No Advance

[bobslaven]

FORDification,
Rig: 1970 F-250, 360. Pertronix Ignitor II ignition and Flamethrower coil.
Problem: No timing advance.
Question: Why?
Some details: Truck really doesn't sound bad and fires right up...although I think it runs warm, power may be a bit low and the exhaust leaks are crushing me. The timing doesn't advance though. At all. Not at idle. Not at 2000 or 2500 rpm. Not with the vacuum connected. Not without it. It's just rock solid at about 8 degrees BTDC. I can rotate the rotor CCW maybe 15 degrees and it snaps back. I can get the breaker plate my vacuum advance is hooked up to to move by hand. The springs under the breaker plate are present and seem to expand/compress easily. The distributor is a Chinese unit. I'm thinking it's somehow jammed up/sticking in there. I was just going to replace it and see what happens, but didn't want to throw parts at it ($$$) prior to troubleshooting and I really can't find much about my issue in here or on the interwebs.
More questions:
- TDC on my truck sits at like 8 degrees ATDC on the stamped scale on the balancer. Should I care where it really falls on the scale? Seems like it'd be spot on. If it should be closer to TDC on the balancer, then why isn't mine? Maybe an aftermarket cam in there?
- All y'all with 195 degree thermostats: what temperature does you truck operate at? Assume idle, warm day, 20 minutes in the shade.
Learning as I go. Thanks much.

Harrumph!
Billy Bob

[cep62]

There used to be lighter springs available to tune the advance to come in earlier.
The Chinese may not be aware of this.

[bobslaven]

They're pretty good at copying stuff. Besides, the two springs in there are pretty darn loose as it is. It's gotta be something else.

[markguiver]

Check the vacuum advance can to see if it's functioning. You can hook a MityVac to the hose going into the can or suck on it to see if the linkage moves the plate inside the distributor. If you can't build vacuum or just suck air through the tubing, then the diaphragm in the can is shot and the can needs to be replaced. If the vacuum advance checks out OK and your not getting any advance above 8 degrees even when at 3,000 RPM then either something is sticking or broken in the mechanical advance portion of the distributor. If the mechanical advance is working, you should see the timing marks jump up to 35 to 40 degrees BTDC with a timing light hooked up.
Mark.

[390FE1972]

Here are a couple youtubes that show how to check if the vacuum canister is working, and doing adjustments on advance on the canister.
Hope these help! Keep us informed of what you find out.

https://youtu.be/CUh9trW75k4
https://youtu.be/XKSXpD_K6Go

Regards

[bobslaven]

Thanks for the input, fellas. Good words for sure.

The vacuum advance canister tests bad. Got a replacement on the way.

Seems to me like I should still get centrifugal advance though. It's completely independent of the vacuum advance, right?

[390FE1972]

Here are some interesting youtubes that talk about distributors, vacuum advance, and ported vs manifold use for advance. Hopefully there is something in here that help. They are by Autorestomod and Thunderhead 289.

https://youtu.be/UInmE9hg8Rk
https://youtu.be/vC3MS9fqEso
https://youtube.com/watch?v=Qz_cYOe2B20
https://youtube.com/watch?v=yNF8tma6VNY

Regards

[bobslaven]

Hey thanks for the additional videos. Good gouge. The lack of mechanical advance is still a mystery. I'm going to put on a new working vacuum canister and see what happens. Got another distributor to test if that doesn't solve it. We'll see.

[sparky72]

As far as the timing marks go, you probably need a new harmonic balancer. It sounds like yours has spun, which can happen when the rubber which bonds the outer ring weight to the inner hub rots and loses its ability to sufficiently hold the weight in place.

[bobslaven]

O.K., harmonic balancer spinning over time makes sense. It appears to be about 5 degrees off. Trying to get a replacement distributor on there now. I'll pretend that 5 degrees is 0 when timing...and replace that balancer on the list of things to do. Thanks.

[bobslaven]

O.K. Got another distributor in there. At idle, vacuum advance seems to be working...advances it about 10 degrees. I get some mechanical advance, too. Unfortunately, it's only about 10 more degrees at 2500 rpm. Doesn't seem high enough, but runs decently and I think it's running cooler. Now those numbers aren't super precise, because the light was poor. I'll nail that down next time. Also, I'm pretty sure that wire to #1 is not delivering a good spark, so I hope to replace that tomorrow. Doesn't seem like it should make a difference with the mechanical advance though. Assuming the new wires don't make a difference, should I just advance it all the way to 36 or so degrees BTDC and accept whatever that gives me at idle? Even if it's like 25+ degrees?

[sargentrs]

I always time that way to achieve max timing of 35*-40* at 2500 rpm. After swapping to a Duraspark electronic ignition system on my '70 302, and set for max timing @ 250 rpm, my initial timing came in at 22*. She loved it there.

[bobslaven]

Well there's a little peace of mind. Hopefully I'll change wires and cap and try that tonight. Thanks.

[sargentrs]

When I did mine I bought 8mm RFI suppressor wires
https://www.summitracing.com/parts/mor-72430/make/ford
and gapped my plugs to .040-.042. Ran great.

[bobslaven]

I think the new distributor fixed my lack of timing advance. Now I'm at 36 degrees total advance, idles at about 18. I'm going to drive it a bit today, and if all is well (enough) then I'll go register it. Next stop is the exhaust shop. Thank you all for the help.