New Distributor question.

I just purchased a distributor from Jeff to replace my old 45D Opus unit. I have never pulled the distributor on a car before. Couple of questions. Do I need to take the whole clamp off of the block, or can I just loosen the cinch bolt enough to pull the dizzy out? Will the new Dist clamp back in if I leave the clamp bolted tightly to the block?

As for keeping the timing fairly close. I'm planning on marking the cap and body to notate correct position of current wires. Then put another mark on dist body to show direction the rotor is pointing. I will also put a mark somewhere on the block that would be a straight line from the rotor. What I'm hoping this will do is allow me to install the new Dist with the body and rotor positioned as close as possible to the original set up. Is this a good method?

On a side note...I can't wait to see the difference from the old stock Opus to Jeff's!

Hopefully the old dist isn't stuck in.

Just pray a little and loosen the cinch bolt. Don't take the whole plate off. Get the cinch loose enough to twist the body back and forth as you pull up on it.

When you go to stick the new unit in push it down as far as it seems to want to go and then rotate the rotor with one hand while applying downward pressure with the other. When you reach the right spot you will feel the rotor sort of click and then grab and stop. What has happened is the off-set dog at the other end has engaged in it's receptacle. Push the body on down until you see that the thin shoulder at the base of the body has slipped into the cinch plate. The rotor will be point to wherever it is supposed to pointing and you can rotate the body back to something close to where the original one was. From that point on all you have to do is follow Jeff's directions in setting the timing for your engine and you are home free.

Jack

Chad, I did this job just a short while ago - may I suggest pictures of the old distributor, with and without the cap, before you pull it? Also, mark your wires position on the old distributor cap so you can get them back to the correct cylinders.

I'm totally inept, but I was able to do it, so I'm sure you can! :D

Keep in mind that you don't have to pull any of the wires off the old cap. Just unplug the wire from the coil and push the whole assembly (cap and wires) aside. Exchange distributors (I make it sound simple) then put the old cap back on. That'll be fine until you get the car started and set the timing. The new cap and wires can be left to install after you get the distributor in place, so as not to complicate things by changing more than one part at a time. Its easier to diagnose problems if you change out one component at a time! By not removing the old cap and wires, there's less chance for error!

Sounds easy enough....I guess we'll see here soon. Getting ready to leave work. Plan on diving into this tonight!

Distributor R & R

first, mark the #1 spark plug terminal on the distributor cap with a piece of tape or something so you won't lose track if it.

Second, take the cap off. put another bit of tape on the edge of the distributor (you may need to clean the edge of grease so the tape will stick. "Brake Cleaner" is usually the best spray stuff to use. Then with a Sharpie marker mark the position of the rotor such that you can later reposition the rotor just as it was before you took the distributor out.

These two little things can save you hours later.

Then

The MGB distributor is held in place by a removable clamp. The clamp is kinda like a C clamp that fits around (and clamps to) the base of the distributor and is in turn held onto the block by 2 5/16" (1/2" wrench) bolts or cap screws.

You can loosed the clamp and leave it (the clamp) still bolted to the engine by loosening the "clamp" part...with a 7/16" wrench. It can be a tussle and hard to get at. It is easier to get to this if the bolt part is pointed up, more or less at 1 o'clock, rather than down (at 7 o'clock). It can be moved by taking it off the block then reattaching it.

You can remove the distributor and the clamp in one assembly by undoing the two 1/2" wrench bolts or by loosening the 7/16" wrench clamp screw.

However you do it, you want both the clamp and distributor off the engine.

Note: you don't "HAVE to"--but having the pieces apart, seeing how they are and fitting them together in your hands and seeing the relationship they have (and should have) with each other can save lots of head scratching for a beginner.

Anyway...

When you remove the clamp and place it on a flat surface you will see that the middle part is raised (or lowered, depending on how you put it down). You want the raised part to be up towards the distributor, it's important.

With the distributor and clamp out and apart, look at how they go together. There is a shoulder on the distributor right at the top of the bottom part. The clamp's raised section must seat evenly and solidly on this shoulder up against the flange at the top. If the clamp is warped or bent (and this happens often) it will pinch the shoulder unevenly, leading to breakage in the shoulder and trashing of the distributor. If bent, I'd replace the clamp with a new one. They are cheap, just put one on your next parts order.

Replacing the distributor.

I go about it (usually) by putting the clamp on the distributor with the clamp snug but not tight. (and with the clamp part up, about in the area of the number 1 terminal). Then feed it into the engine with the cap off (just push it out of the way). It will stop. Then turn the rotor and press inward until you feel it move the final 1/4" in. At this point the rotor should be pointing at abut the mark you made on the tape. A little bit eaitehr way is not important.

The clamp will now be flush with the engine and flush with the distributor. rotate the distributor and clamp assembly until you can ease in one of the 5/16" (1/2" wrench) cap screws into one of the clamp mounting holes. don't tighten. then get the other one in. with both in, tighten them.

Now you need to loosen the clamp (7/16" wrench) just enough to rotate the distributor within it to where the rotor lines up with the marked spot. You are now just about where you were when you took it out.

Make sure the distributor is snug but can still be moved a little, and is not sloppy.

Now you can start the engine and proceed to use your timing light.

Its a piece of cake. Just loosen the clamp, as others have said, take the cap off, note the position of the rotor, turn the body back and forth while you pull straight out. Do not rotate the engine!! If you do, you'll have to find TDC and insert the dizzy by the book. Thursday, I had two different dizzies in and out of my engine at least four times while troubleshooting.

Mike

Maybe I'm thick and missing something...
Mike B said:
Do not rotate the engine!! If you do, you'll have to find TDC and insert the dizzy by the book.

The dissy only goes in one way...how can turning the motor w/the dissy removed require you to find TDC on a B engine before re-installing it?

The problem is that Chad is switching from an Opus type distributor to an older points type 45D, so the vacuum advance position is slightly different, as is the position of the trigger inside the distributor. He needs to start from scratch, as the timing will likely be WAY off if he just installs it in the exact position of the old distributor. Lining up the timing marks and aligning the rotor with the #1 plug terminal is the easiest way to get it right on the first try (per Mac's recommendation)!

I see...that makes sense. Thanks. You must know a little about distributors, Jeff!

---edited to remove bad tribal lore - corrected yet again by those who know better......

Actually, no, it won't fit in both ways. The teeth on the drive gear are offset to one side only allowing it to fit into the engine one way. It is, however, possible to assemble the distributor 180-out. That's a whole different issue though. When your distributor is 180-out, the engine WILL NOT run, poorly or otherwise. Eventually you'll get a shotgun blast type backfire. Maybe a cough out of the carbs too, but it will not run! If it runs poorly, you're just WAY off on timing and should make quick adjustments before you foul the plugs!