engine timing and tuning

[Justin71]

Ok, Did you do what I suggested?

If so what were the results when you drove it?

It seems to run fine at various timing settings as long as the RPMs are below 3-4K RPMs. Adjusting the timing a little at any RPMs below 4k doesn't make much difference.

Rev the engine until it misses then move the distributor in both directions and see if it smooths out.

it misses at very high RPMs (5K RPMs) without load on the engine, so it is difficult to perform this test.

I mentioned it could be plug wires or weak points spring or bad advance or the electric choke . Try some other plug wires from another car and disconnect the choke as I suggested then post the results after you do these tests . You will likely not find the prob unless you simply start changing parts.

If your spark plugs are black they can cause the same prob.

Spark plugs are all in good shape. As I said they were all a nice tan color, and properly gapped. Compression tests were all nominal and generally consistent for all 8 cylinders.

Here's your numbers

800 10

1200 8

2000 16

3000 20

4000 22

5000 25

The numbers below are far more common unless the compression is extremely high.

650 .... 10

2000 .. 20

3000 .. 32

This seems like the key issue. timing is off at the high end. So far, I can't find any malfunction in the mechanical or vac advance systems that are causing my timing to be off at the high end..

Your stock distributor should provide a maximum of 10* vac advance and 21.5* centrifugal. So total should be 10* + 21.5* + initial Adv*. Tuning spec says 6* BTDC so the max you should see would be 37.5*. This is design but optimal for a motor is usually 34 to 36*.

Understand. If you review my previous post, you can see the initial timing is about 10.

Right now, I can't get the initial timing below about 10 due to vac advance module hitting the air conditioner bracket....

What is your initial timing set at and your idle rpm?

again: initial timing is 10deg at idle of about 800-850. 15 in-mg vacuum.

When you replaced the vacuum adv did you adjust it to provide the correct adv?

I tried. I don't have any instructions for how to adjust this device, and it didn't seem to make much difference with the hex screw tightened down or loosened.


I'm posting some pics of the distributor. I disassembled it tonight to inspect, clean. it looks fine to me. If anyone sees something in the pics out of whack, let me know - I don't see it.

I suggest inspecting the breaker plate for mechanical binding or the small round plastic glides being damaged or missing (I'm assuming OEM distributor). If those are good, carefully remove the breaker plate and inspect the mechanical advance, checking for binding of the weights. Look to see what numbers are stamped on the advance limit stops. The one being used will have a stop pin covered with black "rubber" in the slot. If it is stamped 13L that means 26 degrees of mechanical advance at the crank, when it is all in. 15L means 30 degrees etc.. Just my thoughts on the matter.

Chuck

very helpful thoughts here. I did this and when I look at the weights, they seem to be stamped with 13L (although the "3" is backwards???) implying 26 degs advance. I posted pics and I can't find any "rubber in the slot". Can you elaborate on this? this mechanism seems to move freely and the weights are free to move as designed. I can't find any problems looking at it. I noted that one of the weights is stamped with "62" and the other with "64". The springs holding each look a little different, but both seem to work fine.

 

[barnett468]

i can see the rubber is installed over the arm in the 13 slot

you said earlier that the rpms went up a lot when you advanced the timing 4 degrees . . you are now saying that advancing the timing 4 degrees had little effect . which one is it?

the low amount of timing will have ZERO affect on your miss . it seems electrical.

try the things i suggested then post the results.

 

[c9zx]

I'm assuming the vacuum advance is the correct part and working properly. I would double check that the vacuum unit is indeed correct. Try bending the vertical tab that is connected to the spring that has tension on it to decrease the tension. This should increase the amount of mechanical advance. The springs look like the wire gauge is a bit large but it is hard to say. You could also try these springs. http://www.autozone.com/1/products/46984-advance-curve-kit-ford-1965-includes-set-of-springs-mr-gasket-925d.html

You may have to mix and match with the stock springs to get the advance curve you want. Given the 13L slot and 10 initial you should see 36 total by 3500 RPM even with the vacuum advance disconnected and plugged.

As rpm increases more advance is needed because the speed of flame propagation is constant and the time it has to burn decreases as RPM increases. The thing that is confusing is that it seemed to run OK before any changes were made. That brings me back to rechecking the vacuum module. Especially the length and shape of the arm that connects to the breaker plate. Let us know what you find.

Chuck

 

[Don C]

When you checked the breaker plate did you check the pivot bushing for play? If it is worn it will allow the breaker plate to move around, changing the gap/dwell, especially when the vacuum advance moves.

 

[barnett468]

.

there is a light spring and a heavy one on your dist, if you buy the springs, remove the heavy one only and install one of the 925 springs . summit also sells those.

the heavy spring is the one to the right in this photo.

 

[Justin71]

Thanks guys. Working these things.

One of the things I am curious about is this: Could the PO have rebuilt the engine, put in a hipo CAM, and "recurved" the distributor? I have no information about the engine rebuild that was done (but I am virtually certain one was done). The engine only pulls about 14-15 in mg vacuum at 800 rpm idle. I can't adjust anything to get it higher than that.

If it DOES have a performance CAM in it, and I go messing with the distributor curve without knowing what was originally intended, could I make the situation even worse?

Just curious...

When you checked the breaker plate did you check the pivot bushing for play? If it is worn it will allow the breaker plate to move around, changing the gap/dwell, especially when the vacuum advance moves.

that's a good question. I really tried to check this well (because I was concerned about this), and I have to say that I am not sure. I didn't dissemble the upper plate from the lower plate, but I moved them around alot (and added some lube) The two plates don't rotate concentrically, so it seems hard to know if there is slop. When installed in the car, I noticed that there were some movements of the plate that would affect gap. So, I don't have a good answer for this....

there is a light spring and a heavy one on your dist, if you buy the springs, remove the heavy one only and install one of the 925 springs . summit also sells those.

the heavy spring is the one to the right in this photo.

Got it. Thanks!

 

[barnett468]

yes it most likely has a bigger cam than stock.

do what i suggested with the springs that c9zx suggested . the timing test you did has already proven that more timing will help but it will not blow the engine up.

 

[Justin71]

New data.

I went out to garage and thought "well, I've replaced every other damn piece of the spark system -except the coil. I'll go back and grab that flamethrower coil I brought & tried - & then shelved - because it was so "hot" I believed it to be smoking my condensers...

So I pull the "new" coil, only been in 1 year, and was bought specifically to function with the resistor wire in the harness, yada yada. Put the flamethrower coil in and I notice a big change. about 90 % of the problem at high RPM is gone.

I remember that I have also not set the vac advance adjustment, so I go out and tighten that adjustment all the way down and back off about 360deg - 540deg (what I would call 1.5 "full turns" - no I don't all a 180 rotation a "full turn" - just in case you were wondering. I set that and test drive.

So now, rather than being "solved", I have about 95% of the problem knocked out. It still misses... a little.... at high RPMs - especially right before shift into 2nd gear. More noticeable if you're really getting on the throttle.

This tells me there is a problem in the "spark system". Something is causing spark dropout at high-load/high-rpm times, and I just don't get what is going on.

I did find a little "play" in the breaker plate rotation point. I'll post a video later of the motion it has. IDK, this problem continues to evade, but latest data indicates spark quality is a far bigger issue than the timing issues are....

 

[Jeff73Mach1]

Have you pulled the plugs and checked condition and gap? Points systems don't have the oomph of Electronic and you may have a fouled plug. Testing in the car with a timing light only tells you the spark is getting to the plug and not that the plug is performing properly.

Some brand wires just don't perform well, even though they are only two years old, they could be a factor.

 

[Bill73Ragtop]

I had an issue one time with power & spark dropping off at 4500 rpm and higher. Turned out to be worn distributor shaft which was wobbling. Engine was fine at idle up to 4500 rpm, and that was when the issue became apparent.

 

[Justin71]

Have you pulled the plugs and checked condition and gap? Points systems don't have the oomph of Electronic and you may have a fouled plug. Testing in the car with a timing light only tells you the spark is getting to the plug and not that the plug is performing properly.

Some brand wires just don't perform well, even though they are only two years old, they could be a factor.

I did pull each plug and inspect. They are all tan and gaps were good at .054 (if I rem the gap correctly - i checked it against the book) They did not appear to be fouled to visually. Other than appearance, I wouldn't know how else to check them. I did a round the horn compression check also, and all cylinders were within 125-135.

if I get good flashes using the timing light check, does that effectively exonerate the wires, or can they still be bad? I'm assuming if the light flashes, the wire is dumping current at the plug.

I had an issue one time with power & spark dropping off at 4500 rpm and higher. Turned out to be worn distributor shaft which was wobbling. Engine was fine at idle up to 4500 rpm, and that was when the issue became apparent.

This is a good thought. I'm not quite sure how to verify this. I have identified that there is a fair bit of play between the 2 plates. You can see this play in this brief video:

https://player.vimeo.com/video/157382511?app_id=122963

I don't know if that play is sufficient to cause a problem or not.

 

[jpaz]

I know you said you checked plug gap against book, but the gap should be .035.

 

[barnett468]

i told you a few days ago it was electrical and you would have to simply start changing parts and disconnect the choke wire if it goes to the ignition wire.

your plug gap is ridiculously large . reset it to .042.

i told you to leave the vacuum advance hoses OFF until your problem was solved . you are not helping yourself by connecting them.

 

[Justin71]

I know you said you checked plug gap against book, but the gap should be .035.

Yes. I mispoke. I quoted the .054 from a bad memory. I DID go per the book when checking them, and I actually went out tonight and pulled #1 just to verify. Sure enough - exactly .035 The gaps are fine.

your plug gap is ridiculously large . reset it to .042.

Actually, the book says .035, and I verified they are .035.

I told you to leave the vacuum advance hoses OFF until your problem was solved . you are not helping yourself by connecting them.

Yes, I understand this, but I believe I understand the timing and how the vehicle runs without the vacuum. I posted the timing marks without vac. Before changing the coil it ran ok - except at high rpm, and there was spark dropout at high RPM....

So, I changed the coil and that seemed to fix most of the issue. So I reconnected the vac and rechecked timing with the vac connected and ensured it doesn't get more than 36 mech + vac advance. Most problems are solved in this condition, except there is still some spark problem at limited high RPM/high load conditions. So, I guess I am just struggling to find the benefit to disconnecting the vacuum again, and going back to that condition.

Maybe it's time to try to replace the breaker plate? See if the slop I show in that video makes a difference. That's what I am down to, I believe. It's maybe that, ot just replacing the whole damn distributor in case the shaft is just worn and gets wobbly at high RPM as recommended above.

I still appreciate all the input - really. I'm just not getting there from here, and alot of it has to do with the difficulty of explaining every step I am taking, and understanding the motivations and purposes of all the recommendations. Hope this is making sense.

 

[jbojo]

You say your motor may have a mild performance cam installed. Cam'd motors like timing to come in quicker than a stock cam. I read one of your posts that says 32 degrees at 5000 rpm, should probably be 34 degrees at between 2500 - 2800 rpm. I would change the advance springs as previously recommended.

Next the miss at high rpm's can be caused by Electro Magnetic Interference (EMI) generated by the ignition system. Specifically through the coil and spark plug wires. The ignition system is a miniature power station and the spark plug wires are its transmission lines. The wires (in particular, “solid core” wires) can broadcast EMI that seeps into electronics and causes erratic behavior. Are you using solid core wires?

To combat EMI you need to run a set of helically wound spark plug wires such as MSD’s Heli-Core or 8.5mm Super Conductor Wires. Having the conductor wound around a special center core produces a “choke” that holds EMI inside the wire and prevents cross fire at higher RPM. You said your wires are 2 years old but that does not guarantee they are good.

 

[Bill73Ragtop]

I had an issue one time with power & spark dropping off at 4500 rpm and higher. Turned out to be worn distributor shaft which was wobbling. Engine was fine at idle up to 4500 rpm, and that was when the issue became apparent.

This is a good thought. I'm not quite sure how to verify this. I have identified that there is a fair bit of play between the 2 plates. You can see this play in this brief video:

https://player.vimeo.com/video/157382511?app_id=122963

I don't know if that play is sufficient to cause a problem or not.

The video shows the movement in the plate. I was referring to the shaft itself. It should not move laterally in any direction. Just something easy to check.

 

[Jeff73Mach1]

To combat EMI you need to run a set of helically wound spark plug wires such as MSD’s Heli-Core or 8.5mm Super Conductor Wires. Having the conductor wound around a special center core produces a “choke” that holds EMI inside the wire and prevents cross fire at higher RPM. You said your wires are 2 years old but that does not guarantee they are good.

I concur completely. New does not mean good and appearances are deceiving. Even a single wire arcing at high RPM will cause your symptoms.

 

[barnett468]

your plug gap is ridiculously large . reset it to .042.

Actually' date=' the book says .035, and I verified they are .035.[/quote']
I know what the book says but you said you have a high voltage coil and you can run a much wider gap with that.

I told you to leave the vacuum advance hoses OFF until your problem was solved . you are not helping yourself by connecting them.

Yes' date=' I understand this, but I believe I understand the timing and how the vehicle runs without the vacuum.[/quote']
Sorry, but it does not seem that you fully understand timing because if you did, you would plug your vacuum advance hoses until the problem is gone.

So I reconnected the vac and rechecked timing with the vac connected and ensured it doesn't get more than 36 mech + vac advance.

What is the total advance with the vacuum connected?

Most problems are solved in this condition' date=' except there is still some spark problem at limited high RPM/high load conditions.[/quote']
So you disconnected the electric choke and tried different plug wires and US made points like I suggested to eliminate those as a possible cause of the problem.

So' date=' I guess I am just struggling to find the benefit to disconnecting the vacuum again, and going back to that condition.[/quote']
Going back to what condition?

Maybe it's time to try to replace the breaker plate? See if the slop I show in that video makes a difference.

Don't know, the video won't play for me.

That's what I am down to' date=' I believe.[/quote']
Not if you haven't done the other things i suggested.

It's maybe that' date=' ot just replacing the whole damn distributor in case the shaft is just worn and gets wobbly at high RPM as recommended above.[/quote']
Remove the rotor and grab the top of the distributor shaft and see if it wiggles.

.

 

[Stanglover]

Justin, somewhere I read that you might just go replace the whole damn thing (distributor). Just a heads up though from my own experience. I bought a Cardone reman. Ford original distributor a couple of years ago and have found out from their own Techs, that they only build to a sort of generic set-up. Mine has been causing problems with timing since. I'm not going into that issue here, but I am having my distributor rebuilt and recurved completely before my engine goes back in the car. You may have to do the same if you go with the original factory distributor. That's just my view from my experience. Good luck,

Geoff.