Non bullnose question, but Ford and need experts

This is the best dang forum there is for Ford trucks.  My issue is a Ford car and I need some of you guys' expert input.

65 Thunderbird 390, 4 bbl.  Had some issues, but have it running again.  Running good, more acceleration than before, BUT at 35-45 at neutral throttle, there is a random miss that has come up.  

Recent maintenance includes new cap, rotor, wire from coil to distributor, new vac advance, fuel filter, oil change, set idle screws on carb back to 1.5 turns out.  

Timing adjusted by ear and vac gauge mostly, as the balance has been painted and hard to read the numbers on it.

This whole ordeal started a few weeks ago when car began running rough at all conditions.  Found loose distributor.  I had not messed with it since buying back in Feb.  Car had been running better and better.  1400 miles trouble free.

So not sure what to do about this miss.  

Any input?  Thanks for answering a non bullnose question.  Or telling me I can't do this.  😄

Good to hear from you Randy!

Are you still running points and condenser?
Why not get under there and chalk up the timing marks?

I'm going to tag Bill. This seems right up his alley..

Two things right off to check, vacuum and centrifugal advance in the distributor (FWIW the under the breaker plate is the same stuff as a DS-I or DS-II unit.

ArdWrknTrk wrote

Good to hear from you Randy!

Are you still running points and condenser?
Why not get under there and chalk up the timing marks?

I'm going to tag Bill. This seems right up his alley..

I still have the 81 F150 and it seems to be as reliable as an anvil and nothing much to do to it.  The bird is not bad, but trying to get it betterer.  

Yes still has points and condenser.  I did mark the damper, but it's been painted and I'm not sure the marks I found are the correct marks.  Afraid I'll lose them if I try to sand on them.  So I've marked it and checked it relative to vacuum.  And I don't trust my Harbor Freight timing light.  

I am getting 20" vacuum at idle in Drive and 22(?!) in Park.  

85lebaront2 wrote

Two things right off to check, vacuum and centrifugal advance in the distributor (FWIW the under the breaker plate is the same stuff as a DS-I or DS-II unit.

I replaced the vacuum advance module because it wasn't holding vacuum.  I'm not sure it's working too much and there isn't a lot of rotation in the mechanical plate when I move it manually.  Not like what is shown in videos.  

What am I looking for when I check?  I know the timing should change as the engine revs.  It does some, but not a lot.  It's not advancing 20-25 degrees, like going from 10 at idle to 35 at higher rpm.  

Vacuum moves the whole plate.
Centrifugal moves the rotor relative to the plate.

You could have a very narrow slot and you could have a pair of heavy springs.
You'd need to take it all apart to see it.

Refer to the Duraspark recurve pages for some detail of how it all works together,

Like Bill said, it's the same mechanism underneath, just with a reluctor and pickup above the backing instead of points and condenser

Good information.  I do have an appointment with an old school mechanic tomorrow to check it out to see if he sees anything else as well.  But I really like learning more and knowing.  This has been a frustrating experience, since I thought I knew enough to get the car running properly again.  I still don't know exactly what made it right again.  I suspect it was the wire from coil to points.  It was in terrible condition.