Ported vs manifold vacuum advance solved!!!

diesel_lv

FBBO Gold Member
FBBO Gold Member
Local time
1:03 PM
Joined
Dec 17, 2018
Messages
1,530
Reaction score
1,825
Location
Arizona
So every always wants to get into the debate of ported vs manifold vacuum advance. I talked at length w the owner of 4 Seconds Flat. He made total sense. The ported is for cars that had some sort of computer control/smog control. Manifold is for those that do not. It is a lot to go into, but actually very simple. But for further proof, here is the definitive from a much respected source. Edelbrock!!!
Screenshot_20210215-120243_Chrome.jpg
 

Kern Dog

Life is full of turns. Build your car to handle.
FBBO Gold Member
Local time
12:03 PM
Joined
Apr 13, 2012
Messages
25,829
Reaction score
73,520
Location
Granite Bay CA
False. That guy is a weird dude.
Some people are so crazy, they are very good at convincing people that they are making sense.
Putting manifold vacuum to the distributor makes the engine lose timing as you crack the throttle and leads to unstable timing.
I emailed Don 7 years ago about spark timing and ignition and while he did respond, his ramblings were almost laughable.
 
Last edited:

hunt2elk

FBBO Gold Member
FBBO Gold Member
Local time
2:03 PM
Joined
Jul 15, 2009
Messages
8,850
Reaction score
8,449
Location
WI
False. That guy is a weird dude.
Some people are so crazy, they are very good at convincing people that they are making sense.
Putting manifold vacuum to the distributor makes the engine lose timing as you crack the throttle and leads to unstable timing.
I emailed Ron 7 years ago about spark timing and ignition and while he did respond, his ramblings were almost laughable.
That would be Don, and yes it is his way or the highway, that's for sure.
 

toolmanmike

Henchman #2
Staff member
FBBO Gold Member
Local time
2:03 PM
Joined
Aug 11, 2010
Messages
8,162
Reaction score
14,435
Location
Iowa
I'm with KD on this one and I don't know who the clown at Edelbrock is. Obviously they had some EPA B/S to contend with.

Your engine doesn't need any more that the initial timing while you are idling in the driveway or setting at a stop sign.

Edit:::::: Especially if you have a mild street car. If you have a big ol, cammed up hot rod, you might have to change things around and do something different.
 
Last edited:

diesel_lv

FBBO Gold Member
FBBO Gold Member
Local time
1:03 PM
Joined
Dec 17, 2018
Messages
1,530
Reaction score
1,825
Location
Arizona
False. That guy is a weird dude.
Some people are so crazy, they are very good at convincing people that they are making sense.
Putting manifold vacuum to the distributor makes the engine lose timing as you crack the throttle and leads to unstable timing.
I emailed Ron 7 years ago about spark timing and ignition and while he did respond, his ramblings were almost laughable.
Hmmmm, then I guess the "engineers" at Edelbrock are crazy also. I did not email him, rather a long in depth conversation about it. I was of the mind that it must be Ported also. After listening to his reasoning, not ramblings, it made total sense. And apparently Edelbrock, Holley engineers tend to agree.
 

threewood

Well-Known Member
Local time
12:03 PM
Joined
May 30, 2014
Messages
5,280
Reaction score
7,008
Location
Yuma, AZ
Gotta agree with the others. Ported is way easier to tune when you have a bunch of initial advance already dialed in.
 

Ron H

FBBO Gold Member
FBBO Gold Member
Local time
2:03 PM
Joined
Feb 29, 2016
Messages
6,881
Reaction score
7,594
Location
WI
Hmm - some nice information on the posts here to absorb as I try to find success with the advance/timing on my hepped poly.
 

RemCharger

Well-Known Member
Local time
2:03 PM
Joined
Apr 5, 2014
Messages
2,370
Reaction score
1,956
Location
Sask
I look to the engineers that made the Hemi . Maybe I stand alone.
 

747mopar

Well-Known Member
Local time
2:03 PM
Joined
Oct 30, 2012
Messages
13,516
Reaction score
18,269
Location
ohio
False. That guy is a weird dude.
Some people are so crazy, they are very good at convincing people that they are making sense.
Putting manifold vacuum to the distributor makes the engine lose timing as you crack the throttle and leads to unstable timing.
I emailed Ron 7 years ago about spark timing and ignition and while he did respond, his ramblings were almost laughable.
All I'll say is when it was time to buy a new carb for my Charger he could have one built to my specs for less than I could buy it from Summit for. He was very thorough with gathering the needed information and when the QF showed up at my house I've never been more impressed. I couldn't get it closer than it was.

When I was fighting with my timing issues (aftermarket distributor) he was very helpful, the Charger doesn't have any issues whatsoever under any given circumstances and it's hooked to manifold vacuum. I'm not going to say one way or the other only that mines running great.
 

AR67GTX

FBBO Gold Member
FBBO Gold Member
Local time
2:03 PM
Joined
Jan 28, 2012
Messages
3,012
Reaction score
2,080
Location
Arkansas
I agree with Edelbock. A proper manifold vacuum advance system will improve idle quality, help your engine run cooler, if it’s of any importance to you - improve gas mileage and doesn’t affect street performance in the least. Ported vacuum advance was a aberration of frustrated emissions engineers staggering around in a dark world.
 

oldkimmer

FBBO Gold Member
FBBO Gold Member
Local time
2:03 PM
Joined
Oct 18, 2008
Messages
1,977
Reaction score
917
Location
Kindersley,Saskatchewan, Canada
Manifold vacuum is for a Chevy. I have 1 friend that runs both. Says his car responds better. He tried to convince me but that didn’t happen. Kim
 

JimKueneman

FBBO Gold Member
FBBO Gold Member
Local time
12:03 PM
Joined
Mar 25, 2016
Messages
3,165
Reaction score
3,574
Location
Sonoita, Az
False. That guy is a weird dude.
Some people are so crazy, they are very good at convincing people that they are making sense.
Putting manifold vacuum to the distributor makes the engine lose timing as you crack the throttle and leads to unstable timing.
I emailed Don 7 years ago about spark timing and ignition and while he did respond, his ramblings were almost laughable.

This a video that Uncle Tony had the other day that left me puzzled for this reason.... Of course the timing drops back to initial when you accelerate with it hooked to direct, so what? Can someone explain why that matters? I have one car off ported and one car off direct. I don't see any difference in any normal driving conditions. The off manifold does idle cleaner as I would expect. I run about 12 degrees of initial.
 

diesel_lv

FBBO Gold Member
FBBO Gold Member
Local time
1:03 PM
Joined
Dec 17, 2018
Messages
1,530
Reaction score
1,825
Location
Arizona
Manifold vacuum is for a Chevy. I have 1 friend that runs both. Says his car responds better. He tried to convince me but that didn’t happen. Kim
Distributors are distributors, chevy, ford or Mopar. Mopar used "Lean Burn" chevy/ford some other form of electronic spark/timing control. "All" of those took vacuum from ported. Pre electronic carbs/spark control, took manifold vacuum.
 

turbine68rt

Turbine Bronze Member
FBBO Gold Member
Local time
3:03 PM
Joined
Dec 1, 2019
Messages
1,928
Reaction score
2,978
Location
SE PA
Distributors are distributors, chevy, ford or Mopar. Mopar used "Lean Burn" chevy/ford some other form of electronic spark/timing control. "All" of those took vacuum from ported. Pre electronic carbs/spark control, took manifold vacuum.
Not exactly. My original 4429S in my 68 has one source for distributor advance and that's ported. Nothing else.
 

diesel_lv

FBBO Gold Member
FBBO Gold Member
Local time
1:03 PM
Joined
Dec 17, 2018
Messages
1,530
Reaction score
1,825
Location
Arizona
This a video that Uncle Tony had the other day that left me puzzled for this reason.... Of course the timing drops back to initial when you accelerate with it hooked to direct, so what? Can someone explain why that matters? I have one car off ported and one car off direct. I don't see any difference in any normal driving conditions. The off manifold does idle cleaner as I would expect. I run about 12 degrees of initial.
Manifold vacuum allows you to run a little less initial mechanical timing and ramp up initial timing via vacuum for a better idle n heat control with a modified engine n crap gas. The key to it is adjusting the vacuum canister. Not all engine combos are the same so can't tell you where yours should be. As you come off idle and accelerate normally, vacuum will rise, ported or Manifold and the distributor will act the same either way. At higher rpms, highway cruising, you want a lot of timing. Vacuum will be very high and the same using either, thus pulling more vacuum advance and using mechanical/centrifugal advance. As soon as you stab the accelerator to pass, Manifold vacuum will drop instantly, reducing timing back down to max mechanical/centrifugal advance that engine makes without detonation. W ported, the venturi effect of the throttle ventures will momentarily increase vacuum at that full throttle burst. For a moment, you will advance timing a little more before vacuum falls back down. The cars that came with old fashioned electronic emissions controls would use a sensor and reduce the timing electronically during that hard initial full throttle. Manifold vacuum on a car with "no" electronic emissions control will never be wrong. Ported vacuum on a car w no electronic emissions control, depending on modifications, weather, driving conditions etc... "may" cause a detonation issue when going to a full throttle "stomp", not always.
 

R413

Well-Known Member
Local time
12:03 PM
Joined
Feb 4, 2019
Messages
3,091
Reaction score
6,247
Location
NW USA
Put down the crack pipe and leave it on ported vacuum.

why on earth would you want to retard timing as you foot goes to the floor? Because It will stop all the pinging because your engine has too much compression.
 

HawkRod

Formerly hsorman
FBBO Gold Member
Local time
3:03 PM
Joined
Aug 8, 2011
Messages
5,407
Reaction score
9,335
Location
Lansdale, PA
This debate has been raging on for quite awhile.

Both ported and manifold vacuum can be used with success. It is all about tuning the engine, mechanical, and vacuum advance to work well. Either can be used and both can run great or run like crap, depending on tuning.
 

HawkRod

Formerly hsorman
FBBO Gold Member
Local time
3:03 PM
Joined
Aug 8, 2011
Messages
5,407
Reaction score
9,335
Location
Lansdale, PA
why on earth would you want to retard timing as you foot goes to the floor?
When you stomp on the accelerator the accelerator pump dumps significant fuel into the engine. So it goes from a lean to a rich setting. Lean mixtures burn slow (need more timing), rich mixtures burn fast (need less timing).
 
Top