Yes I love the way guys respond right away with help.
OK here's what I did this weekend between taking care of the 10 month old future formula one driver.
Blew out the fuel rail. I didn't use Vinny's but I have a spare now. It was fine.
Disconnected all fuel hoses and filled them with fuel with the syrynge.
I know it worked because the backpressure orifice squirted.
Filled the inlet and outlet hoses to the pump including the filter.
Checked the plug wires, all good located correctly.
Changed the plugs to new NGK BPR6ES.
Tried starting, no joy.
Squirted carb cleaner in the vacuum port and got a backfire out the exhaust.
I didn't check to see if I have spark yet that's the next thing.

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Nov/70 late series one HLS3014777 Sunshine Yellow 919

Trust me, if you got a backfire, you have a spark.

Backfires come from unburned fuel which has been pumped into the exhaust system, suddenly igniting. That can be caused by hot exhaust (not in this case, since the engine isn't running), or by a spark which has access to the built-up fuel vapors in the exhaust system.

Since there should be NO CASE of a spark happening while the exhaust valve of that cylinder is open (which is what's happening to you), you have an ignition timing problem (or else a valve timing problem).

Think. What have you done which could possibly alter your ignition timing? Remove your distributor? Remove and replace your plug wires? Twist your distributor?

Your valve timing? That can be altered by interrupting the contact btwn the cam and the timing chain, then reinstalling it wrong. Over-tightening the exhaust valve lash can cause valves to remain slightly open all the time, which would eventually result in what you're experiencing. (You wouldn't get compression, and the raw fuel would be pumped past the slightly-open exhaust valves into the exhaust system, waiting for a spark to ignite it).

If you over-tighten the intake valves, you will get flashbacks thru the carbs, too.

What did you do to the engine since it last ran, please? We'll sort this out systematically.

(And do you have a compression tester handy?)

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1970 240Z

The last time I replaced spark plug wires, I replaced them incorrectly onto the distributor, so that each one was exactly one pin away from where it should have been. (I used the wrong reference for pin#1 on the distributor).

I got backfires and flashbacks but amaZingly, the engine tried to catch several times.
As soon as I put them all proper, it fired right up, of course.

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1970 240Z

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Nov/70 late series one HLS3014777 Sunshine Yellow 919

I agree if the valve train wasn't touched (and you haven't broken or slipped a timing chain), it's not a valve timing issue (thank goodness). But it's easier (by far) to use a compression checker to determine the compression stroke on your #1 cylinder, in order to determine how to set your distributor correctly.

My money now says your distributor was re-installed wrong. A very common mistake, so don't feel like the Lone Ranger. It's not true that "it can only be installed one way", and many guys manage to install it 180* backwards. It's VERY common to get it wrong, and the dizzy will seem to pop right into place but be facing the wrong way. THAT will lead to exactly what you've been describing. Wow, how many of us have done exactly this ourselves!? Too many!

Do you have a shop manual there which describes how to find TDC on #1 cylinder's compression stroke, then properly align the dizzy for re-installation?

With the dizzy removed, looking down onto the oil pump drive (which drives the distributor shaft), the slot should point to 11 and 5 O'clock positions, with the smaller crescent of the circle on the "front" side. It's critical to ensure that this happens when #1 cylinder (the front one) is at TDC on the COMPRESSION STROKE. Many people wrongfully forget there are two TDCs on each 4-stroke cycle, and install the oil pump (which drives the dizzy) at TDC on the exhaust stroke, and the engine of course refuses to run. Also remember that the distributor will twist about 14* while being inserted, due to the gears on the shaft. The rotor, therefore, should be advanced that distance when you begin inserting the distributor shaft. If you do it right the rotor will turn during installation and point to the front of the car when the dizzy becomes fully seated. Usually takes a few tries to get it right.

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1970 240Z

Frank that's just what I was thinking too.
I'm sure it's in wrong.
I didn't take out the whole thing down to the gear.
I just took off the two bolts that hold the top part just below the A/R adjustment.
I have 3 different shop manuals: Haynes, Clymer, and a genuine Nissan 1971 (engine, chassis, and body).
I'll set 1 TDC compression when I get home from work and try again.
I agree many guys don't know there are two TDC's in the cycle.

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Nov/70 late series one HLS3014777 Sunshine Yellow 919

Here's how the oil pump drive should look from above, when #1 cylinder is TDC on the COMPRESSION stroke (please not the exhaust stroke!).

Note the smaller crescent is to the front (left) of the off-set tang and the larger crescent is to the rear (right).

And remember your distributor shaft will twist about 14* as you install it, so compensate for that by twisting it the same distance ~ it should then align perfectly to the #1 pin.

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1970 240Z

Of course, if anyone else has any personal experiences with this procedure, we're all tired of hearing my 'voice' ~ feel free to add (or subtract) to what's been said so far.

I used to know how many gear teeth we needed to advance the distributor shaft before reinstalling it to make it come out exactly in place, but have long since forgotten. If anyone knows the right number of teeth to count, please adviZe us?

Frank T

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1970 240Z

Aha, that's just the next question I was going to ask!
Can't wait to get to it.

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Nov/70 late series one HLS3014777 Sunshine Yellow 919

I finally had some time today to mess with it.
I set the pulley mark to the block arrow, put the distibutor back on, the rotor was at #1 so I tightened everything again and gave it a try.
I yelled "IT'S ALIVE"! like Dr. Frankenstein.
It ran rough initially but it settled out and runs like a top now.
So that was it, 180 degrees out.
It's running a little rich but I don't care as long as it does run, I can fine tune it later.
It's the first time driving with the new clutch. What a difference!
I could only take it around the block because it's not registered yet.
Now when is that next meeting?

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Nov/70 late series one HLS3014777 Sunshine Yellow 919

Opah!!! Pobyeda!!! Success!

Duuuude! You've fixed your 240Z all by yourself!! Who's better than YOU!!??

Congratulations. Nice work.

Wed/13Aug at Grossman's.
Here:

viewtopic.php?f=1&t=8376

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1970 240Z

["It's running a little rich...."]

If you pulled the carbs off and replaced them, you might have forgotten to hook up the choke controls again. The "choke" on our SUs is actually only a drop-down device on the bottom of the carb, which pulls the jet away from the needle, letting richer mixture into the engine.

There's no "choke plate" like we're accustomed to on 'Murican cars, which would restrict the airflow into the carburetor.

You might be driving around with the choke on.

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1970 240Z

Thanks, It's not exactly as hard as timing dual aircraft magnetos but still very satisfying.
Many thanks to you and the guys here with the help.
Your advice and pictures were the perfect aids I needed.
I'll look at the choke, i could swear that I hooked everything back up.
There are two cables one for each carb. Is one the choke?
Wouldn't the engine run terrible if the choke was engaged the whole time?

During my drive the coolant temp was pegged. I replaced the sensor so it could be low coolant or a bad gauge.
Also my oil pressure isn't reading at all.
I have a replacement sensor which I'll install.
I have an extra original gauges in case.

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Nov/70 late series one HLS3014777 Sunshine Yellow 919

["During my drive the coolant temp was pegged. I replaced the sensor so it could be low coolant or a bad gauge. Also my oil pressure isn't reading at all"]

WELL!!! One (the oil) could certainly lead to the other (the water temp). Check all levels before starting the car again, for sure. Hopefully it's just bad gauges or a blown fuse or bad connections (the temp gauge is right there near the distributor, so maybe you bumped it). That same shaft that drives your distributor also turns your oil pump, so if you have one you usually have the other. But you could be out of oil.

And something else happens to these engines which you should be aware of. Unless the coolant is replaced in a specific manner, an air pocket can form beneath the thermostat, keeping super-heated water away from it. The thermo, therefore, doesn't get the message that it's time to open and can sometimes let the engine overheat (blowing freeze plugs and/or head gaskets).

If you drained (or leaked) your coolant any significant amount (a pint or more), you can rest assured there is now an air pocket under your closed thermostat, which is the highest point in your cooling system. Again, please don't ask how I know about this.

We had an extensive discussion about this here in Tech Talk last year ~ I'll try to find it rather than trying to repeat it.

Here it is:

viewtopic.php?f=4&t=7529

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1970 240Z

["There are two cables one for each carb. Is one the choke?"] I'm sorry ~ I forgot to answer this.

Each black cable is a choke. They clamp onto the top/side of each SU and run down under it, to pull the "choke" lever. As I said before, the "choke" action on our SUs is really nothing more than a mixture-enriching action. When you pull the choke lever on the console, that pulls up on the SU choke lever, which in turn pulls down on the fuel jet via a see-saw lever. The jet pulls down away from the tapered needle, allowing more space for more fuel to flow when air is pulled thru the venturi.
It's easier to picture if you imagine a traffic cone inserted into a donut. If you pull the cone up (or pull the donut down), more fuel could flow btwn the tapered cone and the donut hole. When you pull the choke lever, you're moving the donut down away from the tapered needle. I'm sorry ~ I know that's a "Flintstone" way of describing it, but I'm too tired to be articulate right now.

No other cables run to the carbs, because the throttle plates inside are opened by your foot mechanism, and the vacuum chamber float is suspended by a spring and not attached to anything (it only carries the tapered fuel needle under it) and moves according to how much manifold vacuum there is at any given moment.

I'll try to find a good digram of the choke mechanism.

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1970 240Z