Tony got me confused!

[Runner71]

Okay so you probably seen the latest upload on his advance...

I got mine set at manifold vac so i can run high inital timing and get alot off vac with
232/245 for better idle stability and throttle response and the car moves pretty good + helps with burn at idle and light cruise.

or should i try ported with 0 vac @ idle.. have i not fully understand this?

Ive read a couple off old threads about this but can someone just simply it all? Im i overthinking this?!


First ever big block build and tune, think it's sounds pretty healthy?!

 

[khryslerkid]

First ever big block build and tune, think it's sounds pretty healthy?!

Something is wrong with your rear tires!

I think the best comment I heard recently is "what do you want your timing set at, at idle?" The rest of the timing on ported vs manifold is pretty much the same.

My conclusion is how much vacuum do you have to start with? If you have a mild cam with good vacuum go with ported. Large cam with low vacuum go with manifold.

Whichever one you have, the mechanical advance needs to be worked out and the "all in" timing set correctly.

 

[69L48Z27]

If you’re referring to Tony and UTG YouTube channel, I’m not sure how much advice I would follow there.

This topic has also been beat to death here. Half like manifold and the other half like ported.

 

[moparedtn]

FSM says ported. Carb manufacturers say ported.
I defer to Ma Mopar. She got me covered on expertise.

 

[Runner71]

Something is wrong with your rear tires!

I think the best comment I heard recently is "what do you want your timing set at, at idle?" The rest of the timing on ported vs manifold is pretty much the same.

My conclusion is how much vacuum do you have to start with? If you have a mild cam with good vacuum go with ported. Large cam with low vacuum go with manifold.

Whichever one you have, the mechanical advance needs to be worked out and the "all in" timing set correctly.

Everything is all set, 28initial and 37 all in. Pushing 15hg vacuum on 850 idle. Did some testing and on manifold the respons on the paddle is a bit more aggressive and slightly ruffer on the rpm, but then again its advancing on idle.

Ported feels much more stabile and not as aggressive on the gas then again, get alot better on and off gas near idle.

Think i like the "ruffer" and more aggressive response on the paddle.

Am i getting this or totally off? trying to learn and understand how it all gets togheter

 

[myk r sanchez]

28 initial? Wow. I thought I was pushing it at 20...

 

[Runner71]

28 initial? Wow. I thought I was pushing it at 20...

Well, Its tuned on 98 octane and still get more vacuum if i turn it - not even hard to start when hot!

 

[Nate S]

Vacuum and mechanical advance are two imperfect tools to get useful spark timing. With each you have choices, how much advance? When does it happen? If you know what you want you can adjust to get something meaningful. If you were the factory you’d throw the engine on a dyno with exact control over timing and make a matrix of 10% - 100% power at idle to 5500 rpm. At each point you’d find the timing that gives the best vacuum. Then you’d design weights, springs, diaphragms and pick a port that matched what you found on the dyno.

If you are close to stock you can mostly figure that the stock distributor on ported vacuum will give you that setup. As you modify, that stock deal might be less good. Do what works best at that point.

 

[WP29440SE]

that Uncle Tony is a two legged dildo . I wouldn't listen to him explain a valve stem to me. carburetor ported vacuum advance is technically the correct way to use it . I have my advance capped off. just keep experimenting and find what works best for your setup. I have a ton of intitial advance as well.

 

[Runner71]

Good to double check in here, always great knowleadge around, Im learning all the time!

 

[65affair]

Lots of good advice, here are my thoughts. Street use you should use the ported vacuum, as far as the manifold vacuum - Vacuum is highest at idle when the throttle position is closed or slightly open. This results from the restriction of air flow that cannot move in great volume from the air intake to the manifold. As the throttle opens, more air enters the intake, causing a decrease in vacuum. The ported vacuum on the other hand, increases vacuum as you accelerate, there for increasing your advance as you accelerate. You want your advance to increase as you accelerate up to your total timing. The best way is to set all this up on the dyno, as stated above, to be able to set the curves exactly the way you want for your setup. If that is not an option, set the timing is at total advance at "X" RPM (say 3000 rpm), this is where you will need the advance for your set-up. If you feel you need more advance at idle then change the distributor setting (internal springs, weights or vacuum canister adjustments).

 

[Nate S]

You’re close. From 1/8 throttle on up manifold and ported are nearly identical. Below that point manifold stays high to idle, ported drops off to zero. Essentially, do you want or need the extra advance at idle? Manifold gives that.

 

[Runner71]

Ive set it up with only 1 light spring so it comes in really fast! The car ia going great and stays at 850 idle good with manifold. Tryed ported today just a quick run and feels alot smoother on the low end and more like a daily driver. Feels more race and alert on the manifold side. Guess its comes down to preference but i wanna learn and understand the differences in tuning. Dont feel like the car needs that extra advance on the idle doe it feels a bit quicker at the start when launching hard, comes in much harder and throttle is more aggressive. This pick n choose thing..

 

[khryslerkid]

Ive set it up with only 1 light spring so it comes in really fast! The car ia going great and stays at 850 idle good with manifold. Tryed ported today just a quick run and feels alot smoother on the low end and more like a daily driver. Feels more race and alert on the manifold side. Guess its comes down to preference but i wanna learn and understand the differences in tuning. Dont feel like the car needs that extra advance on the idle doe it feels a bit quicker at the start when launching hard, comes in much harder and throttle is more aggressive. This pick n choose thing..

Hope uou have an ample supply of 98 octane. If you happen to get low on fuel and have to stop by some strange gas station somewhere and they only have 92 octane, she'll probably start pinging halfway home. The 98 octane is allowing you to get by with the settings that you are using.

What CR is your engine?

 

[Runner71]

Hope uou have an ample supply of 98 octane. If you happen to get low on fuel and have to stop by some strange gas station somewhere and they only have 92 octane, she'll probably start pinging halfway home. The 98 octane is allowing you to get by with the settings that you are using.

What CR is your engine?

Well the lowest we have is 95 octane around here and 99.8% have 98 so its all good the cr is around 10, its move somewere descent for a driver. Trying to learn from this build as much possible, starting with my 451 stroker this fall

 

[moparedtn]

carburetor ported vacuum advance is technically the correct way to use it .

Which is exactly what he said in his video... just sayin'.

 

[moparedtn]

First off, mine is a fairly mild 440 with what I think is the 484 cam, headers, etc.
I probably do it wrong, but I try to set the distributor up to get around 36 degrees total timing
probably around 24-2500RPM with the stock springs in the distributor.
This time around, that's putting initial timing at about 15BTDC without me fooling with the distributor
(which is a Mopar electronic unit like they used in the "conversion" kits).

I'm not running any vacuum advance at the moment because the thing runs all jittery as hell at light
cruising speeds when I hook it up - obviously, I need to take the tiny allen wrench and play with the
diaphragm if I want to do anything with that.
With the vacuum advance plugged off, she pulls good and strong, no stuttering and most importantly,
no perceptible knocking that I can tell (93 octane no ethanol gas).
There is still just the slightest jittery "mini-surging" at light throttle low speed cruising, though.
I guess that means it needs a little more (or less?) timing still?

 

[WP29440SE]

Which is exactly what he said in his video... just sayin'.

at least you know I won't watch him explain a valve stem LOL
this is also the same guy that claims AMC lifters cause low oil pressure when in fact they are identical to ours

 

[Budnicks]

isn't the way they rate octane "in Europe" different from here ?
theirs is higher #'s than the equivalent of ours

sorry I thought I remembered that from somewhere

carry on

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do what the engine needs, what makes it run best
there's really not a right & wrong way, unless it's an extreme
to be a Band-Aid, only covering for something else
why it has to be tuned a certain way

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28* initial seems a tad high
(for not being either a locked out or a mech. advance dist.)
more timing, maybe that's compensating for something else
but it maybe over cam'd &/or lower compression, for the cam etc.
less than 9:1 actual, or possibly a rebuild, with pistons way down in the bores
& a thicker head gasket etc.
& it needs all that extra timing, to "actually perform" well

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since we don't know all the pertinent actual build spec.'s
best wild *** guesses

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Seems like, just spit-balling here
It must have a mechanical limiter plate (?) in the distributor
to stop it climbing at 37* total
(like something from FBO, www.4secondsflat.com good tech subject matter there too)
usually with a Org. style vacuum advance, it goes way past that total
it'd nearing almost 50*'s of advance if you had 28* initial
(unless maybe it's an adjustable/limited VA canister like the MP CEI distr. have
& it'd have to be adjusted almost all the way in)

 

[383man]

Something is wrong with your rear tires!

I think the best comment I heard recently is "what do you want your timing set at, at idle?" The rest of the timing on ported vs manifold is pretty much the same.

My conclusion is how much vacuum do you have to start with? If you have a mild cam with good vacuum go with ported. Large cam with low vacuum go with manifold.

Whichever one you have, the mechanical advance needs to be worked out and the "all in" timing set correctly.

I agree with this. You have to understand that ported vacuum is still manifold vacuum once it comes in all the way. Its just not applied at idle if you use it that way. Both can work as so much depends on the build and what you and your eng like. I usually prefer ported but in some setups manifold vacuum at idle can be good. With my race type dist I have around 24 degrees at idle and love it like that. My dist does not even have a vacuum advance because its a race type Mallory dist. And my total of 36 is all in by 1800 rpm which works great in my combo. I can hit the gas at 2000 rpm cruising in 3rd gear and it just goes without any vacuum advance. I got my dist at a great price and knew with my build it would work fine with no vacuum advance. Would I use it if my dist had it ? Sure I would see if the combo likes it and go from there. Nothing is written in stone about which vacuum works best on the vacuum advance as to me it all depends on the combo and the cars use. Ron