V.advance setting?
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Lead Driver
Joined: Mar 2008
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From: Near Los Angeles
V.advance setting?
I was checking my vacuum advance setting. Can someone post a good setting for mpg and power, I mean at what rpm should the vacuum advance begin to kick in.
My cam is the Isky 256, rpm power range 1500 up. The vacuum advance was set to kick in at 900 rpm. Is that so it will reach full advance at 1500 rpm?
My cam is the Isky 256, rpm power range 1500 up. The vacuum advance was set to kick in at 900 rpm. Is that so it will reach full advance at 1500 rpm?
Moderator
Joined: Nov 2007
Posts: 22,415
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From: Denver Metro Area, CO
restorer,
Please take this in the spirit intended... I'm not trying to be critical or judgemental or be a dick or anything, OK? Just trying to help...
The way you abbreviate a lot of things can be really confusing and irritating sometimes. For example, the title of this thread - V.advance setting. I saw that and had to wonder what that is!
When you're in a certain frame of mind as you are when you're writing, it likely makes perfect sense what you're talking about. But for those who are reading it for the first time, it can be a bit of work to figure out what you're probably talking about.
Just thought I'd mention it, hope I'm not coming across as a dick or anything.
Please take this in the spirit intended... I'm not trying to be critical or judgemental or be a dick or anything, OK? Just trying to help...
The way you abbreviate a lot of things can be really confusing and irritating sometimes. For example, the title of this thread - V.advance setting. I saw that and had to wonder what that is!
When you're in a certain frame of mind as you are when you're writing, it likely makes perfect sense what you're talking about. But for those who are reading it for the first time, it can be a bit of work to figure out what you're probably talking about.
Just thought I'd mention it, hope I'm not coming across as a dick or anything.
Thread Starter
|
Lead Driver
Joined: Mar 2008
Posts: 7,173
Likes: 377
From: Near Los Angeles
restorer,
Please take this in the spirit intended... I'm not trying to be critical or judgemental or be a dick or anything, OK? Just trying to help...
The way you abbreviate a lot of things can be really confusing and irritating sometimes. For example, the title of this thread - V.advance setting. I saw that and had to wonder what that is!
When you're in a certain frame of mind as you are when you're writing, it likely makes perfect sense what you're talking about. But for those who are reading it for the first time, it can be a bit of work to figure out what you're probably talking about.
Just thought I'd mention it, hope I'm not coming across as a dick or anything.
Please take this in the spirit intended... I'm not trying to be critical or judgemental or be a dick or anything, OK? Just trying to help...
The way you abbreviate a lot of things can be really confusing and irritating sometimes. For example, the title of this thread - V.advance setting. I saw that and had to wonder what that is!
When you're in a certain frame of mind as you are when you're writing, it likely makes perfect sense what you're talking about. But for those who are reading it for the first time, it can be a bit of work to figure out what you're probably talking about.
Just thought I'd mention it, hope I'm not coming across as a dick or anything.
Postmaster
Joined: Mar 2005
Posts: 2,949
Likes: 6
From: Earth
Vacuum advance isn't directly correlated to rpm. Vacuum at 1,500 rpm with the throttle just cracked and 1,500 rpm at WOT are completely different.
I used a hand-operated vacuum pump to see when the advance can started advancing the timing and the total advance it kicked in. I didn't write it down, but IIRC it started advancing at about 4" and was all in by about 15" of vacuum.
Adjust the vacuum advance based on what happens at cruise - if you get pinging going uphill or at part throttle acceleration from cruise then adjust the advance back until it stops.
I used a hand-operated vacuum pump to see when the advance can started advancing the timing and the total advance it kicked in. I didn't write it down, but IIRC it started advancing at about 4" and was all in by about 15" of vacuum.
Adjust the vacuum advance based on what happens at cruise - if you get pinging going uphill or at part throttle acceleration from cruise then adjust the advance back until it stops.
Tuned
Joined: Jun 2003
Posts: 307
Likes: 1
From: South Florida
The vacuum advance changes the timing according to the load on the engine nothing to do with rpm.
Without getting into a bunch of theory, a leaner (light throttle) mixture burns slower and can use a more advanced timing.
At cruise on the highway (high vacuum, light throttle), total timing can be as much as 50° btdc
At idle (high vacuum, no throttle), total timing can be as much as 25-30° (10° base timing + 0° centrifugal adv + 15-20° vacuum advance if connected to manifold vacuum)
Using manifold vacuum at idle will increase the advance, generally making the engine run smoother and cooler.
Easiest way is to adjust the can until it pings, then back off.
You can also do it with an adjustable timing lite and a hand vacuum pump.
Without getting into a bunch of theory, a leaner (light throttle) mixture burns slower and can use a more advanced timing.
At cruise on the highway (high vacuum, light throttle), total timing can be as much as 50° btdc
At idle (high vacuum, no throttle), total timing can be as much as 25-30° (10° base timing + 0° centrifugal adv + 15-20° vacuum advance if connected to manifold vacuum)
Using manifold vacuum at idle will increase the advance, generally making the engine run smoother and cooler.
Easiest way is to adjust the can until it pings, then back off.
You can also do it with an adjustable timing lite and a hand vacuum pump.
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