Giving Up On Vacuum Advance |
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Giving Up On Vacuum Advance |
Ansbacher |
Jan 18 2019, 06:22 PM
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#1
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Senior Member Group: Members Posts: 689 Joined: 4-July 14 From: Tampa Bay, Florida Member No.: 17,589 |
Car = '74 2.0 Liter, Dual Dellorto Carbs
For years I have been 'adequately" running an 009 mechanical only distributor. Finally took the pervasive advice out there to go with a vacuum advance dizzy from a 1.8L 914. Since only one of my Dellorto carbs had an existing vacuum port (ported type), I had to drill a port in my other one (no problem there). I used good quality anti-pulse valves in the lines and measured a maximum vacuum of 12 inches of mercury with partial throttle. Installed the 1.8 dizzy and set the timing, first without the vacuum lines attached. To satisfy my usual 30-32 degrees at 3500 RPM, the idle timing had to be at about 5-6 degrees (quite low for my setup which is happier at about 10 degrees. When I attached the vacuum lines my timing at 3500 RPM went sky high into the 40s. This seems way too high. Is this normal? Overall, I found the car to run better without the vacuum attached and the carbs plugged off. Am I doing something wrong here? I don't like the numbers I am getting. Everyone said this was the way to go with carbs, but I am not seeing results. Advice appreciated. Ansbacher |
72hardtop |
Jan 30 2019, 10:46 PM
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#2
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Member Group: Members Posts: 120 Joined: 11-September 13 From: Seattle/HB Ca./Fujieda-Japan Member No.: 16,378 Region Association: Pacific Northwest |
Corrected. Got ahead of myself there. Ported vac always with a distributor vac advance.
Distributor on mine is fairly new (Bosch SVDA). Used an LM-2 for jetting. |
tmessenger |
Jan 31 2019, 08:23 AM
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#3
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Member Group: Members Posts: 70 Joined: 6-December 18 From: Iowa Member No.: 22,707 Region Association: Upper MidWest |
Ported vacuum with vac port covered by the throttle plate at idle, connect in your vacuum gauge and check that you have no vac at idle.
Jake Raby likes to set up carbs at a/f 13:1 throughout so a bit different than the lean burn under light loads that John at aircooled.net aspires to. Note: this is a heavy read. The mother of all carb tuning threads (including timing theory) is on the samba here: https://www.thesamba.com/vw/forum/viewtopic...c74c2cf44f55a21 Good luck, Tim Corrected. Got ahead of myself there. Ported vac always with a distributor vac advance. Distributor on mine is fairly new (Bosch SVDA). Used an LM-2 for jetting. |
cgnj |
Jan 31 2019, 08:31 PM
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#4
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Senior Member Group: Members Posts: 623 Joined: 6-March 03 From: Medford, NJ Member No.: 403 Region Association: None |
Ported vacuum with vac port covered by the throttle plate at idle, connect in your vacuum gauge and check that you have no vac at idle. Jake Raby likes to set up carbs at a/f 13:1 throughout so a bit different than the lean burn under light loads that John at aircooled.net aspires to. Note: this is a heavy read. The mother of all carb tuning threads (including timing theory) is on the samba here: https://www.thesamba.com/vw/forum/viewtopic...c74c2cf44f55a21 Good luck, Tim Corrected. Got ahead of myself there. Ported vac always with a distributor vac advance. Distributor on mine is fairly new (Bosch SVDA). Used an LM-2 for jetting. ]Good link Tim, going to take a week to read it all (99 pages). I find myself drawn to the "we tune carbs/timing with the wrong approach". |
tmessenger |
Jan 31 2019, 10:06 PM
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#5
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Member Group: Members Posts: 70 Joined: 6-December 18 From: Iowa Member No.: 22,707 Region Association: Upper MidWest |
There are 11 years of knowledge in those 99 pages. I started with it about a week ago and I'm now on page 85. If your engine is mechanically healthy to start with you'll be way ahead of the curve when it comes time to solve carb tune and timing issues with this knowledge.
Do yourself a favor and copy and past the basic concepts into a word doc as you go and anything else that is relevant to you. I went through the first 20 pages and then the light went off and ding I had to backtracked to collect the gold into a condensed version for future reference. You're also going to need one of these or something like it if you don't already have one: https://www.14point7.com/products/sigma-lam...ntroller-free-2 Tim [quote name='72hardtop' post='2685043' date='Jan 30 2019, 10:46 PM'] Corrected. Got ahead of myself there. Ported vac always with a distributor vac advance. Distributor on mine is fairly new (Bosch SVDA). Used an LM-2 for jetting. [/quote] [/quote] ]Good link Tim, going to take a week to read it all (99 pages). I find myself drawn to the "we tune carbs/timing with the wrong approach". [/quote] |
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