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#2451287 - 02/13/18 03:08 PM Where do you have your vacuum advance hooked up?
wesgtx440 Offline
enthusiast

Registered: 10/12/11
Posts: 283
Loc: Dayton, WA
Ported or manifold vacuum.

And if you feel like sharing. Why did you choose one vs the other?
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#2451333 - 02/13/18 04:18 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
BigBlockMopar Offline
master

Registered: 01/22/03
Posts: 3254
Loc: The Netherlands
I always prefer manifold.
Makes for a cooler running (idling) engine.
(And my MegaSquirt ECU wants it there smile )

On another car with a large(r) cam it's connected to ported, to prevent too much ignition advance fluctuations at idle.

IMO, ported is mostly more an emission thing because it helps for a more complete burn and hotter exhaust temps (at idle), although the factory used ported advance for as long as I know. Perhaps they installed it like that for a more steady/stable idle-quality.
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#2451343 - 02/13/18 04:26 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
BlueRacer69 Offline
mopar

Registered: 10/25/15
Posts: 404
Loc: Michigan
Ported. Or the port that is more to the passenger side of the carb.

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#2451359 - 02/13/18 04:48 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
scratchnfotraction Offline
I Live Here

Registered: 05/29/03
Posts: 15157
Loc: Florida
I followed the tips in the Book from Don at FBO I use one of the mech advance plates.

I set my base timing at 14* with the mech advance 18* - 32* total. 88-440 truck-whiplash cam 230/245 @.050 .518/.518 with the edelbrock RPM duel plane intake....running the holley 440 STREET dominator single plane intake I run the dist locked out on 0* timing set at 34* IIRC

I installed a new reman 318 1st of January. got a new stock replacement points dist. -ditched PCV for a evac system. -stock tbi roller cam/headers/q-jet.

set the timing at 10* adjusted carb A/F ratio with vac gauge for highest reading re-adjusting curb idle to 750 rpm.

hooked can up to full vac port on carb and that raised curb idle but cleaned up the idle and very smooth. re-adjusted to the 750 rpm.

nice smooth daily driver 16.5 mpg no ping anywhere in the rpm range and have dropped back to 87 pump gas..still no ping under load.

after reading the book I understand it a little better. at first with the big lumpy cam I had no power and heated up driving.

once I got the initial timing advance to where the engine wanted it and limited the mech advance it tuned right up and became street friendly.

got to get the spark ahead of the slow burning pump gas so it all burns in the cyl not the exhaust tubes. it had killer exhaust fumes that had me thinking it was way rich but it was really going lean. which in the book it said this is cause by it burning all the oxygen and leaving the unburned fuel trying to burn as it goes out the exhaust tubes thus making the engine temp rise and header tubes glow red with lots of smelly fumes.

so after 20 yrs of ported vac with mostly stock cams/dist/daily driver junk I have them on full vac and very happy with the results set up this way.

this is the first time I have had a 318 on 87 pump gas not PING! over 1/2 throttle from a stop light in traffic running a 195* thermostat.

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#2451365 - 02/13/18 05:21 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
BigBlockMopar Offline
master

Registered: 01/22/03
Posts: 3254
Loc: The Netherlands
FYI, my 'smogger' (mid '80s) 318 with its now digitally controlled ignition through a MegaSquirt ECU idles in 'Drive' with 24° ignition advance at 550-600rpm (Propane fueled).

At that number it makes the highest engine vacuum / lowest engine load, so generating the least amount heat.
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#2451392 - 02/13/18 06:33 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
BDW Offline
master

Registered: 05/12/05
Posts: 3449
Loc: Florida
I've always used ported, but had to switch to manifold when I converted to FiTech.
Their poor design didn't open the port until 2500rpm or higher.
Couldn't understand why my gas mileage went down after the conversion, then checked timing and found this is a known issue with them.

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#2451394 - 02/13/18 06:36 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
5thAve Offline
master

Registered: 01/19/03
Posts: 2711
Loc: Posts: 4034 - Register...
Ported here. Once you're off idle and on the throttle it's all the same it just keeps the timing down at idle.

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#2451404 - 02/13/18 06:50 PM Re: Where do you have your vacuum advance hooked up? [Re: 5thAve]
YO7_A66 Offline
master

Registered: 01/20/03
Posts: 5154
Loc: Indiana
I run the FBO distributor that is made for manifold vacuum. 30 degrees timing at idle as long as my idle vacuum is above 12". up
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340 (SL.P. 226/238@.050,270/288 dur,.538"/.528" w/Yella Terra 1.65 rockers, 9.7:1, 63cc Sidewinders (Bowl Ported),RPM intake, QF SS-750 Annular DP, MSD Street Fire Ign., & TTI's. 727/Dynamic 9.5" 3800, TF-2, & 3:91's

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#2451421 - 02/13/18 07:41 PM Re: Where do you have your vacuum advance hooked up? [Re: YO7_A66]
ahy Offline
master

Registered: 01/22/07
Posts: 7568
Loc: IN
A key is to make sure the distributor curb, carb and tuning specs are set up correctly for one or the other.

With a carb, I prefer ported vacuum. Keeping timing steady at idle helps stabilize idle. With manifold vacuum, vacuum and timing will jump around and harder to keep idle steady.

With FI and computer controlled timing, manifold vacuum. Set the timing curve as it needs to be. It can be vacuum in-sensitive at idle if desired. Or it can advance if idle speed drops to hold it steady (opposite what manifold vacuum does with a carb!).

Beyond that, manifold vacuum with a carb is a Chevy thing...

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#2451440 - 02/13/18 08:11 PM Re: Where do you have your vacuum advance hooked up? [Re: ahy]
hooziewhatsit Offline
master

Registered: 10/05/07
Posts: 2765
Loc: State of Jefferson
As long as your vacuum at idle in gear is higher than the vacuum needed to actuate the vac advance can, you'll have a steady idle. If your vacuum is too low and the can moves, then nothing will ever settle, and you'd be better off using ported vacuum.

I have mine hooked to manifold since I didn't want to take the distributor out to put in the limiting plate, and I wanted more timing at idle.
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#2451558 - 02/14/18 01:03 AM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
StevenMcGovern Offline
member

Registered: 02/14/18
Posts: 4
Loc: California
I will go with manifold vacuum as it has more advantage compared to the ported. Vacuums helps in stabilizing and steady timing. so I will prefer this.

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#2451568 - 02/14/18 02:58 AM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
RamblerMan Offline
master

Registered: 02/02/03
Posts: 4045
Loc: Castlegar, BC, Canada
All my junk is mostly stock, so they all run full manifold. Nice smooth idles, no overheating. Good gas mileage and smooth steady cruising.

I can see the guys with modified engines running ported and that's Ok too!
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#2451661 - 02/14/18 11:15 AM Re: Where do you have your vacuum advance hooked up? [Re: RamblerMan]
wesgtx440 Offline
enthusiast

Registered: 10/12/11
Posts: 283
Loc: Dayton, WA
All good stuff, thanks for all the input. So is there a difference in vacuum cans for ported vs manifold vacuum?? Say like a stock points dist. in '70 was hooked to ported vacuum correct? Are the newer distributors ie: mopar performance electronic ones, firecore, FBO, set up with a different advance unit that is designed to use manifold vacuum? or does it basically just boil down to how much vacuum your engine makes at idle and what it prefers timing wise?
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#2451662 - 02/14/18 11:24 AM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
hooziewhatsit Offline
master

Registered: 10/05/07
Posts: 2765
Loc: State of Jefferson
Originally Posted By wesgtx440
All good stuff, thanks for all the input. So is there a difference in vacuum cans for ported vs manifold vacuum?? Say like a stock points dist. in '70 was hooked to ported vacuum correct? Are the newer distributors ie: mopar performance electronic ones, firecore, FBO, set up with a different advance unit that is designed to use manifold vacuum? or does it basically just boil down to how much vacuum your engine makes at idle and what it prefers timing wise?


A vacuum can is a vacuum can. The only real differences are how much additional timing they provide, and what vacuum level they start to move at.

Most can have the vacuum level changed by using an allen wrench through the nipple to adjust the spring load on the diaphram. (A mity-vac comes in very useful for adjusting this)

To adjust the amount of advance a physical stop needs to be added to the arm.

Otherwise, it's based on your specific engine's idle vacuum, how much mechanical advance your distributor has, and how much total timing you want.
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If you ever find yourself in a fair fight, your tactics suck.

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#2451694 - 02/14/18 12:56 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
Cab_Burge Offline
I Win

Registered: 08/23/03
Posts: 30814
Loc: Bend,OR USA
Early GM, Chevys, used manifold vacuum until the early to mid 1960s, Mopar and Ford have always used ported vacuum advance that I'm aware of shruggy
The major difference in using manifold vacuum advance it is advanced most at idle and then drops off as the vacuum declines to the throttle, ported vacuum doesn't start to work until there is airflow past that port work scope


Edited by Cab_Burge (02/14/18 12:57 PM)
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#2451740 - 02/14/18 02:50 PM Re: Where do you have your vacuum advance hooked up? [Re: Cab_Burge]
wesgtx440 Offline
enthusiast

Registered: 10/12/11
Posts: 283
Loc: Dayton, WA
I guess the way I see it is if you have an engine that starts fine with the static advance setting and it idles good, then ported vacuum is the way to go. If you have an engine that idles good with more advance than allows for starting with out kickback, then manifold vacuum is the better one since you can retard the timing to allow it to start and then have it advance a set # of degrees with the vacuum to where it idles good. So at WOT, both manifold and ported vacuum signal will drop significantly and mechanical advance takes over at that point correct? Sorry for all the questions, just trying to educate myself on this subject beer
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68 Charger R/T 440 auto

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#2451743 - 02/14/18 03:03 PM Re: Where do you have your vacuum advance hooked up? [Re: scratchnfotraction]
Triggerfish Offline
top fuel

Registered: 07/25/05
Posts: 1872
Loc: Blairsden, CA
Originally Posted By scratchnfotraction
I followed the tips in the Book from Don at FBO I use one of the mech advance plates.

I set my base timing at 14* with the mech advance 18* - 32* total. 88-440 truck-whiplash cam 230/245 @.050 .518/.518 with the edelbrock RPM duel plane intake....running the holley 440 STREET dominator single plane intake I run the dist locked out on 0* timing set at 34* IIRC

I installed a new reman 318 1st of January. got a new stock replacement points dist. -ditched PCV for a evac system. -stock tbi roller cam/headers/q-jet.

set the timing at 10* adjusted carb A/F ratio with vac gauge for highest reading re-adjusting curb idle to 750 rpm.

hooked can up to full vac port on carb and that raised curb idle but cleaned up the idle and very smooth. re-adjusted to the 750 rpm.

nice smooth daily driver 16.5 mpg no ping anywhere in the rpm range and have dropped back to 87 pump gas..still no ping under load.

after reading the book I understand it a little better. at first with the big lumpy cam I had no power and heated up driving.

once I got the initial timing advance to where the engine wanted it and limited the mech advance it tuned right up and became street friendly.

got to get the spark ahead of the slow burning pump gas so it all burns in the cyl not the exhaust tubes. it had killer exhaust fumes that had me thinking it was way rich but it was really going lean. which in the book it said this is cause by it burning all the oxygen and leaving the unburned fuel trying to burn as it goes out the exhaust tubes thus making the engine temp rise and header tubes glow red with lots of smelly fumes.

so after 20 yrs of ported vac with mostly stock cams/dist/daily driver junk I have them on full vac and very happy with the results set up this way.

this is the first time I have had a 318 on 87 pump gas not PING! over 1/2 throttle from a stop light in traffic running a 195* thermostat.

I have the same FBO complete system (with coil) on my 64 Belvedere's orig stock 383. PIA to get it to stop pinging at WOT. Don says my carb is too lean & I must use manifold vacuum. I don't know if the orig afb has manifold vacuum so he says to find a port on the intake. I tried adjusting the can & still no help. Might ditch the system & go back to the dual point with pertronix dizzy.




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#2451745 - 02/14/18 03:09 PM Re: Where do you have your vacuum advance hooked up? [Re: Triggerfish]
wesgtx440 Offline
enthusiast

Registered: 10/12/11
Posts: 283
Loc: Dayton, WA
Did you previously run the dual point with no issues?
_________________________
68 Charger R/T 440 auto

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#2451751 - 02/14/18 03:18 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
hooziewhatsit Offline
master

Registered: 10/05/07
Posts: 2765
Loc: State of Jefferson
Originally Posted By wesgtx440
I guess the way I see it is if you have an engine that starts fine with the static advance setting and it idles good, then ported vacuum is the way to go. If you have an engine that idles good with more advance than allows for starting with out kickback, then manifold vacuum is the better one since you can retard the timing to allow it to start and then have it advance a set # of degrees with the vacuum to where it idles good. So at WOT, both manifold and ported vacuum signal will drop significantly and mechanical advance takes over at that point correct? Sorry for all the questions, just trying to educate myself on this subject beer


Pretty much up

Some cams like more timing at idle. This raises the idle speed, giving you enough room to close the throttle blades so it will idle on the idle circuit. Some don't.

To do this, you can:
use ported vacuum
crank up the initial timing, and limit the total timing.
But, like you mentioned, you might run into kickback issues.

Or,
use manifold vacuum
a more reasonable initial timing (maybe still limiting the total),
And have the base timing jump to initial + vac advance once it starts.

Once the throttle is open past idle, both manifold and ported are the same. At wot, both are near zero so there is no advance added. The only difference is at idle with the throttle closed.
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If you ever find yourself in a fair fight, your tactics suck.

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#2451754 - 02/14/18 03:22 PM Re: Where do you have your vacuum advance hooked up? [Re: wesgtx440]
hooziewhatsit Offline
master

Registered: 10/05/07
Posts: 2765
Loc: State of Jefferson
Quote:
PIA to get it to stop pinging at WOT.


At WOT, there's no vacuum advance, so I would look at the total timing, fuel, or both.
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If you ever find yourself in a fair fight, your tactics suck.

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