Timing question..
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Team Owner
Joined: Jul 2001
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Timing question..
I'm trying to set the timing on my 406 and it seems to me as if the timing only goes up 2 - 3 degrees from idle when reving up the engine....
Could it be that there's a problem with my mechanical advance?
Could it be that there's a problem with my mechanical advance?
Burning Brakes
Joined: Nov 2004
Posts: 1,028
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From: San Antonio Texas
sounds like either mechanical advance has seized up in the distributor or (and this happened to me once) the advance weights have gotten crossed over each other and won't allow advance mechanism to work. check the weights first. if they're crossed over it will lock out the distributor. also, check to be sure shaft rotates freely by turning it gently.
Melting Slicks
Joined: Dec 2004
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From: pr, frederick md.
the mech. advance weights use centrifugal force to push them open. so unless theyre stuck or installed backwards they should move. sure you put them back on right way? even the center piece has a right way, so it can push on the weights. second if the mech. side is ok, how much vac. you got now with a bigger cam? no vac = no vac. advance. .02
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Team Owner
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Originally Posted by redc3
the mech. advance weights use centrifugal force to push them open. so unless theyre stuck or installed backwards they should move. sure you put them back on right way? even the center piece has a right way, so it can push on the weights. second if the mech. side is ok, how much vac. you got now with a bigger cam? no vac = no vac. advance. .02
Race Director
Joined: Dec 1999
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From: Forked River NJ
Something is hanging up in the mech. advance.The vacuum should have ne bearing on it. You should have about 20 degrees of mech advance. If your initial is 12 to 14 you should rev it a little and it should jump to 30+ degrees. You want it all in by 2500 or so rpm.
Team Owner
Joined: Jun 2001
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From: Virginia USA
What brand of distributor do you have?
My MSD distributor has changeable bushing of different diameter to increase or decrease the amount of centrifuge advance. Maybe that’s what’s going on.
My MSD distributor has changeable bushing of different diameter to increase or decrease the amount of centrifuge advance. Maybe that’s what’s going on.
Melting Slicks
Joined: Aug 1999
Posts: 3,123
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From: Hollywood, Florida
Originally Posted by GrandSportC3
The vacuum advance isn't hooked up... Doesn't make sense with that cam..
They sell adjustable vac cans to tailor it to your needs.
As far as the other issue, like others posted, you have a mechanical issue. Pull the cap, "twist" the rotor. You should have some play. Then pull the rotor and check the weights and spring. You need about 18-22 deg. of mechanical advance.
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Team Owner
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Originally Posted by shoptek
IF you use the car on the street, you can and should use your vac. advance. The cam has little bearing on it....you will need to hook it up to ported vacuum, which is vac. off idle i.e. crusing, when your engine will develop vac regardless of the cam. The added timing will help with cooling and general driveability. I know....You have wonderful fans and a wonderful radiator, but don't tax the system for something as benign as a vacuum advance unit.
They sell adjustable vac cans to tailor it to your needs.
As far as the other issue, like others posted, you have a mechanical issue. Pull the cap, "twist" the rotor. You should have some play. Then pull the rotor and check the weights and spring. You need about 18-22 deg. of mechanical advance.
They sell adjustable vac cans to tailor it to your needs.
As far as the other issue, like others posted, you have a mechanical issue. Pull the cap, "twist" the rotor. You should have some play. Then pull the rotor and check the weights and spring. You need about 18-22 deg. of mechanical advance.
I took the distributor apart and the springs seek kinda worn... I have some replacement springs.
There are the little gold ones, silver ones and black ones.. The gold ones seem to have the least resistence...
What springs should I install??
Last edited by GrandSportC3; Feb 6, 2005 at 01:21 PM.
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Race Director
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From: Forked River NJ
A way to tell if you aregetting full advance with out reving the crap out of the motor is just remove the springs and fire the motor up. It will go to full advance and stay there, even at idle. This will confirm what the dist. will give you at full advance. If you have a degreed balancer you can check out which springs bring in full advance by 2500 rpm. Put on theweakest springs and slowly bring up the rpm while watching the timing. See at which rpm you hit full advance. Do this for all the spring and and you can taylor your advance curve this way.
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Originally Posted by Gordonm
A way to tell if you aregetting full advance with out reving the crap out of the motor is just remove the springs and fire the motor up. It will go to full advance and stay there, even at idle. This will confirm what the dist. will give you at full advance. If you have a degreed balancer you can check out which springs bring in full advance by 2500 rpm. Put on theweakest springs and slowly bring up the rpm while watching the timing. See at which rpm you hit full advance. Do this for all the spring and and you can taylor your advance curve this way.
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
Olivier -
If you have a very quick advance curve in your distributor (soft springs), it is most likely that the majority of your centrifugal advance has come in at your idle speed. This will make it appear that your advance curve is very short. To check for this, install a stiffer set of springs and see if the curve becomes longer. If it does, mystery solved.
I don't, however, advocate use of the stiffer springs: The engine combo you have is going to want a lot of initial timing, and having it all slam in just off idle is just fine as long as the total is limited to 35-36 and you don't get any indication of detonation at lower rpm. Without vacuum advance, you want to have a whole bunch of timing in it at idle, and your setup sounds just fine. Even though the advance may be partially, or nearly fully, deplyed at idle, it is still pulling back during the low-rpm engine cranking/starting, so you should still have easy starts. No problem. Sounds good!
If you have a very quick advance curve in your distributor (soft springs), it is most likely that the majority of your centrifugal advance has come in at your idle speed. This will make it appear that your advance curve is very short. To check for this, install a stiffer set of springs and see if the curve becomes longer. If it does, mystery solved.
I don't, however, advocate use of the stiffer springs: The engine combo you have is going to want a lot of initial timing, and having it all slam in just off idle is just fine as long as the total is limited to 35-36 and you don't get any indication of detonation at lower rpm. Without vacuum advance, you want to have a whole bunch of timing in it at idle, and your setup sounds just fine. Even though the advance may be partially, or nearly fully, deplyed at idle, it is still pulling back during the low-rpm engine cranking/starting, so you should still have easy starts. No problem. Sounds good!
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Team Owner
Joined: Jul 2001
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From: Lakeland, FL
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St. Jude Donor '03, '06, '17
Originally Posted by lars
Olivier -
If you have a very quick advance curve in your distributor (soft springs), it is most likely that the majority of your centrifugal advance has come in at your idle speed. This will make it appear that your advance curve is very short. To check for this, install a stiffer set of springs and see if the curve becomes longer. If it does, mystery solved.
I don't, however, advocate use of the stiffer springs: The engine combo you have is going to want a lot of initial timing, and having it all slam in just off idle is just fine as long as the total is limited to 35-36 and you don't get any indication of detonation at lower rpm. Without vacuum advance, you want to have a whole bunch of timing in it at idle, and your setup sounds just fine. Even though the advance may be partially, or nearly fully, deplyed at idle, it is still pulling back during the low-rpm engine cranking/starting, so you should still have easy starts. No problem. Sounds good!
If you have a very quick advance curve in your distributor (soft springs), it is most likely that the majority of your centrifugal advance has come in at your idle speed. This will make it appear that your advance curve is very short. To check for this, install a stiffer set of springs and see if the curve becomes longer. If it does, mystery solved.
I don't, however, advocate use of the stiffer springs: The engine combo you have is going to want a lot of initial timing, and having it all slam in just off idle is just fine as long as the total is limited to 35-36 and you don't get any indication of detonation at lower rpm. Without vacuum advance, you want to have a whole bunch of timing in it at idle, and your setup sounds just fine. Even though the advance may be partially, or nearly fully, deplyed at idle, it is still pulling back during the low-rpm engine cranking/starting, so you should still have easy starts. No problem. Sounds good!
