Help setting timing
Thread Starter
Burning Brakes
Joined: Mar 2016
Posts: 1,008
Likes: 159
Help setting timing
Ok so im new to older vehicles.
I was trying to set my timing again today.
I loosened the distributor bolt, unplugged the vacuum advanced and plugged the vacuum hose.
I set my dial back timing light to 35 degrees, reved the engine to 3000 rpm, and adjusted my distributor until the mark on the pulley lined up with the 0 mark.
I tightened the distributor bolt and reattached my vacuum line. Then i decided to just double check my timing with the vacuum advance attached and it was showing about 44 degrees at 3000rpm?!
Is that correct? I thought by setting my timing to 35 degrees i was setting the maximum timing.
Am i missing something? Dont want to hurt my motor.
I was trying to set my timing again today.
I loosened the distributor bolt, unplugged the vacuum advanced and plugged the vacuum hose.
I set my dial back timing light to 35 degrees, reved the engine to 3000 rpm, and adjusted my distributor until the mark on the pulley lined up with the 0 mark.
I tightened the distributor bolt and reattached my vacuum line. Then i decided to just double check my timing with the vacuum advance attached and it was showing about 44 degrees at 3000rpm?!
Is that correct? I thought by setting my timing to 35 degrees i was setting the maximum timing.
Am i missing something? Dont want to hurt my motor.
Pro
Joined: Jun 2004
Posts: 543
Likes: 2
From: Miami FL
St. Jude Donor '11, '14
3000 in neutral, there is no to very little load on the motor, so it doesn't take a lot of throttle opening to achieve that RPM, so you have engine vacuum, and advance. At the same RPM, in gear, pushing 3500 lbs down the road, your throttle will be wide open, and your timing will be at 35 degrees.
Rob
Rob
Melting Slicks
Joined: Jun 2011
Posts: 3,114
Likes: 592
Ok so im new to older vehicles.
I was trying to set my timing again today.
I loosened the distributor bolt, unplugged the vacuum advanced and plugged the vacuum hose.
I set my dial back timing light to 35 degrees, reved the engine to 3000 rpm, and adjusted my distributor until the mark on the pulley lined up with the 0 mark.
I tightened the distributor bolt and reattached my vacuum line. Then i decided to just double check my timing with the vacuum advance attached and it was showing about 44 degrees at 3000rpm?!
Is that correct? I thought by setting my timing to 35 degrees i was setting the maximum timing.
Am i missing something? Dont want to hurt my motor.
I was trying to set my timing again today.
I loosened the distributor bolt, unplugged the vacuum advanced and plugged the vacuum hose.
I set my dial back timing light to 35 degrees, reved the engine to 3000 rpm, and adjusted my distributor until the mark on the pulley lined up with the 0 mark.
I tightened the distributor bolt and reattached my vacuum line. Then i decided to just double check my timing with the vacuum advance attached and it was showing about 44 degrees at 3000rpm?!
Is that correct? I thought by setting my timing to 35 degrees i was setting the maximum timing.
Am i missing something? Dont want to hurt my motor.
When the engine is under load (Acceleration) engine vacuum drops and therefor the vacuum advance module on the dist. will also remove vacuum advance.
The vacuum advance on the dist also has a curve based on the engine vacuum. Remove advance as vacuum drops and add advance as vacuum increases. At idle and just revving the engine is usually no load therefor higher vacuum which adds more timing.
Last edited by cagotzmann; Jun 10, 2016 at 07:47 PM.
1st Gear
Joined: Jun 2016
Posts: 1
Likes: 0
The max 35 degree's is for under engine load which equals 0 vacuum advance.
When the engine is under load (Acceleration) engine vacuum drops and therefor the vacuum advance module on the dist. will also remove vacuum advance.
The vacuum advance on the dist also has a curve based on the engine vacuum. Remove advance as vacuum drops and add advance as vacuum increases. At idle and just revving the engine is usually no load therefor higher vacuum which adds more timing.
When the engine is under load (Acceleration) engine vacuum drops and therefor the vacuum advance module on the dist. will also remove vacuum advance.
The vacuum advance on the dist also has a curve based on the engine vacuum. Remove advance as vacuum drops and add advance as vacuum increases. At idle and just revving the engine is usually no load therefor higher vacuum which adds more timing.
Le Mans Master
Joined: Aug 2006
Posts: 7,411
Likes: 1,550
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
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Have you seen this writeup?
Ok so im new to older vehicles.
I was trying to set my timing again today.
I loosened the distributor bolt, unplugged the vacuum advanced and plugged the vacuum hose.
I set my dial back timing light to 35 degrees, reved the engine to 3000 rpm, and adjusted my distributor until the mark on the pulley lined up with the 0 mark.
I tightened the distributor bolt and reattached my vacuum line. Then i decided to just double check my timing with the vacuum advance attached and it was showing about 44 degrees at 3000rpm?!
Is that correct? I thought by setting my timing to 35 degrees i was setting the maximum timing.
Am i missing something? Dont want to hurt my motor.
I was trying to set my timing again today.
I loosened the distributor bolt, unplugged the vacuum advanced and plugged the vacuum hose.
I set my dial back timing light to 35 degrees, reved the engine to 3000 rpm, and adjusted my distributor until the mark on the pulley lined up with the 0 mark.
I tightened the distributor bolt and reattached my vacuum line. Then i decided to just double check my timing with the vacuum advance attached and it was showing about 44 degrees at 3000rpm?!
Is that correct? I thought by setting my timing to 35 degrees i was setting the maximum timing.
Am i missing something? Dont want to hurt my motor.
You might find this link very helpful.
https://www.corvetteforum.com/forums...long-post.html
Melting Slicks
Joined: Jun 2011
Posts: 3,114
Likes: 592
I had the same issue when I was setting my time and it was advancing to like 42 degrees when I hook my vacuum advance up I called blueprint engines and they told me not to run it to go ahead and unhook the thing I tried unhooking it bad that a hesitation when I started taking off it would bog down and then pick back up.:
During WOT the only advance curve that is in play is the centrifugal advance. So setting the engine with 36 at 3000 rpm this is the most timing you will get under engine load (WOT), cruising @ 3000 RPM is not the same load.
I would expect the engine to BOG because the timing is not idle during the load transition, eg going from a leaner to richer when you press the gas.
Engines without vacuum advance only perform well in drag race or racing conditions. For street drivability you need vacuum advance to smooth out timing during load changes.
My ZZ383 manual shows 32 degrees max @ 4000 RPM and to run without vacuum advance. This is what I program my MSD for Track use, but for the street I program in vacuum advance. Without vacuum advance, transition feel sluggish and gas mileage is poor vs running with vacuum advance.
Last edited by cagotzmann; Jun 11, 2016 at 12:54 PM.
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
Ok so im new to older vehicles.
I was trying to set my timing again today.
I loosened the distributor bolt, unplugged the vacuum advanced and plugged the vacuum hose.
I set my dial back timing light to 35 degrees, reved the engine to 3000 rpm, and adjusted my distributor until the mark on the pulley lined up with the 0 mark.
I tightened the distributor bolt and reattached my vacuum line. Then i decided to just double check my timing with the vacuum advance attached and it was showing about 44 degrees at 3000rpm?!
Is that correct? I thought by setting my timing to 35 degrees i was setting the maximum timing.
Am i missing something? Dont want to hurt my motor.
I was trying to set my timing again today.
I loosened the distributor bolt, unplugged the vacuum advanced and plugged the vacuum hose.
I set my dial back timing light to 35 degrees, reved the engine to 3000 rpm, and adjusted my distributor until the mark on the pulley lined up with the 0 mark.
I tightened the distributor bolt and reattached my vacuum line. Then i decided to just double check my timing with the vacuum advance attached and it was showing about 44 degrees at 3000rpm?!
Is that correct? I thought by setting my timing to 35 degrees i was setting the maximum timing.
Am i missing something? Dont want to hurt my motor.
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Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
I disagree with this, not that I'm advocating no vaccum advance, but the vaccum advance on my hei was hosed and my vaccum is 8" in gear, I've got the engine in my vette to running really well with out it. Once I find one to work at lower vaccum and I know they make them, i might dick around with it, but it's all in the tune, same to be said for locking the distributor out, is it optimum for the street no, but you can get them to run well.
Burning Brakes
Joined: Jul 2015
Posts: 823
Likes: 57
From: Austin TX
This might be a little confusing. WOT and cruising are generally thought of as two different load conditions. There will be vacuum advance when cruising steady-state. If the mechanical is max at 36, total advance will be greater than that on the road.
Melting Slicks
Joined: Jun 2011
Posts: 3,114
Likes: 592
I disagree with this, not that I'm advocating no vaccum advance, but the vaccum advance on my hei was hosed and my vaccum is 8" in gear, I've got the engine in my vette to running really well with out it. Once I find one to work at lower vaccum and I know they make them, i might dick around with it, but it's all in the tune, same to be said for locking the distributor out, is it optimum for the street no, but you can get them to run well.
Long term reliability meaning you don't need to change the plugs re-tune every 10k miles, no carbon build up in the engine etc.
This is almost impossible with most engines without proper vacuum advance running.
Run well based on how it feels ( seat of the pants acceleration etc) is too far off for my liking.
I want long term reliability.
Last edited by cagotzmann; Jun 11, 2016 at 12:52 PM.
Melting Slicks
Joined: Jun 2011
Posts: 3,114
Likes: 592
I forgot to complete the sentence.
cruising @ 3000 RPM is not the same load.
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
To clarify when I say run well This includes gas mileage , acceleration , clean plugs, clean emissions within the limits of what the design can work with.
Long term reliability meaning you don't need to change the plugs re-tune every 10k miles, no carbon build up in the engine etc.
This is almost impossible with most engines without proper vacuum advance running.
Run well based on how it feels ( seat of the pants acceleration etc) is too far off for my liking.
I want long term reliability.
Long term reliability meaning you don't need to change the plugs re-tune every 10k miles, no carbon build up in the engine etc.
This is almost impossible with most engines without proper vacuum advance running.
Run well based on how it feels ( seat of the pants acceleration etc) is too far off for my liking.
I want long term reliability.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
I disagree with this, not that I'm advocating no vaccum advance, but the vaccum advance on my hei was hosed and my vaccum is 8" in gear, I've got the engine in my vette to running really well with out it. Once I find one to work at lower vaccum and I know they make them, i might dick around with it, but it's all in the tune, same to be said for locking the distributor out, is it optimum for the street no, but you can get them to run well.
Scotty
Le Mans Master
Joined: Mar 2004
Posts: 7,424
Likes: 1,458
From: Little Rock AR
Nobody said much about the curve not being all the way at the top when the timing was set. If the distributor was still stock, 3000 RPM is in the middle of the curve and it is not topped out. Bad information is worse than no information. Better to close this one down. We have plenty of better threads on the subject.