Lucas 25D4 Distributor Rebuild Pictures



    Before stripping your distributor, you should read as much info as you can get your hands on. One useful place to start is HERE. This site, Teglerizer.com, has all sorts of useful resources and information.

    One such piece of info, embedded within the page I just pointed you to, is this PDF Lucas 25D4 tuning manual . Well worth a read.


  • Filthy distributor ready to be disassembled.

  • First, remove rotor, points, condensor and LT lead from the base plate. The points adjuster screw was very tight! Had to be patient and resist urge to whack it with a hammer!

    Slide the vacuum advance spring off it's post and after removing 2 screws lift off the baseplate.

  • NOTE: BEFORE removing the cam, make a note of the relative position of the offset drive dog w.r.t. the notch in the cam shaft for the rotor arm. Failure to do this could mean reassembling the distributer with the timing 180degrees off and you'd never find out why!

    Unhook the counter weight return springs from the cam plate posts. Be careful not to stretch or bend them.

  • After undoing the center screw holding the cam to the shaft, lift off the cam to reveal the guts of the distributer, the mechanical advance mechanism.

    It's not a bad idea to count the number of turns of the "AR" thumb wheel when removing, so you can reinstall later back to approximately the same position. Remove the wheel and pull out the vacuum unit.

  • It's a simple matter to pick out the weights and springs.

  • Remove the drive dog retaining pin with a drift. It's a bit tricky and blocks of wood are a good idea to prop the body to prevent cracking the aluminum casting. Once the dog is slid off, the drive shaft can be pulled up and out of the bearing. Note there is a metal shim and plastic cup between the body and the underside of the action plate

  • Before and After! Scrub all parts in carburettor cleaner then it's ready to be lightly oiled and reassembled. The shaft bushing was fine, no wear at all discernable. If the shaft bushing is knackered you may be better off buying a recon distributer. Check out Kragen for an astonishingly reasonable deal with virtually no core charge!

  • Scrub the body and get all the gunge out of the cracks and crevices. Note the annulus of the clamping flange is broken... Wonder if it'll be ok?

  • Reassembly, as they say, is simply the reverse procedure... Remember to align the cam notch and drive dog in the correct orientation. It's a good idea to have a reference handy for reassembling the weights (print this page!) so as to get everything back in the right place.

  • Hook the springs back on. Install the cam retaining screw in the top. Assemble the moving contact breaker base plate and install with the screws and the grounding wire in place.

    NOTE: I did not read the tuning manual before dismantling my distributor, so was not aware there is a "primary" and "secondary" spring, with different rates and functions... Who knew? But, after reading the manual and checking my photos of the parts, both look the same to me. Further checking is needed, I may have to dis-assemble and poke about a bit more... At least it's clean in there now!

    Insert the vacuum unit and screw the AR thumb wheel back on the same number of turns noted when removing. Hook the spring back onto it's post on the baseplate.

  • Install new points, condensor and LT lead post and wire. Make sure to assemble the condensor and LT leads to the points correctly. Both should touch the points spring but be insulated from the post and nut with the plastic sleeve attached to the points. I.e: the sleeve passes thru the tabs on the leads and acts as a washer on top of which the nut sits.

  • Install the rotor arm and Robert's your father's brother..!

  • Put the clips back on and slide a new O-ring onto the mounting post.

    Completely refurbished and ready to be reinstalled in the motor. The whole job can be tackled by anyone halfway handy and takes about 2-3 hours, depending on the number of tea breaks.