vacuum advance stop plate
Thread Starter
Instructor
Joined: Apr 2012
Posts: 135
Likes: 1
From: Kirbyville Texas
vacuum advance stop plate
I've installed a new dist. (Street Fire HEI). along with it was a advance stop plate. What is the advantage to install the plate?...yes, I'm still learning... Ha Ha.
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
By twisting the plate on the mounting screw to contact the lever on the canister , it will limit the amount of travel of your vacuum advance canister.
You don't want any more than about 52 (engine) degrees total advance on a smallblock. Shoot for about total initial plus mechanical advance of about 36 degrees. (Maybe 12-14 initial, and 20- 22 mechanical, for example).
Add 15-16 degrees of vacuum advance on top of that, and you'll be good to go. Make sure your canister is maxing out at whatever the vacuum signal is normally present at idle and cruise.
You don't want any more than about 52 (engine) degrees total advance on a smallblock. Shoot for about total initial plus mechanical advance of about 36 degrees. (Maybe 12-14 initial, and 20- 22 mechanical, for example).
Add 15-16 degrees of vacuum advance on top of that, and you'll be good to go. Make sure your canister is maxing out at whatever the vacuum signal is normally present at idle and cruise.
Thread Starter
Instructor
Joined: Apr 2012
Posts: 135
Likes: 1
From: Kirbyville Texas
I want to make sure I'm doing this correctly... I installed the stop plate , then disconnected the vacuum advance hose and pluged off.
I set timing @ 12*/ 800 rpm, then 36*/ 3000. I then reconnected hose to vacuum can and set mixing screws on Q-Jet. Am I suppose to advance more?
I set timing @ 12*/ 800 rpm, then 36*/ 3000. I then reconnected hose to vacuum can and set mixing screws on Q-Jet. Am I suppose to advance more?
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
I want to make sure I'm doing this correctly... I installed the stop plate , then disconnected the vacuum advance hose and pluged off.
I set timing @ 12*/ 800 rpm, then 36*/ 3000. I then reconnected hose to vacuum can and set mixing screws on Q-Jet. Am I suppose to advance more?
I set timing @ 12*/ 800 rpm, then 36*/ 3000. I then reconnected hose to vacuum can and set mixing screws on Q-Jet. Am I suppose to advance more?
Then, after that, adjust your carb if required.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
With the current pump gas, I recommend that people limit the vacuum advance to 12 to 14 degrees. Set the total mechanical for 36, as you've done, and get the initial up into the 16-range by shortening the advance curve a little. Then, add 12 to 14 vacuum advance, hooked up to manifold vacuum. This will get you a very nice timing curve for some great throttle response and performance.
Lars
Lars
Melting Slicks
Joined: Aug 2012
Posts: 3,487
Likes: 83
From: Titusville Florida
I think I'm going to have to read over your paper again Lars, after reading this I don't think I have it right and am now thoroughly confused 
my car is running better after putting on the same distributor as the OP and I thought I had it right but now believe I do not....
my car is running better after putting on the same distributor as the OP and I thought I had it right but now believe I do not....
Melting Slicks
Joined: Aug 2012
Posts: 3,487
Likes: 83
From: Titusville Florida
I did mine as described below, taken from Lars' paper.
"Start the engine. If you’re using an adjustable timing light, set the light to 36 degrees advanced. Now rev the engine while observing the timing marks with the light. You will notice that the stock line on the balancer will move up towards the timing plate as rpm increases. Continue to increase rpm until the line does not move any further (centrifugal advance is “pegged out”). Once the timing is “pegged out,” the line on the balancer should line up with the “0” mark on the timing tab. Rotate the distributor as needed to achieve this. "
So maybe I'm not as bad off as I am thinking...
"Start the engine. If you’re using an adjustable timing light, set the light to 36 degrees advanced. Now rev the engine while observing the timing marks with the light. You will notice that the stock line on the balancer will move up towards the timing plate as rpm increases. Continue to increase rpm until the line does not move any further (centrifugal advance is “pegged out”). Once the timing is “pegged out,” the line on the balancer should line up with the “0” mark on the timing tab. Rotate the distributor as needed to achieve this. "
So maybe I'm not as bad off as I am thinking...
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Drifting
Joined: May 2008
Posts: 1,647
Likes: 5
From: Roseville CA
One key thing I picked up from reading Lar's paper is the importance of using a properly calibrated vacuum can. My 454 pulls about 12" of vacuum at idle. The current can I have is full in at 15". Not good. I've purchased a better suited VC1810 (B28) and will be installing that soon.
Thread Starter
Instructor
Joined: Apr 2012
Posts: 135
Likes: 1
From: Kirbyville Texas
I did mine as described below, taken from Lars' paper.
"Start the engine. If you’re using an adjustable timing light, set the light to 36 degrees advanced. Now rev the engine while observing the timing marks with the light. You will notice that the stock line on the balancer will move up towards the timing plate as rpm increases. Continue to increase rpm until the line does not move any further (centrifugal advance is “pegged out”). Once the timing is “pegged out,” the line on the balancer should line up with the “0” mark on the timing tab. Rotate the distributor as needed to achieve this. "
So maybe I'm not as bad off as I am thinking...
"Start the engine. If you’re using an adjustable timing light, set the light to 36 degrees advanced. Now rev the engine while observing the timing marks with the light. You will notice that the stock line on the balancer will move up towards the timing plate as rpm increases. Continue to increase rpm until the line does not move any further (centrifugal advance is “pegged out”). Once the timing is “pegged out,” the line on the balancer should line up with the “0” mark on the timing tab. Rotate the distributor as needed to achieve this. "
So maybe I'm not as bad off as I am thinking...
I unhook hose from can and plug.
I don't have an adjustable light, so I done the math to find 36* and marked it. I should set idle 16* and 36* @3000 + 14* which will be 50* @ 3000? then reconnect to can? or is the 50* @ 3000 what I should have after hose is reconnected to can.
Last edited by kcat-fan; Jan 1, 2013 at 12:01 AM.
Intermediate
Joined: Feb 2012
Posts: 28
Likes: 0
The 36* would be the full mechanical advance (vacuum advance line plugged), which will become 50* after you add the full vacuum advance of 14*. So, the 50* number is your total advance with both mechanical and vacuum operating at full advance.
Thread Starter
Instructor
Joined: Apr 2012
Posts: 135
Likes: 1
From: Kirbyville Texas
[QUOTE=70Speedray;1582704827]The 36* would be the full mechanical advance (vacuum advance line plugged), which will become 50* after you add the full vacuum advance of 14*. So, the 50* number is your total advance with both mechanical and vacuum operating at full advance.[/QUOTE
That's 50* after can is reconnected? Or do I add it before?
That's 50* after can is reconnected? Or do I add it before?
Intermediate
Joined: Feb 2012
Posts: 28
Likes: 0
Yes, 50* is with the vacuum advance reconnected; otherwise you would not have any vacuum advance on top of the mechanical advance.
Don't over complicate this in your head! The mech advance is rpm dependent and comes in by whenever your spring and weight combination dictates, generally by 3000 rpm. The vacuum advance will add to this number, and must be connected to add its portion. With the engine lightly loaded at a steady rpm in the 3000 rpm range you should have enough manifold vacuum to get all of the vacuum advance available added to the mech advance. Hence 36+14=50.
On edit: You got it...You replied to yourself before I could finish! Happy New Year!
Don't over complicate this in your head! The mech advance is rpm dependent and comes in by whenever your spring and weight combination dictates, generally by 3000 rpm. The vacuum advance will add to this number, and must be connected to add its portion. With the engine lightly loaded at a steady rpm in the 3000 rpm range you should have enough manifold vacuum to get all of the vacuum advance available added to the mech advance. Hence 36+14=50.
On edit: You got it...You replied to yourself before I could finish! Happy New Year!
Last edited by 70Speedray; Jan 1, 2013 at 12:38 AM.
Melting Slicks
Joined: Aug 2012
Posts: 3,487
Likes: 83
From: Titusville Florida
After sleeping on it I think I have it figured out and have mine right too. What threw me is when the OP said that he set initial timing then set timing at 3000 RPM's. Why would you even need to set initial, when you set it at RPM then that would change what you set your initial at so why bother setting initial
I set mine at 36* at the RPM I knew all my advanced was coming in and called it good.
I set mine at 36* at the RPM I knew all my advanced was coming in and called it good.
Burning Brakes
Joined: Oct 2001
Posts: 911
Likes: 5
From: TN
VC1810 vacuum advance
One key thing I picked up from reading Lar's paper is the importance of using a properly calibrated vacuum can. My 454 pulls about 12" of vacuum at idle. The current can I have is full in at 15". Not good. I've purchased a better suited VC1810 (B28) and will be installing that soon.
Drifting
Joined: May 2008
Posts: 1,647
Likes: 5
From: Roseville CA