Distributor Question(long)
Thread Starter
|
Senior User
Joined: Apr 2001
Posts: 321
Likes: 1
Distributor Question(long)
Hi,
Background: 79 F100, 351M C6 auto, mostly stock, no EGR or smog pump.
I took my distributor apart last night and noticed that there are two different springs on the mech. advance weights. Is this normal, or should both springs be the same? The max advance in the dist. is on the "19L" side, not the "21L"
Also, I noticed that there is about 1/4" movement in the weights before the springs start to put resistance and restrict the movement of the weights, almost like the springs have streched too far or are worn out? Is this possible?
The reason I ask this is I am having a tuff time getting the inital advance and total advance dialed in such that I have good power from idle, and no pinging at wide open throttle.
Also, with the inital timing set at the correct spot the truck idles much too fast, even with the idle screw all the way out. (20" HG, no vacuume leaks)
I have set the air fuel mixture with a vac. gauge, new cap, new rotor, new magnetic pickup, new vac. advance on the dist.
Any help is appreciated, thanks!
-Brents
Background: 79 F100, 351M C6 auto, mostly stock, no EGR or smog pump.
I took my distributor apart last night and noticed that there are two different springs on the mech. advance weights. Is this normal, or should both springs be the same? The max advance in the dist. is on the "19L" side, not the "21L"
Also, I noticed that there is about 1/4" movement in the weights before the springs start to put resistance and restrict the movement of the weights, almost like the springs have streched too far or are worn out? Is this possible?
The reason I ask this is I am having a tuff time getting the inital advance and total advance dialed in such that I have good power from idle, and no pinging at wide open throttle.
Also, with the inital timing set at the correct spot the truck idles much too fast, even with the idle screw all the way out. (20" HG, no vacuume leaks)
I have set the air fuel mixture with a vac. gauge, new cap, new rotor, new magnetic pickup, new vac. advance on the dist.
Any help is appreciated, thanks!
-Brents
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
Distributor Question(long)
>Hi,
>
>Background: 79 F100, 351M C6 auto, mostly stock, no EGR or
>smog pump.
>
>I took my distributor apart last night and noticed that
>there are two different springs on the mech. advance
>weights. Is this normal, or should both springs be the
>same?
Yes, you should have two different spring rates, one heavy and one light. The light spring gives a quicker advance rate at the lower rpm's until the heavier spring kicks in a higher rpm's. An engine usually needs a quicker advance rate in the lower rpm's but as the engine rev's higher the engine's advance rate requirements are less, hence the heavier spring.
>The max advance in the dist. is on the "19L" side,
>not the "21L"
Don't have any manuals here at work to tell you if that's the right slot, 19L would mean 38 crank degrees. Are the engine tags intact? Then I could look up the calibration for the code.
>Also, I noticed that there is about 1/4" movement in the
>weights before the springs start to put resistance and
>restrict the movement of the weights, almost like the
>springs have streched too far or are worn out? Is this
>possible?
Yes, this is normal. It keeps the weights from sticking in the non-advanced position.
>The reason I ask this is I am having a tuff time getting the
>inital advance and total advance dialed in such that I have
>good power from idle, and no pinging at wide open throttle.
Your total advance should not affect this, it is just the point when the advance stops. It sounds like the rate is too fast or there is too much initial timing.
>Also, with the inital timing set at the correct spot the
>truck idles much too fast, even with the idle screw all the
>way out. (20" HG, no vacuume leaks)
What initial setting are you using? What is the vacuum advance's source?
>I have set the air fuel mixture with a vac. gauge, new cap,
>new rotor, new magnetic pickup, new vac. advance on the
>dist.
Are you positive you got the right vacuum advance? The arm sets the static position for the movable breaker plate. Some vacuum advance cans are adjustable, try shoving a 1/8" allen wrench down the vacuum nipple. Also, did you check the air gap on the pickup? It is critical for proper timing.
Barry
>
>Background: 79 F100, 351M C6 auto, mostly stock, no EGR or
>smog pump.
>
>I took my distributor apart last night and noticed that
>there are two different springs on the mech. advance
>weights. Is this normal, or should both springs be the
>same?
Yes, you should have two different spring rates, one heavy and one light. The light spring gives a quicker advance rate at the lower rpm's until the heavier spring kicks in a higher rpm's. An engine usually needs a quicker advance rate in the lower rpm's but as the engine rev's higher the engine's advance rate requirements are less, hence the heavier spring.
>The max advance in the dist. is on the "19L" side,
>not the "21L"
Don't have any manuals here at work to tell you if that's the right slot, 19L would mean 38 crank degrees. Are the engine tags intact? Then I could look up the calibration for the code.
>Also, I noticed that there is about 1/4" movement in the
>weights before the springs start to put resistance and
>restrict the movement of the weights, almost like the
>springs have streched too far or are worn out? Is this
>possible?
Yes, this is normal. It keeps the weights from sticking in the non-advanced position.
>The reason I ask this is I am having a tuff time getting the
>inital advance and total advance dialed in such that I have
>good power from idle, and no pinging at wide open throttle.
Your total advance should not affect this, it is just the point when the advance stops. It sounds like the rate is too fast or there is too much initial timing.
>Also, with the inital timing set at the correct spot the
>truck idles much too fast, even with the idle screw all the
>way out. (20" HG, no vacuume leaks)
What initial setting are you using? What is the vacuum advance's source?
>I have set the air fuel mixture with a vac. gauge, new cap,
>new rotor, new magnetic pickup, new vac. advance on the
>dist.
Are you positive you got the right vacuum advance? The arm sets the static position for the movable breaker plate. Some vacuum advance cans are adjustable, try shoving a 1/8" allen wrench down the vacuum nipple. Also, did you check the air gap on the pickup? It is critical for proper timing.
Barry
Thread Starter
|
Senior User
Joined: Apr 2001
Posts: 321
Likes: 1
Distributor Question(long)
Hi Barry:
Thanks for the reply!
The initial timing I am using is anywhere from 4 degrees to 8-10 degrees. I only run 94 octane gas, so I was trying to get the most advance I could before "pinging".
The vac advance source is the "Ported" connection off the front of the carb. Just for a test, I have also tried the manifold vacuume, it didn't really make a noticable difference. Since I re-painted the motor I have lost the paper tags on the rocker covers. Are these the tags you are refering to?
I am not positive that I have the right vac. advance, it is just the one the parts man gave me. It looked almost identical to the old one if that matters? Since this vac. advance is aftermarket, it is not adjustable (I tried that already)
How do I check the air gap in the pickup? This is the first time I have heard of this, and now that you mention it, I can hear a slight "ticking" noise from the distributor that sounds like the pickup may be rubbing? There also seems to be alot of side to side slop where that pickup coil sits on the distributor shaft.
Thanks for your help!
-Brents
Thanks for the reply!
The initial timing I am using is anywhere from 4 degrees to 8-10 degrees. I only run 94 octane gas, so I was trying to get the most advance I could before "pinging".
The vac advance source is the "Ported" connection off the front of the carb. Just for a test, I have also tried the manifold vacuume, it didn't really make a noticable difference. Since I re-painted the motor I have lost the paper tags on the rocker covers. Are these the tags you are refering to?
I am not positive that I have the right vac. advance, it is just the one the parts man gave me. It looked almost identical to the old one if that matters? Since this vac. advance is aftermarket, it is not adjustable (I tried that already)
How do I check the air gap in the pickup? This is the first time I have heard of this, and now that you mention it, I can hear a slight "ticking" noise from the distributor that sounds like the pickup may be rubbing? There also seems to be alot of side to side slop where that pickup coil sits on the distributor shaft.
Thanks for your help!
-Brents
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
Distributor Question(long)
Sorry for the delay Brents, been kind of busy today. If you still have the old vacuum advance, compare it to the new one and see if the arms are identical and the hole is in the same place. The arm length sets the correct static position and the proper phase in relation to the cap. The air gap can be checked with a feeler gauge but I don’t have that dimension right here. You could compare gap measurements between the new and old pickups. Since it sits on pins there’s no adjustment but I have seen some replacement pickups that were off so it’s worth checking. Your dizzy shouldn’t tick, try to see what’s hitting. The pickup coil sits on a plate that rotates around the shaft. Is it the pickup and plate assembly that has the slop or is it the distributor shaft itself? Either one is no good and will give you erratic timing. It’s also good to check the vacuum advance motion by sucking on the hose and watch the pickup rotate around the shaft. See if it moves smoothly through the full length of travel and back to rest without any binding.
The decals on the valve covers have the calibration code but I wouldn’t worry about it right now. I think once you sort through the dizzy problems, everything should start coming together.
Barry
The decals on the valve covers have the calibration code but I wouldn’t worry about it right now. I think once you sort through the dizzy problems, everything should start coming together.
Barry
Thread Starter
|
Senior User
Joined: Apr 2001
Posts: 321
Likes: 1
Distributor Question(long)
Hi Barry,
I seem to have the problem fixed!
I ended up tapping the "19L" side of the mechanical advance and putting a screw there to limit the amount of total mechanical advance. ( put the same screw in the "21L" side to keep things balacned)
This allowed me to run more "initial" timing such that the truck would be "snappy" when cold/with the choke on, before the mech. advance took over.
Now I have no pinging under wide open throttle, and great power when cold with no backfireing etc. I am soooooo happy now! It has taken 3 weeks to solve this
The ticking sound was solved by *carefully* filing away about 4 thou off the iron "starfish" thing that spins around on the dist. shaft. This stopped the pickup coil from hitting this "starfish" thing.
Thanks for your help,
-Brents
I seem to have the problem fixed!
I ended up tapping the "19L" side of the mechanical advance and putting a screw there to limit the amount of total mechanical advance. ( put the same screw in the "21L" side to keep things balacned)
This allowed me to run more "initial" timing such that the truck would be "snappy" when cold/with the choke on, before the mech. advance took over.
Now I have no pinging under wide open throttle, and great power when cold with no backfireing etc. I am soooooo happy now! It has taken 3 weeks to solve this
The ticking sound was solved by *carefully* filing away about 4 thou off the iron "starfish" thing that spins around on the dist. shaft. This stopped the pickup coil from hitting this "starfish" thing.
Thanks for your help,
-Brents
