ignition timing results....need some advice
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
ignition timing results....need some advice
just used the new dial in timing light and this is the results, the distributor is a stock HEI with with a proform build kit, with the recommended springs (middle range)...
these are the results
vacuum cannister disconnected RPM/DEGREES 800/16*, 1000/17*,
1500/20*, 2000/22*,2500/24*,3000/28*
vacuum cannister connected 900/16*, 1000/17*, 1500/20*, 2500/24*, 3000/28*
with vacuum cannister connected to steady 9" of vacuum
1200/39*, 1500/40*, 2000/42*, 2500/43*
so does this mean i have a base timing of 16*, centrifugal advance of 12* and a vacuum cannister that has 19* of advance but does not get enough vacuum to work?
edit: just checked vacuum reading at the tube going to vacuum cannister...zippola...0"....even when accelerating and letting up....
these are the results
vacuum cannister disconnected RPM/DEGREES 800/16*, 1000/17*,
1500/20*, 2000/22*,2500/24*,3000/28*
vacuum cannister connected 900/16*, 1000/17*, 1500/20*, 2500/24*, 3000/28*
with vacuum cannister connected to steady 9" of vacuum
1200/39*, 1500/40*, 2000/42*, 2500/43*
so does this mean i have a base timing of 16*, centrifugal advance of 12* and a vacuum cannister that has 19* of advance but does not get enough vacuum to work?
edit: just checked vacuum reading at the tube going to vacuum cannister...zippola...0"....even when accelerating and letting up....
Last edited by bobs77vet; Apr 8, 2005 at 09:12 PM.
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From: Plano TX
Rev it higher with vacuum disconnected. Looks like it may still not be done by 3000. Adjust distributor so you have 36 dgr peak without vacuum.
Where is the vacuum can connected? It should be connected to a regular full vacuum port. Stock was ported vacuum for emissions and you can see the weird results you have.
Also: If it continues to advance above 3000 use softer springs. you want all the advance in no later than 3k.
Where is the vacuum can connected? It should be connected to a regular full vacuum port. Stock was ported vacuum for emissions and you can see the weird results you have.
Also: If it continues to advance above 3000 use softer springs. you want all the advance in no later than 3k.
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by zwede
Rev it higher with vacuum disconnected. Looks like it may still not be done by 3000. Adjust distributor so you have 36 dgr peak without vacuum.
Where is the vacuum can connected? It should be connected to a regular full vacuum port. Stock was ported vacuum for emissions and you can see the weird results you have.
Also: If it continues to advance above 3000 use softer springs. you want all the advance in no later than 3k.
Where is the vacuum can connected? It should be connected to a regular full vacuum port. Stock was ported vacuum for emissions and you can see the weird results you have.
Also: If it continues to advance above 3000 use softer springs. you want all the advance in no later than 3k.
ok did some more vacuum testing and this is my conclusion....the vacuum tube going from the PORTED carb outlet to the vacuum canister must have been just slightly too large of a diameter and i was losing vacuum at the port connection....hooked up a smaller diameter tube and got at least 6" of vacuum when i hit the accelerator....i'm running 15" of vacuum from the ported side if i hooked the vacuum can to that wouldn't I have the full pull right from the start just like the 9" reading at 1200rpm of 39*? wheres my 17yr old when i need some one yelling out RPM #s...need to talk to that boy about priorities....
edit: Ok just back from the test drive WOW WOW WOW....it was incredible how much of a difference that extra timing makes....this is what i discovered with just me testing it so its at a idle of about 1100 rpm...the vacuum cannister pulls at 5"/extra7*, 7" /14*
my springs are "silver,crv 600, medium tension for full advance at 2800rpm"
so i now have 16* base at 800 rpm, centrifugal advance of at least 12* and vacuum advance of at least 14* and maybe even 20* if it gets a 9" pull.... so 16 +12+14= 42* or 16+12+20=48*....need to see what my highest vacuum reading is at that ported connection when i'm driving around tomorrow. any thoughts???
Last edited by bobs77vet; Apr 8, 2005 at 10:23 PM.
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by zwede
Rev it higher with vacuum disconnected. Looks like it may still not be done by 3000. .
as i think about this it definitely topped out there....i could see the advance and the higher rpms did nothing more to change the timing mark.
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by zwede
........Where is the vacuum can connected? It should be connected to a regular full vacuum port. Stock was ported vacuum for emissions and you can see the weird results you have.....
.
.
ZWEDE talk to me about this , you have me thinking ..... how exactly is the vacuum cannister suppose to work? when it gets vacuum it advances the spark, i can see this since i measured it....when i step on the gas the ported side gets a vacuum reading...so if it hooks up to ported side the advance increases when the load increases? is that right? if it always had a vacuum pull wouldn't the opposite happen when you got on it? i must have used all my brain cells at work this week....
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From: Plano TX
Ported vacuum is just above the throttle plate. Manifold vacuum is below the plate.
At closed throttle you have no vacuum at the ported port because the port is above the throttle plate. As you open the throttle the port will be below the plate and be the same as manifold vacuum.
At full throttle both ported and manifold ports will have no vacuum.
Depending on how the idle stop screw is adjusted I've seen some cases where there would be no ported vacuum during cruise speeds. This greatly hurts fuel economy. There is no reason not to run a regular manifold vacuum port. Only difference is your NOx emissions increase at idle, but the engine will run smoother and cooler.
It also sounds like your distributor doesn't have the mechanical advance it should. I like seeing 16-20 dgr mechanical. With only 12 dgr you will need 24 dgr base timing and may have hard starts and too much timing at idle in case you run manifold vacuum.
A good baseline is 14-16 base, add 20-22 mechanical for a total of 36. Vacuum can adds another 15 for a total of just over 50 for cruise and high 20's at idle.
At closed throttle you have no vacuum at the ported port because the port is above the throttle plate. As you open the throttle the port will be below the plate and be the same as manifold vacuum.
At full throttle both ported and manifold ports will have no vacuum.
Depending on how the idle stop screw is adjusted I've seen some cases where there would be no ported vacuum during cruise speeds. This greatly hurts fuel economy. There is no reason not to run a regular manifold vacuum port. Only difference is your NOx emissions increase at idle, but the engine will run smoother and cooler.
It also sounds like your distributor doesn't have the mechanical advance it should. I like seeing 16-20 dgr mechanical. With only 12 dgr you will need 24 dgr base timing and may have hard starts and too much timing at idle in case you run manifold vacuum.
A good baseline is 14-16 base, add 20-22 mechanical for a total of 36. Vacuum can adds another 15 for a total of just over 50 for cruise and high 20's at idle.
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by zwede
Depending on how the idle stop screw is adjusted I've seen some cases where there would be no ported vacuum during cruise speeds. This greatly hurts fuel economy. There is no reason not to run a regular manifold vacuum port. Only difference is your NOx emissions increase at idle, but the engine will run smoother and cooler.
It also sounds like your distributor doesn't have the mechanical advance it should. I like seeing 16-20 dgr mechanical. With only 12 dgr you will need 24 dgr base timing and may have hard starts and too much timing at idle in case you run manifold vacuum.
A good baseline is 14-16 base, add 20-22 mechanical for a total of 36. Vacuum can adds another 15 for a total of just over 50 for cruise and high 20's at idle.
It also sounds like your distributor doesn't have the mechanical advance it should. I like seeing 16-20 dgr mechanical. With only 12 dgr you will need 24 dgr base timing and may have hard starts and too much timing at idle in case you run manifold vacuum.
A good baseline is 14-16 base, add 20-22 mechanical for a total of 36. Vacuum can adds another 15 for a total of just over 50 for cruise and high 20's at idle.
Last edited by bobs77vet; Apr 8, 2005 at 11:38 PM.
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To check the full mech. advance remove the springs and start the car. This will move the weights out as far as they are allowed to go. See what the timing is at. Your springs could be so tight that they are not allowing full advance. If you are not still getting enough mech advance you can file a little more where the bushing rides so it gives you more travel in the mech advance.
I have mine hooked to ported vacuum but after reading and hearing from SWDuke on the C2 and a few others I will be switching to non ported. This should clean up my idle and give me a little better throttle response. I have not had time yet this year to do this.
I have mine hooked to ported vacuum but after reading and hearing from SWDuke on the C2 and a few others I will be switching to non ported. This should clean up my idle and give me a little better throttle response. I have not had time yet this year to do this.
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by Gordonm
To check the full mech. advance remove the springs and start the car. This will move the weights out as far as they are allowed to go. See what the timing is at. Your springs could be so tight that they are not allowing full advance. .
i've been driving around this morning heres the vacuum reading from my PORTED carb outlet...
from a stop sign accelerating away:light throttle...0-7"; medium throttle 10"
cruising on flat roads: 45 mph 0-6"; 55mph 0-8",65mph almost steady 9"; 70mph almost steady10".
so where does this leave me....16initial +12 advance+20 vacuum= 48*
Burning Brakes
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From: North Texas
I think the point here is to get you maximum timing estabilished.
Forget about the vacuum for now and your inital timing.
Remove your springs and set your timing to get 36* at 2500 - 2800.
Then find the right combination of springs to give you that reading. It will probably be Silver/Silver - depending on your spring set.
Once you do that, connect your VC to direct manifold vacuum and plug the ported port.
Forget about the vacuum for now and your inital timing.
Remove your springs and set your timing to get 36* at 2500 - 2800.
Then find the right combination of springs to give you that reading. It will probably be Silver/Silver - depending on your spring set.
Once you do that, connect your VC to direct manifold vacuum and plug the ported port.
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by 1970-Bronze
Remove your springs and set your timing to get 36* at 2500 - 2800.
.
.
ok... here we go.....
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Originally Posted by bobs77vet
ok... here we go.....
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
ok ....springs out, weights rotate freely...started the car and dialed back to 0* on timing tab with timing light.....advance dial says 42*
so i have inital timing of 16* and an unweighted centrifgual advance of 26*?
is that what this means?
so i have inital timing of 16* and an unweighted centrifgual advance of 26*?
is that what this means?
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by zwede
That's what it looks like, Bob. Vacuum can disconnected, right?
So your springs are not letting the distrbutor go to its full advance. Try lighter springs.
So your springs are not letting the distrbutor go to its full advance. Try lighter springs.
can i mismatch springs to get there?
ok the lightest springs are going in right now. stay tuned and thks
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
BINGO.....I have not changed any distributor settings.....with the lightest springs i get initial base timing of 24* and total timing of 40* (thats my 16* of centrifugal advance right).....so if i retard the spark to 36* total advance i wonder where that will put me?
Last edited by bobs77vet; Apr 9, 2005 at 11:20 AM.
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
gold springs the lightest gives me 36* total in the 2500rpm -2800 rpm range and a base timing of 20*....sound right?
Pro
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From: Quebec
Watch for those light spring, they helped cause a problem when I had them on. The weights were not returning to their position at idle. You must be sure to have a clean distributor that operate freely. Otherwise the light spring will give you inacurate timing at idle.
Just a thing to check,
Stephan
Just a thing to check,
Stephan
Last edited by American Boy; Apr 9, 2005 at 01:06 PM.
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
badda bing badda boom.....they taught me that when i moved to Jersey.......
ok here we go....gold springs...20* initial timing, total advance 36* by 2800 rpm.....vacuum advance dialed into a measured 13* at 10" of vacuum and stays the same with higher vacuum...
so 20+16+13= 49*
how does that sound ? time for a test drive....
ok here we go....gold springs...20* initial timing, total advance 36* by 2800 rpm.....vacuum advance dialed into a measured 13* at 10" of vacuum and stays the same with higher vacuum...
so 20+16+13= 49*
how does that sound ? time for a test drive....