Mark Maras

No problem with the oil cap or dipstick removal. The only thing I ever noticed when pulling the oil cap was more valve train noise. The plugs are a bit too dark. I'd start with new NGK BP6ES's. A couple of things to check are, choke cable adjustment, sticking nozzles (either one will prevent the nozzles from returning to their top position. Try turning the mixture screws (secondary mixture adjustment) to 2 1/4 turns and check the plug color after a few miles. If none of these suggestions work I'd look at the float adjustment, which is the primary mixture adjustment. The oil loss is likely from poor valve stem seals. Not a difficult job if one has the right spring compressor. These engines are very reliable. It would also be a good idea to take a compression test to see if theirs any problem with the valves or rings. The results will likely set your mind at ease.

Top pic looks like Darth Vader is taking the photo.

I'd have to look under the battery and under the hatch to see if it was done properly.

YET!

Tic Toc, Tic Toc, Tic Toc.

I totally understand and agree. Long ago I used a turkey baster (No I didn't ask, Yes I caught Hell months later) and a piece of rubber tubing. My thought was, now would be a good time to clean up the internals a bit and lay hands on the subject of the discussion.

@tom231 I'd add ATF. That's kind of what it looks like. I used Dexron but I doubt it'll make a difference.

The fuel pressure should be between 3-4 psi. Much more than 4.5 psi and the pressure will overcome the needle and seat in the float bowl which can overflow the float bowls that sit just above the hot exhaust manifold.

I suppose you could mix the two but then you'd never know which one works best. Pull the cap from the domes, then remove the domes and carefully lift the dampers out. Dump the oil out. BE CAREFUL NOT TO BEND THE BRASS NEEDLES and don't exchange parts from one carb to the other. Clean all the parts with Acetone or lacquer thinner and reassemble them. Put oil in them, screw the caps back on and then, lift each damper with your finger. They should be hard to push up and fall relatively easy. The rise and fall of the dampers should feel smoooooth.

Hi @tom231. Pinkish purple sounds like ATF. Give it a sniff and see if you can figure it out. To my knowledge, any ATF will work. One can use motor oil, ATF, hydraulic oil, it's the thickness of the oil that affects the dampers rising. Put either ATF or 20 wt in them and after you've had it on the road for a little while, change the oil in the carbs to the unused option and see if there's a difference in acceleration. The oil in the SU carbs acts as a one-way shock absorber. You'll notice when you manually lift the dampers, you've got to push hard to get them to rise but they drop freely. Keep us posted.

The dampers control air and fuel. At the bottom of the pistons, there are fuel metering needles. When the gas pedal is pushed the butterfly valves in the carb throats open. The incoming air lifts the pistons which allow more air and fuel into the engine. 20w oil is recommended by Nissan. I ran ATF in mine. The oil prevents the damper from lifting too fast. The delayed rise in the dampers temporarily speeds up the airflow and pulls a little extra fuel into the air stream. It functions as an accelerator pump. You really can't over-fill the carbs with oil. Any extra will be sucked into the airstream and burned by the engine. The primary fuel adjustment is in the float height. There are secondary mixture adjustments under the carbs that raise or lower the fuel nozzles.

Another thought. Is the body shop aware of the thickness of the sheet metal in a Z? Sand (media) blasting on thin sheet metal should be done very carefully. It's easy to warp the panels.

Halloween had passed.

Does the darkish white smoke dissipate or does it hang in the air? If it dissipates, it's likely steam. Oil smoke (bluish) tends to hang in the air for a while. That's why Charles recommends a compression test. You'll have more info when you pull the plugs.

Couldn't access the video. My guess is the "it" is a stumble or lag in the transition from cruise to acceleration. Normally one would increase the oil viscosity to eliminate the stumble if the carbs are tuned properly. Crazy idea but instead of weights attached to the piston, one could buy the appropriate sized (steel?) flat washers to sit under the springs. In theory, one could add weight and shim the springs at the same time. My gut feeling is increasing the weight of the pistons may help a lean stumble but it's going to lean the mixture in all RPMs.

I'd thought of doing something similar to this using a pencil, with graduated marks, in place of the stem and "twisty bits".

The wedge-shaped spokes are similar to other Porche wheels but in these, the narrow end of the spokes are on the rim side. All the others I've seen have the wide end of the spoke at the rim side.

Nether region porn.

I don't recall ever seeing those wheels. Couldn't find them using Google search. Any ID numbers or letters on them?

The only two explanations I can come up with are, an elephant sitting on the hood all winter long (doubtful) or the springs missed the tempering process during manufacturing. It will be interesting to see if the springs expand to original unsprung length when they're removed. Be sure to share the unsprung length with Vogtland.

A miss in three cylinders has to be in the cap, rotor, plug wires or plugs. It would seem that you've eliminated wires and plugs (NGK BP6ES?) from the list. Don't know what brand the cap and rotor are nor how old they are but I'd replace them with a quality brand. Nissan and Bosch are the two I'd investigate. Jalex in Panama cleared up a similar problem with Bosch parts.

Good advice above, However, I'm not a fan of pulling spark plugs from a hot aluminum head. I've done it many times successfully but I hate the feel of the plug coming out. @jalexquijano Have you pulled the plugs lately and compared #1,2,3 with 4,5,6 and how many turns down are you running on the mixture screws? Both the same? Deja Vu!

The only two reasons for switching to electric fans (IMO) are increased cooling at low or no speed and a slight horsepower gain. I think you're on the right track suspecting plugs. Especially because you said the problem went away after a quick Italian tune-up. What RPMs did it begin to misfire? Normal for fouled plugs is around 3500 and above. Is your engine still overheating in traffic jams? If so, I'd look into the electric fans. In extreme cases (hot weather and long waits) I just turned the engine off and when I did get moving slowly I kept the RPMs as low as I could. Fewer RPMs equals less heat generated. That said, I never had any percolation or vapor lock problems that would have prevented it from starting right away.

According to my notes and using the mount on both sides of the tail shaft housing for reference, your trans is a 77-79 wide ratio. 1st-3.321, 2nd-2.077, 3rd-1.308, 4th-1.00, 5th-.864

Ah, The Chevelle. It came with the Muncy (rock crusher) 4 speed. There were many things I liked about that car but in 1973 the gas crunch dropped the value of low mileage cars. I sold it in 74 for $800.00. Saw an identical one sell for $67,000 on Barrett-Jackson a few years ago. That said, after buying the Z, I was done with the Chevelle. I fell in love with sports cars at an early age. Thanks to the book "The Red Car", my insatiable mechanical curiosity, my sister's 58 MGA (which I used to hotwire and drive at the age of 15), it was only a matter of time before I ended up with a sports car.