1977 F-250 4x4 with a 400 engine and C6 auto transmission.

The vacuum advance on my distributor is dead. My distributor does not have the aluminum tag plate on it. It looks as though it might be a remanufactured unit... tell tale paint dots. The distributor itself was frozen, so I figured I'd fix that and take it out to see what I have. The oil seal grommet is pretty well shot. The rest of it seems in decent enough shape to my untrained eyes.

Should I just buy a new distributor from a place like RockAuto?
Should I try for a remanufactured Motorcraft unit from a local parts store?
Should I just get a vac advance and put this distributor back in?

Looks like the markings are
​​​​​​C8VF
12131-B
36

There's a 12127 Motorcraft stamped on the side and it has a blue top.

 

My opinion is to get a motorcraft rebuilt distributor. They are a few bucks more than they CHICOM junk you can get, but worth it IMO. So if you order a Cardone from Rockauto, or Ebay or a motorcraft rebuild from your local parts store, your getting the same dizzy, ive played with several in my truck... Had one rebuilt that wouldnt play nice with my truck, but that was my only bad experience, getting your timing set is the key with your new dizzy....

 

If you're comfortable with the distributor you can just replace the vacuum advance. If your dizzy is questionable I would find a rebuilt Motorcraft not an iffy Chinese cheapo. That junk is not worth the headache to me.
Mark.

 

There are things to check on an old unit to determine if it needs rebuilding or replacing, as the case may be. Are the specifications laid out on the internet? I don't think I've ever seen them, but likely that's because most people just replace them with new/rebuilt instead of checking.
I don't have my factory books handy, but it's probably detailed in one of the books. Maybe even in the 400 rebuild books?
But as said, when in doubt, don't hesitate to replace it.

Yours looks pretty clean on the engine side of things. Especially compared to how it looks on the outside. Seems you and the PO kept the oil changed pretty reliably.
And you're lucky it came right out too! Most of them fight you for all they're worth just to adjust the timing. Much less get one all the way out.
Is that brown muck that's above the o-ring, but below the flange easy to wipe off? Or is that what it looks like after wiping?! If it doesn't clean up well, or the o-ring is really toasted (as it sounds like, from what you were saying) then a new o-ring at least would be a good idea.

Paul

 

Look on either side of 12127, there should be a stamped 4 digit prefix and a 2 or 3 digit suffix. This is the ID number for the dizzy, it can be crossed over to the part number.

Example: ID number = D7TE-12127-PA > > Ford part number = D7TZ-12127-P (Motorcraft DA-1584) / 1977/78 F150/350 400/C6 without CA emission (truck in Seattle WA).

C8VF-12131-B doesn't mean diddly, as it's only the casting number for the housing.

 

Thanks everyone. It did clean up pretty well with some aggressive brushing and parts cleaner. Some of the gunk by the o-ring had to be scraped off with a razor blade. Not sure if that stuff was old RTV or what?

NumberDummy, I cannot find any other markings on the thing... The only thing I haven't done is take apart the top and look under the rotating plate, but it sounds like the part number should be stamped on the outside where the other markings are?

I ordered this vacuum advance https://www.rockauto.com/en/moreinfo.php?pk=945334&cc=1123085&jsn=8 Hopefully it will work ok since I can't figure out exactly what distributor I have.

I got a new o-ring from napa. Do you recommend RTV or a mounting gasket?

 

Even if you're cursed with a McParts store 'rebuilt' Motorcraft, you can always give it a proper rebuild yourself, using Motorcraft parts.

 

My recommendation is to use nothing....just the O ring. Make sure the mating surfaces are clean!

 

I just used the new o-ring and a bit of anti-seize on the contacting surfaces to keep it from seizing in the engine again.

 

Being as you were lucky and the screws weren't seized, I'd just get another canister. Why do you think it's dead ? Did you put a vacuum pump on it to see if it worked ?

 

The new vacuum advance canister arrived in the mail so I could put things back together. The old canister wouldn't hold a vacuum. The new unit is physically much larger than what was on the truck, but all the holes and working parts lined up just like the old one. I did notice the arm had a 10 stamped on the old one and the new vacuum advance has a 12 stamped on it.

I wire brushed the harmonic balancer to clean up the timing marks and it's very clear where the compression stroke is on cylinder 1 with the thumb over the spark plug hole trick... but I'm struggling to get the distributor to drop all the way down. I think it's the oil pump (?) thingy that the shaft slides over. I did get it happily in the truck once by bumping the starter once I had the distributor in against the gear, but the truck wouldn't start. I'm guessing I was off by one. When I went to try again, I saw that the fuel filter in front of the carb is shot and it's peeing gas all over... So, off to the store to get a metal one I can screw into the carb instead of this plastic thing.

Any tricks to get the distributor to seat all the way more easily or to make sure you've got things lined up right once you find TDC?

 

Yes, there are two ways to do it. Both totally legit.
The first is the way you did it. As long as you have the gears lined up properly, when you turn the motor over (I usually do it by hand with a wrench on the crank bolt) they will turn in unison until the pump driveshaft and distributor shaft line up and the thing drops in.
Just like you did. But maybe try it again, with moving one tooth backwards.

The second method is simply to put a small socket on the end of your long extension, tape it on good so that there is no chance of it falling off in the heat of battle, and turn the shaft ever so slightly at a time until the dizzy drops in.

Remember that no matter what you do, once you line it up and it starts going down that last bit, the shaft is going to start turning because of the angle of the gears. As the driven gear meshes farther into the drive gear, the dizzy will spin. But only slightly.

And the "correct" position has some leeway on some engines. Are you saying yours won't start because you can't adjust the timing sufficiently? If so, then yes you're off a tooth or so and your vacuum can is hitting some obstacle most likely.
If however, you were just trying to start it without actually confirming you were timed correctly, you should do that first. You can crank the engine while watching the timing light on the marks to see where it's timed currently.
If it's off, adjust the distributor. If you can't, then re-stab it one tooth over.
If it's right on the money and it's not starting, you have another issue perhaps.

Paul

 

 

I know you've already taken a stab at getting your distributor in, but I'll share my experience and maybe it'll help others that read. It's basically the second method Paul mentioned.

When I took out my old distributor I noted the direction of the rotor before I pulled it out and looked for something on the engine to remember it's exact location, like being pointed directly at a bolt head, which was the case for me. Otherwise I would have grabbed a pen or piece of tape and made a mark myself. Once I got the new distributor ready to drop in I lined it all up and started wiggling it down the bore. It wouldn't seat all the way since the spot for the oil pump shaft to slide into on the new distributor wasn't oriented the same as my old one. I found that my "multi tip screwdriver" without a tip installed would fit perfectly over the shaft inside the distributor bore on the engine. I slipped it on the pump shaft and would turn it a bit and then try dropping the distributor in again until it slipped into the shaft on the distributor. Like Paul noted, the starting point where the distributor is before it slides into place will be different than where it finishes because the distributor turns as the two gears mesh together. So, in my case, I had the distributor rotor pointing ahead of where I wanted it and then as I dropped it in and the gears meshed the final resting place of the rotor was right at the bolt head I had made note of earlier prior to removal of the old one. It started right up on the first try after that.

Hope that helps anyone who needs it. Oh, and a picture of what my Crapsman tool looks like that I used on the pump shaft. I think it fits a 1/4 hex without a tip in it.