Timing Question for 360

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dustadude

dustadude

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So I've been reading as much as I can here about setting timing to ensure that I know what the deal is and am able to set my 360 duster up the best I can. I've converted to electronic ignition, and rebuilt the motor with a 68 340 spec cam. My question is when I'm setting the timing, I've got the vacuum advanced unplugged from the carb and plugged up. I get my timing light, vacuum gauge, and I've found, per the vacuum gauge, that the car likes best to be set at about 34 degrees BTDC, so advanced 34. Is this normal, because I read the articles about total timing, initial timing and so on, and I get confused as to if I've done this correct. When I experimented with setting my timing, it ran like a dog, horrible. But as I continued to advance the timing, it began to run better and read on my vacuum gauge to be operating in a "Normal Engine" range. Am I crazy?
 
34* is a bit much for initial timing. That's about where total timing should be. At what RPM are you checking the timing? If it's around 3K then you might be ok. If it's 34* at idle, that's too much. You should be good with around 20* give or take at idle with about 14* mechanical all in by no later than 3K for a total of 34* or so.
 
It might also be that the timing mark is wrong. Sometimes the harmonic balancer slips. Also, if you are using a "dial up" timing light make sure it's correct. MSD ignition has their own problems with timing lights.

Check the marks with a piston stop

How did you decide this is what the engine wants, by the way? As Rusty asked, "at what RPM" did you check this?

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Are you determining this setting with the engine at cruise RPM or at idle? At 34 degrees initial the engine would have a hard time even starting unless the cam timing was off or coil was shot. You could have super light advance springs letting the weights swing out early. We really need to learn more about your procedure.
 
340 with a 68 spec camshaft should run well at idle with 14-18* timing.

What is the current idle rpm? Does the car start easily with 34* timing on it?
 
Starting at 34* isn't an issue on first start, once its been running and I turn it off, the heat soak into the starter makes it chug hard for two seconds then it fires right up. I'm trying to remember the rpm, I want to say that the RPM was high, but I can't remember. I'll try bringing it back today to look to be around 14-18 and see how that goes. I know I sound like the world's biggest idiot with this post but I greatly appreciate the feedback and info. Thanks guys, hoping to have more information after today.
 
Oh and the way I determined that the engine liked this was I started the engine, had my vacuum gauge plugged in and reading the vacuum, then I also had an tach hooked up so I could read the rpms as I was adjusting the timing. I started the engine, then started adjusted the timing, paying attention to the rpms, and also how much vacuum the engine was reading. I would also do a few pulls on the carb to see how much hesitation there was. My first go I got it up to 18-20*. I thought I had it right, but then I had a ton of hesitation when I would hit the gas, so I messed with the timing some more and that's how I wound up so high. I'll try correcting this today and bringing the timing back down to 18*ish and then resetting the thermoquad and see how it goes.
 
Some of the 70's distributors had an electric solenoid on the vacuum pod that was an electric retard. I used one on my 70 Cuda 440+6 so I could run a real short curve with a lot of initial. I just flipped the switch while starting to I wasn't hammering against the starter. Not recommended for a street setup although you could tie it in to the start terminal. The extra timing was a bandaid for not quite enough converter.
 
dustadude said:
Oh and the way I determined t.
Click to expand...

All that you typed, you still didn't say at what RPM. If you are doing this at 1500 is a hell of a lot different than a mild cam idle at say 650-700
 
dustadude said:
Starting at 34* isn't an issue on first start, oy.
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Yah, but..........depending on what you have for a distributor, you are going to be WAY WAY WAAAAYYYYAAAAYYAYAYAYAYAYAAAAAAAAAAAAAAAAAA too far advanced "at speed"

"locked advance"
 
dustadude said:
Sorry Dart273, I can't remember the rpm and didn't get a chance to fix it today.
Click to expand...

'S OK. My point is you should be doing this at a dead slow idle. A stock 68 340 cam should idle well at 600.
 
Thanks for the help guys, I re timed the car, put it at about 18*, about 900 rpm, retuned the carb. Car runs great now. Just have to get the carb dialed in right now, having a delay with the TQ when I first hit the throttle. Always another thing to fix! Thanks for all the help guys!
 
having a delay with the TQ when I first hit the throttle.
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You're on ported I am assuming. take off the air cleaner & under the hood look in the carb throat & pull the throttle & see if you have immediate AP tip in & sufficient stream duration/amount
 
dustadude said:
Not sure what you mean by AP, but steam and duration is definitely weak. The steam tapers off, and the duration is short
Click to expand...

On qualudes. Ignore the old man behind the curtain

pay_no_attention_to_that_man_behind_the_curtain_0.jpg
 
If it's a Thermoquad carb, you may have to adjust the back flap a little tighter to eliminate the "bog" off line wide open.
 
So I pulled the carb apart, for supposedly being rebuilt it's a mess. One bowl was full whole the other was almost empty. Two different metering rods, one is a the step and the other is a two step. Going to have it rebuild soon. The accelerator pump sporting is rusty and crusty as well.
 
That TQ is gonna take a lot to restore.

Power timing.
This is the maximum timing your dizzy will deliver with the vacuum advance disconnected or defeated. On most iron headed SBMs this is about 36 degrees with adequate octane gas. It usually occurs at between 3000 and 4000 rpm in factory unmodded dizzys. If you exceed these parameters the engine will/may get into detonation, and/or preignition/detonation. If the engine is operated in this condition for too long,under load, It can hammer the pistons into pieces,break sparkplugs seize skirts or just generally wreck the engine.
For this reason the power timing has to be limited. The power timing changes every time you change the idle timing. The power timing has to be set independently,after the idle timing is finalized. Most stock dizzys will have around 20 or more,degrees of centrifugal timing in them. So that means you can set the power-timing to say 34* and have 34 - 20 = 14* left for idle. But if your dizzy has 25* in it, then you will only have 9* left for idle. And if your dizzy happens to be engineered for a teener, it might have 30* of centrifugal in it which leaves only 4* for idle.
The problem comes when you crank up the idle timing of the wrong dizzy to say 18*. Then 18 + 25 = 43* of power timing. The engine wont last long under full loadWot at that number.
The factory dizzy has to be removed and diss-assembled to change the power-timing.
 
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