inline6

Yesterday and today, I spent some time working on the car again. I haven't been working on it much, as I have been working on my track Z some more instead, and I had tenants move out, so I have been spending some time over the last few weekends at a rental house doing things that needed attention. I am still hesitant to modify my SM spec SU needles. Taking a lessor path of resistance, I swapped out the 10W-30 oil for some 20W-50 to see what a difference that would make. What got me thinking about doing that was the "drop test" of the SU pistons. From fully up to fully dropped, there seemed to be almost no damping. So, I decided to try a change. Comparing/contrasting, the throttle response is not as lightning quick as it was. However, the lean condition on overrun is noticeably less. I think I like the 20W50 better overall. I might try 10W-40 as well to see about getting a bit better throttle response (for rev matching downshifts). If I am cruising and I snap the throttle fully open, the engine and car respond quickly - it accelerates nicely. So, maybe the 20W50 is fine. I don't know what to do regarding the SU dampers. They are original Nissan ones - probably original to the carbs on the car. The "barrels" seem to have wear, just judging by their appearance. The barrels have an OD of a little more than .346". I purchased an SU rebuild kit, which came with new needle and seats, and dampers recently. However, I didn't use either. I found the problem with the existing needle and seats. The rear one just needed to be polished inside to keep it from sticking as when it was machined, it was finished with a coarse finish. Also, the new dampers have a "longer throw" than the original ones - the sleeve portion of the damper has a longer amount of free movement. I didn't want to introduce that change, so I have held off on switching them out. Also, the new damper sticks do not have low and high marks for oil level like the original ones have. However, the barrels measure at, or just above .346", just like the "worn" originals. So, again, given all of these things, I didn't feel like installing them. At present, I have the mixture nuts turned out precisely 2.5 turns front and back. When warm, the AFR at idle is around 11.8. At cruise on flat road, the AFR is about 14.8. I still see AFR get lean if I try to accelerate a small or medium amount. This often happens when the road changes to a slight incline. AFR on a slight incline, trying to maintain the same speed tends to be in the high 15's and can reach low 16's. If I smash the throttle to the floor, I typically see AFRs in the 12.4 to 13 range. With the 10W-30 oil, on long instances of throttle shut deceleration (like from third to second - rev match, and then just decel in second with throttle shut), the AFR would climb up to 18s... or 19s even. With the 20W50, AFR will spike lean on throttle shut decel for an instant, but then AFR will return to normal range (13 to 14). Much less popping from the exhaust with 20W50. I need to do some data logging again so I am not just pulling these from memory. I haven't heard of anyone with Hitachi SU's changing the springs, but watching various Youtube videos, it seems like changing springs is pretty standard with tuning British SU's, and it is typically done before attempting to modify needles. It looks like order of march is springs, dampers, oil, then needles. I think I'd like to try some springs which are bit stiffer. And I'd like to try 10W-40 instead of 20W-50. Maybe I will do these things before I try to modify the needles.

What do you think it is worth currently - roughly?

Looks to me like nearly every part of that car was touched during a restoration. I would think, even with current valuations for 240z's being lower than their peak, this car would be worth more than $70k.

Just now looked at the pictures of this car. Uh, yeah... no. Nope. Much of the sellers description is inaccurate. Garrett

Do you know about the special site: search? It limits searches to just that one site. If not, try to paste this into a google search: chrome door trim site:classiczcars.com

No-no, I said "My 12/70 (16530) is black. And my 6/71 is orange/yellow."

My VIN is HLS3016530. I will double check my memory. It has been a long time since I put eyes on that switch.

My 12/70 is black. And my 6/71 is orange/yellow. Still a wide range there.

I am thinking there are not many restoration shops that focus on Z's these days. Impatient Creations is doing good quality work. I think they are very expensive. But, they do good work. Looks like they are 30 minutes from Birmingham. https://impatientcreationsinc.com/

Some options to investigate: https://upgarageusa.com/pages/nos-parts-we-have-instock-for-1969-1995-z-cars https://vintagerubber.com/datsun-240z-260z-front-bumper-guard-over-rider-strip-kit-69-72/ https://jdm-car-parts.com/products/front-bumper-over-rider-vertical-strip-set-for-datsun-240z I believe I have a spare set of aftermarket ones as well - I think of decent quality. Let me know if you would like to see some pics of them.

I am about to start on the task of adjusting the profile of my Hitachi SU needles (I have SM needles installed). I read this thread in preparation: https://www.classiczcars.com/forums/topic/59153-modified-su-carb-needles-for-l28/ @240260280 has detailed knowledge on the subject which is impressive! I wish I had the tools and knowledge to do what he knows should be done. Instead of measuring vacuum, etc. as referenced there, I am thinking about rigging up a camera to record a video of the piston movement under certain real world scenarios. For that recording, I am thinking of putting black marker lines on the piston that equate to the station positions on the needle. For the real world scenarios, I would like to record a series of various part throttle applications. I am hopeful that I can locate a specific range of the needle that will need to be modified. Very generally, I believe I have good AFRs at idle, and cruise (at 50 mph for example), and at wide open throttle. On the other hand, I have lean or very lean conditions at part throttle and during closed throttle deceleration (accompanied by popping in the exhaust). I will be making some more AFR reference runs before I attempt to modify the needles to confirm. But then, I am hoping to record the videos, and remove a miniscule amount of material from the "pick up" needle stations. The segment of the needle I need to modify should be confirmed by reviewing the video. Anyone have additional recommendations or thoughts?

Looks like I never finished this thread. I replaced the front yoke and took the propeller shaft to a local shop for balancing. It was there opinion that the shop that did the shortening of the prop shaft did not balance it. When I went to install the shaft into the transmission, the "slop" (the amount I could push the yoke radially) was a lot. As an estimate from looking, I'd say I could move the yoke in any direction about .020". So, that is about a mm of movement radially. It might have been a bit more than that. So, I decided to replace the bushing that is in the tail shaft of the transmission. Looking back on it, I think the bushing developed wear because of the driveshaft being out of balance for the first 500 or so miles I put on the car. I think that the bushing was sacrificial - meaning made of softer material than the yoke. Anyway, after putting the new bushing in (removal and reinstallation of the transmission was required), the new yoke was tight (no discernable movement at all radially). With everything back together, the vibration that caused me to start this thread is gone!

It is there for both of my cars - 12/70 and 6/71.

I was able to get everything back together on the car yesterday. The new yoke (with a new bushing in the back of the transmission) was a very snug fit. After double checking I torqued everything, I was able to take the car on a test drive. What a big difference! I got up to about 80 on some interstate and the severe vibration, which previously could be felt with a hand on the transmission tunnel, and seen in the blurring rear view mirror, was gone. Now, I can get back to the small list of things that I have to do to finish this car: install inside rear tail light trim panel install front right kick panel clean and glue in tool compartment liners repaint tail light trim panels (for better color match) install NOS glove box hinge/inside panel install rear hatch trim panel repair and install factory radio, or install guts of a new radio in the old radio case

Today, I was able to get the transmission back into the car. Because I am one-handed at the moment, I purchased a transmission jack, and I enlisted the help of a friend. This thing is quite the beast - 1000 lb. capacity and it has two telescoping lifting sections (rods). It cost more than I wanted to spend, but I couldn't force myself to buy a cheap, garbage version. I guess as I get older, I'm going to need more assistance for jobs like this one. So, this is a nice thing to have available. I should be able to finish putting the rest back together and take the car for a test drive tomorrow.