Distributors/ Timing

[Loneranger]

I have a 1979 trans am that has a 1968 Pontiac 400 motor, manual transmission. It seems I have to advance the timing past 14 degrees BTDC for the engine to idle at it's best. That makes starting a little harder. The distributor is an Accel 71102E It's an older distributor that is discontinued. I looked up this distributor and it could be used with the vacuum advance or without the vacuum advance. The vacuum advance is still on the distributor, it's blocked off.
I don't know if I should try and hook up the vacuum advance and see if I can get normal timing (9 degrees BTDC) I don't know if any work was done to the motor. I don't think having the vacuum advance connected would be that much of a difference in timing. From 14 degrees BTDC where it is now with smooth idle without vacuum advance to hooking up the vacuum advance and setting the timing to 9 degrees BTDC. I don't think I would get that much advance timing at idle for the motor to run smooth.
I was thinking about getting the MSD distributor with the dial to control the timing. I guess than I would be able to dial it down to 9 degrees BTDC so the car will start easier.
I hope anyone reading this can understand what I am trying to say.
I would appreciate any replies or workable solutions.
Thank you.
I looked at the distributor today, a day after posting the above. The vacuum line on the distributor isn't blocked off. There is a hose from the vacuum on the distributor that is just hanging there (open vacuum, I haven't started it yet to check it). I think the first thing I need to do is try and get vacuum to the distributor and see how the timing responds.
Still welcoming any input.

 

[melsg5]

1. Do you know what camshaft is in this engine?
2. Have you checked for a vacuum leak from either the base of the carburetor, a broken/cracked rubber vacuum line, or the intake where it meets the cylinder heads?
3. What speed are you setting the carburetor idle screw?
4. What procedure are you using to adjust the carburetor idle mixture screws?
5. What carburetor are you using?
6. Any street driven vehicle should be using the vacuum advance with the line connected to manifold vacuum to insure advance at idle.
7. The ideal mechanical advance you want is 12 degrees initial timing with a total of 36 at 3,000 rpm. According to this document you should be able to set the curve for the 12 initial, 36 total, and set the vacuum advance for an additional 10 degrees.
http://gatorperformance.com/catalog_lookup/accel/ACCELdistributors.pdf

 

[Loneranger]

I don't know what cam shaft is in the engine. I purchased the car and had to look up the numbers behind the distributor to see the engine was a 1968 Pontiac 400
The engine has the number 15 heads. I looked up these heads also and the information has them used on a 455 360 HP big car. 1.96/1.66 valve size, 87cc.
The idle speed is set at 900 rpm.
I adjusted the idle mixture screw by turning counter clockwise 1and 1/2 turns and turned more counterclockwise when idle got a little rough I turned it clockwise a little.
Carburetor is a street avenger, not sure of the CFM.
I looked at the distributor a second time and the hose from the vacuum on the distributor seems open and just hanging. I am going to try and get the vacuum connected properly and see how the timing responds.
Thank you for responding, I appreciate the help.

 

[melsg5]

Unless you made a typo on the direction you are turning the mixture screws you are doing it backwards. You are attempting to get the leanest idle possible. To make it lean you turn the screw Clockwise. So turn the screws clockwise 1/8 of a turn at a time watching the tachometer. Which one you start with doesnt matter. Each time you turn the screw 1/8 if the tachometer reading rises adjust the idle speed back down to 900. Go back and forth between the two screws until you see it drop below 900. Once it drops below 900 turn that screw back out counterclockwise 1/4 turn and go to the other screw.

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[Loneranger]

I was trying to say I turn the mixture screws clockwise until they just seat then I back off 1and 1/2 turns counterclockwise and hope the car starts. I keep turning counter clockwise until the rpms reach the highest point. Then I kind of move the screw a little back and forth. That isn't right either.
I connected the vacuum hose from the carburetor to the distributor. There wasn't any hose connected. At idle I couldn't feel any vacuum at the hose when I put my finger over it, the paper wouldn't stay on the hose either. When I revved the motor a little I could feel vacuum at the hose. Next thing I'm going to get is a vacuum gauge.
I bought a timing light with advance. I'm not sure how to use it. I hope it come with directions.
Thank you for explaining the proper way to adjust the carburetor. You know I'm printing that out and hanging it in the garage.

 

[melsg5]

you should find a vacuum source that has constant vacuum, you may have to find that on the intake manifold. The port on the carburetor that has vacuum above idle should be capped if you are not going to use it.

 

[Loneranger]

I actually used the port on the carburetor to connect to the distributor. It only seems to have vacuum above idle. I didn't take the car out for a ride because of 8" of snow more like 8" of ice.
I wasn't sure where to connect the vacuum gauge. Thank you for suggesting connecting the vacuum gauge to the manifold and plugging the vacuum port on the carburetor if I won't be using the port. I'll see if there is any difference with the vacuum connected to the distributor.
I appreciate the help.

 

[melsg5]

you will get a better idle with the vacuum line going to the distributor connected to manifold vacuum. Just remember to disconnect it when setting your timing.

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