"All-in", all the time.
Thread Starter
Racer
Joined: Oct 2007
Posts: 270
Likes: 0
From: Chapel Hill NC
"All-in", all the time.
1977, manual 4-speed. Edlebrock carb, headers.
(Fairly new weights, springs, vacuum can, distributor, etc.) I previously used the Lars papers to set everything up just fine and all was well for 2+ years.
I get a solid 20-22 degrees vacuum from the carb with my gauge. No idle issues (other than being high, @ 950) and the car runs like a demon, no knocking or pinging or hesitation. Plugs look excellent.
Since my idle began to creep higher I thought it might be time to do some adjusting.
Now I seem unable to get any advance beyond idle.
Testing example, I can rotate the distributor and set the timing to 18, or even 36 at idle... and I get no centrifugal advance when going to 2800+ rpm. Plug the vacuum advance can up and get no advance there either. It's a set-it-and-forget-it proposition. "All-in", all the time.
I put in new weights and have tried several spring combinations.
So... my weights/springs are all-in at idle (or not in at all)... and my vacuum can no longer works?
Or, is this shade-tree mechanic missing something more obvious?
(Fairly new weights, springs, vacuum can, distributor, etc.) I previously used the Lars papers to set everything up just fine and all was well for 2+ years.
I get a solid 20-22 degrees vacuum from the carb with my gauge. No idle issues (other than being high, @ 950) and the car runs like a demon, no knocking or pinging or hesitation. Plugs look excellent.
Since my idle began to creep higher I thought it might be time to do some adjusting.
Now I seem unable to get any advance beyond idle.
Testing example, I can rotate the distributor and set the timing to 18, or even 36 at idle... and I get no centrifugal advance when going to 2800+ rpm. Plug the vacuum advance can up and get no advance there either. It's a set-it-and-forget-it proposition. "All-in", all the time.
I put in new weights and have tried several spring combinations.
So... my weights/springs are all-in at idle (or not in at all)... and my vacuum can no longer works?
Or, is this shade-tree mechanic missing something more obvious?
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
If your using the light weight springs, they might be worn out, stretched and there for always advanced. Just a thought. Take one spring off and idle the car to see if it has advance there. If it dont, try replacing the springs to see if it falls back.
Thread Starter
Racer
Joined: Oct 2007
Posts: 270
Likes: 0
From: Chapel Hill NC
Thanks for the information.
The rotor does indeed "snap back", and I cleaned the rotor/VAC plate up and tweaked everything I could.
Unfortunately, I can only get 6 degrees total advance from the distributor. I guess the shaft may be gummed up a bit?
So, I probably need to replace the entire distributor assembly.
I understand that I should expect about 20 degrees advance from a properly working distributor in general.
The rotor does indeed "snap back", and I cleaned the rotor/VAC plate up and tweaked everything I could.
Unfortunately, I can only get 6 degrees total advance from the distributor. I guess the shaft may be gummed up a bit?
So, I probably need to replace the entire distributor assembly.
I understand that I should expect about 20 degrees advance from a properly working distributor in general.
Racer
Joined: Apr 2009
Posts: 331
Likes: 44
From: Cincinnati Ohio
I recommend you start with basics like testing the vacuum canister. Do you have a hand held vacuum pump? If not then confirm that you do indeed have vacuum going to the canister, then unplug it while watching timing and plug it back in to see how much timing changes.
You said the weights and distributor mechanism snaps back, but does it have full range of motion? Before you change distributors, take yours out and throughly clean up the advance mechanism, also check for vertical play in the distributor shaft. If it is more than .010" then shim it to fix.
Your high idle is probably more a function of your carb adjustment than the timing. What have you done to address that issue?
You said the weights and distributor mechanism snaps back, but does it have full range of motion? Before you change distributors, take yours out and throughly clean up the advance mechanism, also check for vertical play in the distributor shaft. If it is more than .010" then shim it to fix.
Your high idle is probably more a function of your carb adjustment than the timing. What have you done to address that issue?
Thread Starter
Racer
Joined: Oct 2007
Posts: 270
Likes: 0
From: Chapel Hill NC
It snaps back, but I have no idea if it is a full range of motion. (The rotor will turn about an inch, and then snap back.)
How is the best way to test the range of motion? What should I expect to see?
The vacuum can is new and is an adjustable unit. It is definitely getting vacumm. You can hear a change in idle when you plug/unplug it, but it has no effect on the timing. Maybe the unit is bad, so I will test it.
As far as idle, I can adjust it at will and it responds nicely... but if I have to set my distributor so far advanced to get to 36 degrees all-in, I loose my 22 degrees vacuum at the carb when I adjust the idle back down to 750 rpm. I understand that I want the highest vaccum from the carb that I can get by adjusting the idle screws?
** Just to reiterate, I am not an advanced mechanic, so my process of doing this may seem amateurish, so bare with me ***
How is the best way to test the range of motion? What should I expect to see?
The vacuum can is new and is an adjustable unit. It is definitely getting vacumm. You can hear a change in idle when you plug/unplug it, but it has no effect on the timing. Maybe the unit is bad, so I will test it.
As far as idle, I can adjust it at will and it responds nicely... but if I have to set my distributor so far advanced to get to 36 degrees all-in, I loose my 22 degrees vacuum at the carb when I adjust the idle back down to 750 rpm. I understand that I want the highest vaccum from the carb that I can get by adjusting the idle screws?
** Just to reiterate, I am not an advanced mechanic, so my process of doing this may seem amateurish, so bare with me ***
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
Thanks for the information.
The rotor does indeed "snap back", and I cleaned the rotor/VAC plate up and tweaked everything I could.
Unfortunately, I can only get 6 degrees total advance from the distributor. I guess the shaft may be gummed up a bit?
So, I probably need to replace the entire distributor assembly.
I understand that I should expect about 20 degrees advance from a properly working distributor in general.
The rotor does indeed "snap back", and I cleaned the rotor/VAC plate up and tweaked everything I could.
Unfortunately, I can only get 6 degrees total advance from the distributor. I guess the shaft may be gummed up a bit?
So, I probably need to replace the entire distributor assembly.
I understand that I should expect about 20 degrees advance from a properly working distributor in general.
Last edited by bluedawg; Mar 12, 2014 at 12:27 PM.
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Thread Starter
Racer
Joined: Oct 2007
Posts: 270
Likes: 0
From: Chapel Hill NC
I am using a Mr. Gasket advance spring/weight kit.
Currently I am testing a medium (gold) and a (light) black in place.
I had two light (black) springs on it the past few years with good results.
I also tried a test run with two gold springs (medium) and had some hesitation on the road.
* The instructions that came with my springs seems different than what I read online as far as the colors of the springs and their stiffness... but you can easily tell which of the springs is stiffer.
Currently I am testing a medium (gold) and a (light) black in place.
I had two light (black) springs on it the past few years with good results.
I also tried a test run with two gold springs (medium) and had some hesitation on the road.
* The instructions that came with my springs seems different than what I read online as far as the colors of the springs and their stiffness... but you can easily tell which of the springs is stiffer.
Last edited by 81_vette!; Mar 12, 2014 at 12:35 PM.
Thread Starter
Racer
Joined: Oct 2007
Posts: 270
Likes: 0
From: Chapel Hill NC
What springs are you using? You could either take one spring off and idle the engine, this would show you the total advance at idlle, or you you can note the timing as is, add the heavy thicker springs and renote the timing,I've had the springs wear out and stay advanced, mostly with the light weight copper colored springs.
Had a 1976 L-82, 4-sp
Joined: Mar 2011
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From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
You only need to remove one. See what the change is, if you dont see any change, install the heaviest spring and see if it drops timing.
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
I think your misreading the timing light. I say this because
"idle increases when i hook up the vac can but timing does not change"
If not then the vac advance is causing a vac leak , it can not increase the idle speed with out doing one of those two things ,, Adv timing or cause a vac leak,
"idle increases when i hook up the vac can but timing does not change"
If not then the vac advance is causing a vac leak , it can not increase the idle speed with out doing one of those two things ,, Adv timing or cause a vac leak,
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
I think your misreading the timing light. I say this because
"idle increases when i hook up the vac can but timing does not change"
If not then the vac advance is causing a vac leak , it can not increase the idle speed with out doing one of those two things ,, Adv timing or cause a vac leak,
"idle increases when i hook up the vac can but timing does not change"
If not then the vac advance is causing a vac leak , it can not increase the idle speed with out doing one of those two things ,, Adv timing or cause a vac leak,
Burning Brakes
Joined: Aug 2001
Posts: 1,160
Likes: 3
From: Greensboro NC
I have a very similar situation. My Distributor will only add about 7 degrees of timing. To have 32 degrees (Vortec heads) all in I would have to have an initial of 25. It doesnt ping there but sounds kind of wacked to have mechanical (no vacuum) only add 7 degrees.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Many stock and even aftermarket distributors offer a very small mechanical advance limit. The basic Summit HEI distributor does not give a lot of mechanical advance.