Vacuum advance issue

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Cam1399

Cam1399

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I have a mild 360 in a 1974 duster with vacuum advance issues. Trying to see if I’m doing something wrong or if it’s the vacuum advance. Idle timing is at 11 and wide open is 34 with the vacuum advance plugged. I have edelbrock carb. The one I’m hooking it to is the passenger side. As soon as I hit the throttle the timing goes crazy and starts pinging. Thanks guys
 
Easy --- hook up timing light, look at timing with hose connected vs hose disconnected at idle and see if it changes.
Some setups can give trouble. I used to have this trouble with a 340 in my old Landcruiser with a Quadrajet. Evidently the vacuum signal was a bit too quick, or I might have had a bit too quick mechanical and the added vacuum triggered it.
 
34 timing is 3400 rpm without advance in park. Runs great without the vacuum advance. I’ve hooked light up to it when I hood the vacuum advance up. As soon as I hit the throttle with the vacuum advance hooked up it starts pinging and the timing mark shoots off the light to the right. Timing at idle doesn’t change
 
Next thing I would do is map out the vac advance. Use a vacuum pump and your timing light. Connect the pump to your advance canister and add vacuum 1” at a time and check the timing just to see what it’s doing.

Probably wouldn’t hurt to map the mechanical advance by rpm also. Say @500-1000rpm increments w/o vac advance. Never hurts to know exactly what’s happening and when.
 
It could be that the the vacuum is coming on too easily. If the vacuum canister has a hex shape it should be adjustable with an allen key.
 
Cam1399 said:
34 timing is 3400 rpm without advance in park. Runs great without the vacuum advance. I’ve hooked light up to it when I hood the vacuum advance up. As soon as I hit the throttle with the vacuum advance hooked up it starts pinging and the timing mark shoots off the light to the right. Timing at idle doesn’t change
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Sounds like the vacuum advance needs to be adjusted. I think someone has it adjusted so that as soon as it see vacuum, it gives full advance. Try adjusting it and see what you get.
 
RustyRatRod said:
I believe clockwise. @halifaxhops will know for sure. I am almost certain though. I think it's a 3/32 allen wrench size.
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I think it's the other way. IIRC the threads in there are standard and turning clockwise relaxes the tension on the spring and allows earlier and quicker advancement.
 
Cam1399 said:
34 timing is 3400 rpm without advance in park. Runs great without the vacuum advance. I’ve hooked light up to it when I hood the vacuum advance up. As soon as I hit the throttle with the vacuum advance hooked up it starts pinging and the timing mark shoots off the light to the right. Timing at idle doesn’t change
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Hang on a sec. Don't hit the throttle.
Tee a vacuum gauge into the Vacuum-advance line. Bring the rpm up slower and record the rpm when the vacuum advance signal hits a significant and repeatable number, like say 2 inches. If this happens at 900 rpm(in Neutral/park), that's crazy. If it happens closer to 1600 that would be closer to normal. If it takes a lotta throttle, the line may be plumbed to venturi vacuum which increases steadily with throttle opening and never drops to zero.
Also to-do, is to figure out how much timing your can is able to bring in, and how much vacuum it takes to do that.
The 11* at idle and 34* all in at 3400rpm is about right.You may be able to increase that just a tad, but what you have is a great start.
 
If its pinging in neutral something is way wrong. It will ping when there is too much advance and load is added. For example accelerating gently up a hill at 50 mph can be enough to result in ping. This is annoying but will not cause major damage. Ping under full throttle or nearly full throttle can rapidly lead to damage. Back off the throttle. This is too much mechanical timing for the conditions (rpm & load).

First step is to map out the mechanical timing. By that I mean is measure timing and rpm from as slow as it wil lrun through the rpm you are willing to take it. Write down both and rpm as you go along. Then you can compare that to a factory 360 or mopar performance generic timing. If its in the ball park, then drive it and see how it does. If it pings or has other timing related issues, they must be addressed before using vacuum advance.

Second step is to map out the vacuum advance.
Then with both the mechanical advance and the vacuum advance you have information needed to decide what to do.
 
Here's a good example of measuring and plotting out timing.
www.forabodiesonly.com

Need some help with my timing curve.

So after running an eBay Ready-to-Run Hei distributor for the past 5-6 years, I finally got around to putting a timing light on it and mapping out the advance curve. Come to find out, the curve was severely lacking! I ended up swapping out that distributor with a factory electronic distributor...
www.forabodiesonly.com www.forabodiesonly.com

Mattax said:
Then with both the mechanical advance and the vacuum advance you have information needed to decide what to do.
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Decisions such as 67Dart273 mentioned here
 
I don't think he is saying it pings in neutral. I think he is saying it pings when he hits the throttle while driving. Op should clarify.
 
it will ping in park as soon as I hit the throttle if the vacuum advance is hooked up. I’ll map it out like stated above
 
It's FREE and takes 30 seconds to adjust.
 
How is it possible, with the Vcan plumbed to the spark-port, to initiate a ping at WOT, on a throttle-stomp? The spark-port should be zero at idle, increasing at Part-Throttle with rpm, and go to atmospheric, as the throttle moves past it. And this should be instantaneous, with that footstomp.

But if somehow the Vcan is plumbed to a Venturi-vacuum source, then, yes the port will switch from zero at idle, to full manifold vacuum as the throttle moves past it, and could, at WOT, end-up higher than manifold vacuum, cuz it's measuring from the venturi............
Venturi-vacuum was used in the pollution era to either power up or signal, certain devices. I wouldn't expect to see one on an aftermarket 4bbl, but I have seen them on Thermoquads. Jus saying, put a vacuum gauge on the source port.
 
AJ/FormS said:
How is it possible, with the Vcan plumbed to the spark-port, to initiate a ping at WOT, on a throttle-stomp? The spark-port should be zero at idle, increasing at Part-Throttle with rpm, and go to atmospheric, as the throttle moves past it. And this should be instantaneous, with that footstomp.

But if somehow the Vcan is plumbed to a Venturi-vacuum source, then, yes the port will switch from zero at idle, to full manifold vacuum as the throttle moves past it, and could, at WOT, end-up higher than manifold vacuum, cuz it's measuring from the venturi............
Venturi-vacuum was used in the pollution era to either power up or signal, certain devices. I wouldn't expect to see one on an aftermarket 4bbl, but I have seen them on Thermoquads. Jus saying, put a vacuum gauge on the source port.
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How ******* DUMBFUCK is it for people to argue against something that will take literally 30 seconds and ZERO money to check? He said it does it in park and neutral. Right? Vacuum only drops for an INSTANT with no load and then Katie bar the doors. If his vacuum can is adjusted ALL THE WAY counter clockwise (and I was right, I confirmed it) it will pull in ALL the advance at once and MIGHT produce his spark knock while NOT UNDER LOAD. Under load it would not, because vacuum drops off. What YOU don't get is, I'm not arguing the point. I'm just giving him something FREE and EASY to check.
 
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AJ/FormS said:
Thank you Rusty for once again seeking vindication for something not requiring any. The colorful language is especially touching.
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I'm glad you liked it. Simply letting you know I am not arguing. All I'm doing is suggesting that he check something SO simple and yet here you are AGAIN making damn sure any suggestions other than yours are covered up with your bullshit and forgotten about. Yours isn't the only brain on this forum, despite what you may think.
 
RustyRatRod said:
I believe clockwise. @halifaxhops will know for sure. I am almost certain though. I think it's a 3/32 allen wrench size.
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Clockwise it requires less vacuum (lower spring tension). Pic will help. Also make sure the ported vac is working right the lower throttle plate might be out of adjustment also. By chance any one put MP springs in there also?

vac1.JPG


vac2.JPG
 
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RustyRatRod said:
I'm glad you liked it. Simply letting you know I am not arguing. All I'm doing is suggesting that he check something SO simple and yet here you are AGAIN making damn sure any suggestions other than yours are covered up with your bullshit and forgotten about. Yours isn't the only brain on this forum, despite what you may think.
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wait what? Here you are, back again, slaughter tool in-hand, with yet another reminder to check the V-can. If nothing else, you sure are tenacious with your suggestions.
Wait a sec, I'll give you my opinion;
My opinion is that you are just cranky. Whether it be because;
Maybe you need your medications adjusted,
Or maybe you just need more sleep,
Or maybe you just ain't getting any lately,
Or maybe you got a whole heap of whatever going on.
Well, guess what, you ain't the only one brother, but there's no need to take your frustrations out on a fellow human-being who just wants to help..........
same as you.

Now, just so I continue to stay healthy and strong;
I forgive you for insulting me and trying to offend me...... yet again,
twice in the same thread already.
Now, IDK what I ever did to piss you off so bad, you've never told me. Instead you just throw genades at me all the time. Look, my armor is pretty thick, so you ain't hurting me. However, in the interest of staying healthy and strong; I humbly ask you to forgive whatever it was.
 
AJ/FormS said:
wait what? Here you are, back again, slaughter tool in-hand, with yet another reminder to check the V-can. If nothing else, you sure are tenacious with your suggestions.
Wait a sec, I'll give you my opinion;
My opinion is that you are just cranky. Whether it be because;
Maybe you need your medications adjusted,
Or maybe you just need more sleep,
Or maybe you just ain't getting any lately,
Or maybe you got a whole heap of whatever going on.
Well, guess what, you ain't the only one brother, but there's no need to take your frustrations out on a fellow human-being who just wants to help..........
same as you.

Now, just so I continue to stay healthy and strong;
I forgive you for insulting me and trying to offend me...... yet again,
twice in the same thread already.
Now, IDK what I ever did to piss you off so bad, you've never told me. Instead you just throw genades at me all the time. Look, my armor is pretty thick, so you ain't hurting me. However, in the interest of staying healthy and strong; I humbly ask you to forgive whatever it was.
Click to expand...
Hush up fool.
 
AJ/FormS said:
wait what? Here you are, back again, slaughter tool in-hand, with yet another reminder to check the V-can. If nothing else, you sure are tenacious with your suggestions.
Wait a sec, I'll give you my opinion;
My opinion is that you are just cranky. Whether it be because;
Maybe you need your medications adjusted,
Or maybe you just need more sleep,
Or maybe you just ain't getting any lately,
Or maybe you got a whole heap of whatever going on.
Well, guess what, you ain't the only one brother, but there's no need to take your frustrations out on a fellow human-being who just wants to help..........
same as you.

Now, just so I continue to stay healthy and strong;
I forgive you for insulting me and trying to offend me...... yet again,
twice in the same thread already.
Now, IDK what I ever did to piss you off so bad, you've never told me. Instead you just throw genades at me all the time. Look, my armor is pretty thick, so you ain't hurting me. However, in the interest of staying healthy and strong; I humbly ask you to forgive whatever it was.
Click to expand...
Even through all this you still FAILED to see my point. My only argument is let the guy check it out. Stop dismissing other peoples suggestions as incorrect. You're not always right.
 
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