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jovanybg
Samba Member
Joined: January 02, 2016
Posts: 150
Location: Houston, TX
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 Posted: Tue Dec 04, 2018 6:55 pm Post subject: Re: Question about carb, dist, and vacuum can correlation |
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And update on the vacuum canister: It is perfectly good! I've measured it at 250 Hg for about 5 minutes each port and the gauge stayed the same for the whole time!
This brings me a mixed feeling, as I do not have to look for and buy another canister, but at the same time now I am lost at what causes all the problems with my timing!?!?!  
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1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor |
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wcfvw69 
Samba Purist
Joined: June 10, 2004
Posts: 13389
Location: Arizona
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| Posted: Tue Dec 04, 2018 7:51 pm Post subject: Re: Question about carb, dist, and vacuum can correlation |
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| jovanybg wrote: |
And update on the vacuum canister: It is perfectly good! I've measured it at 250 Hg for about 5 minutes each port and the gauge stayed the same for the whole time!
This brings me a mixed feeling, as I do not have to look for and buy another canister, but at the same time now I am lost at what causes all the problems with my timing!?!?! |
Re-explain how you're hooking up your timing light. Your putting the pick up clamp on the #1 spark plug wire, correct? If you're static timing it to say 7.5BTDC and it fires up, your retard side of the vacuum canister will pull the timing back to around 5° ATDC with the engine running. Set the timing with both vacuum hoses connected to 5° at idle of 850.
With the hoses removed from the vacuum canister and plugged so you don't have a vacuum leak, rev the engine and see where the mechanical advance is at 3800 RPM. It should be 28°-30° BTDC.[/quote]
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vamram
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Joined: March 08, 2012
Posts: 7304
Location: NOVA
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| Posted: Tue Dec 04, 2018 8:42 pm Post subject: Re: Question about carb, dist, and vacuum can correlation |
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Bill, looking at his engine picture, it's a semi-auto. I think the idle RPM is supposed to be 950...?
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ashman40
Samba Member
Joined: February 16, 2007
Posts: 15987
Location: North Florida, USA
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| Posted: Tue Dec 04, 2018 9:05 pm Post subject: Re: Question about carb, dist, and vacuum can correlation |
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| jovanybg wrote: |
| And update on the vacuum canister: It is perfectly good! I've measured it at 250 Hg for about 5 minutes each port and the gauge stayed the same for the whole time! |
This confirms your vacuum can is not leaking. Next you need to confirm each side is working as well.
Warm up the engine until the choke is OFF.
Remove and plug both vacuum hoses at the distributor end.
Pull out the strobe timing light and confirm your idle timing. Lets assume it is 7BTDC.
Connect the vacuum retard hose to the upper left port on the rear face of the carb. The timing should change. How much has it changed?
Disconnect and plug the vacuum retard hose.
Connect the vacuum advance to the same rear port. This should fully activate the vacuum advance. How much did the timing change?
Disconnect and plug both hoses once more.
Now using your vacuum hand pump with gauge test the vacuum can ports and now measure the amount of vacuum needed to reach full retard/advance.
Report back your finding.
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AshMan40
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'67 Beetle #1 {project car that never made it to the road  }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!} |
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jovanybg
Samba Member
Joined: January 02, 2016
Posts: 150
Location: Houston, TX
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| Posted: Tue Dec 04, 2018 9:39 pm Post subject: Re: Question about carb, dist, and vacuum can correlation |
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| wcfvw69 wrote: |
Re-explain how you're hooking up your timing light. Your putting the pick up clamp on the #1 spark plug wire, correct? If you're static timing it to say 7.5BTDC and it fires up, your retard side of the vacuum canister will pull the timing back to around 5° ATDC with the engine running. Set the timing with both vacuum hoses connected to 5° at idle of 850.
With the hoses removed from the vacuum canister and plugged so you don't have a vacuum leak, rev the engine and see where the mechanical advance is at 3800 RPM. It should be 28°-30° BTDC. |
Correct, I'm clamping it to spark plug #1 wire. I have also a small arrow on the clamp that should point towards the spark plug. I am statically timing it to exactly TDC. I have to mention I have my carburetor adjustment screws (volume and idle) set to 2.5 turns open from fully closed positions. I am starting the engine and it runs at very high rpm - about 2500rpm untill it warms up gradually and the rpm go to 2200 rpm all the way down to 1500-1600 when the engine is fully warmed up.
Next I do is firing up the stroboscope and I can see the notch at 30-35BTDC.
If I pull on the accelerator, rpms go up, but the notch stays at exact same 30-35 BTDC (under the stroboscope light (USL)).
Then I am trying to time the engine to 5ATDC, but as soon as I turn the distributor and the notch closes up on about 10-15BTDC the engine stumbles and dies.
If I am quick enough and am able to turn the distributor the other way before the engine dies it picks up again and runs at high rpm with the notch USL again at 30-35 BTDC.
I know these 1600rpms are too high, but until I have the engine timed correctly at 5ATDC I cannot play with carburetor adjustments to bring the rpms to the normal 950 rpm at idle (I have an Autostick).
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1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor |
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jovanybg
Samba Member
Joined: January 02, 2016
Posts: 150
Location: Houston, TX
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| Posted: Tue Dec 04, 2018 9:57 pm Post subject: Re: Question about carb, dist, and vacuum can correlation |
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| ashman40 wrote: |
This confirms your vacuum can is not leaking. Next you need to confirm each side is working as well.
Warm up the engine until the choke is OFF.
Remove and plug both vacuum hoses at the distributor end.
Pull out the strobe timing light and confirm your idle timing. Lets assume it is 7BTDC.
Connect the vacuum retard hose to the upper left port on the rear face of the carb. The timing should change. How much has it changed?
Disconnect and plug the vacuum retard hose.
Connect the vacuum advance to the same rear port. This should fully activate the vacuum advance. How much did the timing change?
Disconnect and plug both hoses once more.
Now using your vacuum hand pump with gauge test the vacuum can ports and now measure the amount of vacuum needed to reach full retard/advance.
Report back your finding. |
I could do all of that, but should I even bother when I have my timing mark under the stroboscope with the engine warmed up at 30-35 BTDC and the rpms at about 1600? And I cannot bring the mark to where it supposed to be - at 5 ATDC
What should I try first to adjust from this situation?
Last weekend I felt like whatever I do first, I am wrong!!!!
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1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor |
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jovanybg
Samba Member
Joined: January 02, 2016
Posts: 150
Location: Houston, TX
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| Posted: Wed Dec 05, 2018 6:46 pm Post subject: Re: Question about carb, dist, and vacuum can correlation |
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Unless I get a better advice in here I will be bring my distributor for testing this weekend, together with my spare distributor and depending on the results will decide which one to try and use!
After I know I have a good working distributor I will try the timing again.
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1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor |
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bnam
Samba Member
Joined: July 02, 2006
Posts: 2936
Location: El Dorado Hills CA/ Bangalore, India
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| Posted: Thu Dec 06, 2018 4:16 am Post subject: Re: Question about carb, dist, and vacuum can correlation |
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| jovanybg wrote: |
| wcfvw69 wrote: |
Re-explain how you're hooking up your timing light. Your putting the pick up clamp on the #1 spark plug wire, correct? If you're static timing it to say 7.5BTDC and it fires up, your retard side of the vacuum canister will pull the timing back to around 5° ATDC with the engine running. Set the timing with both vacuum hoses connected to 5° at idle of 850.
With the hoses removed from the vacuum canister and plugged so you don't have a vacuum leak, rev the engine and see where the mechanical advance is at 3800 RPM. It should be 28°-30° BTDC. |
Correct, I'm clamping it to spark plug #1 wire. I have also a small arrow on the clamp that should point towards the spark plug. I am statically timing it to exactly TDC. I have to mention I have my carburetor adjustment screws (volume and idle) set to 2.5 turns open from fully closed positions. I am starting the engine and it runs at very high rpm - about 2500rpm untill it warms up gradually and the rpm go to 2200 rpm all the way down to 1500-1600 when the engine is fully warmed up.
Next I do is firing up the stroboscope and I can see the notch at 30-35BTDC.
If I pull on the accelerator, rpms go up, but the notch stays at exact same 30-35 BTDC (under the stroboscope light (USL)).
Then I am trying to time the engine to 5ATDC, but as soon as I turn the distributor and the notch closes up on about 10-15BTDC the engine stumbles and dies.
If I am quick enough and am able to turn the distributor the other way before the engine dies it picks up again and runs at high rpm with the notch USL again at 30-35 BTDC.
I know these 1600rpms are too high, but until I have the engine timed correctly at 5ATDC I cannot play with carburetor adjustments to bring the rpms to the normal 950 rpm at idle (I have an Autostick). |
If you running 1600rpm at idle with both screws at 2,5turns out and other carb adjustments correct, then I'd look for a vacuum leak first and get the rpms down. At 1600 centrifugal advance has kicked in. At about 1600 rpm, about 15 deg is centrigfugal advance is possible. And your initial position may be off by 15deg resulting in 30deg of total advance.
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ashman40
Samba Member
Joined: February 16, 2007
Posts: 15987
Location: North Florida, USA
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| Posted: Thu Dec 06, 2018 6:32 am Post subject: Re: Question about carb, dist, and vacuum can correlation |
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| jovanybg wrote: |
| I am statically timing it to exactly TDC. I have to mention I have my carburetor adjustment screws (volume and idle) set to 2.5 turns open from fully closed positions. I am starting the engine and it runs at very high rpm - about 2500rpm untill it warms up gradually and the rpm go to 2200 rpm all the way down to 1500-1600 when the engine is fully warmed up. |
These initial settings sounds normal just to get the engine running. Personally, I'd go with static timing of 5~7BTDC but TDC will work.
Until you can get the engine idling below 1000rpm leave the vacuum hoses disconnected and plugged. Work just with static timing + mechanical advance + carb settings for now.
Something is wrong if the idle rpms cannot drop below 1500rpm once the choke turns OFF. How have you adjusted the screw at the end of the throttle arm? It should be set so it is 1/4~1/2-turn IN when on the lowest level of the fast idle cam. This is just enough to keep the throttle plates off the inside of the carb throat. You do not want it open more than this or it will expose the progression holes which start to flow fuel.
You need to fix the idle issue BEFORE you can set idle timing.
| jovanybg wrote: |
Next I do is firing up the stroboscope and I can see the notch at 30-35BTDC.
If I pull on the accelerator, rpms go up, but the notch stays at exact same 30-35 BTDC (under the stroboscope light (USL)). |
If you statically set timing to TDC it should NOT be showing 30-35BTDC at only 1600rpm. I would expect a small additional advance due to the mechanical advance, maybe 10BTDC? Getting full mechanical advance at only 1600rpm suggests a problem with the mechanical advance. Maybe a broken advance spring?
| jovanybg wrote: |
Then I am trying to time the engine to 5ATDC, but as soon as I turn the distributor and the notch closes up on about 10-15BTDC the engine stumbles and dies.
If I am quick enough and am able to turn the distributor the other way before the engine dies it picks up again and runs at high rpm with the notch USL again at 30-35 BTDC.
I know these 1600rpms are too high, but until I have the engine timed correctly at 5ATDC I cannot play with carburetor adjustments to bring the rpms to the normal 950 rpm at idle (I have an Autostick). |
If you cannot get the engine idling below 1000rpm don't bother trying to set it to 5ATDC. With the engine idling at 1600rpm what happens when you screw the bypass screw IN? This should reduce the idle air-fuel flow and the idle rpms should go down. As long as the carb is warmed up and choke is OFF you should be able to adjust the carb idle so low the engine will stall/die. If you don't have this kind of control, check the throttle arm screw adjustment. This could be holding your throttle plate open too much.
Some of what you have described suggests that the distributor is over advancing at low rpms. When the engine is idling at 1600rpm and you twist the distributor to retard the timing does the idle go down? This would suggest that the high idle is due to the extra timing advance and not due to the carb settings. If the timing drops and there is no change to the engine rpms it is your carb that needs adjustment.
Try this...
with the engine warmed up, choke OFF, vacuum hoses disconnected and plugged and idling around 1500rpm... rotate the distributor to bring the timing down to around 10BTDC. Do the idle rpms drop?
Turn off the engine. Using your test lamp confirm where the static timing is now? If the distributor is working normally the static timing should be only slightly different (dropped to TDC~5BTDC).
If the static timing has dropped to around 10ATDC it means you are getting the full range of mechanical advance but it kicks in too early. Remove the distributor cap and grasp the rotor. Twist CW. You should feel tension as the advance springs expand. Release the rotor and it should SNAP back into place. If there is no spring tension or it doesn't return to the at rest point your mechanical advance is bad.
Double check you throttle arm screw adjustment.
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AshMan40
---------------------------
'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!} |
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JonRich55
Samba Member
Joined: April 06, 2018
Posts: 378
Location: Leesburg, VA USA
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| Posted: Thu Dec 06, 2018 8:26 am Post subject: Re: Question about carb, dist, and vacuum can correlation |
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I have seen the Carb/Dist for VW charts and the associated Vacuum A/D specs. Is there a chart that shows the centrifugal advance curve for the various Distribs?
knowing how fast the weights spin out and the timing curve of mechanical part should help understand the way the engine performs. When you add the Vacuum components, they complete the picture. |
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ashman40
Samba Member
Joined: February 16, 2007
Posts: 15987
Location: North Florida, USA
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| Posted: Thu Dec 06, 2018 9:37 am Post subject: Re: Question about carb, dist, and vacuum can correlation |
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| JonRich55 wrote: |
| I have seen the Carb/Dist for VW charts and the associated Vacuum A/D specs. Is there a chart that shows the centrifugal advance curve for the various Distribs? |
The Old Volks home listing of distributor part#s/specs had mechanical advance numbers for some models.
Type2.com has replicated the listing here:
http://www.type2.com/~keen/ignition.html
Find your distributor model# and see if there is a spec.
For example, here is what it says for the '71 autostick distributor:
| Quote: |
Distributor: VW 113-905-205AH, Bosch 0231 167 070 > 043-905-205D, 0231 176 033
<...>
Timing Set At:: 5deg ATDC @ 800-950rpm w/strobe, vacuum hose(s) connected.
Advance/Retard Range: Vacuum: 2-5deg Adv, 11-13deg Ret; Centrifugal: 12-16deg @ 2200rpm, 22-25deg @ 3800rpm |
With the vacuum hoses disconnected and plugged so they are not affecting your readings, if you are getting more than 16deg of advance over your static timing @2200rpm... your distributor would be over advancing.
Note that this model distributor produces a max of 25deg of mechanical/centrifugal advance. This means if your static timed the distributor to TDC the mechanical advance should ONLY be advancing the timing to 25BTDC.
This is a key point... the practice of setting timing at high rpms is to make sure the mechanical advance is not pushing you into a dangerous situation at high rpms. 32BTDC is the max safe limit of initial timing + mechanical advance. This can only be measured with the vacuum hoses disconnected. Check the distributor advance mechanisms SEPARATELY. Use vacuum pumps and gauges to measure the vacuum advance and vacuum retard systems. Use engine rpms to measure mechanical advance by itself.
There is no spec for adjusting ignition timing with vacuum hoses connected at any rpm above idle.
I'm wondering if your 30-35BTDC measurements were with the vacuum advance hose connected? Static timing of TDC + 25deg of mechanical advance + 5deg of vacuum advance = 30BTDC.
What was the timing reading with the vacuum hoses disconnected and plugged?
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AshMan40
---------------------------
'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!} |
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jovanybg
Samba Member
Joined: January 02, 2016
Posts: 150
Location: Houston, TX
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| Posted: Thu Dec 06, 2018 10:16 am Post subject: Re: Question about carb, dist, and vacuum can correlation |
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| Quote: |
These initial settings sounds normal just to get the engine running. Personally, I'd go with static timing of 5~7BTDC but TDC will work.
Until you can get the engine idling below 1000rpm leave the vacuum hoses disconnected and plugged. Work just with static timing + mechanical advance + carb settings for now. |
When I did the static timing I left all the hoses plugged.
Next time should I plug both vacuum hoses and plug the ports of the carburetor when static timing the engine?
| Quote: |
Something is wrong if the idle rpms cannot drop below 1500rpm once the choke turns OFF. How have you adjusted the screw at the end of the throttle arm? It should be set so it is 1/4~1/2-turn IN when on the lowest level of the fast idle cam. This is just enough to keep the throttle plates off the inside of the carb throat. You do not want it open more than this or it will expose the progression holes which start to flow fuel.
|
I will take a picture of the fast idle adjustment screw, but once the engine is warm it is at the lowest step and the throttle is fully open.
| Quote: |
| You need to fix the idle issue BEFORE you can set idle timing. |
Ok. That will be my plan. Warming up the engine, making sure the throttle plate is completely open and then try to down the idle to about 950rpm. even so the timing mark USL show 30 BTDC. I will follow that with turning the distributor towards the 5 ATDC USL and I am sure the idle rpm will drop even more. I will increase the rpm with the carburetor adjustment screw and keep on going the same way, turning and adjusting the rpm untill at 5 ATDC.
| Quote: |
| If you statically set timing to TDC it should NOT be showing 30-35BTDC at only 1600rpm. I would expect a small additional advance due to the mechanical advance, maybe 10BTDC? Getting full mechanical advance at only 1600rpm suggests a problem with the mechanical advance. Maybe a broken advance spring? |
I will double check functionality of the distributor at a fellow Samba member this weekend on his Sun machine.
| Quote: |
| If you cannot get the engine idling below 1000rpm don't bother trying to set it to 5ATDC. With the engine idling at 1600rpm what happens when you screw the bypass screw IN? |
I haven't try that, but that will be my aproach on Saturday when I can play with the adjustments.
| Quote: |
| This should reduce the idle air-fuel flow and the idle rpms should go down. As long as the carb is warmed up and choke is OFF you should be able to adjust the carb idle so low the engine will stall/die. If you don't have this kind of control, check the throttle arm screw adjustment. This could be holding your throttle plate open too much. |
How can I check if the trottle plate is open too much? The stepped cam has an oval cut-off for the pin and when fully warmed engine the pin is at the end of the cut-off and the trottle plate cannot move any more open. It is pretty vertical at that moment.
| Quote: |
| Some of what you have described suggests that the distributor is over advancing at low rpms. When the engine is idling at 1600rpm and you twist the distributor to retard the timing does the idle go down? This would suggest that the high idle is due to the extra timing advance and not due to the carb settings. |
If I remember correctly the rpm do go down, but I was not measuring rpm at that moment, but holding the stroboscope to bring the mark close to 5 ATDC. The rps actually did go down with turning the distributor and that is when the engine scrambled and died.
| Quote: |
| If the timing drops and there is no change to the engine rpms it is your carb that needs adjustment. |
No. That is not the case.
| Quote: |
Try this...
with the engine warmed up, choke OFF, vacuum hoses disconnected and plugged and idling around 1500rpm... |
It is probably on the stupid questions side, but do I need to plug the hoses and the ports at the carburetor?
| Quote: |
Turn off the engine. Using your test lamp confirm where the static timing is now? If the distributor is working normally the static timing should be only slightly different (dropped to TDC~5BTDC).
If the static timing has dropped to around 10ATDC it means you are getting the full range of mechanical advance but it kicks in too early.rotate the distributor to bring the timing down to around 10BTDC. Do the idle rpms drop? |
I will try that on Saturday and will report.
| Quote: |
| Remove the distributor cap and grasp the rotor. Twist CW. You should feel tension as the advance springs expand. Release the rotor and it should SNAP back into place. If there is no spring tension or it doesn't return to the at rest point your mechanical advance is bad. |
I've tried that and the spring functions very well. It snaps the rotor back in place after I turned the rotor by hand!
| Quote: |
| Double check you throttle arm screw adjustment. |
That is one of the unclear adjustments! I am warming the engine untill the throttle plate is vertical and then adjusted the screw to touch the very last step. Then I've pulled the accelerator and the adjustment is gone! I can see about 1/16" of space in between the adjustment bolt and the last step of the cam. Another pull of the accelerator and the distance is probably 1/32". Another pull - it goes to 1/32", to 1/16" again and so on. Do I need to adjust my accelerator cable attachment to the carburetor lever to certain specs?!, as I remember I've played with this how much tension should I have on the accelerator cable ( I've slid the end of the cable more towards the rear of the car and then tightened the small holding bolt). Thinking back it all went downhill from there with my adjustments of the timing?!?! Strange....
_________________
1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor |
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JonRich55
Samba Member
Joined: April 06, 2018
Posts: 378
Location: Leesburg, VA USA
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| Posted: Thu Dec 06, 2018 11:45 am Post subject: Re: Question about carb, dist, and vacuum can correlation |
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Ashman - Thanks for the link to the complete Dist configurations. The example you chose was the reason I was asking, as the Autostick in particular only has a 2-5deg advance through the vacuum, and I was wondering if it's all-in max was less than the 35deg at 3000rpms that everyone says to check.
Autosticks have a totally different driving pattern that the 4spd, they stay underload and have a very gradual increase in RPMs and speed if driven with the gear in 1 from a stop through 2 at speed (bypassing L) They also have a higher idle speed and most likely have more of their advance engaged at a stop.
What I find interesting is that for the 4spd of 73, they show 6-12deg adv @1500rpms, while the Autostick is shown at 12-16deg @2200rpm range. It would have been nice if they had shown the mechanical advance at the same relative RPMs. since 12 deg is both the top @1500 and the low @2200, I would think the curve is much slower on the Autostick AH. |
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ashman40
Samba Member
Joined: February 16, 2007
Posts: 15987
Location: North Florida, USA
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| Posted: Thu Dec 06, 2018 1:15 pm Post subject: Re: Question about carb, dist, and vacuum can correlation |
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| jovanybg wrote: |
When I did the static timing I left all the hoses plugged.
Next time should I plug both vacuum hoses and plug the ports of the carburetor when static timing the engine? |
Static timing is done with the engine OFF. So it doesn't matter if the vacuum hoses are connected or not. The engine is not creating vacuum.
| jovanybg wrote: |
| I will take a picture of the fast idle adjustment screw, but once the engine is warm it is at the lowest step and the throttle is fully open. |
Just to be clear... by "lowest step" you mean the lowest level of the cam, right? I've gotten into a misunderstanding with someone before because they considered the "last raised step" before the lowest level as the last "step"... the lowest level not being a "step" (when you reach the bottom of the stairs do you refer to the ground as the bottom/last "step"?... that was the argument)
Post a pic so we can agree on what is the last step, but all you will be able to show is that the screw is resting on that step. You need to confirm that it is just barely touching the step and turned in 1/4-turn more. From a pic I doubt we will be able to confirm that it isn't 1/10-turn in or 3-turns in. It all looks the same.
Did you actually mean, "...engine is warm it is at the lowest step and the choke butterfly is fully open"? When the engine is warmed up the throttle plate is fully CLOSED. See pic below.
| jovanybg wrote: |
| Ok. That will be my plan. Warming up the engine, making sure the throttle plate is completely open and then try to down the idle to about 950rpm. even so the timing mark USL show 30 BTDC. I will follow that with turning the distributor towards the 5 ATDC USL and I am sure the idle rpm will drop even more. I will increase the rpm with the carburetor adjustment screw and keep on going the same way, turning and adjusting the rpm untill at 5 ATDC. |
You seem to be focusing on the idle timing. You need to reach IDLE rpms FIRST then worry about the timing at idle.
If you set static timing to TDC and disconnect vacuum hoses... but at idle rpms see more advance than TDC it means the mechanical advance is kicking in when it shouldn't.
Below 1000rpm the mechanical advance should NOT be adding any timing advance.
With the the vacuum retard hose disconnected and plugged the vacuum retard should NOT be removing timing advance.
With the vacuum advance hose disconnected and plugged the vacuum advance should NOT be adding timing advance.
By setting timing at idle rpms you eliminate the mechanical advance as a variable. By disconnecting and plugging vacuum hoses you eliminate vacuum advance/retard as a variable. All that is left is the static/idle timing which you set to TDC. With all other variables eliminated, static timing and idle timing are usually exactly the same.
If you cannot get the rpms below 1000rpm you can't tell how much of the timing USL is from the static timing and how much is from mechanical advance. This is why you need to get the rpms down to 800-900rpms BEFORE you try to set timing.
| jovanybg wrote: |
| I will double check functionality of the distributor at a fellow Samba member this weekend on his Sun machine. |
This should be able to confirm if your distributor is working properly.
| jovanybg wrote: |
| How can I check if the trottle plate is open too much? The stepped cam has an oval cut-off for the pin and when fully warmed engine the pin is at the end of the cut-off and the trottle plate cannot move any more open. It is pretty vertical at that moment. |
Ok, clearly you are talking about the choke butterfly plate and NOT the throttle plate. Here's a pic from gulamodo:
The choke butterfly is the large plate at the top of the carb that CLOSES when the choke is ON and OPENS (vertical) when the choke is OFF.
The weight of the stepped cam rotates the choke butterfly OPEN. The spring tension of the choke coil in the right side round housing rotates the butterfly CLOSED when cold. The choke butterfly isn't dependent on the steps of the cam, only on the rotation of the shaft cause by the offset weight of the cam.
The throttle is the plate at the BOTTOM of the carb. With the carb installed you can only see it by looking down into the carb throat. When you pull on the throttle arm it OPENS/CLOSES. The screw at the top end of the throttle arm controls how far the throttle plate is opened. The screw should always rest on the cam. At the different steps of the cam the throttle is opened different amounts. It is open wider when colder to raise the engine rpms and prevent the engine from stalling.
The proper adjustment of the throttle plate is 1/4 to 1/2-turn IN from just touching the lowest level of the cam. If the screw is NOT touching the cam then the throttle plate is resting on the inside of the carb throat and could get wedged in place or scratch the smooth inner surface. Turn the screw in too far and it opens the throttle plate too much and exposes not only the idle holes but the progression holes.
| jovanybg wrote: |
| If I remember correctly the rpm do go down, but I was not measuring rpm at that moment, but holding the stroboscope to bring the mark close to 5 ATDC. The rps actually did go down with turning the distributor and that is when the engine scrambled and died. |
You can ONLY set the 5ATDC "idle timing" AT IDLE.
Above idle there are too many other variable in play that are affecting your measurements.
Analogy: You are basically trying to tie your shoe laces while actively jogging down the road... and then wondering why you can't make the bow nice and even. And you are wondering if maybe you bought the wrong size shoe laces. Shoe laces are tied ONLY while stationary. 
| jovanybg wrote: |
| Quote: |
Try this...
with the engine warmed up, choke OFF, vacuum hoses disconnected and plugged and idling around 1500rpm... |
It is probably on the stupid questions side, but do I need to plug the hoses and the ports at the carburetor? |
You only really need to disconnect the vacuum hoses at the distributor end and plug the open hose ends with a screw or golf tees. The distributor canister doesn't create any vacuum. If you disconnect the hose at the carb end, you MUST cap the open ports on the carb. The carb DOES make vacuum and an open port is a vacuum leak.
| jovanybg wrote: |
| Quote: |
| Remove the distributor cap and grasp the rotor. Twist CW. You should feel tension as the advance springs expand. Release the rotor and it should SNAP back into place. If there is no spring tension or it doesn't return to the at rest point your mechanical advance is bad. |
I've tried that and the spring functions very well. It snaps the rotor back in place after I turned the rotor by hand! |
Great! This suggests the mechanical advance is working. Your weekend test on the Sun machine should confirm this.
| jovanybg wrote: |
| That is one of the unclear adjustments! I am warming the engine untill the throttle plate is vertical and then adjusted the screw to touch the very last step. Then I've pulled the accelerator and the adjustment is gone! I can see about 1/16" of space in between the adjustment bolt and the last step of the cam. Another pull of the accelerator and the distance is probably 1/32". Another pull - it goes to 1/32", to 1/16" again and so on. Do I need to adjust my accelerator cable attachment to the carburetor lever to certain specs?!, as I remember I've played with this how much tension should I have on the accelerator cable ( I've slid the end of the cable more towards the rear of the car and then tightened the small holding bolt). Thinking back it all went downhill from there with my adjustments of the timing?!?! Strange.... |
If the screw at the end of the throttle are is NOT touching the cam there are usually only two reasons.....
1) Most likely, the screw is not turned IN far enough. The cam may be loose and there could be some play. Keep turning in the screw until there is no more play and the screw is resting on the cam, then turn in 1/4-turn MORE. The screw should now be resting firmly on the cam holding the edge of the throttle plate off the walls of the carb throat.
Unlike other carbs where this fast idle cam screw is used to control the rpms while the choke is ON... since this screw primarily controls the opening of the throttle plate when fully warmed up it is NOT used to "adjust" the rpms when the engine is cold. You just live with whatever those higher rpms are until the choke turns OFF.
2) There is too much resistance in the throttle cable (or linkage) or too little tension from the return spring (see pic above). The spring should pull the throttle plate closed until the screw prevents any further movement. If you must, disconnect the throttle cable completely from the carb. Then the only thing the return spring has to deal with is the throttle linkage on the carb.
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jovanybg
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Location: Houston, TX
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| Posted: Thu Dec 06, 2018 3:44 pm Post subject: Re: Question about carb, dist, and vacuum can correlation |
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Thank you Ashman!
I will try to get the rpms below 1000 at idle and only then worry about the timing!
I think my throttle arm return spring is either too weak, or I haven't adjusted the tension of the throttle cable correctly, but as you suggested I'll disconnect the cable all together and try the adjustments that way!
These were the advices I was looking for! Type of given (routine) for you, but priceless for me! Thanks again!!!!
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1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor |
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vamram
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| Posted: Thu Dec 06, 2018 3:46 pm Post subject: Re: Question about carb, dist, and vacuum can correlation |
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Jovanybg, you could just disconnect the throttle cable at the carb while you work on your idle adjustments. Don't even worry about connecting and installing it until you've done that.
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wcfvw69
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| Posted: Thu Dec 06, 2018 7:17 pm Post subject: Re: Question about carb, dist, and vacuum can correlation |
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The 113905205AH has the same specs as the 211905205Q distributor. One is for the heavy bay bus and the other is for the slow moving autostick. They will start to mechanical advance around 1100 RPM.
Van made a great suggestion. Remove the throttle cable. Make sure the carb is adjusted correctly. Lots of good video's on Youtube. Get it idling down at 900 rpm.
Unhook both vacuum lines at the distributor and plug them. At idle of 900 RPM, the distributor is just a switch firing each cylinder. It won't mechanically advance unless it's jacked up internally. Set the idle timing to 7.5 BTDC. Rev the engine to 3800 RPM at set the max mechanical advance timing to 28° then let it return to idle. Hook the vacuum hoses back up and see where the idle timing is at. The retard on a 853 DVDA vacuum canister is around 12° so it will pull the timing back to around 5° ATDC.
You will have to fiddle with the RPM adjustments on the carb as you do this procedure.
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jovanybg
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Joined: January 02, 2016
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Location: Houston, TX
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| Posted: Fri Dec 07, 2018 9:46 am Post subject: Re: Question about carb, dist, and vacuum can correlation |
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| wcfvw69 wrote: |
The 113905205AH has the same specs as the 211905205Q distributor. One is for the heavy bay bus and the other is for the slow moving autostick. They will start to mechanical advance around 1100 RPM.
Van made a great suggestion. Remove the throttle cable. Make sure the carb is adjusted correctly. Lots of good video's on Youtube. Get it idling down at 900 rpm.
Unhook both vacuum lines at the distributor and plug them. At idle of 900 RPM, the distributor is just a switch firing each cylinder. It won't mechanically advance unless it's jacked up internally. Set the idle timing to 7.5 BTDC. Rev the engine to 3800 RPM at set the max mechanical advance timing to 28° then let it return to idle. Hook the vacuum hoses back up and see where the idle timing is at. The retard on a 853 DVDA vacuum canister is around 12° so it will pull the timing back to around 5° ATDC.
You will have to fiddle with the RPM adjustments on the carb as you do this procedure. |
That is my plan for Saturday! Thanks for the simple description - it is exactly what I was looking for! Thank you and Ashman for the sequence of adjustments I need to do! Now everything makes sense! Before that I was lost trying to jump from idle adjustment to rpm adjustment to throttle cable adjustment! I was missing the relation between those! Thanks again! After I have some results tomorrow, I'll post them in here!
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1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor |
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jovanybg
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Posts: 150
Location: Houston, TX
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| Posted: Sun Dec 16, 2018 8:01 am Post subject: Re: Question about carb, dist, and vacuum can correlation |
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I've spent 2 hours yesterday figuring out the trouble after confirming on the Sun machine both distributors I have are good .
I haven't been able to do any adjustment using the one that still have the points in - after static timing at 5BTDC I was not able to even start the car. These tries were made with both vacuum hoses removed and plugged. I've slightly turned the distributor to both positions where the static light lights up and lights off, as in the middle position, but still the car started and in 1-2 seconds died.
After switching to the distributor with the Pertronix ignition I was able to start the car and warm it up (with both vacuum hoses ATTACHED). It run with high rpm and once fully warmed up I found I need to adjust the fast idle screw. After doing so the car stalled. I've then detached the throttle cable and added 1/2 turn to the volume (idle) screw at the carburetor. Tried to start the car, but could not with no ability to push on the gas. Attached the cable then at the very end of the cable, so I would have some control over it. Started the car, but in order to keep it running needed to constantly have my foot on the gas. After adding a few more half-turns of the volume(idle) screw at the carby and turning slightly the distributor I was able to keep the car running, but idling at about 1200-1300rpm and not running smooth. USL I observed it running at about 20BTDC. Turned the distributor a little to about 10BTDC, adjusted again the volume(idle) and after few more adjustments, including the mixture(small) screw at the carby was able to time the car at 5ATDC and bring the rpm to about 950. The advance at about 3000rpm is steady at 30BTDC and I can say the engine is running very smooth!
What my mistake from the very beginning was that I assumed the carby adjustment is pretty close to 2.5 CCW turns from fully closed on both adjustment screws and didn't play with idle screw a lot. Now with the correct timing and adjusted the big, idle (volume) screw is out about 5-6 turns and the small (mixture) screw is out about 3.5 turns.
Also my fast idle screw was out of adjustment because I think the throttle cable was too tight.
Overall a great experience thanks to all of your advice!
And another proof that there are a lot of working together parts and adjustments that need to be synchronized in order for the engine to work nice and smooth!
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1971 Karmann Ghia Autostick
Solex 34 Pict 3
DVDA Bosch 113 905 205 AH distributor |
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