Ignition Problem? Not Sure, Need Help

[Bike papa]

Julian,
When I installed the Pertronix system I also installed one of their Hi output coils and completely bypassed the inline resistor. looking back had I not screwed up something when I disassembled / reassembled the Distributor to clean and lubricate the advance weights and rotating plates before I installed the Pertronix system this story might've had a much happier ending. the questionable coil would have been replaced before it failed. etc, etc, but then again I wouldn't have discovered the sticking float valve which might have left me stranded somewhere or worse. so I guess it all works out in the end.
I still want to look at a couple more thing before I close the book on this .
BP

[510wizard]

The reason I asked about the plug wires is that you are running resistor plugs and you shouldn't run resistor wires too. I run resistor wires (MSD) and BP6ES plugs.

[Bike papa]

Monte,
Honestly I don't know. I know they are NGK plug wires. I'll have to check. Since I don't have a radio installed I guess neither are required regarding your comment about working in the cold last week, the back garage is fully insulated. And an infrared heater keeps it nice and warm. It only sucks when I have to open the door while running the engine.

[SteveEdmonton]

Hmm-- I'm severely underqualified to be rendering any sort of authoritative judgement on this, but it seems to me that using 5W30 in dashpots would be equivalent to using 5W, no? The second number in a multi-grade oil represents its viscosity when the oil is hot, and that ain't gonna be happening in an SU dashpot, unless I'm very much mistaken. A little warm, yes of course, but not enough to reach operating temperature the way it would within the engine itself. So the first number is the one that describes the viscosity of the oil under your "actual" conditions.

As well, multi-viscosity oil just seems to be wrong for this application. I can't see the value in having the piston response-rate vary at all due to changing temperature / viscosity. Of course the springs provide a different sort of variability to that response rate (well, variability triggered by a different cause). But multiplying the types of variability in play just seems like a bad idea.

Unfortunately this bit about dashpot-oil viscosity probably won't help your trouble-shooting at all, but "good luck" with all of that too!

Steve

[okayfine]

Straight-weight oils are easier to deal with since there isn't uncertainty about what weight you actually have in there.

The viscosity of a multi-grade oil still varies logarithmically with temperature, but the slope representing the change is lessened. This slope representing the change with temperature depends on the nature and amount of the additives to the base oil.

Unless you have a curve for your particular oil brand/viscosity and you know what temp your SU dome carb bodies run at...

As for springs, they are supposed to be spec'd by spring rate to allow the piston to reach full height at peak HP

[Bike papa]

Here's the latest update:

After chasing Ghosts for the last three weeks I took my car to the only independent Nissan Dealer that I could Trust (He has been in business in Las Vegas for 35 Years) After verifying everything I had done (including checking the valves and sync'ing the carbs) he determined that is was / is definitely an electrical problem. While poking around he noticed the wires for the tach. Since he couldn't remember exactly how they were supposed to be wired he unplugged the terminals and the motor smoothed out immediately. we took it out for a test drive and it pulled nice and smooth with no stumbling or hesitation. He also noticed a slight voltage drop at the input side of the external resister as compared to the actual voltage at the battery. I had also noticed it but i didn't think it was excessive. I guess that's what I get for thinking! So now I'm down to three possibilities 1. the Tach might have a small internal short that is reducing the voltage to the coil even lower which is causing a weak spark. 2. the wire somewhere between the ignition key and the external resistor is going bad thus reducing the voltage. or 3. both conditions exist.
I Have a Spare Tach that I could install if that is the problem. And now I will start running some jumpers between the key and the coil to see if I can eliminate the voltage drop, all the way back to the battery if I have to. I already tried jumpers between the resistor - coil - distributor. but I didn't think to go back to the ignition. Maybe a slight rewire is in order. that being the case is 18Ga. wire sufficient or should i go heavier?

One nice surprise is that the Mechanic only charged me $125.00 and i know he spent way more time than that on the problem.
At least I know I'm looking in the right direction