Timing and Tuning

[Valhallo]

Hey guys,

After a month of troubleshooting my mustang is running again, but the problem I have now is my tinkering. I had tuned my carb. up previous to this whole fiasco, but since then I have adjusted my timing.

Now I'm looking at a power problem I am having. The first problem is the engine runs pretty terribly when it's cold. After 5ish minutes of driving it runs a whole lot better. The second problem is I feel I'm loosing low end power. There isn't much power when I launch compared to how it used to feel before playing with the timing and ignition, but I don't feel much power loss on the high end.

I guess what I'm asking is do any of you think this problem could be coming from either an incorrect timing adjustment or incorrect carb tuning? I used my Chilton manual to time the engine to exactly 6 BTDC, and the engine idles just under 600 rpms.

 

[TommyK]

Hey guys,

After a month of troubleshooting my mustang is running again, but the problem I have now is my tinkering. I had tuned my carb. up previous to this whole fiasco, but since then I have adjusted my timing.

Now I'm looking at a power problem I am having. The first problem is the engine runs pretty terribly when it's cold. After 5ish minutes of driving it runs a whole lot better. The second problem is I feel I'm loosing low end power. There isn't much power when I launch compared to how it used to feel before playing with the timing and ignition, but I don't feel much power loss on the high end.

I guess what I'm asking is do any of you think this problem could be coming from either an incorrect timing adjustment or incorrect carb tuning? I used my Chilton manual to time the engine to exactly 6 BTDC, and the engine idles just under 600 rpms.

The factory initial timing setting and the distributor advance curve in general were set up with emissions and smooth operation in mind, not performance. IMO you should be running as much initial timing as your starter will allow without kicking back. That should be somewhere between 12 and 16 degrees initial timing. You must then modify the mechanical advance to allow total timing of no more than 36 degrees. The springs should be changed/adjusted so all the timing is in by 3000 rpm. It will also be necessary to limit the vacuum advance. This will restore the bottom end "punch" you feel you have lost and possible help the cold start operation.

 

[will e]

Set the initial timing to the highest manifold vacuum and then follow tommyk's advice about adjustments.

 

[midlife]

Another benefit of increased initial timing is that the engine runs much more efficiently. You know what that means? Better MPG!

Your cold-starting problems sounds like your choke isn't working correctly.

 

[Valhallo]

Lol, while messing with the carb I disconnected my choke. Thanks Midlife. That solves one problem. And thanks for the info about the initial timing.

 

[Wolverine]

Engine Timing, Carb Jets, etc.

In my searches I have been unable to find a comprehensive guide regarding engine tuning in regards to Carb Jet selection, setting idle lean/rich mixture, setting mechanical timing, setting vacuum advance timing.

Could one of you guys write something up with specific information? For example, I would like to know if I run a 351W 262 cam with 1.6 rockers, what kind of idle vacuum pressure can I expect? How should I compensate my timing for this?

Even just a list of general rules, like set the timing WITH/WITHOUT timing to match your idle vacuum at 800 RPM.

These little things really make a difference in how an engine performs. Me, I don't give a crap how much my engine is shaking. As long as it is loud enough so I can't here the windows rattling and the yuppie wench in the BMW next to me complaining about how my car is stinking up the environment(actually had that happen once), it works for me.

But, when guys hop up their cars a little bit and want to know why their idle isn't smooth/consistent, it would be nice to prepare them for the task at hand: distributor springs, vacuum advance adjustment, and maybe carb jetting.

 

[Valhallo]

The factory initial timing setting and the distributor advance curve in general were set up with emissions and smooth operation in mind, not performance. IMO you should be running as much initial timing as your starter will allow without kicking back. That should be somewhere between 12 and 16 degrees initial timing. You must then modify the mechanical advance to allow total timing of no more than 36 degrees. The springs should be changed/adjusted so all the timing is in by 3000 rpm. It will also be necessary to limit the vacuum advance. This will restore the bottom end "punch" you feel you have lost and possible help the cold start operation.

Alright, I took my timing all the way up to 18, then back down to 14. Now I'm getting much better throttle response, but still lacking the power, and I still have backfiring. The problem might be that I'm just too far over, because I'm not 100% certain what I'm looking for when you say "Without the starter kicking back".

Also, when you say "total timing" and "all timing is in" are you saying that no matter how high it is revving it never advances past 36 degrees?

Sorry bout the rookie questions, but I really appreciate the help. Learning lots from you guys.

 

[TommyK]

The factory initial timing setting and the distributor advance curve in general were set up with emissions and smooth operation in mind, not performance. IMO you should be running as much initial timing as your starter will allow without kicking back. That should be somewhere between 12 and 16 degrees initial timing. You must then modify the mechanical advance to allow total timing of no more than 36 degrees. The springs should be changed/adjusted so all the timing is in by 3000 rpm. It will also be necessary to limit the vacuum advance. This will restore the bottom end "punch" you feel you have lost and possible help the cold start operation.

Alright, I took my timing all the way up to 18, then back down to 14. Now I'm getting much better throttle response, but still lacking the power, and I still have backfiring. The problem might be that I'm just too far over, because I'm not 100% certain what I'm looking for when you say "Without the starter kicking back".

Also, when you say "total timing" and "all timing is in" are you saying that no matter how high it is revving it never advances past 36 degrees?

Sorry bout the rookie questions, but I really appreciate the help. Learning lots from you guys.

When increasing the initial timing you will reach a point where the starter will be unable to turn the engine over when it is fully heat soaked. This is what I mean by kick back. When this occurs you have too much initial timing because obviously you need the car to start reliably under all operating conditions. What I do is take the car for a drive on a warm day until it is fully warmed up, usually on the highway for at least 10 or 15 minutes. I then find a place to pull over and shut the car off and wait 2 or 3 minutes so that the engine becomes fully heat soaked. I try to re-start the car. If the starter kicks back (engine won't turn over) I reduce the initial timing to the point where the car will turn over. I have now determined the maximum amount of initial timing the engine will tolerate. Now I gingerly drive the car home because by advancing the initial timing I most likely have too much total advance for safe operation under "spirited" driving conditions. I make sure the vacuum advance is disconnected and plugged. THIS IS VERY IMPORTANT TO AVOID DAMAGING YOUR ENGINE!!

Once I am home I break out the dial back timing light to determine how many degrees of initial advance my new max setting gives me. For sake of argument let's say it is 16 degrees. Now using the curb idle screw I raise the idle in 500 rpm increments recording the timing reading at each setting until the timing stops increasing, usually somewhere between 3000 and 4000 rpm. When you reach that point lower the idle speed by 100-200 rpm and check the timing again. If it doesn't change lower it some more until you find the point it starts to go down. Record the timing reading and the rpm at which it occurs. That is your total timing reading. It will probably be well north of 36 degrees. It is now time to do some surgery on your distributor known as "re-curving". The procedure for this will vary depending on what type of distributor you have. Here is a link to instructions on re-curving a Duraspark. You can get a general idea what is involved.

http://www.reincarnation-automotive.com/Duraspark_distributor_recurve_instructions_index.html

As far as the specific problems you are experiencing it would be helpful if you posted as much info on your combo as possible as well as details as to exactly what changes you made to the carb. I gather from your post that the car was running well, then you made some changes and now it does not?

 

[c9zx]

The fact that it is back firing may mean the distributor is installed one gear tooth off from where it is supposed to be. It will run but, not well. Just a thought. Chuck

 

[Wolverine]

1. Make sure you set the timing with the VACUUM ADVANCE on the distributor removed.

2. After setting the timing, Rev the engine a little. Your timing should advance (INCREASE BTD)a little otherwise your centrifugal advance plates are stuck. I don't know what the timing should advance, but if it advances measurably, you are probably ok.

3. Put on the Vacuum Advance hose. The timing should advance about 20 degrees more than in step 2.(spec will vary based on your engine/setup/etc.) If it doesn't your vacuum advance needs to be replaced.

4. I think if you jumped a tooth, you would be off by:

15 Teeth/ 360 Degrees= 1 tooth / 24 CAM degrees

1 Cam Degree = 2 Crankshaft Degrees(Cam rotates once every time Crankshaft rotates twice)

24 Cam Degrees = 48 Crankshaft Degrees

That is pretty serious, and can't really be fixed by adjusting the timing.

 

[c9zx]

With one tooth off, and distributor rotated from normal location, it will "run" just not well. If it is off by a tooth, it needs reinstalled properly to operate properly.

 

[Valhallo]

Well I just got back from taking the car for a nice 20 minute highway drive with the vacuum advance plugged. I got back, gave it a minute or so to get heat soaked and hooked up the timing light. It read just how I had set it earlier, at around 14. At this timing it started up beautifully, so I adjusted my timing up to 18. Then I turned the car off, tried to start it again and no problems. It started up just fine. I repeated the process with my timing at 24, and again at 28. Every time it started just fine. Based on what you said, this is way high, right? With my initial at 28, revving the car up to 1,600 put my timing Arctic north of 36. At 28 my initial timing is high enough that it idles pretty rough now (not to the point that I'm worried it will die), but still starts up without a seconds hesitation. I've backed my initial down to 18 for now, but I'm wondering why I can't get the starter to kick back? Did my timing chain jump, or maybe TDC is off?

 

[TommyK]

Well I just got back from taking the car for a nice 20 minute highway drive with the vacuum advance plugged. I got back, gave it a minute or so to get heat soaked and hooked up the timing light. It read just how I had set it earlier, at around 14. At this timing it started up beautifully, so I adjusted my timing up to 18. Then I turned the car off, tried to start it again and no problems. It started up just fine. I repeated the process with my timing at 24, and again at 28. Every time it started just fine. Based on what you said, this is way high, right? With my initial at 28, revving the car up to 1,600 put my timing Arctic north of 36. At 28 my initial timing is high enough that it idles pretty rough now (not to the point that I'm worried it will die), but still starts up without a seconds hesitation. I've backed my initial down to 18 for now, but I'm wondering why I can't get the starter to kick back? Did my timing chain jump, or maybe TDC is off?

Given your most recent experience with trying to advance the initial timing, I would do as Chuck suggests and verify that the distributor is installed correctly. With the #1 piston at top dead center on the compression stroke and the timing mark at zero on the pointer the rotor should be pointing at the #1 plug wire on the cap. If it isn't the distributor has been installed a tooth (or more) off. If the piston is at top dead center and the rotor is pointing at the #1 plug wire and the timing reads anything other than zero the balancer is fubar'd.

 

[Valhallo]

Set the initial timing to the highest manifold vacuum and then follow tommyk's advice about adjustments.

After I couldn't adjust it based on my starter, I went out and bought a vacuum gauge and I just hooked it straight to my intake manifold, then adjusted my timing until my vacuum was at max (16 Hg I believe it was). My timing at idle now reads somewhere between 21 and 22 without the vacuum advance connected.

Given your most recent experience with trying to advance the initial timing, I would do as Chuck suggests and verify that the distributor is installed correctly. With the #1 piston at top dead center on the compression stroke and the timing mark at zero on the pointer the rotor should be pointing at the #1 plug wire on the cap. If it isn't the distributor has been installed a tooth (or more) off. If the piston is at top dead center and the rotor is pointing at the #1 plug wire and the timing reads anything other than zero the balancer is fubar'd.

Would the distributor being a tooth off affect the vacuum running through my intake as well?

 

[Tnfastbk]

After I couldn't adjust it based on my starter, I went out and bought a vacuum gauge and I just hooked it straight to my intake manifold, then adjusted my timing until my vacuum was at max (16 Hg I believe it was). My timing at idle now reads somewhere between 21 and 22 without the vacuum advance connected.

Is your balancer new if not your marks may be off, just a thought

 

[Valhallo]

Is your balancer new if not your marks may be off, just a thought

Actually, I think it's the original. I'm using the dashes that are cut into the balancer itself. Should I be using one of those stickers/tape?

 

[Tnfastbk]

Sometimes the outer ring will slip. Here is a few article/links

http://www.network54.com/Forum/119419/thread/1314981923/Harmonic+Balancer+-+Why+not+stock-

http://forums.vintage-mustang.com/vintage-mustang-forum/457294-60-degrees-advance-idle.html

 

[c9zx]

Did it stop back firing and running poorly?

 

[Valhallo]

After driving it around with the vacuum advance disconnected and my timing set to the highest vacuum I could get from the intake it runs noticeably better, but I won't be able to tune or curve my advances if the balancer has slipped, becuase haven't done anything with the balancer yet. Before I pull the old one and try to align the new one to TDC I had two questions for you guys....

Is there any way to fix the old one, or do I have to replace it?

Is there a way to easily tell whether the outer ring has slipped before I take the old one off?