Car runs best with vaccum hoses unplugged/plugged.

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Big D

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I’ve been fine tuning the engine of my Duster but notice that the engine runs smoother at normal driving with the vacuum ports plugged and the distrib. Vaccum hose unplugged from the carb. and plugged. This is odd to me as I’ve understood the vacuum advance should help the driving. But with the vacuum advance plugged into the carb., it lurches at normal driving. Is this a symptom of too much initial?
The engine has a dual plane Mopar intake, Eddie 600 carb., Mopar purple 4452992AC cam, headers, 360, J heads with 2.02 intake with bowl work, headers with x pipes.
Thanks for any help. David
 
Have you tried hooking the vac advance to both timed and manifold vacuum on the carb? See what difference (if any) it makes. I'd suspect that maybe your vac canister is at fault though. If it runs better with just the mech advance then maybe your vac canister is not pulling the timing in like it should...could try replacing it. Relatively cheap thing to rule out...
 
You should be hooked up to the timed vacuum port. If you are getting vacuum out of the port then your idle is open too far and you need to re-tune the idle until it goes away. The other vacuum port should be plugged unless you need it for something else.
 
You never said if you have the Mopar ECU and distributor. I found out over the years that the Mopar electronic ignition distributors advance to fast for some cams. I would set your timing at full mechanical advance around 34-36 degrees at 2500-3000 RPMs and let the vacuum disconnected. Unless you want to play with the weights and springs in the distributor. Just what I found that works!
 
Sounds like your vacuum advance needs a new vacuum advance. Part throttle stumble is classic symptom of a leaking unit.
 
As my boss likes to say, "...give me some time to wrap my brain around what you just said." The ECU is stock but the distributor is a cheap O'reilly's unit (budget constraints). I did try plugging the vaccum line to both ports and with similar results, and I do believe that I have the idle screws out a bit too much and will try that fix too. The initial is around 19* as it seems to like it there, any more and it doesn't start. I pushed it there since I can't seem to get it to rev enough to get flow through those heads.

David
 
For some reason I have the same symptoms with my 360 with the same cam. I just run it with it plugged off. Runs good with it plugged off.
 
i tend to agree with 68 dodge. my 35 plymouth 340 4 speed 8/34 posi runs just fine with 35 degrees advance and vacuum lines plugged ,and who builds these cars with fuel economy in mind anyway?
 
mine is unhooked and plugged........runs on 87 octane and runs like a scalded dawg 72 340 in 73 duster steel crank 10.5 to 1's
 
Green 1 - I say "around" as my painted stripes on the Damper is only as close to 10* and 20* as I can paint them on. When I shoot it with the timing light, the second stripe is a hair over TDC. The vacuum on the distributor is getting close to 14 inches at idle, and when I time the car to work good at idle, it runs like crap at mid to full throttle and not want to rev. So when I set it advance and the vacuum disconnected and all ports and hoses plugged, it likes it. But I haven't gotten hard on it yet either so I don't know.
 
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