Question on vaccum at idle and warm restarts....

[Volfandt]

Looking for opinions...
I purchased a new Chinese 34PICT-3 last yr and I've noticed from day one that I had vaccum out of the distributor vaccum port at idle. The port I'm talking about is the port on the left side of the carb. I also have vaccum out of the rear facing port also but I'm running an SVDA so I keep it capped off. Vaccum for the dist is from the side port.

From what I've read here and there, the consensus is that there shouldn't be vaccum present at that port until the throttle is opened, i.e. rpm is increased over idle and more air is moving through the venturi. At idle I can remove the vaccum line and the rpm will drop 100 rpm or so.

I haven't pulled the carb to see exactly where the vaccum port hole is located in the venturi but my older Bocar branded 34PICT-3 has the drilling about even w/the closed throttle plate.

I trying to improve my warm restarts and think I may be getting alittle to advanced at low rpm.

The engine runs great. Timing is at 30 degress BTDC at 3k rpm w/the vaccum line disconnected. Electronic ignition. Theres no pinging under load or when going up hill etc. Cold starts are immediate and all around performance seems great.

I recently changed my main jet from 127.5 to 132.5 and altho my low range power has improved noticably, warm restarts and vaccum at idle remains the same.

Am I chasing my tail or do others have vaccum at idle?

Dave
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1972 Karmann Ghia, the Dragon slayer....
1949 Chevrolet 3100 1/2 ton pkup.
1966 Wheel Horse 856 (gear)
1966 Wheel Horse 876 (hydro)

[toddb_67]

I don't have an SVDA and I'm running a 009 so this is just my .02
Have you tried disconnecting the vacuum prior to warm starting the engine to see if it makes a difference? That would essentially be like starting with no vacuum right?
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1970 Pastel White Westfalia
1969 Chrome Blue Karmann Ghia

[JerryB]

Looking for opinions...
I purchased a new Chinese 34PICT-3 last yr and I've noticed from day one that I had vaccum out of the distributor vaccum port at idle. The port I'm talking about is the port on the left side of the carb..

Im not up on that particular carb ...but a carb is a carb......
If that is a true ported vacuum port you will have no or very little vacuum. Possibly you have too much throttle blade angle (uncovering the hole in the carb bore too much). Try a lower idle.

I also have vaccum out of the rear facing port also but I'm running an SVDA so I keep it capped off. Vaccum for the dist is from the side port.

That would be the manifold vacuum take off. It operates the opposite of a ported spark port. At idle the vac. signal is high and at higher rpm and a load the vac signal will be a smaller number.

From what I've read here and there, the consensus is that there shouldn't be vaccum present at that port until the throttle is opened, i.e. rpm is increased over idle and more air is moving through the venturi. At idle I can remove the vaccum line and the rpm will drop 100 rpm or so.

Your right....little or none vac signal.The drop of RPM at idle when the line is disconnected, validated too hi an idle OR the ported spark slot/hole in the carb venturi is too high in the carb bore or too much throttle blade angle (opening).

I haven't pulled the carb to see exactly where the vaccum port hole is located in the venturi but my older Bocar branded 34PICT-3 has the drilling about even w/the closed throttle plate.

Maybe compare the two?

I trying to improve my warm restarts and think I may be getting alittle to advanced at low rpm.

If the starter labors when key on/start then U have too much initial lead or a stuck advance inside the dist. This might happen in conjuction with a very hot engine on a restart after shutting off for a minute or so. IF you have good cranking speed but long cranks B4 a fire, I would look to percolaton of the gas (on a hot restart) or a high float level.

The engine runs great. Timing is at 30 degress BTDC at 3k rpm w/the vaccum line disconnected. Electronic ignition. Theres no pinging under load or when going up hill etc. Cold starts are immediate and all around performance seems great.

I recently changed my main jet from 127.5 to 132.5 and altho my low range power has improved noticably, warm restarts and vaccum at idle remains the same.

Am I chasing my tail or do others have vaccum at idle?

[scotty timmerman]

the throttle plate is probably open too far. if u adjust the idle with the throttle plate stop screw this will open the throttle and make it so there is vacuum at idle. there should be a idle adjust plug on the side of the carb.
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71 ghia coupe
71 type 3 fastback auto
71 type 3 fastback manual
73 super beetle

[Volfandt]

Thanks for the reply's, great answers.

Some more info:

The idle is set to 900 rpm. Anythjing below 900 causes excessive vibration so 900 is this engines sweet spot.

The fast idle adjustment isn't making any contact w/the throttle step cam after it's warmed up. I don't recall the clearance spec but it's not touching the cam hense it's not effecting idle speed or throttle plate angle.

The throttle plate appears to be fully closed from the outside at idle. I can adjust the mixture screw (large screw) to idle the engine all the way down to cutting off.

There is a hole in the throttle plate that I assume is there to allow "some" air to pass through when the throttle plate is fully closed and I'm now wondering if it's enough to cause the amount of vaccum I'm getting?

Basically what I'm requesting is for anyone out there in Samba land w/a 34PICT-3 carb and SVDA to disconnect & plug the vaccum line to their SVDA dist with the engine warm and see if the rpm drops.

I played around w/it alittle last night and the 132.5 jet I installed is makinmg the engine run too rich. I'll be swapping back down to a 130 shortly.
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1972 Karmann Ghia, the Dragon slayer....
1949 Chevrolet 3100 1/2 ton pkup.
1966 Wheel Horse 856 (gear)
1966 Wheel Horse 876 (hydro)

[Altema]

I have the original German carb on mine, and there is zero vaccum at idle with the choke off. If your fast idle screw is not contacting the cam and you have vaccum at the advance port, then your carb is defective.

By the way, your fast idle screw should be touching the cam when the engine is warmed up. To set it, adjust the screw so it just touches the cam, then turn the screw in 1/4 turn. Then you have to adjust your bypass and volume screws. There are other methods, but this one is per the Bently manual. Hot idle speed is 850rpm, plus or minus 50rpm, so 900 is fine.

Paul

[Volfandt]

Thnaks Paul. I suspect I have a defective carb.
The fast idle screw has approx .006" clearance from the step cam once the engine is warmed up to normal operating temp.
This is how it came out of the box. Like you said, looks like it's off per the Bentley.
But for my purposes at this time, I'm leaving it as it as I want the throttle plate fully closed at idle.

I got some time to play around w/the carb alittle last night.
I swapped the main jet to a 130 and started at ground zero to adj it.
At one point I had the idle at 800 rpm, big screw out 2 turns and little volume screw out 2.5 turns. Get this, I could unplug the idle cutoff solenoid and the engine wouldn't die! The solenoid does work too!

So I hooked up my old Craftsman diagnostic tach/Dwell meter, made sure the timing was still spot on and proceeded to adj the carb per the meter as opposed to by ear. This is good because my hearing ain't what it used to be
I set the idle to 900 rpm and had to turn the small volume screw out an additional 1/2 turn (makeing 3 full turns) and after tweaking the large mixture screw I had the engine purring w/that new 130 main jet.
At this setting when I disconnected and plugged the vaccum advance the rpm dropped approx 100 rpm. Fast idle screw was not touching the step cam so for all practical purposes the throttle plate appeared fully closed....

I get about the same amount of vaccum out of the rear facing retard vaccum port at idle and for a simple test I swapped the dist's vaccum advance between the 2 and my meter indicated almost the exact same rpm, hense I'm assumeing the same amount of vaccum.
So it looks like the manufacturer has drilled into the incorrect location within the venturi (according to Pauls test).

At this point the only adverse condition I see w/this is hard starting when warmed up. When I say hard starting I'm not meaning theres a problem w/the starter as it turns the engine just as fast warm/hot as it does when cold.
The hard starting I'm seeing is that at times I have to fully depress the throttle pedal to get it to start and at other times I have to slowly depress the pedal when cranking to get it to start. There doesn't seem to be any rhyme or reason.
I tried warm restart w/the vaccum disconnected to see if that had any effect and it didn't seem to change a thing.
In any case, it's running very strong, gets nearly 30 mpg and will run upto 85 mph on the interstate so it'll do for now.
Course I can see duals in the future
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1972 Karmann Ghia, the Dragon slayer....
1949 Chevrolet 3100 1/2 ton pkup.
1966 Wheel Horse 856 (gear)
1966 Wheel Horse 876 (hydro)

[Altema]

I think you have it pretty much nailed down, and you're right about the port opening being in the wrong place in the carb throat. The advance port opening should be immediately above the edge of the throttle plate, so that it picks up vacuum as soon as the throttle opens. Your retard port opening should be just below the throttle plate so it receives full vacuum at idle, then goes away as the throttle opens. This is the type of problem we run into when companies make copies without understanding the functions. "Oh, this one has a hole on the left, lets put one in ours too! There, that looks about right..."


Take care my friend, and happy cruising!

[Volfandt]

Beware the cheap repro 34PICT-3.
Warm restarts weren't my only problem. Lately the idle has gotten irratic and the engine started backfireing through the exhaust on rapid deceleration. Last night I even put the std 1.275 main jet that came w/the carb back in and it still had all the above problems.

I pulled the carb this morning and verifed the suspected defect in the vaccum port location and discoverd a more serious issue. My 1 yr & 1 month old repro carb with no name, that was just out of warranty, had a nice clean looking float that was 1/2 full of gas!!!! Yesser, found the root of my carb problems.. I'm guessing it finally got heavy enough to where it wouldn't close the float valve which inturn caused fuel to dribble into the carb while it idled (irratic idle) and it continued to dribble fuel into the carb after shutdown (basically flooding the engine out which made it hard starting). My local supplier doesn't carry carb parts so thank goodness the float in my old Bocar was still servicable....
While I had the carb off I verfied that the vaccum port was infact drilled too low in the throat and the throttle plate couldn't cover it when fully closed.
So I cleaned it all up, blew out all the passages, put it back together and bench adjusted the carb to Bentley specs and I'm back up and running like a sewing machine again, oh and with the 1.325 main jet too I really like the engines performance w/that jet in.
The warm restart problem is history too.

For a test drive I took her on a nice 40 mile run on the interstate to Sevierville and visited the spring "Circle Your Wagens" VW show & swap meet and she did great. Oddly there were no Ghia's in the show and only 2 in the for sale section. Based on some of the bugs I saw in the show, I should have entered my Ghia, being the only one I figure I could have won something

Anyways, this bares repeating, Beware The Cheap repro 34PICT-3..
Get a good rebuilt German or one that atleast has a name on it...
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1972 Karmann Ghia, the Dragon slayer....
1949 Chevrolet 3100 1/2 ton pkup.
1966 Wheel Horse 856 (gear)
1966 Wheel Horse 876 (hydro)

[DrakeB]

[Volfandt]

No dimmer switch. I did pickup a few other goodies tho. Got a right side mirror, one of those tools for the oil filler nut and a degree cranksaft pulley that I hope will cure a small leak. I was hopeing to find a good deal on a header & quietpack muffler, seems glass packs and stingers are the rage I heard a 1600DP w/dual glass packs and it sounded pretty good. They weren't as loud as I thouight they'd be.
I looked real hard and long at a new aluminum block that was bored for 94's and had all the mod's done, I'm itching to build a stroker but really need to get on w/the body work.
Your right about the lack of vendors.
I talked to the guy w/the 2 Ghia's and gave them a quick look over, he wanted $8k for the green 71 which he said was all original and $6k for the 72. Both looked OK for the brief once over I gave them.
Hows your project coming along?
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1972 Karmann Ghia, the Dragon slayer....
1949 Chevrolet 3100 1/2 ton pkup.
1966 Wheel Horse 856 (gear)
1966 Wheel Horse 876 (hydro)

[DrakeB]