NewZed

Looks like the power antenna switch.

Coil resistance determines, along with module resistance, the current through both the coil and the module. More current = more heat. You're already under the factory spec. with the 8202 coil. The 8707 resistance is about half of the 8202. You'll be reducing the odds of E12-80 survival. But there are probably people out there using .355 ohm or lower coils with E12-80 modules. Maybe they'll give some real world results.

If you're signed in, at the bottom right of the Reply window is a "More Reply Options" button. Click that. You'll get a new window with a "Choose File" button below the text window. Click that. Should be figurable from there.

Actually, I screwed up. The injectors are controlled by the ECCS, off of the signal from the CAS. Since you have spark, you're pretty close. You didn't say what engine management system you're using. 81, 82, 83, Z31?

Screwed up suggestion... better two posts down. http://www.xenons130.com/reference.html

He's on the forum here as fast-datsun: http://forums.hybridz.org/user/1361-fast-datsun/ He doesn't post a lot. Send a message.

Plain old metal fatigue? Fatigue is its own special world, fairly independent of strength or modulus. Even tiny amounts of flex, of which there's always some, over time can eventually fatigue a part. 41 years is a long time.

How do you know it's 3 or just 3? These engines will run with the plug wires in reverse order. Spark in correct sequence but on wrong cylinders maybe.

I misunderstood which car you were working on. No MSNS. I would find out where the green and red wires go first. Know what you have. Check the tach adapter too, if you have one. Maybe they go bad. If you find that you're using the stock ignition module to trigger the MSD box, that would be the most likely problem source and changing the distributor won't fix it. The GM HEI module and the various performance versions will trigger from the 78's stock reluctor (green and red wires). If you decide to get rid of the MSD box or need to fix the stock module. The MSD instructions are on the internet.

MSNS stands for Megasquirt and Spark, doesn't it? Spark control is waiting. As noted, it could be that the MSD box is just doing what it's told to do. It might be fine. The tach works off of the trigger, not the Multiple Sparks, I believe. Bad tach signal means bad trigger activity.

Try the same way you found this web site - an internet search engine. Or open a book - http://www.nicoclub.com/datsun-service-manuals

Check your voltage regulator. It's external.

Show a picture of the "clutch". Hard to understand how it can distribute power between the two axles if it's attached to the ring gear. Sounds interesting. Most diffs, open included, have two different length axles. How can you switch sides in yours and get the same result? Seems odd. Pictures of the two axles, out and side-by-side, might give someone a clue also.

You're right, there is a centrifugal mechanism, advancing timing with RPM, and a vacuum mechanism, advancing it with intake vacuum when the port is open. What happens if you disconnect only the hose to the vacuum canister on the distributor? It's not really clear what hoses you're disconnecting that cause the idle to increase and the timing to drop 11 degrees. If there's no vacuum on the hose to the distributor hose, then nothing at all should happen when you disconnect it, since it won't be a vacuum leak and it's not pulling on the advance mechanism. Try to isolate cause and effect, specifically.

When you say "ruin" do you mean you want to be able to convert it back to working mechanisms in the future, or you just want to lock the advance mechanisms permanently and use it that way forever?

Is there a T fitting on the vacuum line to the distributor? It sounds like you're getting intake vacuum to the vacuum advance mechanism, at idle, from another source. The fact that timing drops to zero when you remove the hose indicates that. It also shows that the vacuum advance mechanism might be working correctly (11 degrees is right for an automatic transmission car), although it should hold vacuum, so may have a hole. The new distributor will have the same problem unless you find out why the vacuum hose is actuating the vacuum advance. You were almost there.

Read the reply to your post on zcar.com.

I clicked to see what an F20C was.

Good that it's fixed. I guess I don't understand how the pull-type LT1 linkage works. I thought the fork was getting pulled, but it must be the TOB, pulling on the diaphragm spring fingers. Kind of odd. Thanks for not getting all uppity on me.

I understood the picture. The rub marks will only happen when the clutch fork for is unloaded, that was my point. When the fork is just hanging there. When you press the pedal the end of the fork that has the rub marks moves away from the pressure plate.

Looks like a short lever arm, with the small bolts in to the tunnel as the fulcrum, and a hinge at the nose of the diff. Seems like a strut (the basic solid engineering kind) straight up from the nose of the diff (the hinge point) to something solid above would remove those problems.

Don't the RB's have hydraulic valve lash adjustment? Spinning the engine at low RPM seems unlikely to pump up actuators that have leaked down after sitting for a while. Seems like big decisions being made on iffy test procedure.

Aren't the rub marks on the wrong side of the fork pivot point for what your problem is? When you press the clutch pedal you move that part of the fork away from the pressure plate, if the pivot point is where it appears to be. Looks like collateral damage, but not the cause.

You'll need to make the tough decision of Phillips head or straight blade. It's possible though that either will work. It would really be nice if Nissan had put more detail n to their drawings.

Can't be that hard. The manual says just "replace pivot". After removing the rocker arms.