- Thread starter David G
- Start date
Ultradog MN
Well-known Member
- Location
- Twin Cities
I don't know of any gas engines with a distributer that didn't have vacuum or mechanical advance.
Ultradog MN
Well-known Member
- Location
- Twin Cities
Ok.
Yeah all the Fords did have mechanical up till 1965. Then they went to vacuum.
Dunno why.
Yeah all the Fords did have mechanical up till 1965. Then they went to vacuum.
Dunno why.
Anonymous-0
Well-known Member
Olivers with Holley distributors such as a 1550/1650 ect. have vacuum advance.
old
Well-known Member
- Location
- Camdenton Missouri
Vacuum advance would have added another hose to get hooked in weeds etc and then in turn cause other odd problems. Back when the tractor first came out they where made with the thinking of keep it simple stupid. (KISS) that way they where easier to work on
Determined
Well-known Member
Could it be that a governor would constantly be chasing itself on an engine with a vaccuum advance as the timing would move every time the governor tried to adjust RPM?
Tom in TN
Well-known Member
- Location
- Southern Middle Tennessee
My 1973 Ford 2000 has mechanical advance weights in the bottom of the distributor and a vacuum advance diaphram.
Tom in TN
Tom in TN
I was always tempted to try a distributor with manifold vacuum advance on a tractor but it was just another one of my ideas that never seemed to provide the right opportunity. If you ever had a vacuum gauge on a tractor while it was actually working though, you would see that even loafing along on a light load the vacuum was usually pretty low and most vacuum advanced were fully retarded at about 8 inches of vacuum so I doubt if it would have done much for economy. Never know though. Now you could get into venturi vacuum advances also which is a whole different animal. The old flat head ford v-8 engines used that method. IH did a variation of that also on their latest large gasoline v-8 engines. Little vacuum chambers inside dist operating the advance off of venturi vacuum. The higher the rpm and greater the volume of air through venturi produced max vacuum, just opposite of manifold vacuum.
RandyB(MI)
Well-known Member
Vacuum advance was actually vacuum retard. High vacuum like you would have at idle or whenever throttle was closed actually held the point plate in a neutral or non-advanced state and instantly when you opened throttle and vacuum dropped then it gave advance for acceleration and once rpm was up then centrifugal weights swung out and give it more advance based on rpm instead of vacuum. As a rule , acceleration requires advance and a steady speed engine not so much. Since you aren't usually accelerating and stopping all the time with a tractor like you are a car , you don't need it instantly and you don't need near as much.
buickanddeere
Well-known Member
Tractors were designed to work and have low manifold vacuum most of the time. The advantages of vacuum advance exists on a 200HP highway engine making 50HP during cruise conditions.
fixerupper
Well-known Member
Dboll, I was just scratching my head thinking my neighbor's 1650 had vacuum advance but I wasn't quite sure. But you confirmed it for me. If I remember right, it'd ping a little when the throttle was cracked open. Maybe the timing was off. Jim
pete black
Well-known Member
my 73 ford 2000 also had vacuum advance.
Heat Houser
Member
Don't think he can use this as proof....
The second method used to advance the ignition timing is called vacuum timing advance. This method is almost always used in addition to mechanical timing advance. It generally increases fuel economy and driveability, particularly at lean mixtures
Another one.....
the vacuum advance mechanism allows the distributor to supply a more optimum spark timing proportional to the load and speed output. Without the vacuum advance the distributor can only vary spark timing in proportion to speed and ignores its need for approximately 20 additional degrees of spark timing ("advance") at light loads: (idle and cruise conditions)
The basic reason for the change in optimum timing at light loads is that when operating at light loads, the mixture is leaner for fuel economy and less dense because of light load. These conditions cause the charge to burn slower, and thus, to reach peak pressure at optimum point in the cycle, the spark must be initiated earlier. Failure to do this will result in "retarded" spark timing and all the aforementioned losses.
The second method used to advance the ignition timing is called vacuum timing advance. This method is almost always used in addition to mechanical timing advance. It generally increases fuel economy and driveability, particularly at lean mixtures
Another one.....
the vacuum advance mechanism allows the distributor to supply a more optimum spark timing proportional to the load and speed output. Without the vacuum advance the distributor can only vary spark timing in proportion to speed and ignores its need for approximately 20 additional degrees of spark timing ("advance") at light loads: (idle and cruise conditions)
The basic reason for the change in optimum timing at light loads is that when operating at light loads, the mixture is leaner for fuel economy and less dense because of light load. These conditions cause the charge to burn slower, and thus, to reach peak pressure at optimum point in the cycle, the spark must be initiated earlier. Failure to do this will result in "retarded" spark timing and all the aforementioned losses.
MarkB_MI
Well-known Member
- Location
- Motown USA
Like B&D said. Tractors are designed operate at rated horsepower most of the time. No benefit to vacuum advance if the engine isn't operating at conditions where the vacuum advance would kick in.
Interestingly, most recip aircraft engines operate at a fixed timing. No advance, vacuum or centrifugal.
Interestingly, most recip aircraft engines operate at a fixed timing. No advance, vacuum or centrifugal.
rustred
Well-known Member
who told you that crock? at idle you have full vacuum advance. when you stomp on the throttle it retards the timing. thats why when setting timing on the older engines with a light you had to unplug the vacuum advance. when the engine is under full load the timing is not at full advance but goes to the original timing setting.
BushogPapa
Well-known Member
Seems Milk producers are headed toward using Another Hose on their Cows....
How and when does the Carbon Footprint Tax kick in for everyone..???
Ron..
Fritz Maurer
Well-known Member
Hey, Pete got a quick question about the I.H. 446. Should the diaphragm be on manifold vacuum?
gene bender
Well-known Member
Tractor engines have a govenor and if the manufacturers thought vacuum advance would work they would have built them they dont run like a car with many rpms.
gene bender
Well-known Member
Go look at a pre 65 Ford and see the vacuum line on the dist.
the tractor vet
Well-known Member
Most vac. advance systems use Carburetor vacuum rather then manifold vac. Now some dist. of the OLD days had a dual vac system one part did run on manifold vac. to retard the timing and one to advance the timing when carb vac overcame manifold vac.And was a real pain in the arres. Ford used this back in the late 60's and early 70's for emission . You had to remove the vac lines to set the curb timing then hook the vac lines up and it would chop five to 8 degrees off the set And caused a lot of driveablity problems and grief for us working on them and a ton of mad customers . as for a WORKING engine they do not need the extra advance as most do not get much over 2500 RPM. and most do not go over 28 degrees total advance . Myself i ran a 390 FE block Ford on the streets and the strip and i did not have a vac advance on the dist. that i ran as it was all centrifugal all the way. Also tractors of the day did not run the high compression of a car engine and gas powered trucks do not run a high compression And there are truck dist. that do not have a vac advance in them but they do sometimes have a gov. retard To hold back top RPM.
Walt Davies
Well-known Member
Thank you that is the best description that I have read. It's right on with what I have learned. As far as timing goes some engines require that you disconnect the vacumn line and then plug it. Others don't require this that's why we always check the manual before timing an engine.
Walt
Walt
Allan in NE
Well-known Member
You are totally backwards on that one, Pard.
Falling vacuum retards the spark.
Hook a timing light up and watch it sometime.
Allan
Falling vacuum retards the spark.
Hook a timing light up and watch it sometime.
Allan
MarkB_MI
Well-known Member
- Location
- Motown USA
Not true.
First thing to consider is "why have timing advance at all?" Why not just fire the spark plug at top dead center and be done with it? Well, the answer is that things don't happen instantaneously in the combustion chamber. It takes time for pressure to develop after combustion starts, and you want to time the spark so maximum pressure in the cylinder occurs roughly at the middle of the piston's stroke, where its velocity is greatest and the mechanical advantage of the crankshaft is greatest. And it turns out that to do this you need to fire the spark plug in advance of TDC. How far in advance depends on how fast the engine is turning. Understand that the flame front in the cylinder doesn't care about the position of the crankshaft; all the flame responds to is time and pressure. So the faster the engine is turning, the more degrees of advance are required to give the proper advance in milliseconds.
Pressure is dependent on throttle position and elevation; as pressure rises the flame travels faster and the advance must be retarded to compensate. What we call "vacuum" is really manifold absolute pressure, zero inches of vacuum is really 30 inches MAP. As MAP decreases (vacuum increases), the timing can be advanced. Anyone who lives at a high elevation knows to increase timing advance to compensate for thinner air; vacuum advance does the same thing, only it's responding to throttle position rather than elevation.
First thing to consider is "why have timing advance at all?" Why not just fire the spark plug at top dead center and be done with it? Well, the answer is that things don't happen instantaneously in the combustion chamber. It takes time for pressure to develop after combustion starts, and you want to time the spark so maximum pressure in the cylinder occurs roughly at the middle of the piston's stroke, where its velocity is greatest and the mechanical advantage of the crankshaft is greatest. And it turns out that to do this you need to fire the spark plug in advance of TDC. How far in advance depends on how fast the engine is turning. Understand that the flame front in the cylinder doesn't care about the position of the crankshaft; all the flame responds to is time and pressure. So the faster the engine is turning, the more degrees of advance are required to give the proper advance in milliseconds.
Pressure is dependent on throttle position and elevation; as pressure rises the flame travels faster and the advance must be retarded to compensate. What we call "vacuum" is really manifold absolute pressure, zero inches of vacuum is really 30 inches MAP. As MAP decreases (vacuum increases), the timing can be advanced. Anyone who lives at a high elevation knows to increase timing advance to compensate for thinner air; vacuum advance does the same thing, only it's responding to throttle position rather than elevation.
Similar threads
We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.
Copyright © 1997-2024 Yesterday's Tractor Co.
All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.
Yesterday's Tractors - Antique Tractor Headquarters
Website Accessibility Policy