siteunseen

Normally efi isn't effected by the gas pedal on start up. Not like a carbed car. I wonder if the light gas peddle push is enough to open the throttle blade allowing more air? I'm not sure how ported/nonported effects starting. If it had already been talked about you need to try opening the big phillips head bypass screw in front of the dashpot. It's got a spring around the threads.

Your numbers look good to me. My first thinking was lower spark on #4 but you've tried everything. The valve clearance on #4 may be off. The locking nut could be bad or something with that one valve? When I fouled plugs all the time on a 2 stroke dirt bike I had we put an anti foulet on and helped from what I remember. It was a 1982 motorcycle too. I do not know if they work on cars? Maybe someone else can explain? https://www.google.com/search?q=spark+anti+fouler&source=lmns&bih=449&biw=320&client=ms-android-americamovil-us-revc&hl=en&sa=X&ved=2ahUKEwiu6ZqO08X9AhUFrIkEHfBMAxcQ0pQJKAB6BAgAEAU

I've seen some nice collections displayed as art in guy's offices. My dad had 1957 until he lost his man cave when my lovely mother divorced him. He was so angry he left them up on the walls and the property was sold. I was too young to realize the value. He used them to repair rotted gutters and holes that squirrels had eaten into the sofits. I've been late to the hobby but never throw mine away and buy them at yard sales and trade day events. One day after I'm gone hopefully the new owner will keep it going. I've picked the nephew I want to get my stuff but it'll be a problem. He has 3 other brothers.

I watched the video and it shows the screwdriver trick to hold the carbs open. That'd be the easiest thing to do.

Big help setting valve lash by yourself while they're hot. Hell when they're cold too! I do mine cold now after a few years break-in.

You might find one in these threads? A lot of people remove them and just feather down the throttle by downshifts I suppose. Mine works but I do think I've read they are adjustable. Seems like you run them out further on the threaded section to get up against the plate. It's been a long time for me but good luck, I think you can figure it out. Here's the threads with the info... https://www.google.com/search?q=280z+throttle+dashpot+replacement+classiczcars.com&client=ms-android-americamovil-us-revc&sxsrf=AJOqlzVsrRCCr4v1H1MhXQyklV95Oob-xQ%3A1677801463922&ei=9zcBZIbvN-W8ptQP4bqU8AM&oq=280z+throttle+dashpot+replacement+classiczcars.com&gs_lcp=ChNtb2JpbGUtZ3dzLXdpei1zZXJwEAMyBQgAEKIEMgUIABCiBDIFCAAQogQyBQgAEKIEMgUIABCiBDoICAAQogQQsAM6BwgjELACECc6BQghEKsCSgQIQRgBUMMQWIhzYIeCAWgAcAB4AIAB9gKIAZcUkgEHMC45LjMuMZgBAKABAcgBBcABAQ&sclient=mobile-gws-wiz-serp

I found front and rear plates from 1960 something in the ceiling of my garage. The guy that built the place was a mechanic and must have thrown them up there. Anyhow I traded both of those to Dr Tag in Georgia for a pristine 1972 Alabama tag, did the initial pay and paperwork now it's like a vintage tag. I won't have to pay another nickel for that car's plate nor the '77 280 which has the standard vintage plate as well as my '87 hardbody pickup. They get me for way more but I jab them when I can.

That's the throttle dashpot. It keeps the throttle from slamming down to nothing after letting off. https://www.classiczcars.com/forums/topic/39698-throttle-return-dashpot/

@wal280z THE guru for that type stuff. I have his upgrade "from the junkyard" Cadillac parts. How are you Wayne? Long time no speakie. Hope you are good.

$104,000 with 5 days to go. $150,000 is my guess. You want to play?

You might figure a way to put a screwdriver through the loop on the throttle rod and keep it pried open?

You can hold the throttle rod, carbs, wide open by tying or wiring the loop to the fuel rail. That way you stand outside the driver's door and reach through the window to turn the key. Make sure and pull the coil wire off at the coil. It's kind of hard to mange all at the same time by yourself but it is possible to turn the key with your right arm and hold the gauge with your left arm to see the reading of the needle on the gauge. A helper is best but like me, hard to find when you are ready to do the test. Good luck. Hope for higher numbers.

I found this at a yard sale last weekend, $5 and it is flawless. My birth year but if someone in Alabama has a '69 automobile I'd consider letting it go for a "year of manufacture" which is legal in many states. I have a '72 plate on my 240. I took the tag frame off I remembered, looks better to me.

Would a leak down reading show the valves aren't seating tight or the rings are worn? I've never performed one so I am curious and just to get more Z dialogue on the forum I'll wait for your reply and not use google.com. Thanks for any information about our cars.

Love Navin! "These cans are defective"

Squirt the belt(s) and pulley with Windex or something similar. See if that stops it. It does have the symptoms of squeaking belts as @jonbill mentioned earlier.

I happened upon that too, today. Hadn't tried looking at a member's profile in years though.

It looks good to me as is. I have what jonbill suggested done to mine. They called it "collapsing" the springs. I run 15" wheels and really like the look. Looking closer, the front may be a little higher? I'm not sure the brand name but I've read there are "front" and "rear" specific struts that have been installed wrong.

https://www.championautoparts.com/Technical/Tech-Tips/Common-Spark-Plug-Problems.html#:~:text=Oil fouling occurs when oil is allowed to enter the combustion chamber.&text=Oil deposits cover the spark,sign of advanced engine wear.

How about trying a retorque of the head bolts. Low in the front and rear is odd. I torque mine from the center out.

Damn, that looks familiar. @Diseazd Except the tag.

Typing to twisting wires! Hope the weather gets better soon. Down here cold equals kids. I bought a heat lamp when I was 15.

Mowed mine and my neighbors yards. Let the 2 sleeping Zs idle in the garage for an hour, accidentally too! I forgot about them until I got my blower.

It looks carbon fouled to me but "we are still guessing here".. I would run Sea Foam through every so often because extended idle causes carbon fouling.

I don't know how but mine blow with the motor rpm's until the thermostat opens. I crank them at least once a month holding at 2,000 inside the garage, the fan gets quiter and then I see coolant flowing across the top of the radiator. This is something you guys already talked about I'm guessing but I finally read what explains it to me in simpleton speak.