Vacuum advance on 318

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DQ81

'73 Dart
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Nov 12, 2008
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The Netherlands (Holland)
As I patch up my 318 and look for performance parts to bolt on, something just occured to me. I'm not quite sure the timing is set up properly.

The vacuum advance port I just noticed isn't connected to anything! It isn't plugged either.

I tried connecting it to a port above the butterfly on my 2bbl carb but the engine stalled instantly.

There is another port to which the (non working) choke is attached at the rear under the butterfly but this results in a stalled engine also.

Can I leave it like this? What are the hazards? How can I get it right/how it should be?

TIA

David
 
A lot of people don`t use vacuum advance but I like it for street driving and gas mileage. First thing you would need to do is get your timing set correctly (factory specs if you haven`t changed things on the engine) and then find the port on your carburetor base that does NOT pull vacuum at idle but only as you increase the engine speed. That should be the correct port to attach the vacuum line to. Next, adjust your idle speed and you should have an effective vacuum advance intergrated.
 
DQ81 said:
That's what I was thinking...

Thanks I'll try that tommorrow after work.

David
Click to expand...

You`re welcome. For some reason it was disconnected, it`s possible somebody just didn`t want to mess with it but it could be bad. One thing you might try is just connecting a vacuum line to the vacuum advance and put the other end in your mouth. Draw on the line and make sure you can feel resistance. It`s possible the canister is blown out and that was the reason it was disconnected. If you feel resistance when you draw on the tube then the advance should be okay.
 
I did try that, the result was the engine shut off.

Is that right?

I might just go for new ignition but unitll then what I can save in gass money could pay for it lol!
 
It must be working then but either your timing is way off or the vacuum plate in the distributor has a problem. The engine should increase in speed when you draw on the tube or if any vacuum is applied to the tube. If it`s cutting off then something is not right.
 
Or the idle speed is too high... or something's amiss and you have to open the throttle plates too far to keep it running. The right port will not have vacuum present at idle (curb idle IIRC is like 600-650rpm) but will have vacuum as the throttle is opened.
 
I didn't have a timing light, I bought one today, it's digital, I feel like the coolest kid on the block just looking for cars to check the timing on lol. At curb-idle 70
0rpm (therabouts) I'm looking for a 10* advance?

and around 3krpm a total of 36 assuming the mechanical is advancing 12* ?
 
Unless your car is modified in some way and/or you`re running a MP electronic ignition I would guess that your base timing would be closer to TDC or even a couple degrees ATDC.
 
Longgone said:
Unless your car is modified in some way and/or you`re running a MP electronic ignition I would guess that your base timing would be closer to TDC or even a couple degrees ATDC.
Click to expand...

My 318 was at almost 10* ATDC when I first got it. You never know, sometimes the timing chain slips a tiny bit or the distributor gets fiddled with.
 
For best performance, around 10* BTDC. Stock they came with less than that, but it was purely for emissions and a "safety gap" in case of crappy gas.
 
DQ81 said:
The higher the quality fuel I run the more I ca advance correct?

I usually run a 98 octane..
Click to expand...

Yes, but only run what you have to run to prevent detonation. You`ll get more power from a lower octane gas. The timing is something you can experiment with. Try to find the spot where you get proper performance without detonation. A 318 2 barrel engine is a low compression engine and should run well and without detonation on regular gas with moderate advances in timing, for example 5* BTDC.
 
Yeah, I ran 12* advance on my 318 with 85 octane gas. Of course I live at a high altitude (7000 ft. above sea level) so the thinner air allowed me to run more timing.
 
I think something is way off in my distributor.

My advance hose has been disconnected since I bought it. It's a transplant engine, from /6 to 318 (came out of a truck)

First off, this is an electronic ignition correct?:

090120091051.jpg



I set the ignition timing to 10*BTDC today, attach vac advance (to port above butterfly) engine stalls.

Leave vac advance hose disconnected for now. Plugs are still fouling out, the carb is good and not running rich but my MPG is terrible.

I want to get the vac advance working properly, this is a street car and I could benefit from the extra MPG etc. It may have a sporty exhaust and I'm putting in a mild cam and a 4bbl but the stock ignition or close to it should be fine for what I need it for. Definatly not a high RPM motor.

I think the vac advance diaphram is fried or overly sensetive, it wasn't disconnect for nothin' I suppose. What else could give simliar symptoms?


TIA

David

David
 
yup, thats an electronic unit.

theres no vacuum above the throttle plates at idle. if it stalls when you
hook the vac.hose up. your doing something wrong. ie: wrong port.
cheers
PS
nice duct tape on the wiring.
 
360Z28 said:
yup, thats an electronic unit.

theres no vacuum above the throttle plates at idle. if it stalls when you
hook the vac.hose up. your doing something wrong. ie: wrong port.
cheers
PS
nice duct tape on the wiring.
Click to expand...


There's gotta be some vacuum otherwise there is no air. If it made no difference you wouldn't have to remove the vac-hose to set initial timing.

I'm doing something wrong or somethings wrong: there's only one port, not much to do wrong there.

Duct tape = PO

Cheers
 
DQ81 said:
There's gotta be some vacuum otherwise there is no air. If it made no difference you wouldn't have to remove the vac-hose to set initial timing.

I'm doing something wrong or somethings wrong: there's only one port, not much to do wrong there.

Duct tape = PO

Cheers
Click to expand...
a vacuum is void of air (or atmosphere). on my engines, there is no pull on most ports above the throttle plates.
easy to find out. hook up a vacuum gauge to the port yor using now, let it idle and see how much its pullin.
nutter possibility is that the idle speed is set to high, exposing the vacuum channel to that port.
now before you say "nope". check to see if the mixture screws are cranked almost all the way seated.
whats a "PO"
even if the vac.diaphram is blown, it won't kill the engine. unless its way outta tune.
cheers
 
360Z28 said:
a vacuum is void of air (or atmosphere). on my engines, there is no pull on most ports above the throttle plates.
easy to find out. hook up a vacuum gauge to the port yor using now, let it idle and see how much its pullin.
nutter possibility is that the idle speed is set to high, exposing the vacuum channel to that port.
now before you say "nope". check to see if the mixture screws are cranked almost all the way seated.
whats a "PO"
cheers
Click to expand...

Will do, get a vac gauge on there tommorrow, it's dark here now.

Idle speed is set to 700rpm, my timing light gives me that reading in any case. If my mixture screws are in too far the mixture would be too lean and thus be compensated by a the idle screw being screwed in too far as to keep the engine running at idle is what your thinking?

On the other post it was your abreviations I didn't get lol.

A PO is a Previous Owner

When they did the engine swap I geuss all they had is duct tape, when the weather gets above freezing I'll make that right, it's just embarassing. lol
 
360Z is spot on with his advice. In addition if you have a manual bleeder or some other method of creating a vacuum ,hook it up to the chamber and watch to see if you can see the plate rotate. By the looks of the inside of your distributor there`s been a lot of moisture in there. I would check the cap and rotor contacts for corrosion and clean up some of the rust inside. The gap in between the stator and reluctor should be .008. Set it with a non-magnetic feeler gauge.
 
Longgone said:
360Z is spot on with his advice...
Click to expand...
thanks! its a been there done that kinda thing. just happy to offer my experiance/advice!
even tho a nameless MOD wants me outta here.. and no i'm not talking about rumblefish360 LOL!

DQ81 said:
If my mixture screws are in too far the mixture would be too lean and thus be compensated
by a the idle screw being screwed in too far as to keep the engine running at idle is what your thinking?
Click to expand...
yup

DQ81 said:
When they did the engine swap I geuss all they had is duct tape, when the weather gets
above freezing I'll make that right, it's just embarassing. lol
Click to expand...
well its just plain jane not safe! and butt ugly.
 
Quote:
Originally Posted by DQ81
If my mixture screws are in too far the mixture would be too lean and thus be compensated
by a the idle screw being screwed in too far as to keep the engine running at idle is what your thinking?

yup

360

What's the correct way to set the carb up baseline. I have a 2bbl not a Holley. Two screws at the front, I've bottomed them out (gently) and then do 2.5 rotations out, that's what I was tought anyway. The I adjusted the idlespeed (only slightly was pretty well on still) to 700RPM.

The vac advance still kils the car and port I'm using, the only port there is, is aprox 1.5 inches directly above the butterfly on the back, it still has vacuum. I haven't measured it yet but it's enough to suck my finger on it and left unplugged obviously makes the engine run at higher RPM.

Maybe a picture would help?

I'd really like to get teh vac advance working on this thing as I do so much city driving and gas costs and arm and a leg here.

Imagine paying 8 dollars a gallon. That'l piss ya off..
 
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