Ported vs manifold vacuum advance solved!!!

[khryslerkid]

Next time someone starts a thread on this subject without doing a search for it first, we need to copy and paste Rons reply. (Better not be a next time!)

 

[Ceedawg]

Next time someone starts a thread on this subject without doing a search for it first, we need to copy and paste Rons reply. (Better not be a next time!)

This is not the only thing that’s gotten all wrong in today’s world of ‘into net’.

 

[R/T Boy 67]

Ceedawg. I agree with you that ported vacuum was not an emissions device. See post 15.The other post that you disagreed with mentions the PVC valve was the first emissions device, which was introduced after ported vacuum. What do you disagree with?

 

[Ceedawg]

Ceedawg. I agree with you that ported vacuum was not an emissions device. See post 15.The other post that you disagreed with mentions the PVC valve was the first emissions device, which was introduced after ported vacuum. What do you disagree with?

1961? My 62 Plymouth had a pipe that sent blow by down to the ground the 64 had a pvc that took its place

 

[R/T Boy 67]

I said it came into use in California in 61ish. California was always ahead of everyone else when it came to emmisions. It was common by 64 as you noted. It is not that much of a strech that they would exist in 61. I do not blindly quote stuff off the internet, without some knowledge of the subject, and I knew that they were used in 64 in Canada,so it made sense to me.

 

[Ceedawg]

I said it came into use in California in 61ish. California was always ahead of everyone else when it came to emmisions. It was common by 64 as you noted. It is not that much of a strech that they would exist in 61. I do not blindly quote stuff off the internet, without some knowledge of the subject, and I knew that they were used in 64 in Canada,so it made sense to me.

No problem then

 

[khryslerkid]

1961? My 62 Plymouth had a pipe that sent blow by down to the ground the 64 had a pvc that took its place

The majority of '62 models had the vent pipe and the California models in '62 had a valve cover cap with valve and a hose that went to the back of the carb. It's how my '62 361 was. Sold in Sacramento.

 

[padam]

I was doing a little light reading today and came across this tidbit. (73 FSM)

It follows that if the factory was using manifold vacuum, it would be impossible to add it when needed.

 

[383man]

I was doing a little light reading today and came across this tidbit. (73 FSM)View attachment 1081479
It follows that if the factory was using manifold vacuum, it would be impossible to add it when needed.

Ford also did that during the emissions time when the cars ran leaner and more retarded timing so they ran hotter. The only thing that 3 prong valve does is normally it lets ported vacuum work the vacuum advance so it has no vacuum at idle and gets vacuum after stepping on the gas. Now if the car gets to hot the valve moves and sends manifold vacuum to the vacuum advance at idle so the eng speeds up and the fan pulls more air and the advance timing also helps the eng run cooler. Thats all that valve does is help cool the eng if it runs to hot. Ron

 

[Kern Dog]

I also dont believe the manufactors went to ported vacuum for emissions because as far as I have seen many used ported vacuum way before they started retarding idle or off idle timing for emissions.

It is hard to know for certain.
You can look at what effects ported vacuum advance has on an engine and take it from there. Personally, I don't know what demands the Feds put on the automakers.

"The Clean Air Act of 1963 is a United States federal law designed to control air pollution on a national level.[1] It is one of the United States' first and most influential modern environmental laws, and one of the most comprehensive air quality laws in the world. The 1963 act accomplished this by establishing a federal program within the U.S. Public Health Service and authorizing research into techniques for monitoring and controlling air pollution.[6]

It was first amended in 1965, by the Motor Vehicle Air Pollution Control Act, which authorized the federal government to set required standards for controlling the emission of pollutants from certain automobiles, beginning with the 1968 models."

If the ported vacuum advance helped mileage, it did so by using LESS fuel, right? This was accomplished by burning the fuel more completely. Anything that aims to improve combustion efficiency should also automatically reduce waste, I.E. emissions. In simpler terms, an efficient engine wastes less so..... less waste goes out the tailpipe.
Above, you see how standards were changed starting with the 1968 models. Ma Mopar went away from closed chamber BB heads in 1968. Coincidence? maybe but maybe not. I've read that they made the same power but that the open chamber heads were an emissions move.
GM cars got air injection into the exhaust manifolds as early as 1967 if I recall.

 

[Ceedawg]

“If the ported vacuum advance helped mileage, it did so by using LESS fuel, right“
I don’t think so, just helped burn better. Very crude then, dump the fuel in. computer managed now, more efficient.

 

[383man]

It is hard to know for certain.
You can look at what effects ported vacuum advance has on an engine and take it from there. Personally, I don't know what demands the Feds put on the automakers.

"The Clean Air Act of 1963 is a United States federal law designed to control air pollution on a national level.[1] It is one of the United States' first and most influential modern environmental laws, and one of the most comprehensive air quality laws in the world. The 1963 act accomplished this by establishing a federal program within the U.S. Public Health Service and authorizing research into techniques for monitoring and controlling air pollution.[6]

It was first amended in 1965, by the Motor Vehicle Air Pollution Control Act, which authorized the federal government to set required standards for controlling the emission of pollutants from certain automobiles, beginning with the 1968 models."

If the ported vacuum advance helped mileage, it did so by using LESS fuel, right? This was accomplished by burning the fuel more completely. Anything that aims to improve combustion efficiency should also automatically reduce waste, I.E. emissions. In simpler terms, an efficient engine wastes less so..... less waste goes out the tailpipe.
Above, you see how standards were changed starting with the 1968 models. Ma Mopar went away from closed chamber BB heads in 1968. Coincidence? maybe but maybe not. I've read that they made the same power but that the open chamber heads were an emissions move.
GM cars got air injection into the exhaust manifolds as early as 1967 if I recall.

I believe one move with the open chamber heads is no quench. Quench with closed chamber heads produces more emissions since the last part to burn is cooler and will leave more HC and CO emissions where the open chamber does not have quench so its not a cooler mixture in a quench area which should burn more in the cyl with the hotter cyl temps. I know when Ford did this if the EGR was unhooked they would ping right away since the EGR lowered the comb chamber temps by putting inert gas into the cyl. So when they took quench out they would ping because of the higher cyl temps and they countered some of that with the EGR system.
As for the vacuum advance helping fuel mileage yes it did as the more timing at light part throttle burned the mixture better and gave a bit more power at part throttle so you did not step on the gas as much and with less throttle it also helped mileage. The mixture at light part throttle is leaner and less tightly compressed then at high eng speeds so it burns slower which by starting the spark earlier will give more complete burn at that throttle angle and better part throttle power. At high eng speeds the mixture is richer and more tightly compressed so it burns faster and the eng can not take all that extra timing at say 6000 rpm where 36 degrees will be enough on most stock engines of the 60's and 70's but at light part throttle they can take 45 to 50 degrees to burn the leaner less compressed mixture. Course when the emissions got to be a big thing they started doing many things to keep emissions low enough. Many manufactors retarded timing by slowing down the vacuum advance as Mopar had an orffice controlled vacuum advance that delayed the vacuum advance about 17 seconds to help emissions and others used trans controlled vacuum advance by stopping the vacuum advance until the trans shifted into third gear and so on. Mopar also had a dist that retarded timing at idle by a solenoid in the dist on some models. They also had another dist that actually advanced the timing while cranking the eng for easier starts as they had a solenoid tied into the starter relay for that one. Ron

 

[Kern Dog]

“If the ported vacuum advance helped mileage, it did so by using LESS fuel, right“
I don’t think so, just helped burn better. Very crude then, dump the fuel in. computer managed now, more efficient.

You missed the point.
If the fuel burned better, the the throttle could then be opened LESS, increasing economy.

 

[Ceedawg]

And why would it be leaner at low speed compared to high speed? Once out of the idle circuits it’s drawing from the main circuits. Now I can see a richer mixture when the vacuum drops by pressing the pedal fast then the rods move out to allow more fuel but RPMs don’t necessarily make it richer.?

 

[383man]

And why would it be leaner at low speed compared to high speed? Once out of the idle circuits it’s drawing from the main circuits. Now I can see a richer mixture when the vacuum drops by pressing the pedal fast then the rods move out to allow more fuel but RPMs don’t necessarily make it richer.?

It is just the overall fuel/air ratio can be leaner at part throttle then at wide open throttle. Sure you get more fuel with more throttle but you also get alot more air with more throttle. Overall the complete fuel/air mixture is a leaner ratio at part throttle then WOT. Even though its alot more fuel and air at WOT it can be a richer ratio. Its just like at idle you get less fuel and less air but the overall ratio can be richer then at other throttle angles. Just depends on the carb and many other things that effect air/fuel ratio. Ron

 

[65-440]

It is just the overall fuel/air ratio can be leaner at part throttle then at wide open throttle. Sure you get more fuel with more throttle but you also get alot more air with more throttle. Overall the complete fuel/air mixture is a leaner ratio at part throttle then WOT. Even though its alot more fuel and air at WOT it can be a richer ratio. Its just like at idle you get less fuel and less air but the overall ratio can be richer then at other throttle angles. Just depends on the carb and many other things that effect air/fuel ratio. Ron

Yep...a quick drive with a wide band O2 would tell someone lots of useful info, especially when tuning a carb

 

[Slap Stick]

At part throttle the rods BEGIN to move out of the mains, allowing less fuel than at WFO when the rods are fully out of the mains making it full rich.
Check out the Dellorto carb tuning guide. I dont have a link to it any longer but it will help one understand how a carb works. Dellortos were used on many motorcycles and are stone simple and reliable.
If you can't tune a Dellorto you can't tuna fish.

 

[383man]

At part throttle the rods BEGIN to move out of the mains, allowing less fuel than at WFO when the rods are fully out of the mains making it full rich.
Check out the Dellorto carb tuning guide. I dont have a link to it any longer but it will help one understand how a carb works. Dellortos were used on many motorcycles and are stone simple and reliable.
If you can't tune a Dellorto you can't tuna fish.

Also remember at light part throttle the vacuum is still very high and usually a tad higher then idle. Since the throttle is only part open and the pistons are moving faster the eng vacuum will usually be a bit higher then at idle. Say you have 14" of vacuum at idle it may have 16" of vacuum at light part throttle which will be trying to still pull fuel through the transfer slots. But since not fully on the main circuits it can be a bit leaner then WOT. Course many factors can contribute to it. Ron

 

[Dragon Slayer]

Mechanical advance compensates timing based purely on motor speed. Vacuum adv compensates for timing needs based on Load on motor.
Ported is just a switch. At idle and off idle it is off. After that it is on and ported vacuum is pretty close to actual manifold vacuum.
Chrysler used ported and chose to have an initial and mechanical rate to work. True emission requirements started in 1966 with CAP.
Good fuel economy probably started in the beginning of automotive industry. Carter, Holley and Chrysler were concerned with it in the 30 and 40s from documentation. So tuning mattered. Burn all the fuel making power, not flushing it out and burning in the exhaust.

Remember that Chevy and Ford also used Air pumps in the late 60s for emissions. So the strategy for controlling exhaust pollution was different then Chrysler who did not use air pumps.

Regardless, once you get too today and modified cars, with what seems like less concern with emissions for old cars, you do what works best for your combo. Motor, distributor, carb, etc... Some guys have such big cams, they idle at higher rpm and the ported is open. So plugging into ported is no different then plugging into manifold. There probably is no right answer for which is best, but there are true facts on how and why Chrysler did it. That is in the chrysler training documents.

 

[biomedtechguy]

For a proper built Street Engine Ported vacuum is the way to go... Sorry, no longer a fan of the Street Hemi Grind Purple Cam.. Not after installing a Stupidly HUGE Hyd Roller with a wide LSA and having 12-15 inches of vacuum

I wish I had time to read all of the posts, but I'm slammed right now.
My 440 6bbl came with a Purple Stripe cam, many people and I believe it's the 292°/.509 cam, because of how it sounds and how it runs, pulling VERY strong to 6k RPMs which can only be explained by having that cam and a 6bbl to feed a lot of air and fuel, and 1⅞" headers to extract the burned combo.
I am an ignition system FANATIC, and I believe it's a critical part of overall and ultimate performance. I have an ignition system from Don at FBO, and yes, he has strong opinions but I respect his passion for his views and the importance of the ignition system. The FBO Ignition has performed well.
Having said that, I am going to get a Progression Ignition system as it is everything I've dreamed of having for an engine that runs carburetors. Full control and easily programmed and tuned.
Amazing!!
Here's their YouTube channel. I can't wait to get one!
https://youtube.com/channel/UClnoUn9MdJ-BoX8Y_wrwq0g
Here's the website:
https://progressionignition.com/