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Old 10-29-2020, 10:52 PM   #26
forestb
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Re: Spark plug diagnosis

I am assuming that I should cap off my vacuum advance when doing this?
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Old 10-30-2020, 12:36 AM   #27
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Re: Spark plug diagnosis

Quote:
Originally Posted by forestb View Post
Okay thanks. Is there an amount of advance that I should not go over when doing this?
You wonít be checking the timing as you set the idle and move the distributor.
Youíll check it after youíve got things set.

Leave the vac pot hooked up if itís plugged onto manifold vac port on the carb.
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Old 10-30-2020, 11:04 AM   #28
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Re: Spark plug diagnosis

Instead of chaining the truck to a pole will it work to lift the rear off the ground and then prop the break peddle down with a pole?
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Old 10-30-2020, 05:02 PM   #29
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Re: Spark plug diagnosis

I shouldn’t have mentioned chaining my truck to a tree!
I only did that because there was no other way to get my idle rpm low enough to accurately set my carb and timing.
You don’t need to do that if you can turn your idle down below the point where your mechanical timing starts kicking in.
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Old 10-30-2020, 05:20 PM   #30
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Re: Spark plug diagnosis

Forgive me if this is a stupid question but how do I know when my mechanical timing starts kicking in?
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Old 10-30-2020, 06:39 PM   #31
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Re: Spark plug diagnosis

Easy, with the engine idling (not in gear) lower the speed as much as you can. Note the timing it's currently at. Now slowly raise the engine speed watching the RPM and keeping the timing light watching the timing. As soon as it starts to advance that the where your timing starts advancing. Using a dial back timing light you can map out your total advance and when it happens. Don't forget to disconnect the vacuum advance with doing this as you want to see true initial and mechanical advance. At idle you can hook up the vacuum advance to manifold vacuum and measure the total vacuum advance you get. If you have a hand vacuum pump you can also see when it starts and total amount. Have fun.
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Old 10-31-2020, 01:42 AM   #32
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Re: Spark plug diagnosis

I don't have a dial back timing light, but i did get one of these https://www.summitracing.com/parts/s...BoChAAQAvD_BwE from my local parts store and used it with my regular timing light along with my tach to view when and how much initial, mechanical and vacum advance my distributor was putting out. It worked great and I picked up a few stray ponies by getting it all dialed in.

Last edited by AcampoDave; 10-31-2020 at 01:47 AM.
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Old 10-31-2020, 03:51 PM   #33
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Re: Spark plug diagnosis

So I tried to lower my rpm and adjust my timing to make up for it. When I got lower than 700 rpm by adjusting my timing idle screw, I was not able to increase my rpm by advancing my timing. So I could not get the rpm adjustment screw down any lower than that. I did make a few observations.

1) my timing is set to around 15 degrees advance at 1000 rpm with the vacuum advance unplugged and in park.

2) at 700 rpm it is around 14 degrees when in park and rpm adjusted using the idle screw.

3) with my vacuum advance disconnect I have around 15 pounds of vacuum.

4) when I plug my vacuum advance in (when in park) my rpm goes from 1000 rpm to 1300 rpm

5) when I plug my vacuum advance in (when in park) my vacuum increases from 15 pounds to 20 pounds

6) when I adjust my mixture screws with my vacuum advance disconnect and the ports plugged I was able to adjust my vacuum but it took several full turn to make any kind of difference.
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Old 10-31-2020, 05:45 PM   #34
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Re: Spark plug diagnosis

We now know a few things.
You can get it to idle at 700 rpm.
You have 14 degrees initial.
Your mechanical timing doesn’t start kicking in until 950-1000 rpm.
Your vac pot is good (not blown).

At 700 rpm in park will it keep running when you put it in drive?
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Old 10-31-2020, 05:49 PM   #35
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Re: Spark plug diagnosis

I don’t try. I will try tomorrow
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Old 10-31-2020, 06:00 PM   #36
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Re: Spark plug diagnosis

Also when at 700 rpm check for vacuum on your ported port on the carb.
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Old 10-31-2020, 06:17 PM   #37
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Re: Spark plug diagnosis

Ported port?
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Old 10-31-2020, 06:26 PM   #38
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Re: Spark plug diagnosis

Yup!
The one directly above your drivers side mix screw.
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Old 10-31-2020, 07:25 PM   #39
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Re: Spark plug diagnosis

Thanks. Please pardon my ignorance
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Old 11-01-2020, 09:28 AM   #40
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Re: Spark plug diagnosis

Hopefully you read this.

If it’s at 700 in park and won’t idle in gear and you need to increase the idle to keep it running (say 800 rpm or whatever it needs to be) then let us know what the vac reading is on the ported port.
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Old 11-01-2020, 02:57 PM   #41
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Re: Spark plug diagnosis

Yes you caught me in time. Keep in mind that the ported port is where my vacuum advance is connected to. So I had to disconnect my vacuum advance to do this. I set the idle to 700 rpm in park and the vacuum read 12 pounds. I shifted into reverse and the rpms dropped to 600 and the vacuum dropped to 8 pounds.
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Old 11-01-2020, 04:16 PM   #42
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Re: Spark plug diagnosis

That says a bunch.
You know it will idle in gear at 600 rpm.
Showing any vacuum On that port says you’re idleing on the power circuit. Need to fix that.
Leave your vac gauge hooked to the ported port, hook up your vac advance to the manifold vacuum port ( blue cap just left of drivers side mix screw), start your motor, warm it up and turn the idle back down to 700. Put it in gear and tell us what your vacuum reading is.
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Old 11-01-2020, 04:37 PM   #43
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Re: Spark plug diagnosis

11 pounds at 700 rpm (park)
7 pounds at 550 rpm (drive)
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Old 11-01-2020, 04:43 PM   #44
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Re: Spark plug diagnosis

Did you hook up your vac pot to the manifold vac port?
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Old 11-01-2020, 04:56 PM   #45
forestb
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Re: Spark plug diagnosis

Hereís how the vacuum pot is hooked up.
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Old 11-01-2020, 04:59 PM   #46
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Re: Spark plug diagnosis

Right side up with arrows
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Old 11-01-2020, 05:01 PM   #47
forestb
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Re: Spark plug diagnosis

Could it be that the vacuum pot needs adjustment? Using the screw?
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Old 11-01-2020, 05:16 PM   #48
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Re: Spark plug diagnosis

I thought so!
That’s not the vacuum pot on the distributor.
That’s the choke pull off pot. Don’t worry about it. Leave it alone.
Looks like you have the manifold vac port (where the blue cap was) hooked with the hose that goes back to the distributor. In that pic.
Leave it there.
Show me your vac gauge and where it’s hooked to.
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Old 11-01-2020, 05:32 PM   #49
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Re: Spark plug diagnosis

Itís the one with the zip tie
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Old 11-01-2020, 05:45 PM   #50
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Re: Spark plug diagnosis

Now, leave all as it is.
Leave vacuum gauge hooked where it is.
Leave distributor vac pot hooked up where it is.
Check your timing at 700 rpm in park.
Let me know what number you get.
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