Vacuum Advance Question

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RJK3

RJK3

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Hi all,
I'm having a heck of a time getting my vac. advance to work properly.
LA 360, Comp 20-418-3, performer intake, 1406, stock distributor, FBO ECU & Chrome ECU both act the same.
20* initial-34* total.
When the canister is plugged into either port, the thing won't run.
Manifold vacuum : dies immediately
Ported vacuum : coughs and farts, then dies.
The question...how much advance does everyone need typically from the canister? I've got 3 different ones to play with. One is blank, one is marked 8.5,the last is marked 11.0
This is obviously a street car...lol
 
Don't worry, about timing vacuum advance right now. That 1406 Eddy carb is fuel economy jetted. How does it run. no vacuum advance attached ? That's a frisky cam( and a damn good one..) When you respond with more information, a more clear picture would help diagnosis. (P.S : A lot of the older electronic stock distributors have a adjustable vacuum advance, via a small allen key through the hose nipple.)
 
RJK3 said:
Hi all,
I'm having a heck of a time getting my vac. advance to work properly.Ported vacuum : coughs and farts, then dies.
Click to expand...

It certainly shouldn't happen with the ported hookup. there's no vac available at that port.......Unless your idle speed is way higher then normal?
 
OldmanRick said:
It certainly shouldn't happen with the ported hookup. there's no vac available at that port.......Unless your idle speed is way higher then normal?
Click to expand...

Sorry, meant to add it does that with just the slightest throttle pressure.
idle is 850-900
 
Abodybomber said:
Don't worry, about timing vacuum advance right now. That 1406 Eddy carb is fuel economy jetted. How does it run. no vacuum advance attached ? That's a frisky cam( and a damn good one..) When you respond with more information, a more clear picture would help diagnosis. (P.S : A lot of the older electronic stock distributors have a adjustable vacuum advance, via a small allen key through the hose nipple.)
Click to expand...

The car should have more power in my opinion, the plugs look decent to my novice eye.
It runs decent without it hooked up, just drinks gas.
I was under the impression that the Allen screw adjusted the amount of vacuum it takes to actuate the canister itself...no?
It seems that one could limit the stroke of any said canister to achieve the desired amount of advance.
Is this a trial and error thing that I need to just keep beating my head against it till it works? lol
 
...........when u adj the vac can u either add degrees of timing or take some away....from what ur saying the pick up in the dist is no good.......kim...........
 
Ok. Lemmie see if I got this right. It will IDLE ok with the vacuum can hooked up to ported vacuum. It will not run with it on manifold vacuum.

With it on ported vacuum, when you give it throttle, it sputters and dies.

"I" would look in the distributor for something that shorts to ground when the vacuum canister moves the breaker plate. JMO.
 
RJK3 said:
The car should have more power in my opinion, the plugs look decent to my novice eye.
It runs decent without it hooked up, just drinks gas.
I was under the impression that the Allen screw adjusted the amount of vacuum it takes to actuate the canister itself...no?
It seems that one could limit the stroke of any said canister to achieve the desired amount of advance.
Is this a trial and error thing that I need to just keep beating my head against it till it works? lol[/ Correct, on all counts......
Click to expand...
 
RJK3 said:
The car should have more power in my opinion, the plugs look decent to my novice eye.
It runs decent without it hooked up, just drinks gas.
I was under the impression that the Allen screw adjusted the amount of vacuum it takes to actuate the canister itself...no?
It seems that one could limit the stroke of any said canister to achieve the desired amount of advance.
Is this a trial and error thing that I need to just keep beating my head against it till it works? lol
Click to expand...

It drinks gas, compared to what ? What. is your reference ?
 
RustyRatRod said:
Ok. Lemmie see if I got this right. It will IDLE ok with the vacuum can hooked up to ported vacuum. It will not run with it on manifold vacuum.

With it on ported vacuum, when you give it throttle, it sputters and dies.

"I" would look in the distributor for something that shorts to ground when the vacuum canister moves the breaker plate. JMO.
Click to expand...

That is correct.
It does this with 2 different stock distributors, both have been looked at for functionality and appear to move as intended.
when in this position, watching the timing mark as throttle pressure is applied, the mark jumps pretty drastically before it dies.
 
oldkimmer said:
...........when u adj the vac can u either add degrees of timing or take some away....from what ur saying the pick up in the dist is no good.......kim...........
Click to expand...

They seem to respond only to vacuum pressure, ie: less or more vacuum to achieve the same amount of "stroke".
 
So the markings on the canisters refer to the degrees of advance it will pull..?
Distributor degrees the same as crank degrees?
 
I get 16 Hg. at idle, it jumps up to 21-22 Hg. at about 1100-1200 rpm then drops as the revs go up.
Is this normal?
 
Not sure where you are measuring vacuum. If you are T'd into the ported hose that goes to the advance, it should be near zero at idle. If not the idle stop adjustment is too high, so ported vacuum is "on," or you are on the wrong port.
 
Vacuum marked on canister is dizzy degrees. 8.5 is 17* at the crank, 11 is 22*, etc.
Adjusting screw changes inches of vacuum to start vacuum curve, CCW less CW more. To limit the total amount of vacuum advance 48* to 52* you can bend the canister housing with a flat blade screwdriver outward. Make sure the canister your using is not leaking.

First thing if you haven't already done it is install a timing tape or mark the balancer so you can see what timing really is. I do not use a dial back timing light, a standard light works best.
Second, Set timing to 25* initial (you may have to go up or down depending on what the motor wants) and get the idle mixture set with the transfer slot squared up. You want to get idle mixture and timing dialed in for the smoothest idle/highest vacuum. Once you determine the initial timing you can now setup the mechanical curve.
My mechanical is 35* total with 9.5:1 93 octane. If I add more it pings under heavy load. Your motor maybe different, you'll need to experiment and see what the engine likes. I'm using an old dizzy that I welded the slots to limit advance. If its to much reduce the slot. Do the mechanical curve with vacuum advance plugged.
After you get the mechanical setup correctly you can now play with the vacuum advance to get cruise and light load timing set for better gas mileage. The allen wrench adjustment adjusts the vacumm it takes to move the advance can. The amount of advance the can has it limited by the stop on the rod. You can lower the amount by bending the can up with a screwdriver. My vacuum at idle is 15" and my vacuum advance is all in at 15" ported. Take the car out and set as much vacuum advance as you can at cruise without pinging. Again you need to see what your motor wants.
 
KitCarlson said:
Not sure where you are measuring vacuum. If you are T'd into the ported hose that goes to the advance, it should be near zero at idle. If not the idle stop adjustment is too high, so ported vacuum is "on," or you are on the wrong port.
Click to expand...

Vacuum on the ported side is zero at idle, it dies with any throttle pressure.
 
I don't have timing tape, but my dial back light is new and was calibrated last month. I'm using a limiting disc in the dizzy that only allows 14* of mechanical, which is all in at 2200 rpm.
I will see if I can shorten up the travel on the 8.5 canister a bit and give it a shot. Should I adjust the can to respond only to the vacuum spike off idle ? (Light load)
 
RJK3 said:
I don't have timing tape, but my dial back light is new and was calibrated last month. I'm using a limiting disc in the dizzy that only allows 14* of mechanical, which is all in at 2200 rpm.
I will see if I can shorten up the travel on the 8.5 canister a bit and give it a shot. Should I adjust the can to respond only to the vacuum spike off idle ? (Light load)
Click to expand...

Hold your hand over the carb intake while transitioning off idle, sounds like you may be lean on pump shot.
What is your compression ratio?
Did you set your intial and idle in my previous post?
Don't get hung up on 34* total, you need to set it to what the engine wants
 
No idea what compression ratio might be.
I've tried all 3 positions on the pump, with no change.
I will try the steps suggested tomorrow, the wife dragged me out of town today.
 
Ok. I put the vacuum gauge on the manifold port. Timing to best vacuum leaves me at 34° !!!???
18-19 Hg.
This can't be right...
 
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