Captain Obvious

In reality, you don't ever want to draw a vacuum against the back of the master cylinder. In fact, on the original system, I there's a hole to prevent just that. You shouldn't block that hole (like with a gasket or something). and because there IS a hole there, the bolting of the master cylinder to the booster will do nothing to retain vacuum.

No, it will not hold vacuum without that front seal. If that seal is not in place, it's a direct link from the vacuum port to that hole.

The Evaporust stuff won't work on generic corrosion. It only works on "real" rust (iron oxide). It a chelating agent and I'm no chemist, but from what I've read It works by actually dissolving the iron oxide and putting it into solution. So if the problem is real rust on the steel cylinder walls and steel rings, it might help. But if the problem is white corrosion on aluminum pistons jamming up the works, then I don't think it will do much to help. The reason I was asking about the oil pan is that evaporust and similar stuff is water based and will (hopefully?) run past the rings and end up in the pan. You might not want a bunch of tablespoons of anything water based in the pan.

I'm anxious to know if it fits!! You mean I have to wait until the weekend??? I was also thinking about your frozen motor dilemma... I was wondering if a couple tablespoons of evaporust in each of the bores might help break down any rust between the walls and the rings. It's aluminum safe, so pistons would be OK. Do you have the oil pans off?

Haha!!!

LOL!!! You don't even want to know! So I decided to go ahead and make it square. I have no idea where the key(s) ended up on your blocks and I was worried that the two flat design would always put the flats in an inconvenient location for putting the wrench on it and getting leverage. It's 2.4 inches square, so your 2.5 wrench should fit fine.

Haha!! I like it !

After a completely unprofitable amount of time, I have this: I mistakenly made the slot a little wider than I wanted. I was aiming for .210, but I got about .230. I think it'll be fine for what you're trying to do. Just don't misinterpret the initial backlash "take-up" for movement of your crank. It should go out Monday.

73 was the last year for points. The 74 260 was the first year for electronic ignition. Oh, and Zed Head types faster than I do.

That means "Don't cut off the staked in portion before taking the nut off. Just put a big enough wrench on it and spin the nut off. The staked over portion (caulking) will bend out of the way as the nut comes off." That's what they meant, but don't believe it. People have done that and it messes up the threads. Not sure why they recommended that. Maybe they thought it was less risky than trying to cut off the staked over section and accidently cutting into the threaded portion? In any event, even though they said to leave the caulking in place... Don't.

Yeah, then yours probably petrified and fell off some time in the past. And for the guys with the O-ring style built into the valve cover, I guess that's the older style. according to the documentation, they changed over to the newer style in 71.

I was only worried about elbows down, and I washed thoroughly with dishwashing soap* in the sink shortly after the event. I heard some long time ago that you have about 45 minutes minimum to get that stuff off your skin and you should be OK. It was about thirty minutes before I got washed up, and with no issues today, I think I'm fine. The only thing bothering me now is my thumb is still swollen and hurts way more than it should from such a small wound. I think I broke the tip of a thorn off inside. Here, have some roses they said. They're beautiful, they said. Haha!! *We usually use Dawn, but couldn't get it last time we needed soap, so we're currently using Palmolive.

Right. It's easy to mistake it for part of the cap. Here's some pics. Cap, as it's normally seen: Close up of the seal in-situ. Looks like all one piece: But in fact, it's not. Used a thin blade to get a little separation and get things started, and the seal comes off. Note the step on the seal and the recess on the cap. Speculation on my part, but I bet the earlier seals (with the different part number) didn't have that feature: And here's a close-up of the cap with the seal removed. You can see the recessed area for the step.

I have one on my cap. It's a black washer and if you poke at it with a screwdriver tip you can see that it's not quite as hard as the plastic cap, but it's pretty hard. Maybe 1/16 inch thick? ID is a snug fit on the threads, and the OD is about the same size as the raised boss on the valve cover? I don't know how compliant they were when new so I don't know if it was always that hard, but I suspect it was slightly more compliant years ago. Every Z I've messed with has had one. I think you might just be not realizing it's there. It's really easy to mistake it for "part of the cap". I'll take a pic tomorrow if someone doesn't beat me to it.

Gotcha on wanting to keep the engine together for now. I'm continuing to work on the nut as time allows. I spent almost all of today outside trying to injure myself with lawn and garden equipment. Couple minor flesh wounds. Won't know about poison ivy until tomorrow.

Thinking about it a little more, there is also the possibility that yours got so completely petrified that it cracked into pieces and fell off sometime in the past.

Yes there should be a seal on the cap, and I bet you DO have one there. It's just hard as a rock from heat and age and it looks and feels like it's hard plastic and part of the cap. But in fact, it's a separate piece. #40 GASKET-OIL FILLER CAP - 15270-78500 Note that the early cars (through mid-71) used a different number, but from that point on, everything used the 15270-78500.

Oh, and after I see that busted damper, I'm thinking that the more meat I leave on the "nut" the better. In fact, how about I skip the flats completely and you just weld a pipe to it? I'm concerned that maybe your adjustable will smear the flats. It's currently a little over 3" OD and maybe 3/4 thick hockey puck. Very thick walls at this point. The weak point is probably shearing the key off.

As I continue to work on the crank nut as I get the chance... Some questions. Do the motors still have the oil pans on them? The reason I ask is that if the do, the insides are maybe less rusty than the top sides? And the reason that may be interesting is that it may be easier to push a piston DOWN rather than up. I'm thinking there's no reason you couldn't pull the crank and try to tap the pistons in the downward direction is there? Block of wood covering the entire piston face (for protection and force spreading) and a hammer? Thinking that if you could move them into a clean spot. Or do you think they were maybe heat seized and have rings welded to bores? Reason I ask THAT is because if that's the case, you'll need to get the block bored and the old pistons won't work anyway. Might just crack them and pull out the pieces? Anyway, just thinking of other alternatives in parallel of me working on that nut.

Awesome. So while you were in there messing around, did you peek inside the brake booster and verify that it is clean and dry? It hasn't sucked in any brake fluid in the past, right?

Derek, That gives me a thought... Instead of spending time on the nut portion of the equation, how about spending it on the TOOL portion. Build a chain wrench designed to grab the teeth on the crank sprocket. Like this, but designed using a length of two row Nissan timing chain: That'll be a project for the next guy...

Thanks much for the offer! I'll keep in mind.

I said wrench, not "wench". Thanks for the data. I'll make sure my opposing flats are within that range. I had already started aiming at 2", but since your wrench will go bigger, I might too. Less metal to remove.

So about these two opposing flats... How wide does your wrench open?

Creative thinking, but having the shaper (and hopefully a broach close to what I need?) I don't think it would save me much. I'd still have to put the slot in the inner piece and for that, I'd use the shaper. Would be a little easier since I could do it as an external operation instead of internal, but not enough to warrant two pieces and welding. I'm not stifling the creativity though! Certainly a way to make use of the tools you have to accomplish the task in a different way. And I like your pic a lot. I wish I had a CAD package I could use to whip up stuff like that! I'm still drawing by hand! LOL!