Zed Head

Looks nice and not a bad price. Location might help interest. Lot of Main Streets around. I can almost read your plate but not quite.

Actually, his basic problem is an idling problem. Lots of traffic, and sitting while idling causes the plugs to load up and the engine to run rough. A good drive and quick engine cut might offer a clue, but the problem is the idling. I know that my old engine would start to run rough at idle, I'd take it out in the country and give it an Italian tuneup and it would idle smoothly for a while. Then load up again. IT was fun for a while but got old eventually. I put my spare engine in to fix it. 246's issue is similar. Not clear how the cracks cause the fouling though.

Sounds pretty good. Nice that the the fuel Injection guys owned up and fixed the injector problem. Although, you'd think they would know better. I see 32 psi on the fuel gauge, and 20 inches of mercury on the vacuum gauge. That calculates to about 42 psi fuel pressure with no vacuum. I think that you can borrow a gauge from the local auto parts store, for a cross-check. They require a deposit but give it back afterward. Looks like you're still working with a gauge of unknown quality. Good luck. Carry on.

That's a good one. 1-5-3-6-2-4 is correct. Maybe he some wires switched. That fits bad spark.

I'm not trying to crush ideas, just reviewing past discussions with Jalex and others. The simplest solution would be to find a mechanic who knows engine basics but they seem hard to find down there. Any good mechanic would look at those six plugs, if they are actually new and came out like that, and have some ideas. The picture of all six plugs fresh from the engine is new info. Seems much clearer than any of the past discussions about Far311 cams, and percolation, and poor idle.

I thought it might be bad valve seals myself. But folks are fairly convinced that the fouling is fuel fouling. My old 76 engines with worn valve seals had all six plugs pretty dirty, but not wet though. He says that all six cylinders give a solid 180 psi pressure reading.

He has carbs though. What would the "compensation" be? The air-fuel mix happens at the carb and should be essentially the same for each of the three runners being supplied. The other side of the view would be "how can an engine run on two (or three) cylinders. Assuming the clean ones are "dead" and the dirty ones live. He said that those plugs were actually in the engine but there's no way to confirm. Hopefully he wasn't just putting new plugs in the picture for comparison. One reason we've focused on ignition is, like you said, internet diagnosis is difficult. If we could confirm that spark is good for all six then we could ignore spark and focus on fuel-air, or oil, or compression, or valve timing, etc. The power balance check is a good idea except for the fact that he has electronic ignition. And ignition modules tend to be sensitive to having nowhere for their spark to go. He might fry his Pertronix module, as CO implied in his comment.

I have another wild arse guess, based on an old memory about the Pertronix trigger ring and the tape holding it on. I believe that the magnetic ring is actually six magnets isn't it? Or it's six bits of iron that pass a magnetic sensor. Not sure which. In the past, Jalex noted that the tape was peeling off of his, if I recall right. If the trigger ring slipped, could this give two bad triggers out of six? Do the bits inside the ring move separately? I've never had a Pertronix igntion system so don't know all of the fine details about how they work. But it might explain why the plug wires and plugs and cap all look good but there still seems to be some misfires. Each magnet or iron piece triggers a certain cylinder. Another reason to use an analyzer, I think, then work backwards to find the cause. In the meantime maybe take a good close at how the Pertronix parts are fitting under the cap. Edit - it's magnets. Hall effect is the term I couldn't remember.

I've never used one of those flashing spark checkers, the kind that fit between the plug and the wire. Has anyone used one of those? Would a misfire show up in the flashing even though it's fast? Don't know if the human eye could catch it. Here'a thought that just came to mind. One of those old engine analyzers. That would show misfires, if I recall right. They might still be around down in Panama. That would be a quick easy way to show if spark is good or bad on all six at the same time. If I was down in Panama I'd try to find a shop with one of these I think. Might make things clear pretty quickly. http://www.enginebuildermag.com/2015/10/old-gold-vintage-engine-analyzers-and-distributor-testers/

I started a new thread on just the unusual pattern of fouling. Somebody might have seen it before. It's weird.

Has anyone ever seen two adjacent cylinders, on two different carbs, foul in an identical manner and in the same amount of time? While leaving the others clean (except for one that's half dirty)? It's an odd thing that might mean something to someone. It's from the poor-idle-when-hot problems on our Panama member's 204Z with ZTherapy SU's. This picture, apparently, comes from six brand new plugs installed, engine started and allowed to run for ten minutes, then plugs pulled. Is there anything carb intake system related that could cause fuel-fouling like this? Has anyone seen such a dramatic difference between cylinders like that? So clean, next to so dirty, all in ten minutes. If it was EFI we'd have all kinds of ideas. Here's the picture, the currently active link, and a drawing from carpartsmanual for reference. Just a new look at an old problem. https://www.classiczcars.com/forums/topic/60072-misfiring-while-cruising/?page=7&tab=comments#comment-558478

This is an unusual problem. Might take a while to figure out. The solution might not be simple.

Man, I was going to suggest that after it cools it would probably get you home. Didn't know you had to wait. Good luck.

1, 2, and 6 are missing.

Still significant that the other three cylinders run clean. That's something that removes many other potential causes. Adds focus.

He has an old set of NGK plug wires. Swap those on and if the problem is exactly the same odds are it's not the wires. Put an old cap or a new cap on, see what happens. Odds are the problem won't stay with 3 and 4 through two different distributor caps. A good mechanic, even with no meter but with the thought that it might be plug wires, would just swap a "good" wire for a "bad" wire. Clean the plug, let it idle, recheck. The good news is that after all of these years (yes, years) "the problem" is narrowed down to 2-3 cylinders (still not clear if the half-dirty plug is #2 or #5), and the problem shows up in 5 minutes of idling. This is Saturday afternoon futzing around kind of work. Make guess, make a change, run a 5 minute test. Learn, rerun process. Our guesses almost don't matter any more. A good mechanic should be able to look at all six plugs and have a good diagnosis within an hour. Three really dirty plugs and three really clean plugs, and test results in 5 minutes. Can't get much easier I think. For all of the time involved, he'd probably just put all new parts on to discount any wire, cap or plug issues. A basic tuneup. The basic problem here, on the internet, is still the same. Incomplete information, incomplete followup (resistance readings on the bad three but not the good three), actions suggested but not taken.

I don't know who your mechanics are but a good one should be able to do something with this picture alone. Show them this picture and tell them that it happened immediately after installing new spark plugs. Don't say anything else.

Driving and looking at plugs has already been done. What will doing more of it tell? You need to find out where the "fuel" is coming from that's fouling those plugs. Why are cylinders 3 and 4 dirtier than the others? This assumes, of course, that spark is good and strong in 3 and 4. What are you using to hold your plug wires as they cross over the engine? And what brand are they? Maybe 3 and 4 are shorting to the engine somewhere and even though the resistance is good, the spark is still bad.

If it's not fouling from excess fuel and all of the spark plugs are getting good spark that leaves something specific to each cylinder. Oil fouling from leaking valve seals or bad oil rings seems reasonable. Oil fouling from bad valve seals would probably show some signs in the intake runners in the cylinder heads and the backs of the intake valves. 3 and 4 will be oily, the others not so much. A bore cam ran down through the carb throats might show something. Or remove the carbs and intake manifolds to get a really good look. There might also be signs from above, under the valve cover. Obviously misplaced valve seals can probably be seen through the valve springs.

Seems like that would show up on the cylinder pressure test. He says that they're all 180 psi. which is actually very high for an engine with a performance cam. It's an odd problem, but at least it's a new one.

That's a definite possibility. If the fouling is from excess fuel, then 3 and 4 could be getting a rich fuel mixture from the carbs and the outside cylinders have air leaks that lean it out. The difference is very distinct though. 3 and 4 are terrible and the others look almost lean.

1, 2 and 6 would be nice, to round out the picture. But your measurements so far are normal. So, to sum up, the question is "what would cause 3 of 6 plugs to foul very quickly?". So far, it seems that the problem is mostly a low RPM, or idling problem. The history has been about driving in traffic and idling and hot weather. A higher RPM shutdown would be interesting but might be painful, due to hot plugs. Ponder...thoughts...ideas.

Keep measuring plug wires! We're so close.

He's editing as he goes. Making progress. Not clear though, if the measurements are from the contact inside the cap to the center electrode. That's what is needed.

Edit - replay to site's #121 post (anybody notice that Patcon's post is 101, after site's 121? Base 120???) I took a look but didn't see anything. Searched Far311 and fouling and misfiring. But really, I'm just glad my car runs so well and that we seem to solve a lot of problems on CZCC. Lots of good advice here for people that want to use it. Horses and water and drinking and all that.