Hello! Log in or Register   |  Help  |  Donate  |  Buy Shirts See all banner ads | Advertise on TheSamba.com  
TheSamba.com
 
TheSamba "makes" me investigate, now I'm confused!
Forum Index -> Bay Window Bus Share: Facebook Twitter
Reply to topic
Print View
Quick sort: Show newest posts on top | Show oldest posts on top View previous topic :: View next topic  
Author Message
PicklePickle
Samba Member


Joined: February 24, 2008
Posts: 933
Location: Gonzales, LA
PicklePickle is offline 

PostPosted: Wed Jun 02, 2010 5:22 pm    Post subject: TheSamba "makes" me investigate, now I'm confused! Reply with quote

So, a couple of nights ago, I'm laying in bed relaxing and reading through threads about timing on my new iPad (which I love for samba browsing btw!) and I come across this heated thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=364435&start=40.

It got me thinking, "am I burning my engine up?" I am paranoid about timing because it can often be a slow killer. I have read a lot trying to do my best to make sure I am doing everything I can to time Kombia (see sig) as well as possible given her OG DVDA dizzy and weber prog carb setup.

For the past couple of years, I always timed Kombia with the vacuum advance hose on and revved the engine to see what the highest number I would see on the timing scale is. I would set it to 30*. Which would fall to about 6* ATDC or so.

After being thoroughly confused with valid arguments by respectable guys both ways on that thread, I decided to try timing the engine to 30* without the vacuum advance connected. She fell to 8* BTDC at 800 RPMs idle. The overall running/performance result? Well, that's where it gets complicated.

If I LEAVE the vacuum hose off, the bus undoubtedly performs in a VASTLY superior manner. No hesitation upon applying gas, smoother speed up, generally smoother running at highway speeds and what appears to be a bit cooler running temps. All around a "good" feeling.

Here is where the REAL confusion sets in. As soon as I reconnect the "advance" hose to the can, the idle JUMPS (that's right JUMPS as in "up") to 20* BTDC.

I cannot make heads or tails of this. I can't believe that the bus should idle at 20* BTDC. I am so confused now, I don't even know if there is a "right" way anymore. So, I just left the hose off and plugged it. The bus seems to run better than it ever has. However, in danger of sparking another war of opinions on this subject, I still would like the opinions of some of the more experienced guys here. Is there something I am missing? Should I just leave the hose off and run the dizzy as a mech advance only given that the weber is NOT the original carb and obviously has quite a bit of advance even at idle?

I'm open to all views and hate mail! Laughing
_________________
"Aircooled VWs are like roaches in that if you let one in, they'll soon be nesting all around you in great numbers."
-------------------------------------------------
1970 Yellow Beetle aka "Melbourne"


Last edited by PicklePickle on Wed Jun 02, 2010 7:59 pm; edited 1 time in total
Back to top
View user's profile Send private message Gallery Classifieds Feedback
busdaddy
Samba Member


Joined: February 12, 2004
Posts: 51057
Location: Surrey B.C. Canada, but thinking of Ukraine
busdaddy is offline 

PostPosted: Wed Jun 02, 2010 5:34 pm    Post subject: Reply with quote

Sounds like you have the hose connected to the wrong port on the carb. Break out your vacuum gauge and see if it makes vacuum all the time or only upon sudden throttle opening or high RPM's.
_________________
Rust NEVER sleeps and stock never goes out of style.

Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!

Слава Україні!
Back to top
View user's profile Send private message Gallery Classifieds Feedback
PicklePickle
Samba Member


Joined: February 24, 2008
Posts: 933
Location: Gonzales, LA
PicklePickle is offline 

PostPosted: Wed Jun 02, 2010 5:42 pm    Post subject: Reply with quote

BusDaddy, I can feel vacuum at all times just by putting my tongue on the hose (gross I know, but it works). It increases a bit with the revs. There is only one port on this carb. I don't think it's the wrong port. I say that because, I've had several different VWs every one has come with this same carb model on it and every one had the dizzy vacuum advance hooked to the same location. So, could be coincidence, but it would seem a whole lot of people are hooking them up to the wrong port if thats the case. I intend to pick up a gauge soon, and will be taking readings, but in the meantime we'll just go on the fact that I KNOW that there seems to be vacuum present at all times (a little at idle, more during short revving and a little at constant revv).
_________________
"Aircooled VWs are like roaches in that if you let one in, they'll soon be nesting all around you in great numbers."
-------------------------------------------------
1970 Yellow Beetle aka "Melbourne"
Back to top
View user's profile Send private message Gallery Classifieds Feedback
busdaddy
Samba Member


Joined: February 12, 2004
Posts: 51057
Location: Surrey B.C. Canada, but thinking of Ukraine
busdaddy is offline 

PostPosted: Wed Jun 02, 2010 6:13 pm    Post subject: Reply with quote

Could still be a smog control port for the Pinto that carb's meant for, there should be no vacuum at all at idle.
_________________
Rust NEVER sleeps and stock never goes out of style.

Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!

Слава Україні!
Back to top
View user's profile Send private message Gallery Classifieds Feedback
SGKent Premium Member
Samba Member


Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
SGKent is offline 

PostPosted: Wed Jun 02, 2010 6:55 pm    Post subject: Reply with quote

on a carb there may be multiple ports. The advance side of the dist always goes to the port that is above the butterfly valve. When the carb is at idle the butterfly should be almost totally closed so there i no vacuum at that port. But if that port comes out below the butterfly it won't work.

Another cause can be that the screw that controls the butterfly closing is screwed in too far so the butterfly is open too much. If that happens on most carbs (you will have to check yours) unscrew the idle stop screw until you see clearance between the tip of the screw and the stop. Turn the screw in until it just bouches the stop then go about 1/8 to 1/4 turn further which barely opens the butterfly. Next time the carb is off you can set it with carbon paper. Then use the idle air speed screw to bring the idle speed back up and the mixture to trim it.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin
Back to top
View user's profile Send private message Send e-mail Gallery Classifieds Feedback
PicklePickle
Samba Member


Joined: February 24, 2008
Posts: 933
Location: Gonzales, LA
PicklePickle is offline 

PostPosted: Wed Jun 02, 2010 7:09 pm    Post subject: Reply with quote

This is my carb. The port is well below any butterfly. You can see it in the pic (sorry it is totally dark outside and I used a flashlight). The line is the small black hose coming out of the center of the base of the carb. So, I guess this means I should not be using that vacuum line at all?

Image may have been reduced in size. Click image to view fullscreen.


BTW, This is my dizzy ( 021 905 205 N):

Image may have been reduced in size. Click image to view fullscreen.

_________________
"Aircooled VWs are like roaches in that if you let one in, they'll soon be nesting all around you in great numbers."
-------------------------------------------------
1970 Yellow Beetle aka "Melbourne"
Back to top
View user's profile Send private message Gallery Classifieds Feedback
PicklePickle
Samba Member


Joined: February 24, 2008
Posts: 933
Location: Gonzales, LA
PicklePickle is offline 

PostPosted: Wed Jun 02, 2010 7:57 pm    Post subject: Reply with quote

Just found a great article written up on a Jeep forum ( http://www.jeepforum.com/forum/f8/weber-ported-vacuum-780290/ ) that explains that the port is indeed called the "advance" port in the Weber documentation. However, it maintains a vacuum at idle and is therefore not really suitable for most vacuum advance distributors. Interesting. Why would weber even call it that then. On the Jeep forum, their advice is to run any distributor with mechanical advance only unless another solution is implimented for proper vacuum advance.

I'm glad I researched this subject. Anyone out there with a Weber like this might want to think hard about disconnecting that "advance" port if they are currently running it connected. It does not perform optimally. If one DOES insist on using this advance port on the weber, it will throw the timing and acceleration out of whack at virtually all speeds except max running/driving speeds. I can atest to this. Kombia would run fine down the highway, but really hurt in the area of acceleration, deceleration, idle, and especially cold start until I retimed the motor without the vacuum advanced connected and LEFT the vacuum advance disconnected.

Hopefully, someone else is going to find this and it's really going to make their day. It sure has made mine. Kombia runs 100x better already. However, I'm considering either switching to an 009 or finding a way to get a better carb that will advance and retard the dizzy as I should.
_________________
"Aircooled VWs are like roaches in that if you let one in, they'll soon be nesting all around you in great numbers."
-------------------------------------------------
1970 Yellow Beetle aka "Melbourne"
Back to top
View user's profile Send private message Gallery Classifieds Feedback
Wildthings
Samba Member


Joined: March 13, 2005
Posts: 50257

Wildthings is offline 

PostPosted: Wed Jun 02, 2010 8:03 pm    Post subject: Reply with quote

I think you are actually hooked up to the correct nipple to get ported vacuum. Why you are getting vacuum all the time is another story. How fast is your idle? If for some reason your throttle butterfly is open significantly more at idle than it should be then the butterfly will be above the vacuum port and you will get vacuum at the port at idle.

If you take your carb off and turn it so you can look up the primary throat, you should be able to watch the throttle butterfly expose and cover a tiny drilling as you open and close the throttle. The tiny hole will be inline with the nipple where you have the hose attached. Your throttle butterfly should close far enough to cover the drilling.
Back to top
View user's profile Send private message Gallery Classifieds Feedback
KlassicBus79
Samba Member


Joined: January 10, 2010
Posts: 121
Location: Nova Scotia
KlassicBus79 is offline 

PostPosted: Wed Jun 02, 2010 9:07 pm    Post subject: Reply with quote

I'm no expert, but the DVDA dizzy needs an advance vacuum line and a retard vacuum line.

It seems the weber carb only has a vacuum advance port.

So you might want to block off the retard side of the DVDA, get a single port vacuum can for your dizzy or get a new SVDA Dizzy.
I think the timing with this should be 7.5 BTDC.

Just my opinion and it's what I would try.

Also I've read the 34 pict 3 carburetor has both advance and retard ports.
Back to top
View user's profile Send private message Gallery Classifieds Feedback
SGKent Premium Member
Samba Member


Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
SGKent is offline 

PostPosted: Wed Jun 02, 2010 9:33 pm    Post subject: Reply with quote

it is not where the port ends up outside the carb, it is as Wildthings explained, where it is inside the carb. When the butterfly is closed, most carbs in the last many years are set so that you can pull a small strip of carbon paper between the butterfly and wall without tearing the paper. That is open enough that the butterfly won't gouge into the wall each time it opens and closes. That port should be above the plate if it is ported. If it is below the plate then it gets vacuum all the time. Then you adjust the idle with an air bypass screw. If the carb doesn't have an air bypass screw then you may be having to open it too far at idle which is pulling a vacuum. If this is the case, that vacuum was probably intended to be used with a distributor from Ford that had a spring in the diaphrapm that needed more vacuum to overcome that what it gives at idle.

Regardless, until you get to the bottom of it, you are doing the right thing by blocking it off and running mechanical only.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin


Last edited by SGKent on Sat Jun 05, 2010 10:23 am; edited 1 time in total
Back to top
View user's profile Send private message Send e-mail Gallery Classifieds Feedback
KlassicBus79
Samba Member


Joined: January 10, 2010
Posts: 121
Location: Nova Scotia
KlassicBus79 is offline 

PostPosted: Sat Jun 05, 2010 9:54 am    Post subject: Reply with quote

The DVDA distributor is a pull pull arrangement.
I got this from Bentley
"NOTE----
On 1971 through 1975 engines with a double vacuum chamber (two hoses to the distributor), the throttle valve(s) must close adequately for accurate timing adjustments. To check the 1971 single-carburetor engine, disconnect the green (retard) hose from the distributor with the engine idling. The timing mark should move 15 mm to 18 mm (19/32 to 23/32 in.) to the left. If it does not, the throttle valve is not closing adequately and the carburetor must be adjusted."

Sounds like PicklesPickles timing is moving the proper amount, as stated by Bentley, when he hooks up his advance hose to the distributor, but without a vacuum retard line to counteract this advance the timing will stay at around 20 degrees BTDC.

You say it runs great at 8 degrees BTDC no vacuum so doing some math

current setting
8 degrees BTDC with vacuum connected (-12 degrees) = 20 degrees BTDC
initial setting
6 degrees ATDC with vacuum connected (-12 degrees) = 6 degrees BTDC

I'm pretty sure this is why it was working adequately with your initial setting of 6 degrees ATDC.
Back to top
View user's profile Send private message Gallery Classifieds Feedback
SGKent Premium Member
Samba Member


Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
SGKent is offline 

PostPosted: Sat Jun 05, 2010 10:27 am    Post subject: Reply with quote

Diet Pepsi King wrote:
The DVDA distributor is a pull pull arrangement.
I got this from Bentley
"NOTE----
On 1971 through 1975 engines with a double vacuum chamber (two hoses to the distributor), the throttle valve(s) must close adequately for accurate timing adjustments. To check the 1971 single-carburetor engine, disconnect the green (retard) hose from the distributor with the engine idling. The timing mark should move 15 mm to 18 mm (19/32 to 23/32 in.) to the left. If it does not, the throttle valve is not closing adequately and the carburetor must be adjusted."

Sounds like PicklesPickles timing is moving the proper amount, as stated by Bentley, when he hooks up his advance hose to the distributor, but without a vacuum retard line to counteract this advance the timing will stay at around 20 degrees BTDC.

You say it runs great at 8 degrees BTDC no vacuum so doing some math

current setting
8 degrees BTDC with vacuum connected (-12 degrees) = 20 degrees BTDC
initial setting
6 degrees ATDC with vacuum connected (-12 degrees) = 6 degrees BTDC

I'm pretty sure this is why it was working adequately with your initial setting of 6 degrees ATDC.


He doesn't have the stock arrangelment that was made to work with a DVDA. It appears his carb has only one port and it is questionable where it gets a vacuum from. The DVDA was made to work with specific vacuum configurations. Once that stock arrangement is changed a SVDA or mechanical advance dist is needed.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin
Back to top
View user's profile Send private message Send e-mail Gallery Classifieds Feedback
KlassicBus79
Samba Member


Joined: January 10, 2010
Posts: 121
Location: Nova Scotia
KlassicBus79 is offline 

PostPosted: Sat Jun 05, 2010 11:32 am    Post subject: Reply with quote

Thanks SGKent
That is exactly what I was trying to say.
Back to top
View user's profile Send private message Gallery Classifieds Feedback
Display posts from previous:   
Reply to topic    Forum Index -> Bay Window Bus All times are Mountain Standard Time/Pacific Daylight Savings Time
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

About | Help! | Advertise | Donate | Premium Membership | Privacy/Terms of Use | Contact Us | Site Map
Copyright © 1996-2023, Everett Barnes. All Rights Reserved.
Not affiliated with or sponsored by Volkswagen of America | Forum powered by phpBB
Links to eBay or other vendor sites may be affiliate links where the site receives compensation.