Total timing...

[RRSweden]

Quick question as Im setting the timing for my 383.

I've read both that the total timing (aiming for 36) is WITH the vac. advance and WITHOUT the vac. advance hooked up.

Wich is it? When I have the vacuum advance hooked up I pass the 36* goal and when it's disconnected I don't reach it. This is with the initial set at 11*

(10,5:1 compression, cam: 224/230 @ 050)

 

[Zeppelin264]

So total "mechanical" timing will be around 36*. That is with the vacuum canister disconnected/plugged off. So set your base, figure out how much mechanical the dist has in it, reset your base accordingly.

So you have 11* now, what is your mechanical total right now? That's the magic number. Your probably going to end up around 14-18 degrees at base for idle which is totally fine. After that's all dialed in then just hook up the vacuum advance and there it is.

So in example if you have 11* now and your total is like 32, then your base needs to be 15* to achieve 36*. Make sense?

 

[RRSweden]

Thanks!

So, that "you don't want any more total than 36-38 degrees of advance" means with the vacuum advance disconnected?

That's what I was hoping for

With the initial set at 11 my total (without vac. adv.) was about 30-32.
I'll turn it up to 15-16 tomorrow!

 

[Zeppelin264]

Correct. I would not go more than 36 total mechanical. And that would be with aluminum heads etc... Best power will come at 34-36 "all in". Forget about what the vacuum advance does. It doesn't really matter.

So 11 now at idle and 32 means you want 15* at idle to achieve 36*. You have 21 degrees of advance built into the dist.

And by "plugging off" that means both the cap on the canister AND the line going to it. Or else you have a vacuum leak and it will idle high.

For the record. Stock spec is 12* at idle. So I'm sure the motor will run alot smoother and be happier around 15*

 

[69L48Z27]

Why would you need to cap off the vacuum advance can on the distributor if the vacuum line is disconnected? I've read that before and see cars that have a cap.

 

[BeepBeepRR]

Ive been dicking around with the same issue. This car I have here has an unknown cam in it. So would it be safe to say that 15 would be a good base to start off with? Not knowing the cam specs could it possibly take 20@ idle and still be good? The car seemed to run better at 20 btdc.

 

[Ranger16]

I set mine in reverse. Using a dial back timing light, I set the total timing to 35* at about 3000 RPM and let the initial fall where it may. When I checked the initial it was at 12 or 14 (I forget now). I was happy with that and locked the distributor down there.

P.S.
Factory spec's call for TDC. I suspect that was an early form of emission control.

 

[BeepBeepRR]

I set mine in reverse. Using a dial back timing light, I set the total timing to 35* at about 3000 RPM and let the initial fall where it may. When I checked the initial it was at 12 or 14 (I forget now). I was happy with that and locked the distributor down there.

P.S.
Factory spec's call for TDC. I suspect that was an early form of emission control.

This makes perfect sense. I will run out and do it. then check initial timing just to see. Doesn't take but a few minutes.

 

[Zeppelin264]

These cars can idle at anything from 12 to 22. The best way to figure out what the engine likes is to set up a vacuum gauge and keep raising the timing until the gauge stops changing/moving.

But that only sets up initial/base. Your total could be waaaaaaay too much, so you'd need to check that as well.

 

[Watchthis]

These cars can idle at anything from 12 to 22. The best way to figure out what the engine likes is to set up a vacuum gauge and keep raising the timing until the gauge stops changing/moving.

But that only sets up initial/base. Your total could be waaaaaaay too much, so you'd need to check that as well.

You're right on the money! Some engines run very well with as much as 25° initial timing. The problem is that the average Joe doesn't recurve the advance and ends up with issues. The vacuum trick is the way to go. Once you get that set, it's a matter of changing the total timing, if needed. This requires changing the advance plate inside the distributor to allow or restrict the advance timing. You'll be amazed at how much better a well tuned ignition will perform. It can be a lot of work, but we'll worth it.

 

[BeepBeepRR]

You're right on the money! Some engines run very well with as much as 25° initial timing. The problem is that the average Joe doesn't recurve the advance and ends up with issues. The vacuum trick is the way to go. Once you get that set, it's a matter of changing the total timing, if needed. This requires changing the advance plate inside the distributor to allow or restrict the advance timing. You'll be amazed at how much better a well tuned ignition will perform. It can be a lot of work, but we'll worth it.

So you set the vacuum gauge up on the carb on the timed vacuum port or full vacuum port? I'm a noob at actual tuning. So these topics are great for me. I have an edelbrock AVS on the car. If that makes any difference.

 

[Watchthis]

So you set the vacuum gauge up on the carb on the timed vacuum port or full vacuum port? I'm a noob at actual tuning. So these topics are great for me. I have an edelbrock AVS on the car. If that makes any difference.

Full vacuum port.

 

[BeepBeepRR]

thanks will do that tomorrow

 

[BeepBeepRR]

Just to make sure I have this correct. I know now about full vacuum I stick the vacuum gauge on it. Here is where I need clarification.
At idle I turn the distributor advance or retard to get no vacuum? And also check total with the gauge. But setting the distributor at either initial or total will lock it in that place. So by doing this total may or may not achieve 0 vacuum if the distributor is not adjusted for the curve? I watched Friburger on Roadkill doing this with a small block 350 I would assume the same is for any engine. They changed springs in a MSD distributor to advance total i think. Does that make sense?

I believe this distributor has a petronix in it. I know its not old school points.

 

[bigmanjbmopar]

http://www.mopar1.us/engine2.html

 

[Ranger16]

The only time you are going to have 0 vacuum is when the engine is off or at WOT.

 

[Zeppelin264]

You should see like 8-20pa of vacuum. As you rotate the dist, that number will go towards the 20 number. When it stops moving in that direction, that's where you stop.

Boost from a turbo is positive pressure, and vacuum is negative. That's why you engine goes to 0 vacuum under WOT, if you had a turbo it would go past 0 and end up wherever the waste gates are set.

At 0% throttle and at idle, your creating whatever the cam shaft dictates for vacuum.

 

[Zeppelin264]

You don't want "0 vacuum". You want the highest vacuum reading you can get. The vacuum moves away from 0 as you advance the motor.

 

[coloradodave]

Correct. I would not go more than 36 total mechanical. And that would be with aluminum heads etc... Best power will come at 34-36 "all in". Forget about what the vacuum advance does. It doesn't really matter.

So 11 now at idle and 32 means you want 15* at idle to achieve 36*. You have 21 degrees of advance built into the dist.

And by "plugging off" that means both the cap on the canister AND the line going to it. Or else you have a vacuum leak and it will idle high.

For the record. Stock spec is 12* at idle. So I'm sure the motor will run alot smoother and be happier around 15*

As has been said, you don't need to plug the canister, just the fitting on the carb or manifold when adjusting the initial and total mechanical timing...

 

[Watchthis]

An engine is more or less an air pump. You draw air in, you move air out. That's why better flowing heads and intakes produce more power. The more air you take in, the more fuel you take in. So by putting a vacuum gauge on your engine, you are basically seeing the rate of air into the engine. The higher that number, the more air being drawn into the engine. By using the vacuum gauge to set initial, you are finding where in the timing scale, the engine draws the most air. Now the back side to this is that now that you have the initial at it's peak performance, the total may or may not be totally off. 35° total is a good starting point. In order to find this number, you have to have timing tape on the balancer or a dial back timing light. If total mechanical advance is to high or to low, then you have to change the restrictor plate or modify your current one. Springs can be replaced to change how quick the timing curve comes in. So it takes a little time and effort to get everything set, but in the end, it's well worth it.