Author Topic: Distributor vacuum line to carb  (Read 846 times)

Offline 73440

  • Sr. Member
  • ****
  • Posts: 1620
Distributor vacuum line to carb
« on: May 24, 2017 - 08:59:44 am »
440 with 833 with Carter carb , 12* initial timing at idle , the distributor vacuum advance is capped at the distributor but noticed the vacuum line from the carb was not plugged, would that cause a bad burble right about at normal driving shift point , maybe 5/8 - 3/4 throttle ?  It does it in all gears? No tach to check.
I have plugged the carb vacuum line with a bolt and will see if anything has changed.
67 440
73 Barracuda w/ 68 440
65 Plymouth Fury III , I sold ,was my Nana's car till 92 yo.
51 Ford F1 239 Flathead, flipped , new cab , stolen
59 BelAir 283 4 door original patina
01 Chevy van 382,031 miles
06 Crown Vic Police Interceptor
75 HD Ironhead converted to RH shift
73 HD Ironhead
82 HD Ironhead
74 Norton 850
80 HD Shovelhead
80 Husqvarna WR 390




Offline burdar

  • Sr. Resident
  • ******
  • Posts: 5928
Re: Distributor vacuum line to carb
« Reply #1 on: May 24, 2017 - 09:32:50 am »
The vacuum advance canister on a Mopar is connected to a "timed" vacuum source.  This means that the vacuum port is "above" the throttle blades and doesn't see vacuum all the time.  With that port open(not capped) the engine should idle just fine.  As you open the throttle though, you'll have a big vacuum leak.

Online cudabob496

  • Sr. Resident
  • ******
  • Posts: 6895
Re: Distributor vacuum line to carb
« Reply #2 on: May 24, 2017 - 10:59:14 am »
would think any uncapped vacuum port on a carb would affect performance
72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.
Up to 4000 RPM, Warp Speed, Up to 5000, Rediculous Speed, Up to 6000 RPM, Ludicrous Speed!

1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"


Offline 73440

  • Sr. Member
  • ****
  • Posts: 1620
Re: Distributor vacuum line to carb
« Reply #3 on: May 24, 2017 - 12:13:33 pm »
Thank you all, I bought multiple caps the other day along with metering rods, jets , squirters, springs to make adjustments and will take her out for a drive and check.
Would be nice if the cap would take care of the stumble , if not , got the parts to adjust.
67 440
73 Barracuda w/ 68 440
65 Plymouth Fury III , I sold ,was my Nana's car till 92 yo.
51 Ford F1 239 Flathead, flipped , new cab , stolen
59 BelAir 283 4 door original patina
01 Chevy van 382,031 miles
06 Crown Vic Police Interceptor
75 HD Ironhead converted to RH shift
73 HD Ironhead
82 HD Ironhead
74 Norton 850
80 HD Shovelhead
80 Husqvarna WR 390

Offline Chryco Psycho

  • Administrator
  • C-C.com Guru
  • *****
  • Posts: 36618
  • 70 Challenger R/T SE 70 tube Chassis Cuda now sold
Re: Distributor vacuum line to carb
« Reply #4 on: May 24, 2017 - 03:38:27 pm »
the port on thecarb is ported vcuum so it is sourced from the venturi in the carb so it is above the throttle plates , so it should have zero effect

Challenger - You`ll wish You Hadn`t

Offline 73440

  • Sr. Member
  • ****
  • Posts: 1620
Re: Distributor vacuum line to carb
« Reply #5 on: May 24, 2017 - 07:55:25 pm »
Thanks, sounds like I'll be using some of the other parts to correct the stumble.
67 440
73 Barracuda w/ 68 440
65 Plymouth Fury III , I sold ,was my Nana's car till 92 yo.
51 Ford F1 239 Flathead, flipped , new cab , stolen
59 BelAir 283 4 door original patina
01 Chevy van 382,031 miles
06 Crown Vic Police Interceptor
75 HD Ironhead converted to RH shift
73 HD Ironhead
82 HD Ironhead
74 Norton 850
80 HD Shovelhead
80 Husqvarna WR 390

Offline jason340

  • Jr. Member
  • **
  • Posts: 196
Re: Distributor vacuum line to carb
« Reply #6 on: May 25, 2017 - 08:18:06 am »
Not to hijack but why does Mopar use a ported or timed vac port instead of a constant vac below the throttle blades? Just asking.

Offline brasil

  • Jr. Member
  • **
  • Posts: 255
Re: Distributor vacuum line to carb
« Reply #7 on: May 27, 2017 - 02:40:41 pm »
emmisson reasons.  Full vacuum lets the engine run cooler. because the timing @idle is way up... I use full vacuum in my 340 ...because of the cam and the compression ratio which is very high.. the full vacuum helps to get around 22 deg @ idle  but static timing is only 10 deg.   the vacuum canister pulls 12 deg. 
just after the engine starts
When you use timed vacuum the engine runs hotter...so NOX is lower..  but you cant get 22deg @ idle with a high compr. engine... the starter will not "love " this set up

Greetings Juergen


Online cudabob496

  • Sr. Resident
  • ******
  • Posts: 6895
Re: Distributor vacuum line to carb
« Reply #8 on: May 27, 2017 - 04:58:05 pm »
the port on thecarb is ported vcuum so it is sourced from the venturi in the carb so it is above the throttle plates , so it should have zero effect
whodda thunk?
72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.
Up to 4000 RPM, Warp Speed, Up to 5000, Rediculous Speed, Up to 6000 RPM, Ludicrous Speed!

1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

Offline 734406pk

  • Andy
  • Sr. Member
  • ****
  • Posts: 1683
Re: Distributor vacuum line to carb
« Reply #9 on: May 27, 2017 - 09:18:46 pm »
Quote:
emmisson reasons.

 :iagree: Once you change to a performance cam, everything changes! :thumbsup:
1973 Challenger 440 6 pack auto 3.91 rear
2012 Dodge Ram 3500 dually 6.7 Cummins Fleece EFI Live
1973 Challenger 318 2bbl auto 2.73 rear 22.5 mpg RIP
1970 Challenger TA 340 4bbl auto-Sold and sad
1999 Dodge Ram 3500 dually 5.9 Cummins Fleece tuned VGT-sold
1995 Kawasaki ZX1100E & still alive

Offline xtopfuel

  • Jr. Member
  • **
  • Posts: 257
Re: Distributor vacuum line to carb
« Reply #10 on: May 28, 2017 - 07:28:06 am »
I do believe you could get a stumble with 5/8 throttle as that port is open, as for idle not from a ported source

Offline jason340

  • Jr. Member
  • **
  • Posts: 196
Re: Distributor vacuum line to carb
« Reply #11 on: May 28, 2017 - 09:59:22 am »
My 440/6 stroker with cam was set up by the engine builder to the ported vac  but it idles better and seems to run better on the full vacuum port. I am going to leave it there unless you tell me otherwise.

Offline 73440

  • Sr. Member
  • ****
  • Posts: 1620
Re: Distributor vacuum line to carb
« Reply #12 on: May 28, 2017 - 10:05:01 am »
I am hoping to do a drive today to check what if anything has changed by capping the carb port.
I appreciate all the replies and help.
67 440
73 Barracuda w/ 68 440
65 Plymouth Fury III , I sold ,was my Nana's car till 92 yo.
51 Ford F1 239 Flathead, flipped , new cab , stolen
59 BelAir 283 4 door original patina
01 Chevy van 382,031 miles
06 Crown Vic Police Interceptor
75 HD Ironhead converted to RH shift
73 HD Ironhead
82 HD Ironhead
74 Norton 850
80 HD Shovelhead
80 Husqvarna WR 390

Offline 73440

  • Sr. Member
  • ****
  • Posts: 1620
Re: Distributor vacuum line to carb
« Reply #13 on: May 29, 2017 - 08:55:27 pm »
The carb port was capped today and still have the stumble , now it is time for carb adjust to eliminate the stumble.
67 440
73 Barracuda w/ 68 440
65 Plymouth Fury III , I sold ,was my Nana's car till 92 yo.
51 Ford F1 239 Flathead, flipped , new cab , stolen
59 BelAir 283 4 door original patina
01 Chevy van 382,031 miles
06 Crown Vic Police Interceptor
75 HD Ironhead converted to RH shift
73 HD Ironhead
82 HD Ironhead
74 Norton 850
80 HD Shovelhead
80 Husqvarna WR 390

Offline Chryco Psycho

  • Administrator
  • C-C.com Guru
  • *****
  • Posts: 36618
  • 70 Challenger R/T SE 70 tube Chassis Cuda now sold
Re: Distributor vacuum line to carb
« Reply #14 on: May 29, 2017 - 10:28:48 pm »
as anticipated
 check float level first if it is low that can cause a stumble .
 
 so here is the deal if you connect vacuum advance to manifold vacuum which is highest at idle or rolling down hill you get full advance with no power & it drops with rpm or power added so it work exactly opposite to the machanical advance in the dist so why would you ever want that unless you want static timing cross the powerband. With ported vacuum the advance runs the same way as the mechanical advance increasing lead time to get the fuel burnt at the peak moment as fuel dos not burn faster at higher RPM  so it needs more leadtime

Challenger - You`ll wish You Hadn`t