Right, if I'm reading this correctly you've 44° BTDC total timing without vacuum advance? It should be pinging at that point, I'd think. This is a tell. What you want to see is 34° to 36° on the damper say, not counting vacuum advance, just to be clear on that. With a timing light on the marks should move smoothly and cleanly up and down the RPM range without scattering.

With vacuum advance hooked up, you can check to see that it adds to the total mechanical timing. Without any load on the engine, it will be a lot higher than on the street, but 50° or more is not unusual.

You could try something like this: Disconnect the vacuum advance port, everything plugged, make sure no leaks. Forget about vacuum advance. Pretend it doesn't exist. This is how distributor timing is always done anyway. Vacuum advance last.

Ignore too for now the marks on the damper. Keep a 1/2" box wrench handy and increase the distributor timing clockwise incrementally until it pings upon hard acceleration. About the width of a pencil line equals 2°, it doesn't take much. When it starts to ping, back off just slightly till the ping is gone. How does it run? Then put a light on it, and see what the timing is indicated on the damper. Might be interesting to see what the timing supposedly is according to the damper. Maybe it's the wrong damper or wrong pointer, the ring has slipped, something. Some people will use a vacuum gauge to set timing, highest vacuum indicated minus about 1" of vacuum on the gauge. This works good when there is no light available.

 

I was just thinking, is there any possibility that a couple of plug wires could be swapped? Maybe a couple of cylinders that wouldn't react with backfiring. Jackburtonme might have an idea, forget the timing light and just turn the dizzy until the engine speeds up. When it gets to max rpm at idle then back it off until the idle rpms start to drop and then try the truck for power.

 

Tedster, that's a great check to see if my light is accurate. When I shine the light on the balancer as I increase through the rpm range, I find that just off idle, say for the first 100 or so rpms, the timing level drops backwards by about 10* and then increases forward steadily through my range. The timing has always been set with the vacuum advance disconnected and plugged. I have only heard this truck ping once. To get it to ping, I was cruising in 3rd gear and stomped it to the floor. Then it let the ping loose! I've read all over the Internet that a big block likes 36-38* timing total.

The damper is the original damper, indicator is also original. I just had both off a couple weeks ago to do a water pump and replace the timing chain (replaced chain with a Cloyes double roller 3 keyway set with the 0* keyway position used). The damper looked good when I was examining it.

I would also think that if the ring had slipped, the TDC mark on the balancer wouldn't line up with the timing indicator when the motor was truly at TDC correct?

So far I would say my timing where it is at right now is too advanced, hence the hard ping on acceleration. I will back it down the next time the weather is decent (went from 70 to 35 in a day...**** wisconsin). Only thing I'm not sure of is if I should flip the dizzy governor to the 10L slot and run more initial advance, or leave it on the 15L slot and let the dizzy do all the advancing and run minimal initial advance.

I will check the firing order again. The truck has always had a slight misfire only at idle ever since I bought it. Just a slight slight shimmy, except sometimes it's worse than others. PO installed a cap, rotor, and wires off a small block car on the truck, so it's got the small cap with female ends, the tiny rotor, and 7mm plug wires instead of the 8mm plug wires

 

Yep right in there anyway. Depending on compression ratio and what octane you run, somewhere around 34° to 38°. It will be interesting to see what ends up being the problem. I gots nothin', sounds like you've hit all the usual showstoppers.

 

44 degrees is way too much. I use full manifold vacuum it works great idles way better. You will open a can of worms asking about manifold versus ported, just study it and decide for your self if considering ported vacuum. I would do what you are doing and try the 10 slot and 14 deg initial.

 

I agree it sounds like he is doing everything right but something screwy is going on. I wonder if the coil is weak. I had one go bad one time and the engine did some weird things. I also was working on the engine one time and left the plug wires off of the 6&7 cylinders and went out for a test drive and it ran like a dog. That’s why I suggested a possible mix up of a couple of plug wires. Might check the coil and see if you have 9 volts on it while it’s running. The resistance wire may be burnt up. Also pull the coil wire and look at the spark and see if it’s a good strong spark. Remember that the coil gets a full 12 volts when cranking and drops down through the resistance wire when running so check the voltage at the coil when it’s running. That sucker should jump a good inch. You might ohm out the wires to the plugs for excessive high resistance. Just a few suggestions.

 

Vacuum advance... lots of people don't even use vacuum advance. It should run fine without it, at least as far as power and acceleration is concerned.

 

Just my two cents worth, I think you are spinning your wheels on this advance issue. I can run mine at 60 degrees advanced or ten degrees retarded and it still runs like a bomb. There has got to be something else wrong with it. Like I said just my two cents worth.

 

The coil, pick up coil, brain box are all new as of 2 months ago. The spark is a very healthy blue/white color when I hold the coil wire am inch off the AC bracket and crank it. I will check firing order again though just to be sure, but it should be correct.

When I had the dizzy set to 14* and on the 10L slot before, this thing ws as much of a dog as it is now. I will try it again, now shooting between 34-38* total timing.

Seems rather odd to me as well that the truck is such a turd without the vacuum advance connected. The weights in the dizzy move freely, yada yada yada...I'm stumped.

I'm just hesitant to move the dizzy to the 10L slot again, because that only gives the dizzy 20* of advice which means I'd have to run 14-18* of initial timing to get anywhere near 34-38* total.

Parts arrived in the mail today though to turn my 1406 into a 1405 jet and rod wise. I will install them when I set my carb back to stock and start off with a base 1405 calibration.

Guess I'll set it up and do a compression test if all else fails.

 

So you do have good spark but the spark cranking but running could be different. Because the voltage to the coil goes through a resistance wire in the running position and it could be burnt up. That why I suggested measuring the voltage right at the coil while the truck is running. It should be around 9 volts. This is really strange and I hope you figure it out before you drive it off a cliff.

 

I will measure the running voltage. That is a good thing to check. I will recheck all the basic stuff like firing order to make sure that's not jacked up. Then check the dizzy. Doubting flipping the governor will fix the issue magically since I tried it before, but I dunno.

I love the truck, but this motor has been the biggest let down ever. PO used the truck to haul a tandem axle gooseneck trailer loaded with horses all over Kansas so this motor being worn out despite having good oil pressure has crossed my mind.

 

Is it normal to have that drop in timing just off idle? When I check my total timing, I let the motor idle in park, with the vacuum advance disconnecgted and plugged, idling around 750rpms. Shining my light on the balancer shows 14* initial timing. As I begin to rev the motor, the timing DROPS about 10* till about 850-900rpms, before slowly picking itself back up and reving to the full 44*. Is that normal? Seems kind of odd that the timing would just fall off a cliff right off idle and slowly pick back up. Might that be part of the sag at WOT?

Still on the fence about which setting I should set the governor to inside the dizzy. If I use the 10L slot, then I have to run more initial timing (which caused the motor to run warmer than usual). If I use the 15L slot though, I'd have to set my initial timing down around 4-8*...which seems rather low. I MAY have a governor with a 12L slot and some other slot I don't remember that I could try to toss in but...I don't know if that would help or hurt the issue.

 

Definitely check compression, but if you're pulling lots of vacuum at a slow idle (17" to 21" at sea level) then like as not compression is good or at least acceptable. Usually there will be lots of blowby on a well worn engine too.

Tune-ups are a package deal, every little bit helps. Strong, hot spark, good timing curve, and a well adjusted carb getting enough fuel. There often isn't just one major thing causing reduced performance, just a bunch of little things that all add up. You'll get it, it just takes some patience.

 

I don’t know about being worn out. I put 256,000 miles on mine before I tore it down and it was still running strong. I tore it down because it was going through oil faster than I could put it in. Oil was even running out of the dipstick and the blow by smell was coming into the cab so strong it made your eyes water but it would still pull that 9k 5th wheel up a 6 percent grade at 65mph. Those engines are just beasts and something is wrong and it might just be something simple. Just finding it is turning into a bitch! I wish you luck.

 

The only other possibility that I can think of is a flat cam. I have heard of cam lobes wearing out but not on the 460. That would be easy to confirm by pulling the valve covers and put a dial indicator on each one of the rocker arms and hand crank the engine checking the lift on each valve. As far as the dizzy jumping back when you start increasing the idle I don’t remember if mine does that or not. I would go out and check mine for you but it is in the body shop.