bottom one on the neck.
A few days ago I set dwell, timing, mixture, idle just as described above, with the hoses routed correctly. Total advance is about 36 deg BTDC, all hose connected. I might could edge that up a little, but maybe I do not need to.
The flat spot only occurs with rapid throttle opening. If I do it moderately or a slow opening, there is no flatness from idle to 3500 RPM. That might indicate, as suggested, that the accelerator pump might need some adjustment.
On a Thing, I can't stick my head over the carb, and I had trouble using a mirror to see if upon a quick punch of the throttle whether I gas a gas injection. So, I empirically turned the acell pump cam 1 notch CCW. This "may" have made it better. I need to drive it around. It seems to be different when testing in the garage vs under load. SO we will see.
I am a little irritated at the PO, who sold this on Bring a Trailer, saying it ran perfectly. The choke was not working, and with that vac routing, it barely could hold idle, and ran rough. Starting was quite difficult.
We will see tomorrow when I road test it. |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50338
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| Posted: Sat Sep 04, 2021 12:19 am Post subject: Re: Help with Vacuum Hose Routing |
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With all new parts from the factory having a lag coming off idle was a common problem, add ethanol and the carb will get a bit leaner still. Pretty much all my old carbureted rigs required going to a bit larger main jet to handle today's ethanol laced fuel.
If you haven't done so yet try adding some FI cleaner to your fuel tank and see what effect it has. Sometime it can work wonders while being cheap and easy to do. |
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