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arick793
Samba Member
Joined: October 18, 2013
Posts: 43
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 Posted: Thu May 26, 2016 6:28 pm Post subject: REALLY poor vacuum from my carb |
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| I'm helping my buddy with his motor, it's a 65 type 3 1500S block with 1641 cylinders. It ran really poorly over about 2500 RPM's, I discovered that the vacuum advance wasn't advancing. When I hooked up my vacuum pump, at about 10 mmhg the advance on the distributor was maxed out. The vac advance also held the vacuum fine, so I knew the assembly was good. I measured the vacuum coming from the vac port on the carburetor, and it was 0 at idle (which I expected), but with throttle it would only go up to about 3, and then go right back to zero. Any ideas why I'm getting almost no vacuum from the carb? I sprayed carb cleaner in the port with no improvement. This motor ran fine last year. It is running a pair of 32 PDSIT's with the original vac advance distributor. thanks! |
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Slow 1200
Samba Member
Joined: July 02, 2004
Posts: 2105
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| Posted: Fri May 27, 2016 3:40 am Post subject: Re: REALLY poor vacuum from my carb |
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| which carbs (engraved VW number) and which distributor are you using? |
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Matthew Tolbert
Samba Member
Joined: March 27, 2004
Posts: 706
Location: Georgia
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| Posted: Fri May 27, 2016 9:57 am Post subject: Re: REALLY poor vacuum from my carb |
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I had this same issue using stock 32pdsits and ZV JCU 4R3 distributor on my notch. below is the thread i started and what i discovered about the way the vacuum port is designed. I was unable to get it to work in its stock configuration. What i did was take the venturi out and block the upper hole behind the venturi and reassembled the carb. this has worked for many miles for me.
http://www.thesamba.com/vw/forum/viewtopic.php?t=435709
i had already blown it out thinking the same thing and still nothing. eric yeah that is what i was thinking is i should see something while reving, i just wasnt 100% sure. one of the above posters mentioned the port being right above the throttle plate. now on these carbs i know for 100% certainty that the passage for the port is very high up in the venturi. there is a fairly large(not huge) factory hole in the vent that matches up with a tiny hole in the carb body that goes out to the hose connection. i have a spare set of carbs that i am going to disassemble and see if there is another passage connected to that one going down to the throtle plate also. if so maybe i missed this when i cleaned them an it is blocked. it just seems odd that it would use 2 different sources for vacuum one high and one low, but who knows. thanks for the help so far.
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Matthew Tolbert
1958 ragtop
1961 doublecab
1965 Notchback S |
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