Captain Obvious

I remember reading the same thing. I read it on the web so it was of questionable validity, but I do remember hearing that. But on the other hand, I've had GM V-6's in the past that used their HEI modules. I had no ignition issues that I was aware of and I easily reached 6500 RPM. Anyone have any thoughts on the matter?

Still wondering if my 77 is supposed to have a fan shroud. Anyone know if it only coming with A/C cars applies to all years?

I think those two tubes you show in the last two pics connect to your flow guide valve. It's an early crude evaporative emissions control system who's purpose is to capturing and store the fuel vapors that evaporate out of the gas tank when the car is not running. It's the predecessor to the carbon canister containment systems that are on newer vehicles. Plenty of details in the fatory service manuals. By the way, I know you've got an L28, and I know you are pulling off flat tops and replacing them with round tops, but what year is the car?? With flat tops and a flow guide valve... I'm guessing it's a 73? If it's a 73, then you can find info on the flow guide valve on page EF-20 in the Engine Fuel section. As for starting it... When you get to that point, you could just crank it and (hopefully) go, but sometimes it can be a pain to get enough fuel to the carbs to get it to catch in the first place. I would recommend filling the carb float bowls with a funnel and short piece of tubing first, before you connect up the real fuel lines to the carbs. That way you shouldn't have to count on the fuel pump until after the car is running. But before you bother even putting the carbs on the car... Have you checked your round top float levels?

Looking forward to the pics. What was the cost, if you don't mind me asking?

Does that hold true for all years? My non-A/C 77 doesn't have a shroud either and I assumed it was tossed by a previous owner.

Well my first foray into the junkyards was unsuccessful... Nissan changed their lock designs to a double sided tumbler design* sometime before 1986 and made the tumblers wider as part of that change. The new ones won't fit earlier locks: I don't know when they made the change, but the oldest Nissan I could find in my local U-Pull was a 1986 pickup. Apparently not old enough. *The new design uses both sides of the key at the same time. Our keys are cut on both sides, but that's for convenience only so you can put the key into the lock and it will work either way. On the early Z locks, you could theoretically get your key cut on just one side only and it would still work if you inserted it the right way. The difference is that on the newer designs, half the tumblers are actuated by one side of the key, and the other half are actuated by the other side of the key at the same time. Not that it matters, but I think it's a better design because the forces of the tumbler springs being on both sides of the key will help keep the key centered in the lock, unlike what we have where all the tumbler springs always push the key in the same direction. The new design has got to be better for minimizing wear inside the cylinder plug.

Pictures worth 1000 words?

Do you have copies of the service manual(s)? You need two copies... One from 74 and one from 72. The 74 will help identifying the hoses from the flat-tops, and the 72 will help identify what you need once you're done. The manuals aren't perfect and there will still be questions, but they will help a lot. OK, Here's your first pic. The two hoses that come off the original flat top balance tube... The larger one should be for your brake power booster, and the smaller one should be the vacuum source for your heater system. If you want power brakes and a heater that works, you're going to need to figure out a way to get vacuum to both of those hoses. Your second pic... A little blurry and tough to figure out what you're identifying, but I'll give it a shot. Going clockwise starting in the upper right. a) Brake booster - You need this. Coolant out of rear flat top returning to water pump - Pull the hose and cap it off near the firewall. c) Coolant supplied from thermostat housing into front flat top - Pull the hose and cap it off at the thermostat housing. d) Bundle of snakes identified with star - Can't tell. Need a better pic. e) Two fittings on front intake manifold - F = Throttle opener system, R = anti-backfire valve system. f) The smaller starred circle - Can't tell. Again, need a better pic. The red and yellow fittings you have capped off in this pic are for the throttle opener system. It's function is to reduce emissions by opening the throttle a little under very high manifold vacuum. There are some good pictures of that system in the FSM. Look there first and after that, if you still have questions, come back and ask. On your last pic, the tube in question is coolant supply to the balance tube. Coolant is supplied to the tube you have identified, flows through the balance tube under the EGR valve, and then returns back to the engine through the cut off tube sticking out the bottom in your pic. Study your service manuals.

Here's the thread that Bruce was talking about. It's not that detailed as far as exactly what to do with the hoses, but it does give a good mechanical overview. http://www.classiczcars.com/forums/showthread.php?44969-Flat-top-carbs-replaced-with-ZTherapy-round-tops I'll get to the details of your hoses in a second. I have to open up your pictures first...

Right. Sorry. :stupid: Didn't read carefully enough. I remember replacing masters in the past, but I don't remember ever rebuilding a master. Not saying it didn't happen... Just saying I don't remember.

I don't know if the annotated pic is showing up, so I'm trying again:

I haven't used their kit, but there's another issue that I will warn you about... I bought a new slave cylinder. Unbolted the old slave from the bell housing. Unscrewed the old slave from the rubber hose, and screwed the new slave onto the hose in it's place. So far, so good. Then when I went to attach the new slave to the bell housing, I found that it was 180 degrees out of place and I could not mount it to the tranny. The real solution is to pull the retaining clip and take the rubber hose off at the other end, spin the hose around halfway (180 degrees), and then reattach it to the hardline. But my clutch hardline is looking pretty rusty down there, and didn't want to come off easily. Not wanting to break the hardline, I just rebuilt the old slave and put it back on. I'll deal with that rusty clutch line some other time, just not right now. The moral... A new slave cylinder might not fit the same way as your old one, and if you don't trust your ability to get the rubber hose separated from the hardline without breaking anything, then you better have a backup plan.

Well then... Be troubled. I'll go on record as number two. I had a 77 intake that had an erosion issue directly underneath the EGR valve. I don't know if it actually made connection between the two areas of the manifold, but it was so bad that you could see cracking and peeling/flaking on the OUTSIDE of the casting under the EGR. I gave that manifold to another member here for experimental surgery and/or practice. I could dig through my notes and get in touch with him if you would like. Maybe he would take some pics of that area (if it's still attached). He said something about making a non-EGR intake out of it.

Awesome. Thanks for both 77 and 78!! How about 74? :pirate:

I annotated the pic identifying the parts of the lock. What I'm calling them, anyway. I haven't given up on fixing this myself. I've got the skills, just not the parts. Right now, I'm running with the bent tumblers (wafers) removed. I just put everything back together and left the bent ones out. Works, but is "less secure". Again, I fear the flatbed more than the lock pick. I'm assuming my hatch and passenger door locks are fine. I expect they would get the least amount of use. Certainly nothing like what the driver's door and ignition would see.

Nice. Where would I find a copy of the one for the 77's?

Well I know for a fact that one of my springs is even LONGER than it's supposed to be! I suppose if the choices are few enough and different enough from each other, I could probably identify my springs through the "load at length" method. If I'm reading that chart correctly, it appears that there are only four applicable choices for the round tops, and they are different enough that I could probably figure out what I've currently got (even if they have been tweaked some).

There is a small diameter pin that holds the lock shell (what I believe you are calling the cylinder) into the steering lock housing. I don't remember offhand how large, but something like .070. Problem is the pin is pressed into a blind hole and there's no way to grab it to pull it out. It's supposed to be "secure", right? Anyway, I drilled into the visible end of the pin until I was deep enough that the pin wouldn't interfere. I was amazed that the pin didn't simply spin in the blind hole, but The result is that after I had drilled enough off the end of the pin, the lock shell comes out of the larger casting. You can see (what's left of) the pin in the lower left portion of my pic. I replaced the pin with a similar sized screw. I'm not overly worried about security with this car. If it's going to disappear, it will happen on a flatbed, not someone who is going to take all the time to properly disassemble the steering column and take the lock apart. Besides, once you have the steering lock off the column and the electrical switch in hand, who cares if you can get the cylinder plug out of the steering lock casting, right? I'm not a locksmith, and I'm not sure that I'm using the proper terms, but I'll update a pic showing what parts I'm talking about.

Blue, Forgot about that... Thanks for the reminder. Even though I can accurately determine the spring constant, that still doesn't tell me what I would call my springs on the open market. By that, I mean... I now know my spring constant (k), but the issue is that the people who sell springs don't use spring constant. The use paint color and "load at length". Problem with color is that mine have been through the carb cleaner dip so many times that there's absolutely no color left on them. Can't use that. And the problem with "load at length" (like what is on that chart) is that it depends on the original at rest length of the spring and since I have no idea if mine are the original length, can't use that. One of my springs is about an inch longer than the other which makes "load at length" measurements invalid. I can assume that the longer one used to be shorter, but the shorter one? Who knows? Maybe it was stretched in the past as well, just not as much. I don't like "load at length" measurements. :mad:

I say skip to the end of the play and toss on a known good set of round tops and see what the afr says. That won't tell you exactly what's going on, but it should tell you if it's the carbs or not. Heck... You've got to be an expert at taking them off and putting them on by now, right? Half hour start to finish, max. I'd even send you a set of round tops to try except that I've modified mine and they wouldn't fit on your car. I know it's a little bit of a cop-out and you've got to admit partial defeat to resort to crude shotgun methods like that, but after thirteen pages, nobody's gonna give you static for taking the easy way out!

I would sure hope they had appropriate springs in them, especially after being through ZT's shop. But, I understand. Straws it is! :classic: I measured the spring rates from my round tops and then as an error check, I calculated the rate as well. Four screw round tops of unknown origin and history, but from everything I've found on the carbs, they look to be pretty much original. One spring is stretched out about an inch longer than the other, but if you do the measurements and calculations correctly, it doesn't matter. I got the following: k (measured) = 0.109 pounds/inch k (calculated) = 0.111 pounds/inch I'm very happy with how closely the calculated reflected the experimentally determined. Before you go swapping springs, you need to know where you are to start, right? You should probably determine the spring rates of what you currently have.

Are there ignition phenomena that would manifest itself in a way to cause the issues you're having? Doesn't misfire at idle, doesn't misfire at WOT, but does misfire at part throttle. What could cause that?

Thanks for the additional info. So it seems that I'm relegated to circumstantial evidence... I've got a five speed in the car. A 5-Speed insignia came with (but not attached to) the car. I checked the serial number on my bell housing and the numbers are shallow and filled with paint, but there's no mistake that the first two numbers are "74" which, if the number stampings really do mean something, puts it at a mfg date of April 77 and that is the same as the build date of the car. Next time I have the car out of the garage, I'll check visually to see if I can verify that it is an early "wide ratio".

Haha. You need to cut down a little!

My 280 is a 77. Build month of April, 1977. What I'm asking is... Is there any way to tell if it was originally a five speed, or did a previous owner pull a four speed and stick in a five speed in it's place? I don't have the "Five Speed" insignia on the hatch, but I do have one in a box of trim parts that the previous owner says he took off when he painted the car. Doesn't guarantee that it came like that originally, but certainly supports the theory. The previous owner did a whole bunch of work to the car and there's very little left that's "factory fresh". I know the engine and transmissions have been out, and painted. I know that the previous owner that I bought it from did not replace the engine or tranny, but I have no idea about owners before him. I know that I'm missing the ID plate that's supposed to be inside the engine compartment. The transmission type isn't built into the VIN in any way, is it?