Mark Maras

Sometimes you just have to go with the limited info and have faith that it will work out.

1100 rpms is a nice busy idle. That should help eliminate the plugs loading up. Watch your temp gauge. Things can get hot pretty fast at a busy idle unless your fan-or fans are pulling a lot of air.

I hope you've checked all the connections. Don't reuse any of the black ones.

You asked. Here's my gut feeling. It's based on what I'd do (if it were mine) to get your car back to a RELIABLE DAILY DRIVER. Honestly I'd put a stock engine back in it. Zs didn't like hot temperatures from day one and Nissan never did successfully solve the problem. You'd be a lot happier with a stock engine. My daily driver (summer and winter was a bone stock early 71. The most reliable, trouble free car that I've ever owned. Don't know what the availability of stock engines is in Panama but they're pretty cheap around the Pacific Northwest. Engine and shipping costs may be cheaper than importing a mechanic and an engine swap is very easy.

I didn't give up on #5. That plug looked pretty darned good, imho, having idled for a long time. I was just glad to see that all the plugs weren't black. It doesn't matter to me if the other five were black. The fact that at least one plug looked good narrows the problem down. Also, the original problem was always isolated to #4 until the dist was removed and reinstalled. Then #5 started doing the same thing as #4 did previously. Seems to me that moving the wires and or disconnecting them and reinstalling them is the cause for the #5 gremlin and probably #4 too. I considered valve seals too but the two dark plugs looked sooty not oily. I'm hoping that re-seating the wires will eliminate the misfire. With Alex removing and reinstalling the wires the misfire may move to another cylinder until all the wire connections are right.

Only if they feel loose. I've experienced connections that are too loose as well as connectors that were so tight that they wouldn't slip over the plug connection. Same thing with the dist. cap connectors. You'll have to assess each connection and determine if it's too loose, too tight or just right. I think we could call the just right connection the "Goldilocks Connection.

I agree you'll need a new set of plugs but installing them now and letting it idle without finding the problem is just going to foul a couple of new plugs. Check you spark plug wire connections either with a meter or by unplugging both ends and reinstalling them. Be sure that all the wires go into the cap and onto the plugs the same depth. Based on past descriptions of the problem I'd guess that the #4 wire problem is the wire to the cap connection. #3 could be either connection but I'm leaning toward the plug connection.

Do the test with the engine stone cold. We're looking for a poor electrical connection, or a bad wire or two. I know all the ignition parts are nearly new that's why I think it's a poor connection. When you installed the plug wires into the cap were you sure they all went in all the way? Same question applies to the plug wires onto the plugs.

You'll need another set but not for the test. When you Z is sitting and idling does the idle sound smooth and even or does it sound like it's missing on a cylinder or two. My guess is in the beginning it sounds ok but gets worse the longer it idles.

No, don't let it idle. You'll only end up buying new plugs. The fact that only a couple of plugs are fouled narrows the problem down to, what I believe is, poor spark plug wire connections at one end or the other. Compression is good, new ignition parts, there's not much left to blame it on. Try re-seating the spark plug wires onto the plugs and into the cap. They all should snap into place. If you have a volt-ohm meter, you could pull the cap with the wires connected (leave the wires in the loom), pull the plugs, reconnect the wires to the plugs and measure the resistance from the terminals inside the cap to the center pole of the plugs. The resistance should be nearly identical on all six. Btw, congrats on the dist removal and replacement. Success is sweet.

You know which is the "right" decision. Four days and nights is a loooooooong time on a small boat under the best conditions. Ask yourself, What could possibly go wrong? Now ask yourself what could possibly go right at ZCON. Looking forward to good conversation with you at ZCON.

@jalexquijano It seems to me that you're kind of walking up and kicking fate in the shins by letting the engine idle for long periods of time. Especially an engine with a performance cam. Performance cams do wonderful things to engines but as a rule they don't idle well and if you idle them too long the rpms start to drop and you've got to blip the throttle a few times to get the idle back to normal. In that ten minutes of idling did your rpms change at all? Perhaps you're asking too much of the engine to idle that long. And I still want to know if all the plugs were black.

NO.

I still think that the original problem with #4 was a poor wire connection at one end or the other. I think we ruled out other possibilities. That said, @jalexquijano have you explored the possibility that Previously #4 had a bad connection and now #3 and #4 have the same problem? Oh yeah, I still want to know if all the plugs were black.

I'd really like to know if all the plugs are black. If only #3 and #4 are black it narrows down the possibilities from a wide range of causes to the cap, rotor, wires and wire connections.

Check the other plugs to see if they're all black or if the problem is isolated to #3 and #4. Verify that the choke cables are adjusted properly and that the cables aren't pulling the nozzles down when the choke knob is all the way forward.

First things first. Were all the plugs black or just #3 and #4.

Flying, unfortunately.

Kathy and I are in.

You found #s three and four black. What did the others look like? Just curious if the problem is isolated to those two cylinders or all of them.

To confirm that fuel percolation is the problem, next time you shut it down when it's warm. crack the hood and let some heat out from the engine bay. Then see if it starts easier.

Since you didn't tell us "the rest of the story", I'm going to assume that when you reassembled it, the engine fired up and drove fine. Congratulations, learning is fun. Especially when it goes well.

Ztherapy sells heat shields for $100.00, no core. They list one part # but I believe there were three (somewhat) different heat shields over the years.

Do you have a heat shield under the carbs?