Captain Obvious

True, but the only thing most people would care about is peak HP. Maybe you could convince them that the power stab transition is important, but other than that?

Yeah, I'm not a fan of the polishing either, but I couldn't rightly flag that as a "flaw" since it's a style choice. Valve cover, oil fill cap, carb bodies, backfire valve polished... I personally don't care for any of that. I'd love to participate in that dyno test to compare round tops to flat tops, so if you hear of something like that brewing, let me know! It's not necessarily going to show anything though since the dyno test is just running full bore output at WOT. Under those conditions, you're not using many of the technological improvements of the flat tops and both sets of carbs should easily be able to be tuned to produce the same results. It's kind of a "static" test. In theory, the flat tops should shine in other areas like idle cleanliness, mixture consistency under varying operating conditions, gas mileage, and transition power on pedal stab. None of that would show up on a dyno test.

That wooden "tool" looks very similar to what I did as well. Mine's shorter though, and I screwed a couple blocks to the ends that I can squeeze together with my vise. I lost leverage because my planks are shorter, but I gained force by being able to put it in my large bench vise.

Jayhawk, That's a beautiful flat top pic. Is that yours some many years ago? I looked it over pretty closely, and the only fault I can find is the failed insulation on the throttle opener and EGR solenoids. That's the only little nit-picking issue I could come up with! I think it's a whole bunch of things. The extra pollution controls, the more complex throttle opener system, the more complex idle mixture adjustments, the power valve, the water running through the carb bodies. All the extra plumbing associated with all that stuff. A whole host of things. Capped off by the fact that you can't compensate for faults elsewhere by adjusting the nozzle depth like you could on the round tops. You have to get things right... You can't just cover them up like you could with the round tops.

What'cha testing? Besides your previously disclosed rust test...

LOL. And it's exactly this kind of claim that I'm talking about when I said the damage to the reputation is already done, and (I believe) is irreversible.

Agreed. And the damage to the reputation is already done, and (I believe) is irreversible. So, that 2+2 you posted about... I don't know anything about cars that were stock gear in other countries, but that 2+2 would not have had all the pollution equipment in the US. If it were here, it would have had EGR, and throttle opener, just at quick glance. And air injection with the pump. So if you think flat tops were complicated in your part of the world, you aint seen nothing! So how long did the flat tops run in Australia? I assume they started in 73 just like they did in the US, but here they stopped in 74. In Australia (and elsewhere in the world), they ran the flat tops for a number of years beyond 74, didn't they?

Well if yours is like mine, (and based on your description of slathered silicone grease, I bet it is) then you absolutely need to degrease first. And even so, I wouldn't be surprised if you don't get some fish-eye like I did. With that much silicone floating around, I think it's inevitable. Did you split the clamshell open, or are you just working on the parts you can get to from the outside?

Haha! Agreed!

Nice video. Is that the definition of too much time on your hands?

Nice work! Certainly can't be worse than the original pitted finish! From my brief foray into that realm, I found that front vacuum seal had significant compliance and held pretty snug against the shaft. You should be able to tell how much metal you removed by comparing your sanded one to the originals. The JB weld rod looks nasty. Like someone grabbed it with pliers at some point. And the one you have labeled "unknown"? I don't think that's zinc plating. I think someone sand blasted it. That one may clean up nice with the sandpaper treatment.

There are several technological advances built into the flat tops, but as always... With more technology, comes more complexity. And attention to detail is paramount. I'll never expect a huge groundswell of flat top love and people ditching their round tops to replace them with flat tops, but I do believe that if they are working properly, the flat tops are better carbs. However, because of the additional complexity, you must be willing to put in the time and effort to set them up right and keep them that way.

They will all do that eventually. It's because of the stress riser where the potting ends and the way they bent the wire to make connection to the harness. If you've got a usable one now, I would recommend you pot some more of the wire and move that stress riser further from the solenoid.

Certainly good enough so you at least don't have to winch it onto a trailer. Awesome! You've probably got 30 somewhat dirty and corroded connections (some of which are in the fuel injection system), and probably 30 small vacuum leaks in various places. You got it running, but getting them to run great is in the details. I have no idea what's going on with the whine at 3000 RPM, but there isn't anything in the tranny that should cap acceleration like that. I'd be interested in hearing more about that issue once you get it home. Does SWMBO know it's coming?

Thanks bud. Appreciate the help. I did some digging around and I've turned up a couple of the cast iron versions. Now I have to wait a couple days while paypal uses my money for free. I didn't notice, but my acct had gone too low to pay for the wheel cylinders. As soon as they are done fondling my dollars, I'll buy some cylinders. I'm hoping the cast iron versions used the smaller hole seals. So in the event that I have to go through this again, I'll have the correct rebuild parts next time. @madkaw, Did your old ones turn up? Or did they leave the premises?

I put that wheel cylinder back together with my modified pistons and made it around the block, but I really have no idea about the longevity. I do know just from messing with them that the pistons really should be hardened, even if it's just a case hardening like the original. I know this because I had put a seal on the first piston just as a trial test fit, but when I took it back off, I could see the scrape marks from the tool I used to pry the seal off. With the machining modifications, I can now get the seal ON without tools, but I can't get it off by hand. Tools area required. The original hardened surface was hard enough to prevent those marks, but the softer underbelly beneath the hardening is not. So they may be fine until it comes time to replace the seals, and then I'm gonna scratch them up getting the seals off. So I'm going to order two new cylinders from the crapshoot that is rockauto, but the basic underlying mystery still remains... "The rebuild kits they sell do not fit the wheel cylinders they sell. WTF?" So a little more about the cast iron wheel cylinder you got. Guessing by the shape of the dust boot and the piston seal, it looks like the small seal design. I have a couple rebuild kits here that have boots and seals that look exactly like that. What brand cylinder were you ordering when you got that one? Of course, I have no idea if I would get the same version though. Even you didn't get two of the same when you ordered two of them!

Looks great. I bet mine looks like yours did. @zKars, So did your bearing fix result in the velvety smooth pedal feel you were striving for?

Yes, Granny... Sorry, I was talking to you. I saw the feet and got all confused. Thanks for the info. I suspect the cast iron units are older and have been knocked around. I think the aluminum casting versions are newer. In theory, form, fit, and function should all be the same. In theory. And Zed, I've actually got SIX cylinders and five of them leak. One good one on the car, and one leaker, and then four old ones hoarded away in a box on the shelf. I have a bunch of old dead seals there too, but the old dead ones are even worse than what's on my car. I looked everything over carefully trying to come up with a combination I could just run for a couple days while waiting for new replacements, but to no avail. However...... Because I hate to lose (well, that and some OCD), I figured I had extra pistons, so I chucked up a piston on the lathe and started cutting: First one turned out OK, so I did a second. Original pistons and seals on the left, modified on the right with the smaller hole seals: Put seals on the pistons, and they look great. Looks just like the one that Granny got: They slid nice and snug into the wheel cylinder, and while this is a temporary fix, I'm hoping it holds until new replacements get here. Someone may ask why it's just a temporary solution? Because during the machining, it was clear that the piston was case hardened, and I cut through the hardened skin down into the softer interior. If I were to heat treat the modified pistons, they could become a permanent solution, but I could probably purchase a lifetime supply of wheel cylinders for the cost of that heat treating.

Well I managed to force a small hole seal from one of the rebuild kits onto one of my pistons, and NFW is that gonna work. Here's the cylinder parts. Old original seal style on the bottom piston, and the newer small hole style on the top: And here's a closeup of the seals. You can clearly see that the seal on the top piston sticks out way to far. I did try and couldn't even get it into the cylinder bore. I couldn't even get that seal up over the piston rear without tools. I had to stretch it so far I was worried about tearing it. With lube, I managed to get it on with the help of two screwdrivers, but it's clearly wrong: This is killing me... I took the car down last Thursday with the expectation I would have it back together in a day. Slap some new seals in there, and put it back together. Done! Now it's one of the nicest weather weekends we've had all year, and I can't drive my Z because the stupid seals don't fit!!

And forgot... My spring is different too. Mine is straight and not tapered. And it doesn't "clip" onto the back of either piston. The raised bumps in the middle of the opposing pistons kinda locates it, but doesn't retain. It just floats there between the two.

Thanks for the input guys. Site, You ordered a pair and that's the pair that arrived? Mismatched from each other? So is that darker one that says "made in USA"... That one is cast iron? One of the rebuild kits I have (I think it's a new Wagner) has the same markings and shape on the dust boots. And it looks like the dark one uses the small hole seal. Can't really tell about the other cylinder. I think I'm going to force one of the small hole seals onto one of my pistons just to see what it looks like. I suspect it's going to bulge out so far there's no way it will fit into the bore. And madkaw, if you do manage to pull yours from the can before they get picked up... If they use the small hole seal design, I'd love to have them. I've got a lifetime supply of rebuild kits but nothing to use them on. Seems it's a potluck crapshoot of potentially mismatched castings from Rockauto.

77-78 Rear Brakes - A couple years ago, one of my rear wheel brake cylinders started leaking so I bought a pair of rebuild kits (WAGNER F96618) from Rock Auto. Problem is that when I took my cylinders apart, I discovered that the rebuild kit would not work for my cylinders because the piston seal was a different design and would not fit. Here's a pic showing one of my pistons, and the seals. Old (leaky) one on the left with the large hole, and new one from the rebuild kit that doesn't fit my piston because the hole is way to small: At that time I gave up and just bought a new pair of wheel cylinders (AUTOSPECIALTY / KELSEY-HAYES W51104) and put them in. Problem is that one of those cylinders is now leaking, and I'm back to the same problem again. The rebuild kits don't fit the wheel cylinder. They could use different piston designs inside, but here's what my cylinders look like from the outside: And there is this snippet from the 77 FSM. Seems it may have been a manufacturing source difference, but I don't know who won the contest: So, anyone have any insights? I know I could just purchase yet another pair of wheel cylinders... I mean, they're cheap enough! But the ones on there are so new, there's nothing wrong with them except the seals are leaking. A rebuild kit would be perfect. Problem is that all of the rebuild kits on Rockauto have pics of the seals with the small hole, and I've not found anything anywhere that looks like it has the large hole seal. Despite the fact that the new CYLINDERS you buy use the large hole style! At this point, I'm not even confident that I could purchase a pair of wheel cylinders and rebuild kits from the same manufacture at the same time and have them even be compatible! Anyone ever seen a rebuild kit that has the large hole style piston seal??? Any other ideas?

I understand completely, and I'm not telling you not to. Just bringing it up. Do whatever you need to do to finish the race! On a related note... I wonder how much heat the damper rubber can deal with. According to Loctite: The red thread lock "For removal, it may require localized heat (>550°F/260°C), hand tools, and disassembly while hot" And you've got quite a lot of thermal mass there. So hopefully once it's on, you won't have to ever worry about damaging the damper rubber because you just won't have to mess with it! And I hope I never have the problem you did!

There was a bunch of TVV discussion in this recent thread starting here: https://www.classiczcars.com/forums/topic/59296-bringing-a-1977-z-back-life/?page=12&tab=comments#comment-548626 And I believe @Av8ferg did find a suitable replacement for sale, but I don't know what the source was. Note that 78 is different than the earlier years.

Maybe it's because I've never had a damper come loose, but I don't think I would use red Loctite on those threads. I'm thinking thread lock blue would be enough? And when you said green on the bore... Are you talking about their sleeve retainer? If so, I wouldn't do that either. That's like belt, and suspenders. And nails, and screws, and bungee cords, and duct tape. If you use sleeve retainer on the bore and red on the threads, it's gonna take a lot of torch to get that stuff apart if you ever need to. Of course, all of my opinion might change if I ever had one come loose like you did, but that really sounds like a bit much. YMMV