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Your compression test would seem to rule out anything mechanical in cylinders one and two. And yes, front carb supplies all three front cylinders, so I would not suspect a "no fuel" issue. How confident are you that the carbs idle settings for the carbs are where they should be - so both carbs flow the same amount at idle? And, when revving? Spark plugs can be dead right out of the box. I'd move plugs around and move plug leads around with them. I'd try swapping known good, perhaps from six to one and from four to two and vice versa. I think a Z engine will have a very hard time running if it has two totally dead cylinders. They may be intermittently firing a bit. So, new plug wires, new plugs, and new distributor cap?

I have had bad spark plugs before...brand new ones. Ended up cleaning an old one and sticking that back in.

Distributor I'm running Cody thinks the car starts on all six and then starts misfiring. An exhaust obstruction might do that... eBayNew L6 Electronic Distributor Replace For 1970-1983 Datsu...1970-1983 Nissan Datsun 240z 260z 280z. Product Type: Electronic Distributor. 1 x Electronic Distributor as Picture. (The Compatibility Is Just For Reference. -Will dramatically improve the sporty app

More info: Pulled the float bowl lids, fuel was within 0.10" of the same level in both bowls. Pulled the front carb. No obstructions as far as I could see with my ancient borescope. Clear into the head but couldn't see the valve stem. Took the valve cover off and all valve actuate as they should appear to have the proper lift and return. No wiped out lobes Reassembled it all and tried it again. #1 & #2 are both dead. #4-#6 are over 100dF within 15 seconds. The front two are 80dF. Rev it up and hold it for a short while and no change... Next weekend the exhaust will come off and we will look for FOD... Hopefully I can get it apart. The exhaust paste I used is pretty tenacious and I haven't found anything that will dissolve it yet

Probably not your issue, but thought I would share. I had an issue with my white Z where it ran great driving to a show 20 miles away and then horribly on the return drive. Cylinders 2 and 3 were bad. I was convinced it was fuel and wasted a couple hours rebuilding and then replacing the front float bowl shut off valve. Eventually I took off the valve cover and saw that the #2 and #3 valve rocker arms had 'relocated'. The end that was supposed to depress the intake valves was no longer touching the valve. Long story short, took the head to the machine shop and was told the valve stems were all gummed up from running old/bad gas. Sadly, I do not drive the cars enough. Anyway, put it all back together and it runs great now. Machine shop cleaned all the valves and guides. Fortunately, no damage was caused to anything except for my wallet. You can see the two valve 'nicks' on cylinders 2 and 3 in the pic.

I ruined a GM HEI module by running the engine with two spark plugs disconnected. I assume that a stray high voltage discharge, or some sort of "flyback" (it's a thing), made its way through the module. After I turned the engine off and reconnected the wires the engine wouldn't start. I checked spark and got a weak orange spark. The engine would start with starting fluid but would not without. Put a spare new module in and it fired right up. How about some details, just for fun, on the new electronic? Is it a ZX type or Pertronix or something else?

Plugs are new numbered Nissan. Don't suspect them... Distributor is new electronic from Ebay. No resistor. The cap doesn't locate very positively. So being made in China makes it a suspect...

I'm still trying to figure out what caused this kind of damage 🤔

I've also seen old plug wires crossfire or short to ground. Waaayyy back in high school working with old worn out car parts. Used to have to arrange the wires to avoid problems. Also seen that visible weak spark does not always spark under cylinder pressures. Had a weak ignition module once. You're probably running points though?

Correct firing order? 1-5-3-6-2-4 CCW?

You can back out combustion chamber volume using compression ratio and displacement. The 1972 FSM has the numbers. And if you have the head and block in hand you can take some measurements.

How about the old standard of mixed up firing order? Just watched a pro do that. It happens.

Do they have good grounds? Have you tried to bench test them?

New quandary. Need some help! The car is not running on all six cylinders. Using an IR gun the rear 4 are fine over 200dF in just a short period of time. #1 is cooler in the 150dF range and #2 is cold at about 90dF. So we ran a compression test this afternoon. All of them in the low 180#'s except #6 is 178#. So we ruled out valves or stuck rings?? With a timing light I checked all six yesterday and the light strobed on all 6 cylinders. So the plugs are firing?? We moved the plug wire from #2 <-> #3. Same problem and plug #2 was pretty clean... It seems to me if we had a fueling issue then #1-3 would all have issues?? So grasping at straws: An obstruction in the intake manifold or exhaust header? #2 isn't actually sparking? Some problem in the distributor cap? There is not enough fuel in the front intake manifold and #4 just takes it all?? Don't have the patience for this... :(

My horns are not working, I've checked and get power to both so I'm guessing it's the horns themselves. I am thinking I'll replace them and take my time taking them apart to fix when I get around to it. So today's question is what do people suggest? I found this set that seems like a good option: https://www.godzillaraceworks.com/electrical/hella-supertone-horn-kit-for-datsun-240z-260z-280z-280zx-fairlady-z I know that the red will stand out, i could always paint them black.

I happen to have a complete E30 head that I have never been able to sell, quite a niche market for sure. I’m in Western Canada, send me a PM if you want to discuss getting it to you.

Hi guys, this week i sold my 240z! It needed a good service as the engine leaked some oil, the body needed some work and.. i don't have the energy to work on it i will now concentrate on the engineroom of the 280zx i had restored in the past years.. I kept my self made mahogany steeringwheel and gave the new owner the rear wheel arches that i had stored on my attic with the car and some other nice parts to make an nice driver car for every day. As you can see in this pic the car has glassfiber rear arches and they are not original. As i said, i will now with some help of a friend, going to work on my almost ready 280zx! He also helped to get the lighting ready in my carport as he is a electrician as i am also! I finished also the air to air heat pump in my garage, so we can work on the 280zx coming winter. It was a bit difficult to let the 240z go but i had it for 27 years, and drove it for 25 years! It was a blast!

Thanks, so i took a look at my own, also orange model and that is a 1971 240z model.. so not the Franklin Mint model.

I think that I saw that or something similar on PBS or one of those channels. It was more focused on the main guy with the mustache. Rick Hall. Pretty fascinating show. https://en.wikipedia.org/wiki/Rick_Hall

Hello all, long time lurker, first time posting. I have a L20A engine that I am currently rebuilding and I have some questions I am hoping someone can help me with since there’s not a lot of information on the earlier engines in the US. First, my problem is the original E30 cylinder head was missing and all I was able to obtain was the E31. It’s my understanding that the E30 had smaller valve(s) and a smaller combustion chamber. I think the E30 was 36-38cc and the E31 is 42.5? My second issue is, the original pistons were garbage, and I can’t seem to find factory replacements. I have been looking at the KAMEARI light weight street pistons (SP-L20401-79) that are 79mm. I understand that I would need to go to a full floating rod to utilize these. I was looking at the CXracing L24 rods which are 133mm long like the L20a rods. My questions are, possible valve interference with the engine block due to the small boar and the oversized E31 cylinder head valves. Next, low compression ratio due to the higher cc head and the new pistons. Any advice on this situation would be much appreciated. Links for the rods and pistons below: Pistons https://www.kameariengineworks.co.jp/4-catalogue/2024.8.7-English-cataloge-v4/E0011.pdf Connecting Rods https://www.cxracing.com/ROD-L6-1330x6?srsltid=AfmBOoq1seHAZKHRIzfi8Ty5q1oPRFdG1V-m7n75OsCHTH5WlRE-H_q4i8Y

Here's a nice No Reserve 72. Already up to $25K. https://bringatrailer.com/listing/1972-datsun-240z-379/

Here's one of those weird songs you might have heard once or twice but never knew who played it. Interesting story behind the band.

Here's the Franklin Mint model.

First: Thanks Carl! for your explanation. This happened also overhere in the Netherlands with one of ..i believe.. member of the Dutch z & zx club! (many years ago) To make a euro version from the 240z.