Vacuum advance questions

[maytag]

Vacuum does not "increase steadily to a point then goes to nil at WOT".
The only way to accel under high vacuum conditions is to be going down hill with throttle closed.
Keith

Majic, if you're trying to quote ME saying this, then you've still got it wrong!

Vacuum will never increase as you open the throttle, just as you've described. Of course it drops. But if you are "casually" accelerating, as most of us do in every day driving (and I'm not talking about when you're leaving a dead-stop) then you WILL have vacuum. And I never used the phrase "binary switch". Here's what I DD say:

it is true that the wider-open the throttle, the less vacuum will exist, to the point of zero vacuum under WOT load.

And of course I still stand by that.

[bradartigue]

I suffer from the fact that I can't follow Keith's posts. I'm not trying to prove you right or wrong.

Here's a few ideas:

1) Well if it works on a Subaru...

2) You're talking about slamming the thing to WOT, which is something I've repeatedly said is not at all what I'm talking about. If you immediately go wide open to accelerate then great.

3) I said it doesn't work like a binary switch. Because it doesn't.

4) Open the hood - of a FIAT - and look at the distributor. Rotate the throttle. You'll see the vacuum advance actuator rod move in the direction of the intake manifold. Release the throttle. You'll see the rod move the other way.

I've had this same argument with people probably 20 times in the last decade. Then you go over and look at their car and the timing is set wrong, the distributor is set wrong, the vacuum advance is set wrong. They say the same bunch of stuff being said here, it doesn't do anything for acceleration, you can compensate by over-advancing the crankshaft, etc. etc.

[majicwrench]

Maytag,
Certainly don't wan't to confuse or offend, do not think I was quoting you in that previous post, did not use your name in association with it, and am not gonna read back thru it all to see just who I WAS quoting. At this point it is all getting pretty muddy anyway

Brad, I THINK we are in the same camp just struggling with the words and the details. In the interest of finding common ground, I too, think that a vacuum advance, if it came from the factory with one, is a worthy piece of equipment to keep funtioning. If that is not your thoughts as well, forgive me.
Keith

[maytag]

Majic..... yer a class-act dood.

[bradartigue]

For the sake of it though are we talking about the same thing? I'm not trying to argue (never was) but getting it right is important. For my own sanity - when you say there is no vacuum at WOT what are you describing? Because I think we're talking about the same thing. I'm asking because the term "vacuum" is misused so much.

[majicwrench]

Brad,
You are right "vacuum" is really not the right term, and is often misused. We could more accurately call it " low pressure" but that usually just confuses everybody.
No vacuum at WOT....if you hook a vacuum gauge to the intake, take it out on the road, and go WOT gauge will read no vacuum. There is no vacuum....just atmospheric pressure... in the intake while at WOT.

And I totally understand, and appreciate, the diff tween argueing and discussing things like gentlmen. Feel free to correct me if I ever forget the difference.
Keith

[bradartigue]

Right on. It was the WOT thing that kept throwing me. I understand the need to always have the hammer down, believe me (I drive a 1438, so it is the only way to drive it).

I think with the bumpers off the vacuum advance stops working. Discuss.

[TulsaSpider]

Well I went today to a friend's shop so he could help me figure out which shims to order. In his horde of parts there is one of the distributors without the vacuum advance. So I am going to buy that one from him. I will post about this in another thread. I sure hope this thread has helped some folks!

[kolls]

Just reporting back. Finally took my fiat out since i removed the vaccum advance pod. I dont really see any difference, no pedalling the gas when taking off or performance issues. i cant tell mpg until i actually go threw a tank a gas and figure it.

[backyardbill]

Ok. I have to chime back in. I originally wanted to rebuild or replace my vacuum advance unit with anything that would work. I couldn't fine an OEM unit anywhere.

I had my eye on a 1965 Buick unit on Ebay for .99 cents.

But in the meantime, I found some rubbery material at Elloitts Hardware and decided to try to rebuilt my old unit. I finished it yesterday. I bench tested it and it starts to pull at 2-10psi, and reaches full movement at 20psi. I set the total travel of the rod to that of the original unit. I tested the vacuum at the port with the engine running: idle=0 PSI, transition from idle to about 1500rpm=10-12 psi, 2000rpm=20 psi, then drops back to 0.

I will install the vacuum advance this coming Saturday and report the results for anyone interested.

BTW: total parts were $7.23.

[majicwrench]

How exciting and creative of you. If you want to rubber to last a long time, you should put a vapor seperator in the vacuum line to the advance unit. Not sure where to get one, lots of cars ( jap imports) used them on vacuum devices. Keeps the fuel fumes from reaching the rubber.
Good job BTW

[mPedro08]

Okay, how about this one folks, a wealth of knowledge out there and I need a little help. I've done a search on here and on Google and I can't find much information on our dizzy.

It is a Magnetti Marelli with S144CBY, then 401-R1-P1, then in smaller writing 5E stamped on it.

There appears to be no provision for any type of vaccum advance though it was once a dual point and now only contains one set of points and one condenser. Trying to figure out if our advance curve is intended to just be mechanical, and if so what the max is so we can decide if it is correct for our motor. I can't see any numbers stamped on or near the weights.

Thanks,

Peter.

[divace73]

Been reading this thread with interest and I did have a vaccum unit which broke (again), then replaced with a pure mechanical unit out of an Argenta, however soon I'll be going EDIS.....but mark allison has a kit that is simple to install and doesn't need the 36-1 wheel or computer, that would solve all the Vacuum VS WOT, I think after 5 pages of discussion it is worth a serious l k.....

[mPedro08]

Been reading this thread with interest and I did have a vaccum unit which broke (again), then replaced with a pure mechanical unit out of an Argenta, however soon I'll be going EDIS.....but mark allison has a kit that is simple to install and doesn't need the 36-1 wheel or computer, that would solve all the Vacuum VS WOT, I think after 5 pages of discussion it is worth a serious l k.....

I love Mark's kit, but I don't have the spare cash right now so I personally need to figure out what I have and what it will take (if anything) to optimize it.

Thanks much for any advice forum members!

[backyardbill]

Ron (rlux4),

Ok. I tested the rebuilt vacuum advance (VA). It doesn't work very good coming off idle. It works good in the mid range of 2000-3000rpms and up. Turns out the original spring in the VA is too strong for the rubbery material to move when only 5-10psi are present. I am going to open it back up and replace the spring with something with around 25% less stiffness. And test again. This could take a while because I am getting my Fiat ready for painting now.

I think the material is FCB2606 Neoprene Rubber 60 Duro Hardness, 1/16" Thick.
They sell it here: http://www.foambyconbuilt.com/2606neorubber.htm

Here is a picture of the dissambled VA: http://www.glocktech.net/fiat/d.jpg

Bill