miss after advancing timing

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7duster4

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I fooled around with the timing on my Duster today at work. I was using a friends dial back timing light. First I want to make sure I did this right.

I disconnected the vaccum from the carb and plugged the hole with a vaccum cap. Start the car, while idling check where the horizontal dash is on the balancer. I revved the engine to around 2,500rpm or so and turned the distributor until the dash on the balancer was lined up with the "0" in the middle of the timing tab. At the same time I had the dial on the light turned to 36*. Did I do this right? So I should now have 36* for my total timing. Before the initial was around 5-6* now it's 14* or so. I also adjusted the ideling screw.

It seems like the car has more balls once the rpms increase. I was getting on the on-ramp in first and punched it but didn't floor it. The tach has never moved so quick. In a split second I was nearing five grand. But here is my problem. When ideling in park and leaving from a stop there seems to be a noticable miss. But smoothens out once I get going. I can hear the rpms skipping while the car is ideling. It isn't a huge concern but I know it didn 't do this before. Is it possible the the ideling screw needs to be turned more? The timing had to affected this. The wires and plugs are nearly new.

Any info is greatly appreciated. Sorry for the long post.

Thanks
 
1. Yes you did it right. :)

2. Yes, you should re-adjust your idle mixture anytime a timing change has been done. It sounds like it's a bit lean now.

Adjust your idle mixture to the highest vacuum possible, go for a test ride and get back to us.
 
NO.....why are you reving it up....no need to do that...set timing at idle unless you are circle track racing
 
ramcharger said:
1. Yes you did it right. :)

2. Yes, you should re-adjust your idle mixture anytime a timing change has been done. It sounds like it's a bit lean now.

Adjust your idle mixture to the highest vacuum possible, go for a test ride and get back to us.
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Right now in park it idles around 600-650rpm. But if I turn the screw clockwise the rpms obviously increase but how far do I go? I know it shouldn't idel near 1,000rpm in park. What exactly do you mean the highest vaccum possible?

Thanks
 
Does it smooth out at idle when you disconnect the vaccum hose to the dist? If so you have to much intial timming.
 
chasduster said:
NO.....why are you reving it up....no need to do that...set timing at idle unless you are circle track racing
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Don't I have to rev the engine in order to get see what the total is? Isn't the initial timing not as important as total. I ususally have a friend do this so sorry if anything sounds dumb. Im somewhat new to this. It's interesting how much difference adjusting the timing makes.

Thanks
 
SGBARRACUDA said:
Does it smooth out at idle when you disconnect the vaccum hose to the dist? If so you have to much intial timming.
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I'll give that a shot tomorrow morning. Thats a great tip. I wasn't really focusing on that when advancing the timing. But I will try it.

Thanks
 
chasduster said:
NO.....why are you reving it up....no need to do that...set timing at idle unless you are circle track racing
Click to expand...

He's trying to set total advance minus the vacuum advance.

7duster4 said:
Right now in park it idles around 600-650rpm. But if I turn the screw clockwise the rpms obviously increase but how far do I go? I know it shouldn't idel near 1,000rpm in park. What exactly do you mean the highest vaccum possible?

Thanks
Click to expand...

OK, I think you have the idle speed screw and and idle mixture screws mixed up. What kind of carb are you running?
 
It's a 500cfm edelbrock electric choke. After thinking a bit are you refering to the two small screws near the base of the carburetor? If so how much do I turn them?
 
7duster4 said:
It's a 500cfm edelbrock electric choke. After thinking a bit are you refering to the two small screws near the base of the carburetor? If so how much do I turn them?
Click to expand...

Yes! The two small screws near the base of the carb. Don't turn them at all until you get a vacuum gauge! Someone who knows what their doing can do it by ear and get 'em darn close, but if you've never tuned a carb before, I highly suggest you get vacuum gauge first. They're pretty cheap from the auto parts store.

First with the car not running, carefully turn one of the screws in and count EXACTLY how many turns it take to bottom the screw and make a note of it to the nearest 1/8 turn. Use a light touch when doing this as it's pretty easy to break or damage the screw and seat.

It should be anywhere from 1 1/2 to 2 1/2 turns out. Turn the screw back out to where it started. Screw in the other screw till it bottoms and screw it out the same number of turns.

Now, attach the vacuum gauge to a manifold vacuum source and fire up the car and let it get up to operating temp. Turn both idle mixture screws out a 1/4 turn and see if the vacuum rises or drops. With experience, you'll just hear the engine run smoother or rougher.

Adjust both screws until you get the highest vacuum reading possible. Both screws should be within 1/4 turn of each other when your done and the idle should be within a reasonable range. Adjust it down if it starts to race.

I can't tell you exactly what your idle rpm should be without a heck of alot more info. I'll say about 750-850 in gear if it has an auto trans, or 850 in nuetral if it's a manual.
 
wouldn't you want 36* total timing with the vacuum advance?? 36* sounds really high to then add vacuum advance to it.
 
dodgefreak8 said:
wouldn't you want 36* total timing with the vacuum advance?? 36* sounds really high to then add vacuum advance to it.
Click to expand...

No. With the vacuum advance, most stock engines will be up around 50 degrees. If a MP distributor is used, vacuum advance can be limited via a set screw in the vacuum canister port.

36 total w/vacuum advance on some stock distributors will have you running 12 degrees retarded at idle!!!

Full race and even a lot of modified street cars will run quite well without vacuum advance at all, but there will be some drop in overall driveability and mileage, but that is entirely dependent on the combination that is being run.

Cam, compression, bore, stroke, carburation, intake manifold, valve size, head port size, style of ignition box, auto or manual trans, torque converter stall, etc. and the combinations of the above will affect how much timing is needed, at what throttle opening and at what rpm.
 
dodgefreak8 said:
wouldn't you want 36* total timing with the vacuum advance?? 36* sounds really high to then add vacuum advance to it.
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Understand the vacuum assisted advance feature only functions at low partial throttle. At WOT there is little to no vacuum. That is why I suspect there is to much initial timing, and if he has the vac hose to a constant source like below the throttle plates, I'm sure there is to much initial advance.
 
SGBARRACUDA said:
Understand the vacuum assisted advance feature only functions at low partial throttle. At WOT there is little to no vacuum. That is why I suspect there is to much initial timing, and if he has the vac hose to a constant source like below the throttle plates, I'm sure there is to much initial advance.
Click to expand...

Yep, very little vacuum at WOT, so vacuum advance is out of the picture. There should be both a timed and constant vacuum port on the carb. Some very low compression engines with retarded cams from the factory such as the Ford 400M built after 75 actually run well on manifold vacuum. Again, it depends on the combo.
 
ramcharger said:
Yes! The two small screws near the base of the carb. Don't turn them at all until you get a vacuum gauge! Someone who knows what their doing can do it by ear and get 'em darn close, but if you've never tuned a carb before, I highly suggest you get vacuum gauge first. They're pretty cheap from the auto parts store.

First with the car not running, carefully turn one of the screws in and count EXACTLY how many turns it take to bottom the screw and make a note of it to the nearest 1/8 turn. Use a light touch when doing this as it's pretty easy to break or damage the screw and seat.

It should be anywhere from 1 1/2 to 2 1/2 turns out. Turn the screw back out to where it started. Screw in the other screw till it bottoms and screw it out the same number of turns.

Now, attach the vacuum gauge to a manifold vacuum source and fire up the car and let it get up to operating temp. Turn both idle mixture screws out a 1/4 turn and see if the vacuum rises or drops. With experience, you'll just hear the engine run smoother or rougher.

Adjust both screws until you get the highest vacuum reading possible. Both screws should be within 1/4 turn of each other when your done and the idle should be within a reasonable range. Adjust it down if it starts to race.

I can't tell you exactly what your idle rpm should be without a heck of alot more info. I'll say about 750-850 in gear if it has an auto trans, or 850 in nuetral if it's a manual.
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Thanks for the great info. I'll have to try this. I should have mentioned before about my distributor. It is a stock replacement piece. But the springs were ditched in favor of two equal size mopar performance springs. Is this what the vaccum advance is? From what I was told they make the timing come in quicker.
 
7duster4 said:
Thanks for the great info. I'll have to try this. I should have mentioned before about my distributor. It is a stock replacement piece. But the springs were ditched in favor of two equal size mopar performance springs. Is this what the vaccum advance is? From what I was told they make the timing come in quicker.
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Those would be your mechanical advance springs and yes, they do allow your mechanical advance to come in quicker but doesn't change the amount of total advance and does not affect your vacuum advance in any way. :)
 
I'll pick up a vaccum gauge tomorrow and take the car out and try to tune this properly. Hopefully it dosn't rain like they have been saying.

As far as getting vaccum, will the hose coming from the pcv valve work with the guage?

I will let you know how it goes. Thanks for all the great help.
 
The line from the PVC valve won't work. The line from the carb to the PVC would work but it's really big.

I suggest coming off the fitting that's screwed into the intake manifold. If you don't have a free nipple on the fitting, use a vacuum "T". If there is no vacuum fitting on the manifold, one of the nipples on the carb should be manifold vacuum.
 
I tinkered around with the car today. I bought a good vaccum gauge and removed the vaccum cap coming off the front of the carburetor to plug in the gauge. I turned both idel mixture screws to get the highest vaccum reading. Right now it's around 18-19psi while in park. Sounds much smoother. When I drove the car there still appears to be a miss at low speeds. The best way to explain is while at a stop light it sounds like this: (These are the best words I could come up with lol)

rumprumprumprumprumprumprump-knock-rumprumprumprumprump-knock-rumprumprumprump...

then when I take off like normal the knocks happen more until I get to around 25-30mph. While in drive and not moving the rpms are around 750-800rpm. I know some Mopar people and I may take it to them this week to check it out. Im sure it's just a simple tuning issue.

Any other info is still appreciated. I wouldn't have been able to do this without "ramchargers" help. Thank you.

Oh yeah it still appears unable to burnout. I only tried once though from a stop but didn't give it all I could. Didn't have enough space lol
 
Oh oh, the "knock" sound is not good. Dial back the timing 2 degrees and see if it stops knocking or at least gets better. If it gets better, dial it back another 2 degrees and see if it stops knocking.
 
I gave the timing light back to my buddy becuase he needed it. If I need to i'll try and get it back from him this weekened. Would it be safe to lossen the distributor and turn it clockwise just a tad? Just a small amount should be about 2* and make it 34* total.

What exactly is making this "knock" sound? I can even feel it while sitting in the car. I didn't recall hearing any pinging.

Thanks
 
Hard to say and I'm hoping it's not bearings and could be just the timing being too advanced but that's hard to believe if there's no ping. Can you get a movie or sound clip and post it? It might be just your exaust hitting somthing under the car, or it could be motor mounts allowing the engine to move around.

You're best off using a timing light but check the above stuff first.
 
They way you timed it works but it seems you're assuming the total advance is all in by 2500 rpm. If your total is actually in at a higher rpm then you may have a lot more timing dialed in than you should - which will cause detonation.

You need to get that timing light back and run the rpm's up past 2500 (with vacuum disconnected and plugged like before) to see if still advances or not. If you put heavier springs in your distributor it won't hit full mechanical advance until a higher rpm. You can set it to 34 or 36 degrees once you know the dizzy won't advance farther. Your initial will then fall where it may. Then you can turn your attention to the vacuum advance pod and adjust it to that you don't get a part throttle ping.
 
70Duster440 said:
They way you timed it works but it seems you're assuming the total advance is all in by 2500 rpm. If your total is actually in at a higher rpm then you may have a lot more timing dialed in than you should - which will cause detonation.

You need to get that timing light back and run the rpm's up past 2500 (with vacuum disconnected and plugged like before) to see if still advances or not. If you put heavier springs in your distributor it won't hit full mechanical advance until a higher rpm. You can set it to 34 or 36 degrees once you know the dizzy won't advance farther. Your initial will then fall where it may. Then you can turn your attention to the vacuum advance pod and adjust it to that you don't get a part throttle ping.
Click to expand...

I got the timing light back tonight. I'll try messing with it tomorrow sometime. What exactly do you mean by "assuming the total is in by 2,500rpm?" I guess what I need is a step-by-step process. Don't know if I mentioned before but im somewhat new to this.

So really the timing needs to be retarded to around 34*?
 
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