Dave WM

https://www.youtube.com/edit?o=U&video_id=tFB1J7hWUQw this is the little bugger that may be rusted up. If they have been in an open system that is. this is me testing it

that's a propane and 134a mix I think. You should have no problems with the simple system based on your shop pic, anybody with a lift can do it. Just check that condenser for leaks that's the biggest problem. I was luck to find a NOS OE unit. the used stuff sold on ebay is iffy.

yea 4 something, but you can find shops that will still work with R-12 and it works pretty well. If you get new stuff under the hood (mainly the condenser) then R-134a would prob work fine, may work with the OE condenser, just not sure as I have not tried that. There are a lot of options for refrigerents including "dust off". You just have to know what kind of oils etc... the advantage of R-12 is you don't have to worry as much about oil compatibility. Of course if you are replacing all the under the hood stuff only have to worry about purging the evap with some cleaning solvent.

on the AC, you would prob be better off going with a new stuff in the engine bay, compressor/drier/condenser. IIRC there is a kit for this about 400$. Hopefully the evap/exp valve will be ok. Or, baseline what you have, confirm the compressor is locked up. If it is before you do anything pressurize it with nitrogen and look for leaks (soapy water spray all around under hood connections and condenser. IF no leaks you may get a way with a new OE style compressor and drier. Stay with R12 (find someone that will do this for you), and call it a day. likely you will have leaks at the condenser, I did. If you see leaks there and the compressor is locked up, then you may go with the new stuff I listed 1st. I would stay away from a complete system like vintage air inside unit (evap and blower) I don't like all the duct work and loss of vent air with those systems. The good thing is these are very basic AC units that use flare fittings and very simple controls. the flare fittings are pretty much bullet proof (no o rings to rot out). Biggest prob could be the TVX, or leak in the evap coil. You are going to need a GOOD ac guy that will do it right. I have seen NEW evaps with modern style exp valves for about 300$ that say they will fit like OE so that plus the 400$ for the under hood stuff plus about 700$ labor should get it going. 1500$ seems about right for a complete redo, and no body will get rich off that. If you can do the labor yourself all the better, just pay for the parts and the Freon charging. On the OE evap TVX, if the system has been open to air for a long time, its possible there will be rust in there. They can disassembled, let is soak in rust dissolving solutions, test, and re install. I have some videos on all this stuff btw, look for them on Dave WM youtube.

I think one of those expensive induction heaters may pay for itself on a 40+ year old car. Good for heating up bolts before removing.

if its largely original, I would say keep it that way at least for a while. In stock trim they are fine for daily around town driving. Things to watch for besides rust Fuel tank rust electrical connection in the EFI (corrosion on plug in connectors and grounds) Oil leaks (engine rear main, stuts if original) normal stuff like belts and hoses water pump (see if its noisy and or loose in the bearing). This is very important, I have owned 2 Z cars both had issues with pump breaking or leaking. I would go out on the limb here and just say replace it and the fan clutch ASAP. Broken bolts (see water pump). beware the bolts on the engine can break when trying to remove. Best bet here is find someone that is good at working on old cars and has a "feel" for how to do remove (that is unless you feel comfortable on this subject).

yep new annual thing, easy to get at no reason not to do it.

ok new gasket on the way, lets hope it is the correct one. Manifold is at a local shop (Revmaster) in Orlando to LASER out the remaining broken stud, hopefully will get that back tomorrow. I am also thinking going with some grade 12.9 hex sockets bolts for 1st/last exhaust manifold bolts of the correct length while I am at it with anti seize. Hopefully that will put an end to what ever is causing those to break. while I had thermostat housing off I noticed the non OE temp sensor was loose, the two prong plastic part was no longer solidly attached to the brass body. I figure that would be a fail point at some time since the internal connetions likely are getting a lot of vibration. Dug thru my stash and found an OE sensor that test well so that will be addressed as well. I also found some EV-1 injector boots to finish up the remaining connectors (air bypass heater, CSV, thermotime and temp sensor. All of those needed new boots. I asked the vendor to be sure and box the gasket, I don't want some UPS person to fold up a package and bend it all up. Paid a bit extra but glad to do it for the added insurance of getting the gasket.

don't buy the pictured gasket sold by Advance Auto parts for a 75/76 Z. I did and they shipped (could only get it shipped to home, not in store pickup) something that has round ports for the exhaust, not the square ones on a N42 head. Looks like a P79 head manifold gasket.

seems like a zener diode and resistor could make for a very nice mod to run off 12v

Or the vent line could be plugged up with rust as mine is. FSM has a check for "stuffiness" of the vent line. Think there is a check valve in there as well, that check valve #8 can be hard to find.

there was one at the JY not that long ago I passed on figuring I would never need it (gone now). Will see how this ends up.

something to think about on the manifold studs exp the end ones. Perhaps over tightening them esp cold could contribute to the failure mode of spontaneous breaking? Expansion and contraction on the ends of the manifold would cause repeated stretching. So maybe under tighten them just a bit or at least on the low side of the torque settings? as too why the ends, guessing less mass out there so more rapid expansion and contraction?

Wow that was easy (the back one anyway) Used a right angle air drill to start the pilot hole using a drill bit that fit snuggly (a tiny bit larger than the hole) after I established a good dimple I hit it again with a punch for a deeper sharper point right in the center of the dimple from the drill bit. Put in a small (1/8) reverse drill and started about 1/4" max checking by eye for square to head. Upped the bit to a couple sizes larger, opened up the hole a bit, then one more increase and the drill get stuck (air drill has low torque it seems) so I switch out to the electric VSR drill. Much harder to get in position so I am glad I had the small air drill to start and get squared up. a couple hits of the bit, it bites hard and out comes the stud just a pretty as you please. Taking a break (have to get back to work, only work on lunch hour during work days) will savor the success before moving on the front one. Will clean up the hole prob leave it at 8mm since its in such good shape. Dropped of the exh mani at the machine shop, they could not get to it for a week, so I asked about just welding on a nut and giving that a try, said they could do that today so will get it back later, then hit up JSM for his big torch to heat up mani to cherry red (no way my punk a$$ map/oxy can do that). Hopefully the guy at the shop will just take pity on me and do it while there.

it will be the one that got away and your son will be able to complain about in 20 yrs.

roger that rcb280z

was I right about pulling the distributer? need to remove and easy to figure out how to re install?

Good to know I just bought a kit of those recently.

will try one of these things OTC Robinair Bosch OT6982DGS Drilling Guide System

how hard was it to get a good straight hole drilled? I presume you had to remove the T stat housing and the distributer?

Deep into it now, pulled the manifolds off, left the injectors and rail attached, just disconnected the wire harness from the various parts bolted to the intake manifold. Turns out both the first and last exhaust mount studs were broken, below the surface. I found the 1st one just laying there, guess it heat cycled out like the last one. The two broken down pipe studs actually had about 3/16 of the stud sticking out (the non threaded part). I tried heating with the small torch but no joy. I will take to the machine shop tomorrow and see what they say. I tried the vice grips, not working, I don't have a mig to try and weld on a nut and the vice grips will just keep eating up the nub. On the broken manifold nuts on the head, they are below the surface, which I think may be a good thing since I may try drilling them out, and the hole that is open above them would be a good guide for a pilot drill to center drill a starting point. The one in the back is easy to get at, so I may try it. The on up front would require pulling the thermostat housing (no prob the bolts are NOT stuck) and the dizzy. Never removed a dizzy before, I assume its keyed and should just go in worse case 180 out so if I note the rotor I assume its a no brainer. I sure would like to have all the studs back in so the exhaust bolts up tight. I don't think I am up to pulling the head just to take to the shop for drilling out the studs, but maybe that is the best way to go. I don't want to goof up the head with a bad drill job.

that's s beauty, someone is going to be very happy to get it. I remember when I "out grew" my 71 240z back when I was about 22 yrs old back around 1980, sure do regret that, at least I was able to find a nice 280 36 yrs later... when I grew back into it.

success! and it was the nut after all that came off. So now I can continue with the manifold removal. I put it back on for now after using some anti seize compound. Now it goes on and comes off easy.

progress, I decided to try my el-cheapo maf/oxy torch, got the last stud on the down pipe moving, its unscrewing from the manifold (the nut is staying on the stud). got it about 1/4 inch down, I hope it come soon.

it looks like I can leave all that attached ( injectors and rail) to the intake manifold, just disconnect the fuel supply and return line. I think I recall someone doing this, and not even disconnecting them just lift the intake up and balance on the valve cover long enough to clean up the gasket surfaces.