Mark Maras

I'd clean the plugs before the test. You're looking for high resistance in one or more plug wire circuits. Measure from inside the cap to the center electrode on the sparkplug. Please post the results. Although I used liberal amounts of silver anti-seize on sparkplug threads for over 50 years without a problem, I always had that nagging feeling that one could use too much and screw up the electrical continuity between the plug and head. I recently discovered that the nagging feeling was correct. I guess I never used too much. Gundee is correct. Use the copper-colored anti-seize on sparkplug threads and likely it's good for everything else too. I just bought my first can.

And I want to know if you're using anti-seize on the sparkplug threads.

When centering the needles, screw the nozzles all the way up to the top. If the needle encounters resistance at closed throttle and you can't get it perfect, lower the nozzles to the running position (2 1/2 turns down) and it's likely they'll be fine.

@jalexquijano Modified test plan. Perform the test as described above except don't unplug the plug wire from the cap. Remove the cap with the wires intact and measure the resistance from inside the cap to the positive electrode on the plug.

@jalexquijano Thanks for the needle pics. It appears the needles are set to the same depth. I can't be sure about the float levels without some sort of measurement but they appear to be the same height😊. Let's assume, for now, that they're correct or close enough. Last year, when #4 was fouling, I had convinced myself that the problem was somewhere in the rotor, cap, wire, or plug connection because all parts were new and of good quality. Now the problem seems to have spread to 3 cylinders. One question. Are you using anti-seize on the plug threads? As I recall you have a multi-meter. Unplug the #1 plug wire from the plug and cap. Remove the #1 plug from the head and plug the wire into it. Measure the resistance from the cap end of the wire to the spark plug center electrode. Log it on paper and reassemble #1. Now go through the other cylinders and log those too. I can't tell you what they should be. What we're looking for is a glaring difference.

We need to confirm the needles are installed in the pistons to the same depth. Measure from the piston bottoms to the tips of the needles. No need to unlock them and change their height if they're the same.

@jalexquijano As mentioned above, check that both needles are installed to the same depth. If they're not, it would explain needing an extra turn down on one carb. The other possibility is one or both floats aren't adjusted properly.

@jalexquijanoIMO, it looks like the rear carb is too rich, and the front carb may be too lean. Both nozzles down 3 1/2 turns. I'm left with the float level(s) being wrong. @siteunseenCan the difference in the later lids be a possibility here? I've only dealt with the early lids with identical float hinge bosses.

I'd try BP6ESs.

Obviously, the plugs are still dark. Two questions. Did the plugs clean up well and is this all new fouling? How well did it run at 2 1/2 turns down?

If the floats are correct and I believe they are, 2 1/2 turns down should be close. I seem to recall yours being 3 to 3 1/2 turns down.

Replace or clean them. If the engine is running stronger with the wire change, the carboned-up plugs may (hopefully) be too much fuel. How many turns down are the carb nozzles?

@jalexquijanoI agree, time for new plugs. How many turns down are the carb nozzles now and how much better did it run?

@jalexquijano

@NocturnalEmber What was different when you said "slightly different positioning"?

If cranking is describing the engine turning over using the starter, the coil has nothing to do with the starter. The engine will turn over using the starter without any coil.

Yeah, I remember they were ZTherapy carbs. What I was wondering was how many times have they been adjusted (specifically balance and float level) and if they were adjusted properly. Last year we were dealing with #4 fouling and I thought (at least in my mind) that the problem was somewhere in the cap, rotor, wire, wire connection, and plug, all of which were replaced with quality parts. So, I was left thinking it was a bad sparkplug wire connection. Now we've got five plugs fouling. What happened between then and now? Any thoughts or explanations?

I used the bread method on a RX7 a few years back. I'll never use anything else in the future.

@jalexquijano If you'd like someone in Panama City to check out your carbs there's a JDM shop there. Also, look into any British or Volvo repair shop that has an older mechanic. Volvos used Hitachi SUs (I think) and any older British mechanic should know SUs inside and out..

Well, I can't imagine why a stock cam wouldn't work. It might not be the first choice but it would certainly work. I think more compression tests (wet, dry, plugs out, throttle wide open) are a good idea. Fresh #s may show something new. I'm curious if you have any theories as to why more plugs are fouling now when it was only #4 in the past. Be sure to try the downhill 4000 RPM throttle-off test. It may provide a clue if there's oil consumption.

It appears you've got the carbs balanced. The mixture screws at the bottom of the carbs are the secondary mixture adjustment. The primary mixture adjustments are the float levels. I'd check those next. They don't have to be exact, just close.

Nine years you've been dealing with these problems. Were all the valve seals replaced and did the problem get worse (more plugs fouling) after that?

@jalexquijano Last year, as I recall, we were dealing with #4 plug fouling. Now it appears the problem has spread to all but one cylinder. What has been done to the engine since then? Were all the valve seals changed? Next time you're out driving find a nice steep hill, drive down the hill with the engine at around 4000 RPMs, and take your foot off the throttle pedal. Watch in the rearview mirror for blue smoke. Tell us what you see.

I ran into this problem of the engine hitting a wall. I was on the freeway when the car slowed to 45 mph, Wouldn't go any faster regardless of which gear it was in. It would free rev to 6000 with no load. It turned out to be a partially plugged fuel filter. The fuel pressure (mechanical pump) was fine but the fuel volume was restricted. Have you tried a fuel volume test along with the pressure test?

@jalexquijano Was the engine running worse back in March and was it still fouling one plug? Now it seems to be worse. All but one plug shows fouling. Random question, does the engine use a lot of oil?