Help With Timing Please!
Thread Starter
Safety Car
Joined: Aug 2000
Posts: 3,909
Likes: 26
From: Clymer PA
Help With Timing Please!
Here is what I found out after hooking a timing light up to my motor. It was recommended to me that 22 degrees be my initial timing and 39 degrees be my total timing.
I hooked the timing light up, removed my vacuum advance line from the carburetor and plugged the port on the carburetor. With my car idling at 1500RPMs (what my car normally idles at) I had 22-23 degrees timing. I revved my motor up to 3000RPMs to get my total timing and I have 29 degrees timing...what the heck?
Can someone help me out here?
I hooked the timing light up, removed my vacuum advance line from the carburetor and plugged the port on the carburetor. With my car idling at 1500RPMs (what my car normally idles at) I had 22-23 degrees timing. I revved my motor up to 3000RPMs to get my total timing and I have 29 degrees timing...what the heck?
Can someone help me out here?
Thread Starter
Safety Car
Joined: Aug 2000
Posts: 3,909
Likes: 26
From: Clymer PA
Re: Help With Timing Please! (ram82fire)
LOL that's an understatment :lol: . I'm running my 1976 GM HEI distributor out of my L48 350. The distributor is stock with the acceptions of an Accel distributor cap, rotor and a Mr. Gasket distributor re-curve kit. With the recurve kit I used the lightest springs that came with it.
Do I need to plug the vaccum advance line? I just plugged the port on the carburetor. Did my proceedure for timing seem correct. This is the first time I have ever hooked a timing light up to my motor. :(
Do I need to plug the vaccum advance line? I just plugged the port on the carburetor. Did my proceedure for timing seem correct. This is the first time I have ever hooked a timing light up to my motor. :(
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
Re: Help With Timing Please! (bence13_33)
Sounds like tight springs or corroded bushings for your mech adv.. My orig dist was had corroded bushings (or at least the rods where corroded) so i was getting almost no adv.
Thread Starter
Safety Car
Joined: Aug 2000
Posts: 3,909
Likes: 26
From: Clymer PA
Re: Help With Timing Please! (Fevre)
Fevre:
Am I correct in thinking that I should be getting total advance of 39 degrees in around 3000RPMs? Could this be why my car has been suffering at the track (12.40 @ 116MPH)?
Am I correct in thinking that I should be getting total advance of 39 degrees in around 3000RPMs? Could this be why my car has been suffering at the track (12.40 @ 116MPH)?
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
Re: Help With Timing Please! (bence13_33)
Your spings might be too light giving too much mech adv at your 1500 rpm idle so there is nothing left. Do you have anymore adv left after 3000 rpm's? At what rpm do you run out of adv?
Melting Slicks
Joined: Mar 1999
Posts: 2,845
Likes: 2
From: Apex NC
Re: Help With Timing Please! (Fevre)
I agree, with the light springs you're surely getting most of the centrifugal advance in at 1500 rpm. Switch to the heavier springs so you can dial in the initial at idle speed w/o any centrifugal coming in yet. Then measure the total advance that comes in throughout the rev range. That'll tell you the range of advance you've got w/your distributor.
Shannon
Shannon
Thread Starter
Safety Car
Joined: Aug 2000
Posts: 3,909
Likes: 26
From: Clymer PA
Re: Help With Timing Please! (Fevre)
Fevre:
I just went back up to the garage and checked it again. This time I set it at 3500RPMs. My advance doesn't seem to have moved at all, it's still at 29 degrees :( .
I just went back up to the garage and checked it again. This time I set it at 3500RPMs. My advance doesn't seem to have moved at all, it's still at 29 degrees :( .
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Safety Car
Joined: Jul 2002
Posts: 3,770
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From: St Louis MO
Re: Help With Timing Please! (bence13_33)
Take off the dist. cap and pull gently on the weights to see if the advance mechanism operates smoothly. It should move smoothly out to the stops.
Brett :thumbs:
Brett :thumbs:
Race Director
Joined: Mar 2001
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From: Living in the Hartland
Re: Help With Timing Please! (bence13_33)
Check out Lars' timing paper in the tech section, he is the man.
One thing to consider, what type of balancer are you running? If a stock type rubber one then you may have some out ring slippage. If a nice fluid dampner type then you should be good. You can just try adv your timing to 39 at 3000 rpm's and see if you feel a diff without getting any pinging under load. Then get some diff springs till you reach your idle and full mech adv goals.
One thing to consider, what type of balancer are you running? If a stock type rubber one then you may have some out ring slippage. If a nice fluid dampner type then you should be good. You can just try adv your timing to 39 at 3000 rpm's and see if you feel a diff without getting any pinging under load. Then get some diff springs till you reach your idle and full mech adv goals.
Melting Slicks
Joined: Dec 2000
Posts: 3,407
Likes: 2
From: Carmichael CA
Re: Help With Timing Please! (bence13_33)
Shane, it's the weights and springs. Sounds like at 1500RPM the mechanical advance is all the way in...not unusual for the stock distributor. Heavier weights and springs should do the trick.
Also, test the advance with the vacuum advance connected. Have everything connected up along with your timing light. Then, using a vacuum T slice in your vacuum gauge into the line running to the distributor vacuum advance so you can take readings of ignition timing vs vacuum signal. Make a chart. Now, disconnect the timing light and use a vacuum line long enough to reach into the cab of the car...take the car for a test spin and have a friend monitor the vacuum signal at various speeds and conditions. Then, use the chart to determine what the ignition timing is at those times. This will help determine whether the port is working for you, and help you when you start playing with the weights.
Of course the optimum fix would be to send the distributor to LARS!
Also, test the advance with the vacuum advance connected. Have everything connected up along with your timing light. Then, using a vacuum T slice in your vacuum gauge into the line running to the distributor vacuum advance so you can take readings of ignition timing vs vacuum signal. Make a chart. Now, disconnect the timing light and use a vacuum line long enough to reach into the cab of the car...take the car for a test spin and have a friend monitor the vacuum signal at various speeds and conditions. Then, use the chart to determine what the ignition timing is at those times. This will help determine whether the port is working for you, and help you when you start playing with the weights.
Of course the optimum fix would be to send the distributor to LARS!
Le Mans Master
Joined: Jul 1999
Posts: 9,206
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From: Sewell NJ
Re: Help With Timing Please! (bence13_33)
Try this. Take the springs off the weights completely. Start the car (it may kick a little) and once started rev the engine to 2500 or 3000 rpm while you set the timing to 39 degrees. Once you've done this you have your maximum mechanical advance set where you want it. Shut the engine down and reinstall the springs. When you start the car again you will probably see that your timing at idle is above where you want to be because the springs are too light and can't hold the weights in at 1500 rpm. Install progressively heavier springs until you get the timing to not advance at idle but to advance at slightly higher than idle. This means your timing at idle will be stable and not advance until you go off idle and your maximum will be 39 degrees. If all this sounds like Greek go to Lars paper on setting timing. He says it much better than I do. I followed his instructions exactly and ended up with my timing just the way I wanted (and I had been trying to get it that way for years). Good luck.
Race Director
Joined: Dec 1999
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From: Forked River NJ
Re: Help With Timing Please! (Fevre)
You can check the total timing by just removing the springs on the weights. This will tell if it is allowing the weights to advance. If the weights are advancing then the sorings are tight. It sounds as if something is binding or you are just not getting the weights to move. Check to see if everything is clean. I have seen many HEI with plenty of rusty crusty weights. This way allows you to check the total timing without reving the motor up.
Pro
Joined: May 2001
Posts: 596
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From: Yardley PA
Re: Help With Timing Please! (bence13_33)
Sounds very much like your mechanical advance is all the way in already at 2900 rpm. Just like many stated above. In order to set TOTAL mech. advance you can disconnect the springs and set advance at idle to 39deg. Then try the different springs and check which ones give you 22deg or around there at idle. Do all this with the vac-advance disconnected!
Then rev it up to 3500 where all the mech advance is in for sure and connect the vac-advance to a mityvac or similar device. Pull a good vacuum (~20") and check your advance. It should NEVER be more than maybe 56 degrees. Otherwise you may get ping. If you get more or less than that you need a different vac advance unit.
Read Lars' paper too. The best thing you will ever have read in terms of cheap performance gain.
Enjoy setting it!
Prost :cheers:
Stefan
Then rev it up to 3500 where all the mech advance is in for sure and connect the vac-advance to a mityvac or similar device. Pull a good vacuum (~20") and check your advance. It should NEVER be more than maybe 56 degrees. Otherwise you may get ping. If you get more or less than that you need a different vac advance unit.
Read Lars' paper too. The best thing you will ever have read in terms of cheap performance gain.
Enjoy setting it!
Prost :cheers:
Stefan
Lars!
Burning Brakes
Joined: Dec 2000
Posts: 962
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From: Carlisle PA
Re: Help With Timing Please! (bence13_33)
With my car idling at 1500RPMs (what my car normally idles at)
I personally thought you disconnected the vacuum when you were setting your initial timing, but when setting by total advance, you have to have it hooked up again.
Then again, what do I know, all my stuff is mechanical advance.
Thread Starter
Safety Car
Joined: Aug 2000
Posts: 3,909
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From: Clymer PA
Re: Help With Timing Please! (bence13_33)
Well here's what I did.
I unhooked the light springs and put the distributor cap back on without any springs. I set my total timing to 39 degrees @ 3000RPMs. I then shut the motor down and put a set of medium springs in. I checked it with a timing light and the total advance ended up being...you guessed it 29 degrees. Am I supposed to be hooking the vacuum advance line back up for total advance?
Seems like it wouldn't make a difference considering once you go wide open throttle there is not vacuum.
70PurpleLS7:
If I idle it down to 1000RPMs it idles fine....but is a good bit more choppy and is kinda soggy when I kick it down. At 1500 it idles a lot better, is a lot snappier and after I'm done in the burnout box it doesn't want to die on me.
[Modified by bence13_33, 2:26 PM 4/23/2003]
I unhooked the light springs and put the distributor cap back on without any springs. I set my total timing to 39 degrees @ 3000RPMs. I then shut the motor down and put a set of medium springs in. I checked it with a timing light and the total advance ended up being...you guessed it 29 degrees. Am I supposed to be hooking the vacuum advance line back up for total advance?
Seems like it wouldn't make a difference considering once you go wide open throttle there is not vacuum.
70PurpleLS7:
If I idle it down to 1000RPMs it idles fine....but is a good bit more choppy and is kinda soggy when I kick it down. At 1500 it idles a lot better, is a lot snappier and after I'm done in the burnout box it doesn't want to die on me.
[Modified by bence13_33, 2:26 PM 4/23/2003]
Race Director
Joined: Mar 2001
Posts: 11,322
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From: Living in the Hartland
Re: Help With Timing Please! (70PurpleLS7)
One sweet thing (well one of many) that comes with the MSD ProBillet is a chart that tells you what spring combo gives you what curve. I followed the curve I wanted and when I timed it out, it was perfect. You can remove the vac adv if you like and even lock out the mech adv. :cool:
Pro
Joined: May 2001
Posts: 596
Likes: 0
From: Yardley PA
Re: Help With Timing Please! (bence13_33)
Well here's what I did.
I unhooked the light springs and put the distributor cap back on without any springs. I set my total timing to 39 degrees @ 3000RPMs. I then shut the motor down and put a set of medium springs in. I checked it with a timing light and the total advance ended up being...you guessed it 29 degrees. Am I supposed to be hooking the vacuum advance line back up for total advance?
Seems like it wouldn't make a difference considering once you go wide open throttle there is not vacuum.
I unhooked the light springs and put the distributor cap back on without any springs. I set my total timing to 39 degrees @ 3000RPMs. I then shut the motor down and put a set of medium springs in. I checked it with a timing light and the total advance ended up being...you guessed it 29 degrees. Am I supposed to be hooking the vacuum advance line back up for total advance?
Seems like it wouldn't make a difference considering once you go wide open throttle there is not vacuum.
Prost:cheers:
Stefan