jonathanrussell

The advice given by the group about removing the plugs and holding full throttle while letting the starter turn 10 seconds or so is what I do. I don't think it would hurt to do another compression test, hot and cold. Fully charged battery too. I don't typically remove the coil wire but I can see where it would be a good idea.

I read through this whole thread again. I have the following thoughts and suggestions. In my opinion, your plugs are fouled with carbon / fuel, not oil. Maybe I would change my mind or confirm my opinion if I could touch and smell the plugs. Who knows. When I look at your spark plug photos, I think 4, 5, and 6 all look carbon fouled in varying degrees. 1, 2, 3 don't look great either, but I think they look weird probably due to the heat range plug you are using. With your compression numbers, and assuming I am right about the plug fouling source, I would assume your engine is fine enough to run correctly. I would stop thinking about oil rings, oil seals, etc, etc....at least until you thoroughly follow some other paths first. 1) In my earlier post, I suggested finding a better mechanic. I still stand by that. 2) Take steps to make sure you have a perfectly functioning ignition system. Start with valve timing....camshaft sprocket, oil pump shaft, distributor all being in the correct position. Next make sure your plugs are connected to your distributor cap and spark plugs in the right firing order. Next make sure that you are getting spark at each spark plug. Also, I would suggest going back to stock heat range NGK plugs. 3) Next, you need to get your carburetors adjusted correctly. If you are having to turn the mixture adjustment screw down 3.5 turns then your float levels are absolutely not adjusted correctly. If the float chamber levels are not correct, then it is possible, likely even that your mixture screw adjustments do absolutely nothing to affect mixture. You have Z therapy carbs. They are great carbs. They almost certainly have stock nozzles and probably SM needles (but it doesn't really matter which needles....you can get any of them to work well enough and not exhibit the symptoms you are having). In broad terms...your carb for cylinders 4, 5, and 6 is richer than the carb for 1, 2, 3. So...how can you get your carburetors adjusted correctly? a) One option is to find a great mechanic who is willing to read, research, focus first on float levels, and really learn how to adjust these carburetors. I read a lot of people saying it is easy. I agree it is easy when you have done it successfully and know what to do. The first time I really learned how though, it took days of trial and error....especially with the float levels. I prefer to take the domes off, turn the mixture screws down 10 turns, and set the fuel to the top of the nozzle hole. Others have different ways. All ways can work. And, getting the tab to the float tab that rubs against the needle jet to the right curvature so it engages smoothly and doesn't get caught is a big learning curve. So, can you find someone willing to go through this learning process and provide you with perfectly adjusted carbs? Probably not. b) This is what I would do. Contact one of the great Z car shops (start with Z Car Garage) in the united states and ask them if you can ship your carburetor assembly (carbs, balance tube, etc) to them (dry out fuel first). Let them know you want them to tune your carb on a stock 240z or stock 260z (yes, I know your z engine has been stroked to 260z but you have a pretty much stock camshaft, etc). Tell them you want to be able to reinstall and run it. Key is to get the float levels adjusted. Yes, you may need to final tune with turns of the mixture screw, but you should be 90% there. I would also suggest purchasing a color tune device which will let you visualize how rich or lean each carburetor is running. Those are my thoughts. I wish you the best and hope you get to enjoy your car someday soon. J

Reading the dialog of this extensive thread, the work that has been done with no progress, and the amount of time that has passed is super frustrating. I feel badly for you @jalexquijano. I am sure your frustration level is quite high. You have a nice car. It is terrible that you can't enjoy it. I am not convinced that anyone who has worked on the car so far has been able to help. I have no faith that the efforts that have been done to adjust carbs, adjust float levels (critical), assess ignition health and valve timing, etc...have been done correctly. Now, when I think about the same local resources taking his engine apart, I think to myself...how does anyone know that they know what they are doing with an L series engine? Have you done an exhaustive search for someone in Panama who has experience with these cars and the L series engine? Absent that, I would look for a great mechanic who is willing to read and learn about this car and the engine (factory service manual, online resources, etc). It feels like you and this collective forum have been attempting to tell the mechanics what to do. I would find a super smart mechanic that will read, assess the car, and tell you what needs to be done. Find someone who is also willing to engage here and ask questions. Just my thoughts. I truly hope you get this resolved and are able to enjoy your car. J

@MH77280Z Sorry I missed replying to you but looking good. Did you finish the project?

I am sure your situation is frustrating. I read back through all of your posts and here are my thoughts. - I am still not convinced you have ruled out whether or not you have a head gasket leak. You have multiple posts where you mention white exhaust. None of your efforts and energy are going to work if you have a head gasket leak. - If you remain uncertain whether the thermostat is an issue....do what Zed Head has suggested and remove the thermostat as a test. If it runs hot without a thermostat then the thermostat is certainly not the problem. - You mention multiple flushes to clean out rust in the block. Is it possible that the flushing freed up debris that is now restricting flow in the new radiator? May need to pull the radiator and flush it out with hose, etc. - If all of the above checked out, I would come up with a way to confirm / visualize that coolant is flowing freely through the system. Might use some clear hoses, watch waterflow in the top of radiator, etc.

I have observed the same thing regarding thermostat hole opening size between original and new Stant etc thermostats. In my 240z at least, the thermostat brand makes no difference regarding the operating temperature...even in Atlanta heat. My point is, and for my car at least, the operating temp depends primarily on all of the other cooling components working properly.

Wow. And, another reason why we should disconnect battery when doing most things on our cars.

I did this job to my silver 240z a few years ago. Blasting wasn't an option for me so I used a combination of wire wheels, paint stripper, putty knives, and phosphoric acid. I soaked paper shop rags in phosphoric acid and placed them on the metal. This is how I removed most all of the rust. I also cut out the rain cover over the fan blower intake so that I could gain access to areas below it. I reinstalled the rain cover using a silicone sealant rather than welding it. After everything was all clean, I epoxy primed, seam sealed, primed again, and painted. I should also mention that I had the dash out of the car and the interior was totally removed. This made it easier to deal with the fan blower air intake. It was a miserable job. I don't ever want to have to do it again.

Really nice work you are doing. Fyi, if you need to clean up the strut housing gland nut threads, the tap size is M48 1.5 pitch. My powdercoater did the same thing a few years ago when I was refreshing my silver 240z.

But isn't the "factory underside finish" just tar undercoating with a coat of paint on top?

Here is a photo of my 5/72 low miles, very original 240z...prior to starting my refresh project.

I decided to create a new topic to continue the discussion regarding factory undercoating and whether primer / paint was used or not. I understand and it makes sense that the factory may have done different things over the years with regard to undercoating so all I can really present and comment on is my 5/72 240z. I would really like to see what @Carl Beck, @26th-Z, @bluezand others think about what I am seeing with my car, relative to what has been written and thought about the topic over the years. My car is a 5/72 240z. It has original 918 orange paint that is in excellent condition. The car shows approximately 24k miles and in every way that I can think of reflects that number. I am refreshing the car but am preserving the original exterior paint and pristine original interior. The car was stored for decades after having a blown head gasket. This probably saved the car and preserved it. I am refreshing everything else- engine, everything under the unibody, rubber, etc. I have refinished the engine bay and front unibody that the fenders, hood, valence, etc mount to. I am currently refinishing the floors and underbody behind the floors. My car has what I believe to be factory tar undercoating top coated with 918 orange (though thinly top coated). It is what 26th-Z describes as a "thicker textured paint finish". In my opinion this is a typical tar undercoating with lots of texture, top coated with the same paint used on the exterior- in my case 918 orange. My eyes and experience with stripping the undercoating tell me that what is beneath the tar undercoating is nothing but galvanized metal. I can remove the galvanization mechanically or with acid. This coating, to me, doesn't behave like a primer or paint and doesn't look like it either to my eye. It won't come off with aircraft paint remover. It only comes off with a wire wheel or acid. Here are some photos that I hope show what I am seeing. This is the floor before stripping. I used a heat gun and a putty knife to remove the "painted tar undercoating". The photo below shows what the painted undercoating looks like when removed. The painted side is painted. The tar undercoating portion is what I know tar undercoating to be. And, there is no primer or paint on the underside of the tar undercoating (the black side). It is just black tar undercoating. The photo below, to me, raises the most questions. To my eye, the left side shows what I now see all over my floors and tunnel- a mixture of bare metal and galvanized metal. Clearly the transmission brace is bare metal. The tunnel surrounding, to me, shows a galvanized / electroplated sort of coating. To me, this doesn't look like and it doesn't behave like a primer. Aircraft paint remover does nothing to it. The only way to remove it and make it look like the transmission braces is to either wire wheel it or treat it with acid. Am I seeing this wrong? Is it really some milky looking super thin primer? The right side shows the painted undercoating. What I see where the undercoating ends and metal begins is painted tar undercoating where my tool has, at the edges, scraped away some of the paint leaving only black tar undercoating. So, I am interested in what Carl, 26tth-z, bluez, and others think. Please let me know if I am wrong about what I am seeing. I truly want to know, and I want others to know, how at least the 1972 (or maybe just the 5/72) cars were delivered. I also have a 10/71 1972 240z in Silver. It is not at all close to the condition of this car....but have seen the same where I have removed some painted undercoating in the past.....though all of it has now been refinished to preserve the metal. Thanks all. J

Welcome! I know of no replacement for that screen but others might. Yes, some of us install an in-line fuel filter between the fuel tank and the fuel pump to protect the pump. I use Wix filters but I think the Fram G3 filters are the same. I think I use wix 3302 (5/16 hose fittings) for a 240z and 3303 (3/8 hose fittings) for a 280z. I replace the filter each year.

I think we have to agree to disagree. The thicker textured paint finish....when you remove it....reveals itself as nothing but black tar undercoating with body paint on top. It is not a thicker textured color mixed finish. And, the black tar undercoat is applied directly to bare metal. Apologies to the OP for me getting us sidetracked.

I have read the forum messages on the undercoating topic and opinions / observations seem to vary. Some are consistent with what you wrote but others are consistent with what I have observed. Here is an entry posted by Mr Camouflage in 2006 that matches what I have observed. "The underbody of the Z was coated from the factory with a black tar type stuff, straight on the bare metal, no undercoat underneath it, This thick tar rippled look coating (If you dont call it undercoating, i dont know what you would call it) was then oversprayed with the color paint. not painted as such. I doubt you would find paint over the top of the tar coating in places like the transmission tunnel above the gearbox. My car is a 72, and has this undercoating. It washes off back to bare metal with a rag a bit of petrol."