Vacuum advance

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Bewy said:
RRR,
Many of your statements in post 72 are incorrect.
The first one is that M & P vac adv will not yield the same results, as described in the posts 67-69 I noted, is wrong. Period!
Also, Australia did NOT have different engines to the US. All GM cars that came to this country, Chev, Buick, Pontiac etc had US built engines.........& most had MVA until 1968.
There were a few locally designed/built engines. In GM, the inline 6, 253 & 308 V8s.
Mopar had the inline Hemi 6 cyl. All other Mopar engines were fully imported & built in the US. Ford had a locally designed 2V head for the Cleveland V8, but all the other V8s were fully imported like GM & Mother.
While I might live on the 'other side of the globe', we breath the same air & use the same gasoline as cars in the US.
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Whatever you say man. You lost credibility from me with about your second post on this forum. You're as bad as AJ. You're all book and no experience.
 
RustyRatRod said:
It also does something no one has mentioned. It gives you a certain amount of engine braking due to the vacuum falling off when you take your foot off the gas. That can make a difference in mileage right there.....and right now, gas ain't cheap. With it on manifold vacuum, when you lift your foot, vacuum goes up and pulls in total vacuum advance, and reduces that amount of engine breaking. It makes a very noticeable difference.
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I agree completely, and thanks for bringing that up. I've always enjoyed taking my foot off of the gas and having the engine do a good bit of the braking. In fact, driving on the street like that *does* save wear and tear on the brakes and gets better economy. Brakes are such a waste of energy anyway! Thanks Rusty!
 
I tried both manifold vacuum and ported vacuum. I was able to get a smoother idle with ported vacuum. The manifold vacuum gave me a slightly erratic idle.
 
dartfreak75 said:
Where can a newbie get a copy of that? Lol
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Without seriously affecting your bank account? I don't know. The cheapest I've seen one lately was like 78 bucks. They're out of print now. Completely. So what's left is "ALL" that's left.
 
RustyRatRod said:
Naw it's no biggie. It's just that several people made the correct suggestion for your build and this yahoo caint keep his trap outta where it doesn't belong. He's just slap wrong about the timing being the same for each and that's just wrong. It's bad information and here's how.

Initial or idle timing with ported vacuum is let's say....like you have now "around" 20 degrees. Let's call it 20 just to make it simple.

Now, remove the vacuum advance from ported and hook it to manifold. Now your initial timing is 20, PLUS "whatever" the vacuum can pulls in....let's call that 12 degrees. So now your initial or idle timing is 32 degrees. Does that sound right? Does it sound the same? No, because it's not. So you have to back that 12 off of the distributor (initial) timing to get it back to 20. Get it? Now, unplug the manifold vacuum from the vacuum can and what do you have? You have 12 less than that 20 or 8 degrees BTDC. There's no way in hell those two timing curves will be the same in this country or his.

You can run manifold vacuum. You can run ported vacuum. You can run no vacuum. But the best way, IMO for YOUR build, since it's really not too far from stock is ported. It also does something no one has mentioned. It gives you a certain amount of engine braking due to the vacuum falling off when you take your foot off the gas. That can make a difference in mileage right there.....and right now, gas ain't cheap. With it on manifold vacuum, when you lift your foot, vacuum goes up and pulls in total vacuum advance, and reduces that amount of engine breaking. It makes a very noticeable difference.

Ported vacuum also cleans up part throttle combustion, reduces NOX gasses and picks up mileage and gives a little extra advance at cruise. There's no down side. This slant 6 I just put in my car has 6 Hg at idle. 14 at cruise, because it has a pretty sizable flat tappet solid cam. I can tell you it benefits greatly from being on ported vacuum and I know yours will too. But my advice is try it both ways. But in order to get initial timing right hooked to manifold vacuum, do not disconnect it when setting timing, because you WANT the vacuum operational at idle. Set it the same 20 degrees initial as you would with the can disconnected from ported. You can plot the two curves yourself and see the difference. Some people like it better on manifold vacuum. You may and if you do, it won't hurt a thing.....but it ain't the same as ported. lol
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This is great information thanks rob! This is the exact stuff im talking about i like learning stuff like this. This is the why I mentioned! Everyone can tell me what to do and how to do it but the why is what I like to learn! Bewy shared some great info as well and like I said in my reply I will have to play around with it and try it different ways. But I fell with everyone's help here im most definitely on the right track and have a far better understanding of the how and whys! Thanks guys!
 
512Stroker said:
I am having a tough time reading this - old eyes.
Where can I get a copy our link?
Thanks
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I scanned it from the Mopar Performance instructions DCF- 194 that came with their conversion kit with the Chrysler built distributor.

RustyRatRod said:
There were very few car that did that here and I cannot think of one Chrysler product that did.
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That's exactly it. Even if it was true that only Chrysler-Plymouth used ported vacuum, that doesn't prove anything. We're dealing with a Chrysler.

Yes I can point to actual examples of engines that used manifold vacuum for the distributor. I know you can too.
We also know the OP is not working on a 1964 Kaiser Jeep OHC 6 cylinder or any of the other examples.

Further its not even true that all other car companies only used manifold vacuum pre-emissions.
I've also pointed to examples from 1964-65 where Chevrolet's used ported vacuum.
Shrinker mentions a 1949 Jewett he owned that used ported.
Then there was the Ford system that used venturi vacuum - a totally different way of matching timing to engine rpm and load.

Almost every different engine combo has somewhat different timing needs. The combustion chambers, the piston dwell time around TDC, etc etc. all have some effect on the burn, and therefore the lead time needed under different conditions.
To the best of our knowledge @dartfreak75 has a fairly stock Chrysler engine with a Chrysler distributor.
However until we see a full set of actual timing-rpm measurements all of these sidetracks are just theoretical distractions.
 
dartfreak75 said:
Bewy shared some great info as well and like I said in my reply I will have to play around with it and try it different ways. But I fell with everyone's help here im most definitely on the right track and have a far better understanding of the how and whys! Thanks guys!
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You're not on the right track. You're jumping around from one idea to another. If you think all information is equal then you don't understand the hows and why's here.
All this theoretical gobltygook isn't getting you anywhere, except possibly in trouble.
I'm not wasting my time on it and that's why I dropped out of the discussion.
 
Mattax said:
I scanned it from the Mopar Performance instructions DCF- 194 that came with their conversion kit with the Chrysler built distributor.


That's exactly it. Even if it was true that only Chrysler-Plymouth used ported vacuum, that doesn't prove anything. We're dealing with a Chrysler.

Yes I can point to actual examples of engines that used manifold vacuum for the distributor. I know you can too.
We also know the OP is not working on a 1964 Kaiser Jeep OHC 6 cylinder or any of the other examples.

Further its not even true that all other car companies only used manifold vacuum pre-emissions.
I've also pointed to examples from 1964-65 where Chevrolet's used ported vacuum.
Shrinker mentions a 1949 Jewett he owned that used ported.
Then there was the Ford system that used venturi vacuum - a totally different way of matching timing to engine rpm and load.

Almost every different engine combo has somewhat different timing needs. The combustion chambers, the piston dwell time around TDC, etc etc. all have some effect on the burn, and therefore the lead time needed under different conditions.
To the best of our knowledge @dartfreak75 has a fairly stock Chrysler engine with a Chrysler distributor.
However until we see a full set of actual timing-rpm measurements all of these sidetracks are just theoretical distractions.
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And that's why I suggested trying both. Simply because ALL engines act differently. You just never KNOW. I think we can "guess" that near bout 100% his will run better on ported vacuum.
 
Mattax said:
You're not on the right track. You're jumping around from one idea to another. If you think all information is equal then you don't understand the hows and why's here.
All this theoretical gobltygook isn't getting you anywhere, except possibly in trouble.
I'm not wasting my time on it and that's why I dropped out of the discussion.
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First of all im not jumping around i asked what the difference was and now I know the difference. I never said I was gonna run manifold vacuum i just said I understand it now. All I said was I would have to try different things to see what worked best on my engine. I don't understand why yall grown *** men are getting butthurt because i want to learn more way than one and understand the difference between the two! Sorry for wasting your time feel free to ignore me so I don't waste any more of it!
 
dartfreak75 said:
First of all im not jumping around i asked what the difference was and now I know the difference. I never said I was gonna run manifold vacuum i just said I understand it now. All I said was I would have to try different things to see what worked best on my engine. I don't understand why yall grown *** men are getting butthurt because i want to learn more way than one and understand the difference between the two! Sorry for wasting your time feel free to ignore me so I don't waste any more of it!
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Easy freak, this kind of bullshit happens on this forum happens all to often.
It's like having a bunch of old bulls in the same pasture.
Just sort the fly **** from the pepper and do what's right for you the rest will sort its self out sooner or later.
 
512Stroker said:
Easy freak, this kind of bullshit happens on this forum happens all to often.
It's like having a bunch of old bulls in the same pasture.
Just sort the fly **** from the pepper and do what's right for you the rest will sort its self out sooner or later.
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Yea I get that. I have not stated anything about how im gonna tune or setup my vacuum I simply have read and politely thanked everyone for their information. But im all over the place and don't understand a damn thing according to him, why because I thanked someone with a different opinion than his?? Clearly he has a ton of knowledge and is a smart guy but im not gonna be spoken down to! Not here or anywhere else!
 
dartfreak75 said:
I just saw this post thanks for sharing. That makes more sense than anything iv read before and I completely agree. I was using 318willruns method of timing setting, basically he just keeps bumping up his timing at idle till the idle no longer increases or it stops idling smooth. Then backs it off 2 to 4 degrees which landed me at 20 degrees. I got all the way up to 24 degrees before it stopped increasing. And it seemed to run really good there. So using MVA I could set my initial at lets say 10* intial and using mva id be back at 24* during idle. Until the engine is under load. I guess im just gonna have to play around with it different ways and see what my engine likes. I appreciate all the help I have a much better understanding of the difference now!
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Keep in mind, i don't run a vacuum advance on any of my cars, so a lot of initial helps compensate for no advance pulling timing into it. Yes, advances will pull timing up to and around 50* and that's ok on part throttle cruis'n. I've played so many games with VA over the years and came to the conclusion it never paid dividends for my purposes so unless the car is factory stone stock, the VA is gone once I change cams, heads, etc.
 
Another thing you can do to monitor your system is run a vacuum gauge while driving and that can help in tweaking the hex vacuum adjustment.
 
dartfreak75 said:
Yea I get that. I have not stated anything about how im gonna tune or setup my vacuum I simply have read and politely thanked everyone for their information. But im all over the place and don't understand a damn thing according to him, why because I thanked someone with a different opinion than his?? Clearly he has a ton of knowledge and is a smart guy but im not gonna be spoken down to! Not here or anywhere else!
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That's why I'm keepin it civil. I really want you to try timing it both ways, so you can see the difference for yourself. You'll see hands on that each way of running the vacuum can has its own different curve. You'll learn it for yourself.....and you decide which you like better. "I" have never liked running manifold vacuum on the advance can......but you might. A lot of people do. I can guarantee you one thing. The mileage will fall off in comparison. But that's neither here nor there really. We're mostly discussing the running differences.....and they are some. You'll see. Keep us posted on what you come up with.
 
@dartfreak75 I'm just telling you straight up what I'm observing. That's not talking down - that's being honest man to man, FABOer to FABOer. Sorry you took it otherwise.
Nothing wrong with thanking people.
The only thing I can say I'm smart about is to say with absolute authority that none of us know what the advance curve is in your distributor.
This is what I have suggested you do.

Take the timing readings from as slow as you can get the engine to run, and then in regular increments of increasing rpm.

All this stuff about how things work, including what I posted, are all distractions.
You can try things randomly and you will get random results.
And maybe because you are you, and we are all different, that's what you need to do.

Here was the detailed version from the previous thread.
Mattax said:
The way to settle what the advance looks like is to get it to idle slow and then lock down the distributor and increase rpm.
If you can get 600 or 650 rpm great.
maybe do the low speed ones twice because one the engine is hot there is a better chance of idling it slow.
Try to measure with increasing rpm rather than letting off the throttle as there is some uh er slop.

You can
measure the rpm for every increase in a degree (or two)
or
measure the timing for every 100 or 150 or 200 rpm. In the mid and upper rpms you can space that out to every 250 or 500 rpm.
Whichever is more convenient.
For 3500 to 4500 rpm I usually just do something that is almost like winging it. I open the throttle quick take a quick measurement and let it come back down.
If it doesnt feel safe to you dont do it. We all of differnt risk tolerances for different things.

When you have that all written down, we can plot it out.
Then you'll know what the advance is doing.

Also, if you are later going to use this lwith vacuum advance you can also see where problems may occur and head them off.
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Then you can use whatever methods you want and you will be able to track the effect of the change or modification you made.
Some techniques will make more sense than others depending on waht you find.
It's something like the debate with aiming a rifle as to whether to use a 6 o'clock or a standard sight picture.
Different people have different preferences, and sometimes that varies with the circumstances.
However if you find yourself with a fixed elevation firearm that shoots best with POA at 6 o'clock then you know what to do if you want to hit center.
But you're not going to know that until you go shoot some 50, 100, 200 and 300 yard targets.
 
Last time I tuned up I set advance at 2600 rpm to 35 total with the light to get it close. Then I unhooked my vacuum advance and went out to the backroads and did a bunch of wot runs, straight stretches and uphill, slightly advancing the distributor every now and then until it pinged under load. Then I backed it off by just a c hair, did some wot runs to confirm no pinging, and then tightened it down. Mechanical is done.

Next, I hooked up my vacuum advance to PORTED vacuum, ran a vacuum gauge into the cockpit from the manifold vacuum connector, and using the gauge set up the vacuum advance to make sure I had all my vacuum advance in to take full advantage of it at part throttle cruise. Vacuum is done. Runs like a top.
 
75slant6 said:
@dartfreak75 were you able to get timing curve all straightened out?
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Yea sorta. I still got some tuning on the distributor to do. Im gonna go with a touch tighter spring right now im at 16 initial and 34 total iirc but im getting to the total early like 2400 rpms. Im gonna go with a stiffer spring and try to get the total around 3000. I may bump it back to 14 initial and 32 total idk yet I gotta drive it more to find out what it likes.
 
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