inline6

I installed the new exhaust clamps today. As is often the case, I had to modify them to fit the pipe that slips over the header collector. The clamps were for 2.5 inch diameter, and while the headers have 2.5 inch outlets, the merge pipe that slips over top of those has an OD of 2.665". The "T bolt" clamps that were supplied originally were not heavy duty enough to clamp the slip fit connection tight enough to eliminate leaks. These new ones are strong enough, but I had to use a die grinder to slot the holes for the bolt and trim a bit off of the aluminum spacer to achieve a larger overall installed diameter when on the pipe: One of them still leaks a tad, but the other seems air tight. I will mess with the one a bit more some other day. With that done, I went about the main task of the day, which was to get some baseline AFR readings. Stock N27 needles, new nozzles, remanufactured carbs, in sync, etc. Mixture screws are turned down 2.2 turns. Here is idle: Let's call it 10.2 - 10.4. Here is steady state cruise. I will note that at a steady cruise on a very slight incline road, the AFR is a bit leaner than steady steady cruise on a perfectly flat, or very slightly declining road. Also, my RPM are only being recorded properly at idle. Any revs, and the signal is getting lost. This run is basically cruising in third gear at something above 3000 RPM Let's call that 16.2 - 16.5. And finally, a near, if not full throttle pull in first, and second, and part of third: This This one is harder to read. Wish the RPM signal was recording accurately. That said, looking at the above and recalling from watching the AFRs while accelerating with near full throttle, I was surprised to see numbers in the 12's and 13's. I am near certain that the two drops in the AFR line above (I put yellow notes at 4 and 9 seconds are shifts from first to second, and second to third. So, "pulling" in second under near or full throttle (look at seconds 6 through 9), I am seeing 12.9 to 13.4? I think I will work on getting the RPM signal attenuated and then I need to make some more full throttle runs. Perhaps I should do a leak down as a check to see if the engine is fully broken in. I've got about 280 miles on it, and until today, hadn't given any full throttle. That's why I was surprised with those AFR readings - I had only been applying moderate throttle and when doing that I am definitely getting lean AFRs. Transitioning from cruise to part throttle acceleration, I am generally seeing 16.9 to 17.1.

Thanks for the reply. I overlooked the RH, but it looks much like the OA6 - leaner than the N27 for the first two stations and richer at every other station. I'll add it to the rather narrow consideration set.

Yes, that is the general concept I was thinking, if I know the percentage more fuel that I need, then I just need to do the calculation properly to back that into the increase in annular area needed to achieve that. https://en.wikipedia.org/wiki/Annulus_(mathematics) "a little lean" at cruise is desirable. That is, lean enough to reduce gas consumption, but not so lean as to cause any noticeable surging. 14.7 at cruise would be a good choice. Yesterday, I noticed that my exhaust joints from the header to the pipes are not sealing well - they leak. So, I need to resolve that before I can take new baseline AFR readings. I have some new exhaust clamps coming today that should solve the issue.

You are probably right, Charles. I'll tell you what I find myself thinking about though. The open height of the pistons in the domes at cruise, for example, is likely very close if not identically the same with needles that are not radically different from each other (and with all other factors (oil, springs, nozzle heights, etc. the same). If cruise is stations 3, 4, 5, and 6, and I am getting an AFR of 16.0 at "cruise", then wouldn't I be able to run a calculation to determine what percentage increase in fuel flow I would need to achieve an AFR of 14.7 instead, for example? And, subsequently, could I not calculate the change needed to the annulus area, and thus back into the width of the needle that I would need at "cruise"? If the issue is which of the four stations is "cruise"... then that might be determinable, perhaps by recording operation of the pistons in a video (with markings or indicators for readability). Also, the needles do continuously taper. So, if I am seeing a consistently lean AFR through the entire range of "pickup" and "cruising" (e.g. 16 AFR for tip in, pick up and cruise) then I may need the same percentage of fuel increase across all those stations. Yah - nice video! I do plan on at least using the AFR info as guidance as to which general portion of the needle needs to change. I have spent some time reviewing specs for needles. Here is a small selection of the few I have found to not be obviously bad choices: From here, I plan to set the mixture screws at 2.2 turns out (per the factory manual spec). Then I will make some recordings with the LM-2 wideband. My RPM signal is not being capture accurately at the moment, so I will have to address that first. I think fixing that will assist with some of the repeatability that will be needed for testing. When I do that, AFRs will change from what I have seen thus far, as right now, the mixture screws are about 2.7 turns out. While I am seeing around 11 at idle, and 16s pretty much everywhere else (other than throttle lift off, which will cause AFR to hit 19-20), I may find that idle moves to 14 instead, and everything else jumps past 18. Who knows. But, I will attempt to get some AFRs with 2.2 out on the mixture screws and use those as my N27 "reference" AFRs. Once I have these, I will review the above needles again, comparing with the N27, and consider the change in "general direction" that will be necessary at each station. Regarding sucking the bowls down, I believe I would observe lean mixtures getting leaner as RPM's increase. In other words, during heavy throttle applications (I haven't gone full yet, but I have gone close) as the revs build, I would expect AFRs to go leaner. I don't have the data to show that is not happening (yet), but I will when I get the RPM signal working properly. From my driving experiences thus far, accelerating near full throttle through several gears in succession, can be repeated, with no notable increase in AFR at any point in time during the series of "pulls". Simply put, the AFRs are lean, but very consistently so. I will do a little run tomorrow, weather permitting, and see what pulling the choke lever up does to the AFR. I have done that a couple of times when the engine is a touch cold and the slight hesitation (from being lean) goes away.

I have been driving my Z a bit with a wide band 02 installed. Generally speaking, the car is rich at idle and lean everywhere else. If I am not mistaken, the needles I have are the stock N-27. I cannot confirm because they have not markings. After reading the following post, I got to thinking... If I have the needle station measurements, and I can record my AFRs for each of the general categories of start, idling, pick up, cruising, and top speed, then might I be able to calculate the station measurements of the needle that my engine wants?

I have found inexpensive Koito headlights are available in auctions in Japan. Like this one: https://www.jauce.com/auction/m1169382716

Thanks. If I recall correctly, the needles don't have any markings on them. Originally, I believe they had N-27 "silkscreened" on the portion that slips inside the piston, as were some replacements I was able to source new from a dealer in the 1990's. Adjusting the float level on the front carb to match the rear carb, my idle AFR went from around 10.5-10.8 to 11.0 to 11.3. I will proceed with something more than 2.5 turns on the mixture screws as an experiment to see how much is required to get more desirable AFRs during acceleration with load and steady state cruise. Anticipating that idle will be unacceptably rich when I attempt this. If so, I will likely look at other needle options.

I don't think so either, but am hoping :) I am using SAE 20 - this one, actually: https://www.acehardware.com/departments/automotive-rv-and-marine/fluids-and-lubrication/lubricants/10705 I carefully put it in and the level is registering on the high line of he SU "dip sticks". Since the engine is not stock, I am thinking the stock needles may not work properly. The engine is over-bored and has .030" cast pistons, and it has an E31 head. It has this Isky cam: Grind No L-475 Stage 1 Intake 26-64 Exhaust 64-26 V. Lift 0.475 V. Lash Cold 0.006/0.008 Advertised Duration 270 0.050 Duration 222 Intake valves are 44 mm SI stainless, exhaust are SI stainless in the stock size The exhaust system is not stock - I am using a Zstory header and exhaust pipes. The carburetors have been completely rebuilt (by Paltech, who I don't think is in business anymore). They are in sync/balanced. And, I have confirmed timing and correct distributor advance functionality. Now, I am off to change the float level...

I got the LM-2 hooked up today and made one run to log some air fuel ratios. The situation right now is basically idle: around 10.5 cruising at around 70 mph is about 16.5 to 16.8 giving it a decent amount of throttle to accelerate: above 17 Of note, I have the front carb fuel level set by the "wet set" method and the back carb set by using a 14-15 mm length of a nail and blowing on the inlet (air will not flow with the specified length nail between the roof of the float chamber cover and the float). Since it is rich at idle, I am going to redo the front carburetor float level to match how I set the rear one. I am hopeful that will lower the level in the front carb and consequently, lean out the ratio a bit at idle. Assuming I do get that result, I will then unscrew the mixture screws equal amounts to attempt to get lower AFR's at cruising and under throttle. If I recall correctly, they have been unscrewed exactly 2.5 turns as they sit now. My rpms signal is not recording well. I need to try a couple of things in the LM-2 manual to see if I can get that registering correctly.

The front right and the back right hooks are the same part. Starting here, I put a couple of posts that you may want to have a look at. https://www.classiczcars.com/forums/topic/63087-restoration-of-bringatrailer-240z-hls30-35883/?&page=50#ipsMenu_elcomment_659473_menu

This past weekend, I moved all of my project cars around to facilitate getting started on the "track car" - my 240Z with a prod date of 12/70: I blew the motor up at Road Atlanta 9 years ago. It took many of those years to get a replacement, but I have that sitting in the corner of the shop. While I had the project cars out of the "shop", I organized some things and put a bunch of parts away in boxes and on shelves. Then I put them back in the garage. My order of attack will be to bring this 240Z back to life, then repair my wrecked 2004 Honda S2000, and then build the 1970 510. Unsure how long it will take, but going to guess 6 months or so on the Z. Hopefully less than a year on the S2000. And, I really don't know how long for the 510: Probably several years. But I still have some things to finish up with this restoration. I removed my wide band O2 sensor from the track car yesterday and will be installing that in the newly restored 240Z soon to see what I have going on for air/fuel ratios. I'll be able to record some data with this and the wide band O2:

(edit): Whoops, just noticed that what you are trying to do isn't match factory - so disregard. I was quite interested in this topic a while back. I think the best replica I have seen is what was used here (starting at about 6:25):

Right, my understanding is that the yellow paint marks were applied at the factory to indicated the fastener had been torqued. If you have a look at the paint markings on the 240z that sold on BringaTrailer for $310,000 US a few years ago, starting at about picture number 168, you will see that the paint was applied quite messily: https://bringatrailer.com/listing/1971-datsun-240z-124/ And, for what it is worth, I personally torqued all of these fasteners to spec!

Let the chrome people know. You don't want to pay for their time to try to fix that rust area.

A cold start video: