Frustrating performance.

[madkaw]

I've got $180 in the dizzy and coil alone, no cap or button. $30 for the junkyard e12-80 that I did get a base and hopefully a good module if I ever need it. The distributor was all rusted up inside so I spent $100 for the reman. $43 for the coil. Few bucks on gas to the junk yard. I'll spend another $50 to $75 on the cap and button plus wires and ZX plugs. $250 by the time I'm done, HOPEFULLY.

...and you could have had my whole set-up for 200$

[HuD 91gt]

Haha. I figure i'd be in over a Petronix. What to do, what to do. Why are you selling? I'm curious of the consequences of switching from a dual points, automatic distributor. Anyhow, were off topic.

[Stanley]

Regarding switching the dual point AT distributor, you can also drop in a new (if available) or rebuilt stock single point distributor, preferably Euro/JDM type. I did, quick fix for poor starting and better acceleration. Only drawback: missing out on the fun of the insanely complicated FSM procedure for setting the timing with dual points.

[HuD 91gt]

There's a reason I haven't purchased a timing light yet!!

What is the difference between a USDM, and Euro/JDM type distributor?

[Stanley]

Euro D606-52 mechanical advance comes on quicker and has less vacuum advance. US type D612-53 is for emissions. A lot more detail is on this site.

The timing procedure for dual point is omitted from my '72 engine manual, but described in a Nissan revision posted here recently.

[ninjazombiemaster]

Hrm. So I brought it to the shop the other day. Timing looks fine. Points are gapped to like .12 inches or whatever.. I can't remember, but it should be on spec. Turns out my water pump was going bad, replaced that. Threw some aluminum powder into the freshly topped radiator. JB welded an exhaust leak on the manifold. It is running incredible for about 10-15 minutes, then it gets to its peak temperature, a little past halfway on the meter. Then all goes to hell. Still afterfires, and sputters. Vapor Lock Maybe? I've never had issues with that before - but whatever it is, it seems to be heat related. The worst part is its really only under load.

Edit:

Btw I live at about 4,500 feet altitude or so. Currently the carb mix knobs are at 2.25 turns or so. Air is set so it idles at maybe 900, which is a touch high, but any less and its kind of rough.

The fact that it runs so well cool-warm makes me think its got to be a minor ignition or fuel gremlin. Maybe its vapor lock after all, and for some reason the engine is just getting hotter than it ever has before.

Edit 2: Took it for a night drive, its currently 75 degrees. Carbs were a bit off, but no real performance issues. Definitely heat related.

Edited June 5, 2014 by ninjazombiemaster

[siteunseen]

Do you have an aftermarket coil? The one I bought a couple of weeks ago had an Accel on it, the Ford mechanics were trying to get it to run and stuck that on. It cut out at 2,500 RPM. I robbed the one off my other '72 and it ran a lot better. After reading up on swapping over to the ZX dizzy I learned the points distributors need a special coil. Just a thought.

[Stanley]

According to fig. EF-40 in the engine manual, at 4500 ft. baseline setting at 86F is about 1.5 turns down. 68F: 2 turns, 50F: 2.5, 32F: 2.75. Depending on float setting, condition of needles and nozzles, and where you want A/F ratio (fine tune for gas mileage or performance).

So from wherever it runs best for summer, maybe a full turn down for winter.

[ninjazombiemaster]

Do you have an aftermarket coil? The one I bought a couple of weeks ago had an Accel on it, the Ford mechanics were trying to get it to run and stuck that on. It cut out at 2,500 RPM. I robbed the one off my other '72 and it ran a lot better. After reading up on swapping over to the ZX dizzy I learned the points distributors need a special coil. Just a thought.

It's the stock coil. Though maybe it doesn't like the heat. The ballast resistor is a few months old, though .

According to fig. EF-40 in the engine manual, at 4500 ft. baseline setting at 86F is about 1.5 turns down. 68F: 2 turns, 50F: 2.5, 32F: 2.75. Depending on float setting, condition of needles and nozzles, and where you want A/F ratio (fine tune for gas mileage or performance).

So from wherever it runs best for summer, maybe a full turn down for winter.

Average temps now are 60s at night, 90s in the day. I could try leaning it out a half turn or so, but I really don't think its the fuel mixture.

The best way to describe it is that it seems like when it gets really hot, a few of the cylinders don't fire. The engine is still running, sometimes just barely, but it has little to no power, and sputters, and then if you keep your foot down, *BOOM* huge afterfire. Like gas was just dumped down the exhaust. There's still an exhaust leak from the head pipe to the manifold that may be overheating the carbs, and the engine in general. I'm ordering a new gasket tonight. I don't have an in depth understanding of the system, but if I'm not mistaken, doesn't some of the coolant get distributed to the manifold and carbs to help bring them to operating tempurature more quickly?

An excerpt from Hybridz "hot water just below the engine thermostat is run into the left side of the intake manifold, touching the carburetors then out the right side of the manifold to a manifold thermostat then around the back of the motor to the input / low side of the engine water pump. The manifold thermostat is normally open and monitors the temperature. At ~140 degrees a valve inside starts to close and closes completely at ~150 degrees. "

What if the manifold thermostat is not closing off? That might overheat the carbs, and the fuel, which then doesn't burn properly, until perhaps it's in the exhaust causing the after fire?

I still haven't eliminated vapor lock, but I don't know how I might short of spending $100 on an electric fuel pump.

But then again, it doesn't really *feel* like fuel at all.

I bought new spark plugs and a fuel filter, even though nothing is really wrong with my current ones that I can see.

Edit: Took it for a longer night drive. 65 degrees at the time. Temp gauge stayed dead center the whole time. Never had a problem. I cruised for about 20-30 minutes.

I'm 100% convinced this is a heat issue.

Edited June 6, 2014 by ninjazombiemaster

[240260280z]

Ignition component can't take the heat and weak spark?

The thermostats are controlled by fluid heat, not ambient air temperature as far as I know. (i.e. the rad can scald you at the beach or at the ski slope...that thar's boil'n wadder sonny)

[ninjazombiemaster]

Ignition component can't take the heat and weak spark?

The thermostats are controlled by fluid heat, not ambient air temperature as far as I know. (i.e. the rad can scald you at the beach or at the ski slope...that thar's boil'n wadder sonny)

Possibly. But there's not a lot left I haven't tried. Maybe the coil getting hot..

[ninjazombiemaster]

Hrm. Went to lunch today, 90 degrees out. Sat idling at a drive through for a while and the gauge only got up halfway today. No problems. Maybe after putting in the new water pump, the coolant hadn't bled enough, leading too some heat problems with the ignition. Right now things *seem* okay - we'll see.