Timing and Tuning

[Tnfastbk]

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?

I'm not saying it did slip, but from all you have said, that is a possible cause of your problems when trying to use the marks. Anything is worth a try.

 

[Valhallo]

I'm not saying it did slip, but from all you have said, that is a possible cause of your problems when trying to use the marks. Anything is worth a try.

Nah, I get that, and I appreciate the input. It would certainly make sense to me. Plus, after doing some research it sounds like it happens in the cars notably often. After asking if there was a way to check, I just realized all I need to is get piston #1 to TDC and check it on the balancer. Now I just have to figure out how to crank it around to TDC... Guess I might have to take the radiator and fan out to get to that bolt, huh?

 

[don29163]

If you are road timing it, the marks don't matter....you are setting it to the best performance, without spark knock or kick back.

 

[TommyK]

Balancers can be rebuilt but unless this is a rare piece like off a Boss it is easier to just change it. A timing tape can temporarily correct the timing marks and make it easier to read.

 

[Tnfastbk]

If you are road timing it, the marks don't matter....you are setting it to the best performance, without spark knock or kick back.

+ 1

 

[Steven Harris]

You should be able to rotate your motor without taking off any accessories. 15/16 socket with short extension. Take out a few plugs and it will make it easier. Your first step is to verify. Veryify TDC in relationship to your balancer. From there you will know where to go.

 

[marks73]

It'e easiest to get on the bolt from under the car with a 1/2 drive breaker bar. As stated engine will turn very easy if you remove your plugs. But before you do that. Why not just bring the rotor to #1 on the cap and see where your balancer marks are on the pointer?

 

[Valhallo]

It'e easiest to get on the bolt from under the car with a 1/2 drive breaker bar. As stated engine will turn very easy if you remove your plugs. But before you do that. Why not just bring the rotor to #1 on the cap and see where your balancer marks are on the pointer?

I thought about that, but if my balancer did slip, it likely slipped somewhere between 20 and 30 degrees off. Would that be noticable in the difference between the rotor and the balancer? I'm just not sure how far up the cylinder 20 degrees is.

Well I took the mustang out for a drive today, and at one point put the pedal to the floor to see how I did with the tune up, and I couldn't get the tires to spin like I used to. Now I realize that this isn't exactly the most accurate performance test, so I then decided to use the the freeway onramp as a test strip, and ended up with a 0-60 time of close to 9.9. Just curious, anyone else running a stock 351C 2V? Anything I can compare to?

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I'm pretty sure I just verified that my balancer is off by bringing my rotor around to #1 with no more than 5 degrees of leeway, but my balancer is reading that i'm more than 20 degrees off. I could just slap one of those tapes with the markings on the balancer after getting the #1 piston to exact TDC, but is it a risk driving with the same balancer after it slipped once? Should I replace it with an after market, maybe an ATI?

 

[73vertproject]

Any update?

 

[Valhallo]

I know this is an old thread with old news, but when Utard asked me for an update on this situation, it reminded me that other people could make use of any results I may have had. Unfortunately, it hasn't been much so far. I confirmed that TDC is where it should be. The piston is at the top of the cylinder when my balancer says 0, which means that I am reading optimal vacuum from the manifold when my timing is too early. As of now, I have my vacuum advance plugged with my timing backed down to an initial of 16 (I think - haven't checked in a while) to keep it in safe operating ranges becuase it is the car I get around in. I've been researching and looking for where to go next, and I have certainly learned a lot looking for my specific answer, but I haven't learned the answer to my question. Anyways there's my update.

Sidenote...

If you are road timing it, the marks don't matter....you are setting it to the best performance, without spark knock or kick back.

Shouldn't I be worried about my timing being too far ahead though? If my engine is running an advance of 40 when it's being worked, couldn't it damage my engine?

 

[73vertproject]

Hey, Mike? (sorry, I'm bad with names) you're right when you say that others could learn something from your experience. I'm in the middle of timing and tuning my 'vert. But since yours is the car you "get around in" it would make it 10X tougher to try to get it figured out.

But if you are driving it, it sounds like something alot less serious than I might have thought (at least, compared to my problems).

 

[Utard]

So, I think I understand.

Please correct me if I'm not.

Zac plays with his timing until he gets max vacuum. He had said at 21 - 22 was where it was max. Let's use the number 20. This seems a bit high, but maybe not too crazy high. My sticker says 16BTDC so, I guess it's not too out of line.

What he needs to do now is recurve the distributor so that it doesn't go any higher than 36.

According to the provided link on how to do a recurve, if he put in an 8L advance slot, which is 16 degrees he would then limit the total mechanical to 36.

Am I understanding or mistaken?

I'm in a similar situation where max vacuum puts me around 24 - 25 initial. I just bought a Pertronix distributor and there are little brass bars that I can install to limit the total mechanical. With no limiter installed I should get a max of 24 mechanical plus initial. I can limit it to 20, 16 or 12. So along the same lines, lets say I back it down to 20 initial and install the 16 degree limiter, I should be in fine shape?

To further my understanding......

If I were to not limit the mechanical advance, and say I set the initial at 20, then my total would be around 44. Wouldn't my engine act inappropriately? If these were my settings and the car didn't backfire or ping or have a loss of power, but actually ran well, what now? While chatting over beers the other day, my buddy who isn't a mechanic, but generally knows his stuff said "your motor will let you know". His belief is that if you're not pinging or losing power or something that you should be just fine.

 

[TommyK]

So, I think I understand.

Please correct me if I'm not.

Zac plays with his timing until he gets max vacuum. He had said at 21 - 22 was where it was max. Let's use the number 20. This seems a bit high, but maybe not too crazy high. My sticker says 16BTDC so, I guess it's not too out of line.

What he needs to do now is recurve the distributor so that it doesn't go any higher than 36.

According to the provided link on how to do a recurve, if he put in an 8L advance slot, which is 16 degrees he would then limit the total mechanical to 36.

Am I understanding or mistaken?

You understand

I'm in a similar situation where max vacuum puts me around 24 - 25 initial. I just bought a Pertronix distributor and there are little brass bars that I can install to limit the total mechanical. With no limiter installed I should get a max of 24 mechanical plus initial. I can limit it to 20, 16 or 12. So along the same lines, lets say I back it down to 20 initial and install the 16 degree limiter, I should be in fine shape?

Vacuum advance not withstanding, yes but as with everything you need to be observant and responsive to the feedback your engine gives you based on how it runs. Every car is different. It should also be noted it is not just initial or total timing that needs to be considered. The timing curve is just as important. If your total advance is in by 2000 rpm chances are it will ping.

To further my understanding......

If I were to not limit the mechanical advance, and say I set the initial at 20, then my total would be around 44. Wouldn't my engine act inappropriately? Possibly If these were my settings and the car didn't backfire or ping or have a loss of power, but actually ran well, what now? While chatting over beers the other day, my buddy who isn't a mechanic, but generally knows his stuff said "your motor will let you know". His belief is that if you're not pinging or losing power or something that you should be just fine.

Theoretically yes but your theory assumes that all detonation which is potentially damaging is audible. Such is not the case. Also, max timing is not necessarily the "best" timing for a particular combo. In other words the engine may tolerate 44 degrees but may make more power with less timing. The recommendation for 36 degrees of total timing is based on a generally understood safe max for iron heads that provides near optimum performance.

 

[c9zx]

+1 on TommyK's post. With a reasonable cam 16 initial + 20 mechanical for a total of 36 mechanical advance is usually good. Have all mechanical advance in by 2600-2800 RPM. Limit the vacuum advance, if used, to a max of 8 to 10 degrees. As Tommy said you can not hear high RPM detonation. But you can "read the plugs" to get a clue that it is or is not occurring. Consider the heat range of the plugs you are using. I usually start with Autolite Racing Plug that is listed as a replacement for the Boss 351 as a starting point on determining the proper heat range. Chuck

 

[Utard]

Sweet.

Thanks Guys!

How do you go about limiting the vacuum?

Do you install some kind of check valve inline, or is there an adjustment in the distributor?

I'm using the ported vacuum on a carter.

If you're looking at the plugs, are you looking for signs of heat? Excess carbon? Oxidation?

Do you pull them all to know for sure, or just one or two is a good enough indicator?

Scott

 

[TommyK]

Sweet.

Thanks Guys!

How do you go about limiting the vacuum?

Do you install some kind of check valve inline, or is there an adjustment in the distributor?

I'm using the ported vacuum on a carter.

If you're looking at the plugs, are you looking for signs of heat? Excess carbon? Oxidation?

Do you pull them all to know for sure, or just one or two is a good enough indicator?

Scott

Plugs will be white with black specs on them that look like pepper.

Some vacuum advances are adjustable with a hex key (3/32"??) through the nipple where the hose attaches.

Even though mine is adjustable, I had to make a stop limit the vacuum advance to 8 degrees.

 

[c9zx]

Again, TommyK nailed it. How you limit it will depend on how the diaphragm is made. Mine has a slot in the arm and I drilled and installed a roll pin to serve as a limiter. Chuck

 

[Utard]

Hi guys,

I'm bringing this up again as today I'm playing mechanic again.

could you please clarify something for me?

One of the last things said was about limiting the vacuum advance.

I'm at 20 degrees initial, and I've installed the 16 degree limiters for a total of 36.

I'm all in at about 3200 rpm.

Now I want to adjust my vacuum advance to be no more than 10 degrees.

Does that mean that with the vacuum advance hooked up I'm at 46 degrees and everything is still OK?

I believe that mine is adjustable. Right now it is adding about 12 degrees more advance, so I'm around 48 - 50.

Is that acceptable or should I play doctor?

Thanks!

Scott

 

[will e]

Hi guys,

I'm bringing this up again as today I'm playing mechanic again.

could you please clarify something for me?

One of the last things said was about limiting the vacuum advance.

I'm at 20 degrees initial, and I've installed the 16 degree limiters for a total of 36.

I'm all in at about 3200 rpm.

Now I want to adjust my vacuum advance to be no more than 10 degrees.

Does that mean that with the vacuum advance hooked up I'm at 46 degrees and everything is still OK?

I believe that mine is adjustable. Right now it is adding about 12 degrees more advance, so I'm around 48 - 50.

Is that acceptable or should I play doctor?

Thanks!

Scott

The vacuum advance won't add to the 'final' mechanical advance setting. So if you ended up at 36 total you are still there. It can pull past the 'current' advance of the mechanical but it will not pull it past the absolute setting.