jonathanrussell

I use an inch pound torque wrench to tighten to 51.6 - 86.4 inch pounds or 4.3-7.2 ft pounds. So, it is a very light amount of torque. I don't know of any fsm that references torque for the valve cover but these values are the same as the oil pan.

The fact that 3 and 4 are different, makes me think you have an internal engine issue. If my plugs exhibited the same, I would check valve clearance and do a compression check to investigate further. Apologies if you have already done these checks and I am being repetitive.

Tips would be much appreciated.

Site...didn't you say that you think your success with Red-Kote has to do with the fact that you let it cure for weeks or something like that? I am trying to figure out what I am going to use to coat one of my tanks I am about to restore.

I use this for a pre-pump filter in my 240z. WIX 33002 My tank hasn't been restored though so not sure I would use a filter if it had.

I would think about how you want to spend your time. I would definitely fix the leaks at some point but maybe you don't want to do it now. If you do everything else on your list, plus install a set of KYB strut inserts, you can start driving and enjoying the car. And, you can assess further what all needs to be addressed. If you pull the suspension apart and start painting all of the black under the car, you are starting a big project that likely renders your car on stands for a decently long time. Same goes for fixing the leaks. Those jobs open up multiple boxes of worms and could leave you without a car to enjoy for a while. Also, fixing the transmission seals is totally doable but it isn't an insignificant exercise. I did it last summer and it was pretty challenging getting the bolt that connects the shift fork to the shift rod removed (without damaging it) so I could replace the shifting o-ring and seal. Not trying to scare you. It is just not a clutch swap. It is a messy less than intuitive job if you have never been inside of a transmission before. Again though, it really depends on how you want to spend your time. If you really want to devote 6 months to getting all of these things right so you can drive and enjoy after then great. If you think you will get worn out and a bit frustrated when the car has been on stands for months and you can't drive it then maybe that tells you something also.

@SteveJ ...Curious whether you have made progress on this.

@240260280...clearly you are correct. I thought I had read 3/3 somewhere but clearly it is 4/2. Probably just an assumption I made with two casings / harnesses. Apologies for the incorrect info.

In your initial post, you write that you checked all 6 dropping resistors. The car only has two dropping resistors- one for injectors 1, 2, 3....and one for injectors 4, 5, 6. I have a 75 280 but have never seen dropping resistor problems and therefore I don't really know whether they either work 100% or fail 100% ...or whether they reduce voltage to the injectors and lower output to cylinders. EF-23 in the 75 FSM covers the testing. The dropping resistor though is the only thing I know of that isolates cylinders 1,2,3 from 4,5,6....unless there is something in the ecu (mentioned above).

To me....the stock rubber hose follows a nice unencumbered path. I don't think I would be comfortable with the rubber hose following the winding path of the S line. Plus, you would need to find a longer male / female rubber hose or use adapter / coupling fitting. Hope I am understanding what you are asking.

What ft pounds are you torquing the head bolts too? I think I read that you are re-using your bolts. I always swap to arp studs / nuts which allow 60 ft pounds of torque. I wonder whether that would impact your leak results?

I thought I would share a problem I had that I have never seen before. My 72 240z with 3 screw carbs was running perfectly. With the floats really well adjusted using the 10mm method, the carbs with SM needles run great at about 2.5-2.75 turns down on the mixture screw. With Colortune, idle is a touch rich while 3k rpm is nice and blue. I had been fiddling around with and testing out a lot of little things including fuel pump, some heat shielding around the carb float bowls, fuel pressure gauge, fuel pressure regulator, etc. Suddenly when out on a drive I noticed that the engine was running out of oomph at 4500 rpm. I went on with my other projects but kept trying to figure out what was going on with this symptom. It got worse though and I started noticing it at all rpms. Just felt like fuel starvation. I felt really good about ignition because I had recently changed to Petronix elect ignition and coil and had tested successfully after. Was getting good spark. Finally, I decided to pull the air cleaner and look at carb adjustment. When I did this, I noticed that the front carb fuel hose from float body to nozzle was crimped some. It wasn't closed shut but was visibly crimped into a kind of drastic angle. I thought...no way that is the problem. But, I had an extra new ZTherapy hose and swapped. Started up and runs perfect. So, the crimped hose was enough to starve the front carb bowl. How did it happen? I am guessing that sometime when I removed the air cleaner backing plate I reinstalled and crimped the hose somehow. Hard to say. Will probably never know. Just thought I would share in case someone else is struggling with similar symptoms and by some chance this solves the problem.

Yes, the later oil spray bar solved the problems the earlier bar had. Here is one on ebay. https://www.ebay.com/itm/1970-TO-1975-DATSUN-240Z-260Z-280Z-E31-E88-N42-HEAD-CAMSHAFT-OIL-SPRAY-BAR/233245657636?hash=item364e864a24:g:WgYAAOSwcbZc9HcH

Just a couple of comments after reading everything so far. - I would make sure that your manual fuel pump is moving enough fuel. Could be a good time to try a low psi Airtex E8016s pump mounted near the tank. And, if you stick with an electric pump, research how to make it work only if you are starting OR you have oil pressure. FYI, my 72 Zs both have a fuel pump harness in the rear. Not sure whether all 240s had the harness. And, the harness doesn't include starter / oil pressure feature. - I was originally concerned about your float levels. You wrote that you sorted them out by using the 10mm method. For me, this is the only way I can get the floats set right...and equal. - If your floats are actually set correctly, you should be able to set the mixture at 2.5 turns and have the car run pretty well. And, you should be able to move the mixture screw up and down and see a definite difference in the mixture. When the floats are not set correctly, mixture screw movement often has no effect because you are beyond the boundary of adjustment because of the incorrect float setting. - Another thing to consider with the float adjustment is the shape / curvature of the adjustment tabs. The needle valves that we are able to buy today suck universally. The original needle valves had a much thicker needle. New needle valves are thin and seem to wiggle around and get lodged sort of easily. One thing that I believe causes the new needle valves to get lodged is if the adjustment tab has too much of a curvature to it. I try to keep the adjustment tab as flat as possible...not totally flat but not dramatically curved. - Assuming the floats are right, I would go back to your color tune. I use it and think it works great for me...with the following tips. 1) Clean your color tune after every few minutes of idling. Use carb cleaner to clean. If I don't keep the color tune thoroughly clean and clean often, I can't discern the color differences. Literally, after 3 or 4 minutes of idling I will pull the color tune and clean. 2) Adjust the carbs when it is dark and keep the lights dim or off. This will allow you to see the color differences more clearly. 3) I adjust so that idle is a bit rich (a bit more red than blue).....and 3,000 rpm is a more blue. This at least is how my SM needle profiles work out at those two rpm levels. FYI, I have ZTherapy carbs too. They are great but were not adjusted well at all when I received them....especially the floats. Hope you are able to get things sorted out soon. One last thing...your red / orange plugs are likely caused by the fuel additive you are using. Most say it is not a problem.

This is what I use to flush the system before track days...not my Z my MX5. If / when I ever do a track day with my Z I will do the same. With this brake fluid I flush at least once per year. If I do more than one track day per summer, I bleed and move a decent amount of fluid through the system for each day. Castrol SRF

Needle bearing from a u-joint cap?

One other thing to check after you have done all of the things mentioned above...tail light seals in particular. On the inside of the hatch, there is a vinyl wrapped trim piece that extends across the bottom back of the hatch. That trim piece needs to be flat and sealed with sealant to the hatch. Otherwise, fumes get sucked into the lock mechanism and in through breaks in the seal of this trim piece. Most of the time, in my experience, after 45 years of not being removed and re-sealed this trim piece is wavy and has many spots where there are air gaps. Last summer, a 72 that I had just rebuilt was filling the cabin with fumes. I had sealed every possible entry point and then it hit me that I had not re-sealed the hatch trim panel. Did that and no more exhaust fumes.

Any chance that a previous owner put some sort of spacer in the bottom of your front struts to make the KYB struts fit?

I use the Vintage Rubber door seals and they have worked great for me. No slamming doors. http://vintagerubber.com/datsun-nissan/

The silicone theoretically indicates that the flapper door tension hasn't been adjusted from spec. Adjusting the tension changes mixture. Of course, someone could have adjusted and re-applied silicone. So, does the AFM flapper door move open and closed freely as it should?

To be clear....it is not the TB flap that is the potential problem. There is a flap inside the AFM. it freely opens and closes as air volume passes. When it opens and closes, it moves the electrical connection creating varying resistance values. It is the AFM flap I am suggesting that you test. If it is stuck open or stuck in any position = BAD.

I have been watching / reading your progress. Didn't want to suggest things already suggested and divert your focus. Early on though I suggested that you remove the air flow meter hoses and do two things. 1) inspect the condition of the hose that connects the AFM and the throttle body. There should be no cracks / leaks. 2) Shine a light into the AFM and view the position of the flap. It should be closed tight and it should not be bent and it should open completely and close completely with free movement. As I mentioned earlier, the worst my 75 280z has ever run was a time when the AFM flap was stuck open. They can bend and get stuck if at some point the car has backfired through the intake. If stuck wide open, the AFM reports WOT all the time. Anyway, I can't recall reading that you checked this. Maybe you did and I missed it. Keep trying. And....I know that the tendency is to stay laser focused on fuel pressure. Personally, I don't have great confidence that you are getting meaningful readings. If AFM checks out, I would look at injector flow and fuel pump.

The choke test...it is a quick way to determine whether the mixture may be too lean at idle. I was thinking that Rossiz's situation might be a lean mixture at idle. These cars, in my experience, like to idle a bit rich. When you add choke, you are dropping the nozzles...which is the same thing you do when you turn the mixtures down, away from the carb body, making the mixture more rich. So, if he adds a bit of choke and the idle stabilizes, it probably means he can solve his problem by adjusting the mixture a bit....if he is okay with the trade-off of potentially running a bit more rich throughout the power band. Regarding the dampening oil in the carbs...I have never paid too much attention to the quantity of oil. I start with one carb and add tiny amounts of oil until I the piston drops steady, all the way to the bottom, makes a slight thump, etc, but doesn't free fall and go clank. It is kind of a feel thing that you get used to seeing and hearing when you have it right. Important too is to have the domes aligned as you tighten down the dome screws so that the piston falls freely. Then, I make the other carb piston drop the same. Having the dampening set correctly ensures that the piston doesn't rise too fast (but rises and drops fully) during wide open throttle.....which would cause a sudden lean condition. Someone correct me please if I am describing this inaccurately. Regarding Oil weight...I think 20w50 would be fine. I have always used the oil ZTherapy provides but I don't remember the weight they use. Probably 20 weight but....

If you add a very small amount of choke does the idle stabilize?

I wish I could but 1) the valve is reassembled and installed in the car and 2) I am on an extended trip and am away from my car/garage/parts. Here is another photo with the larger washer sitting on the spring. Looks like it is about the same diameter as the spring. Its primary purpose seems to be to give the snap ring a solid surface before the spring.