Vacuum Advance Question
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Junior User
Joined: May 2009
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Vacuum Advance Question
I am replacing the vacuum advance module on my 84 F350 dump truck with a 300-6. I determined that I have a bad vacuum advance so I installed an old one that I had from an F150 engine just to check to see if it made a difference. It runs really well with good power and no knocking. The vacuum advance module is set to engage at about 5 inches vacuum and is fully advanced at 16 inches vacuum. I haven't had a chance to drive the truck with a heavy load.
Do these numbers seem correct? I know they're pretty typical for a lightweight vehicle, but should a heavier vehicle be set up such that the advance curve is higher (requires more vacuum to reach full advance)?
Do these numbers seem correct? I know they're pretty typical for a lightweight vehicle, but should a heavier vehicle be set up such that the advance curve is higher (requires more vacuum to reach full advance)?
Elder User
Joined: Sep 2008
Posts: 563
Likes: 0
From: DeKalb, Ill.
You might need to road test it with a load.
Find out what vacuum you're running in a typical loaded down situation.
I think you would want your running vacuum to match advance vacuum pressure.
Meaning, right now you would like to see your truck running at 16 in. cruising with a big load.
I think your negative pressure will be a little less than 16 (just my guess).
You may have to adjust the vacuum diaphragm to match.
Let us know what happens.
Oh yea, keep listening for that knock!
Murph.
Find out what vacuum you're running in a typical loaded down situation.
I think you would want your running vacuum to match advance vacuum pressure.
Meaning, right now you would like to see your truck running at 16 in. cruising with a big load.
I think your negative pressure will be a little less than 16 (just my guess).
You may have to adjust the vacuum diaphragm to match.
Let us know what happens.
Oh yea, keep listening for that knock!
Murph.
Elder User
Joined: Sep 2008
Posts: 563
Likes: 0
From: DeKalb, Ill.
Sorry to leave anyone hanging.
Didn't know I had a following, cool!
Since my most recent posts I've had more and more people tell me the same thing.
Release bearing.
Since the problem isn't so urgent, I'm taking my time putting together the money.
Turns out a heavy duty replacement kit
(clutch, pressure plate, release and pilot bearings) is quite a bit less than I thought.
I'm doing the whole kit 'cause my clutch is starting to show it's age too.
It's getting a little jumpy when I let out the clutch in 1st.
When I get it all done, I WILL post the results.
Thanks for asking.
Sorry to steal your thread here wolfman.
This side note came about because my release bearing
was making a noise that sounded (to me, anyway) like ignition ping.
Long story short, I chased my tail around my whole ignition
system for about a month, and it wasn't the problem.
How are you coming along?
Murph.
Didn't know I had a following, cool!
Since my most recent posts I've had more and more people tell me the same thing.
Release bearing.
Since the problem isn't so urgent, I'm taking my time putting together the money.
Turns out a heavy duty replacement kit
(clutch, pressure plate, release and pilot bearings) is quite a bit less than I thought.
I'm doing the whole kit 'cause my clutch is starting to show it's age too.
It's getting a little jumpy when I let out the clutch in 1st.
When I get it all done, I WILL post the results.
Thanks for asking.
Sorry to steal your thread here wolfman.
This side note came about because my release bearing
was making a noise that sounded (to me, anyway) like ignition ping.
Long story short, I chased my tail around my whole ignition
system for about a month, and it wasn't the problem.
How are you coming along?
Murph.
Elder User
Joined: Oct 2008
Posts: 708
Likes: 1
That'skind of funny. I chased my tail around an ignition timing problem a few months ago too. Replaced the entire dizzy, had the TFI tested, replaced the ECU and put in a new MAP sensor. Then I unplugged the knock sensor and the problem went away LOL. So I relate........
Elder User
Joined: Sep 2008
Posts: 563
Likes: 0
From: DeKalb, Ill.
My biggest problem was my own ignorance.
When I called my noise ignition ping,
everyone jumped onboard giving me advice, trying to help (great help, mind you).
The only problem with this FTE Forum is that all of these
helpful people can't hear the same noise, or peak under the hood with you.
What I have learned here goes back to an old saying-
"Help me help you."
This isn't an "effort free fix" forum.
If you can do the work and diagnose your problem,
the people here can, and will help you fix anything.
Do your part and you'll get great help.
Murph.
When I called my noise ignition ping,
everyone jumped onboard giving me advice, trying to help (great help, mind you).
The only problem with this FTE Forum is that all of these
helpful people can't hear the same noise, or peak under the hood with you.
What I have learned here goes back to an old saying-
"Help me help you."
This isn't an "effort free fix" forum.
If you can do the work and diagnose your problem,
the people here can, and will help you fix anything.
Do your part and you'll get great help.
Murph.
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