Help timing issue?

B

bdog_v

New member
Hello I was going to check my 73 scouts total advance with my new advance timing light. It has a 345 and original points distributor converted to pertronix. My Scout runs fine now, no unusual problems I just wanted to dial in my advance curve. Now when I went to do this my timing was steady at idle like you would normally set it but once I revved it up to check the advance curve this is what I found.

-1000 rpm steady reading

-1500 rpm was fairly wavy reading

-2000 rpm was still fairly wavy reading

-2500 rpm steady reading not sure why?

-3000 rpm was all over and I really couldn't get a reading.

*this jumpy reading was inconsistent one time it would be good and the next jumpy so what could cause this???

Now it is my understanding that inconsistant timing is caused by a worn distributor. So I took it apart and could not really find anything wrong????
-I checked endplay on the main shaft and it was in spec.
-my plastic green colored bushings looked snug and ok no grooves or sloppiness..
-bronze bushings seemed o.k. That the weights ride on
-I did notice the lighter of the two springs had its mount pushed forward so there was not tension on the weight until after it started to spin therefore making the mechanical advance come on sooner. (this couldn't be the cause?)
-do I need to pull the main shaft that the drive gear rides on and check for wear? It has no side to side movement....

-what else do I need to look for? I am lost. Is it possible the jumpy timing is caused by something else besides the distributor?
Thanks,
brandon
 
Your description of the timing light action tells me that ya got a timing light issue to verify first.

Most inductive pickups are "directional" in application. They normally are marked with an arrow, decal, something to denote which way to connect on the plug cable itself. Look for some kind of witness that tells ya how to orient the inductive pickup on the plug cable.

Then...move the pickup around on the cable, some work best right at the plug boot, some need to be near the distributor cap, I don't know why that is but I have an inductive pickup on one of my engine analyzers that is very finicky in that regard.. Also make sure the inductive pickup is not laying adjacent to another plug cable where it can do a possible "cross-talk".

Be certain the inductive pickup jaws clamp shut completely, older pickups won't fit on 8mm or 8.5mm plug cable correctly.

Then if you know your timing light is working properly, try it on another vehicle that has a similar ignition system (anything with a distributor and a single coil, no multi-coil paks) and observe it's operation.

If your timing light can have the advance tester component turned off, then do so and see if the timing Mark is then more stable. Some are turned off when set to "zero", then the light works as a conventional timing light.

If both vehicles then appear normal, the issue is with the distributor itself or the drive. Even a badly worn and botched IH distributor (any version, doesn't matter) will show a fairly decent stability on the timing Mark, never a herky-jerky movement of the timing indicators.

In all these distributors, the advance weights and their springs are real sloppy, otherwise they would bind. The anchors for the springs are actually individually bent to set the curve when doing this on a distributor machine, so the position now means nothing, if one looks to be "bent" leave it alone unless you are gonna have the distributor done on a machine. The point cam/reluctor component however needs to fit properly over it's shaft and not be sloppy side-to-side. Since you have p-tron conversion, are ya certain the magnet wheel fits firmly down over the oem point cam and has no slop or movement side-to-side or up and down?

Is the p-tron conversion you have an "adjustable" type that needs to have the air gap set when initially installed? If so, is the air gap properly locked down? That creates the "dwell" factor for the p-tron hall effect sensor, all inductive ignition systems must have proper dwell locked down before timing is set/verified.

Are all three of the tiny teflon slider "buttons" that are the bearings between the upper and lower breaker plates in the distributor present and serviceable? Otherwise, the breaker plate will cock when it moves making for a very erratic timing signal. It's very common to find one or two of those bearings completely missing.

Is the vacuum advance working correctly and will it hold vacuum indefinitely and not leak down?

Is the bronze bushing that sits in the block below the distributor drive gear installed and tight in it's bore?
 
Thanks for all the tips I really appreciate it. I will give it a shot tomorrow and see what I can find!!!
 
Well here are the results with more questions. I had to move the timing lights cable running to the plug wire as it was touching another spark plug cable and then I also cut the end play in half on the distributor shaft and now my readings are steady! So thanks!! But here comes the questions
scouts specs:
my Scout is a 1973 345, pertronix ignition, accel cheapy coil, 727 auto, 3.73 gears, 33 inch tires, and the motor has the schneider 131 h grind cam with edelbrock 1404 4 barrel carb., stans tri-y headers, and ported heads.

-I wanted to custom tune my advance curve and this is where I need some advice. At initial timing of 10 degrees it does not ping at all and runs well.

Here are the specs with the advance timing light:
1. 1000rpm= 7 degrees * plus 10 for initial = 17
2. 1500rpm= 14 degrees * plus 10 for initial=24
3. 2000rpm= 23 degrees * plus 10 for initial=33
4. 2500rpm= 27 degrees * plus 10 =37
5. 3000rpm= 29 degrees * plus 10 =40

*now that is with the vacuum advance disconnected....

-is 40 getting a little high especially when the vacuum advance isn't connected yet?

-now I think it has a little better take off and throttle response at 12 degrees however it pings slightly on take off with the pedal at 3/4 throttle and also when using passing gear it is more pronounced pinging but it is hard to hear as I have a loud exhaust but I can certainly here it .

-I would like to keep the initial here at 12 and adjust the curve to remove the pinging. My vacuum advance has a #7 on the arm and I have another spare one with a #5 on it. Would this swap lower the timing enough to eliminate the pinging? Or do I need slightly stiffer springs> if so which one or both springs?


-currently I get around 11-12 mpg on the highway 62mph and would like to try and improve this through a new advance curve since my motor is not stock. I am new to this so any advice ideas appreciated!!!!

Thanks, sorry for the long post!!!!!!
 
Doing some more thinking and drinking not sure if that helps any? But it looks like I have a fairly aggressive advance curve as it sits, am I correct? Also since we can't get an adjustable vaccum advance just the factory ones that have one setting. I don't see how much I can accomplish here( now correct me if I am wrong) tommorrow I will try driving it with the vac advance disconnected, if the pinging goes away I know an adjustable vac advance would fix my pinging issue at 12 degrees initial timing. That is all the alcohol has helped me decipher... Any thoughts???????

Thanks.....
 
Well after messing around some more I decided to leave it a 10 as it does not ping there and seems fairly responsive. My curve seems close to where it needs to be and frankly my patience is on the low side so I am leaving it where it is. However, would your msd mallory ignition 6 box and coil that you wrote about somewhere here improve mileage? That is my main focus.
Thanks for all your help

brandon
 
To answer your question regarding what is a proper advance curve for any modded IH motor, we don't know since we haven't actually tried to develop a curve for a performance engine.

Any development would be valid only for the engine in which the distributor is being installed, though there would certainly be some commonality in the setup for similarly-equipped engines (cam, carburetor, ignition system, etc.). To do that requires the use of a distributor machine to be practical, where adjustments can be made right on the distributor and then "tested". And then the distributor must be installed and dialed in also for each application. We can determine some generalities for particular setups, but this is certainly not an exact science. Very few folks still do this kind of work, there is no market for it any longer. And those that still do distributor work are tuned into the common shit such as chryfordrolet with known component setup.

Will a capacitive discharge ignition system "improve" fuel economy on it's own? Not unless there is some failing in the current system that is creating a random misfire, lean misfire under load (very common and undetectable except on a scope used in a diagnostic process), etc. And the upgrade will not fix any issues that are already present such as crappy plug cables, worn out distributor, incorrect distributor adjustments, weak/inadequate components, etc.

But...starting (cold and hot) will be vastly improved as long as a suitable companion coil is also used that can take advantage of the cd box....and the incorporation of a suitable electronic trigger for the distributor that eliminates the design deficiencies of breaker points when used as a switch.

And a cd system can provide a stable ionization of the spark plug gap under any single engine cylinder condition every time it needs a "spark" (some provide multi-spark capability up to a particular rpm) when combined with a suitable matched coil,...that can mean upwards of 40kv output continuous (no duty cycle). That means a conventional plug can be gapped at 0.045" (no more) and will function perfectly for 50k miles if the fuel delivery system is optimized and the engine is in "normal" condition mechanically (minimal oil consumption).

There is no majik bullet regarding "improving" fuel usage. These engines are truck engines, these vehicles are trucks and are extremely heavy for their overall size. These vehicles have the aerodynamic characteristics of two sheets of plywood facing the wind head-on. They are what they are, forget "fuel economy" and simply be thankful the fookin' government allows you to operate one of 'em at least for the foreseeable future.
 
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