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Early 70's Ford 302 V8 Vacuum Advance/Retard Unit Removal

On mine the retard function seems to be stuck. Holds vacuum ok, just not moving the distributor plate when I connect up a hand-held vacuum pump. The advance function is working correctly. How do I remove the distributor vacuum advance/retard unit from the distributor? Is it done the same way as removing the version that only supplies advance? i.e. remove the c-clip from the unit’s arm inside the distributor, then the two screws that hold the unit to the distributor case, and pull it out? Or are there extra steps for the advance/retard version?

You’ve got the correct procedure.

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It’s unlikely that the temperature/speed spark control system works and I’m sure that it’s a tough system to find parts for. The engine will run fine without the retard working. In fact you would likely be very disappointed if you got it working since it will drastically reduce throttle response once the engine is warmed up.

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That’s why I haven’t been in much of a hurry to repair it. The hot rod magazines seem to agree w/your assessment RK. But I’m still curious why it isn’t working, as there may be another problem lurking, perhaps the distributor’s advance/retard plate isn’t moving freely for some reason, which is something I’d want to know about. When the vacuum retard was working I never had a throttle response problem. In any event I can always disable the retard function by disconnecting & plugging the vacuum hose. Now it’s confirmed removal is a simple procedure, next time I mess w/the distributer I’ll remove the vacuum unit for a look-see at what’s wrong.

If memory serves me… the vacume advance dashpot is spring loaded. When you pull vacume it overcomes the internal spring… when vacume is decreased the spring is the return mechanism.

Sounds like you have a rusty, sticking plate inside the distributor or your vac advance internal spring is sprung?

Put her at TDC… remove cap, mark rotor location however you like… and yank the distributor. You can then disassemble the unit however far you like to remedy this shituation. Usually it doesn’t take much to free it up and its possible to do without removal… but removal isn’t difficult either and you may wind up solving other issues at the same time while its out.

Those weights need to advance the timing as well… so you can free those up also… dont lose those springs… and also don’t mix them up, sometimes they are non matching rates and their position does matter.

I’m pretty confident you got this one @George_San_Jose1

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The mechanical advance moves the rotor on the shaft. If the rotor moves against spring tension and returns when released it is not stuck.

Clean the harmonic balancer and clearly mark the TDC mark. Check the timing at idle with the outward vacuum port disconnected and with it connected to MANIFOLD vacuum to determine if vacuum advance is occurring. Remove the vacuum hose and rev the engine to 2,000 rpm to see if the timing advances. Timing should advance about 10* with vacuum and near 20* when revved.

I’ve fixed this by just spraying WD-40 all over the inside of the distributor.

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There are 3 ball bearing between the shaft mounted plate and the movable point mount plate and a drop or two of oil occasionally can make a lot of difference.The centrifugal advance swings the cam ahead and the vacuum swings the points ahead.

Both the vacuum advance & the centrifugal advance works. It’s the vacuum retard that doesn’t work.

I may be mixing up my distributors…but I could swear that basically every vacume dashpot has an internal spring that it fights against. Pulling vac overcomes the internal spring…and when vac is reduced the internal spring is what returns the points to their starting position.

Everything needs to be very easy to move inside that distributor of course… the rotor weights and springs should also advance and retard the timing as well.

Maybe I just have the wrong distributor in mind however?

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