Greg’s ‘69 SRL311-07324

[Stick]

Disassembled the top of the distributer today to see what cam plate was in there ... looks like a 7.5. which should be non-smog (good)? I looked back through the records that came with the car and it looks like Datsun Spirit did the install and they must have changed the cam plate as well. I couldn't make any determination on the springs, but they looked a little older and covered with a little dust and grease ... forgot to take a picture.
I'll likely recheck all of the timing still with the dial back light to get a bigger picture of total timing and advance.

IMG_1202.jpeg

After I was done monkeying around with that I was looking at the coil, wires etc which are all fairly new. The coil is also a pertronix Flame thrower and 1.5 ohm resistance ... any one know if that is the correct resistance coil to be run with a resistor as well? The resistor looks new, but I didn't see that as part of the installation invoice. I measured the resistance across that and got 2.2 ohms....

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Edit - forgot to mention - I got the "Snail" delivered yesterday morning. Played around to validate what I balanced the day before and it was spot on, but you were right ... it's nicer to be able to keep in place while making adjustments, but with it being much longer it can get hard to read if pushed up against the inner wall of the fender.

[JT68]

That is a Pertronix ignition unit. The switching transistor in it will run cooler and probably last longer if you add the ignition resistor (1.5 ohms is working it pretty hard). There won't be any noticeable reduction in spark by adding the resistor, but it may keep you from failing the EI module.

[Gregs672000]

I think that's Right! Non-smog, so you're safe setting idle timing at 17. Should smoothly advance past the last mark. Test with the vacuum advance line disconnected. If it was at 8 or 9 initially you should notice much better performance with proper initial advance at 17. Unfortunately I know nothing about ohms, and electrical stuff is a weakness, but JT68 and others do!

Well done!

[Stick]

Thanks Greg ... I'll be testing all of the timing again this week when I get my new light.

I did remove the vacuum line from the port and test the advance with my Mity Vac hand vacuum pump and it appears that the vacuum overcomes the mechanical springs and mechanism at about 5in Hg and maxes out the advance around 16in Hg. It doesn't look like a ton of movement, though ... I think the vacuum arm only moves in/out about 1/2 inch. Maybe that's enough and it should reveal when I recheck the timing.

I do have a question regarding the vacuum line routing however ... Currently the distributor vacuum line is hooked to a port that sits on top of the thermostat housing (has 3 ports). There is another line that runs from there across to the front carb. Should the line be directly connected to the carb or is this fitting just a manifold that draws vacuum from the carb port?

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[Gregs672000]

I have a lack of knowledge here, but I believe that is the "thermo-modulator" used for the now non-existent smog system. I don't know if that set up will work or not. Early cars ran direct from a port barb on the underside of the (rear?) carb to the distributor. I wouldn't expect a lot of movement, as it's only adding (or subtracting?) a few degrees and only under certain loads. Since I've never had one on my car (Solex) and my current system is computer controlled to reduce timing under load based on vacuum (manifold pressure actually) I'm not sure what does what... I just know that a stock system cannot go to the intake manifold... must be to the carb barb.

[david premo]

Greg,
DO NOT USE, that is one part of the factory emissions system and needs to be used only when everything else is there and functioning properly. What that thermal vacuum valve does is switch the distributor vacuum advance from carburetor to manifold vacuum when the engine is too hot. At the same time the fan clutch will engage, the combination of these two components will cool the engine down. So if you recurve your distributor with the non-smog curve you will eliminate the need for all those components and your engine will run much better for it. If you need the recurve parts I sell them and so do a few of the other vendors on 311s.
Dave

[Stick]

Thank you Greg and Dave! The distributor was hooked up to this valve since I have owned it, as well as when my father owned it.

I'm glad I asked .. I couldn't (and still don't) understand how that thing works ... I have always had the vacuum advance hooked to the carb. I'll have to check the rear carb and see if there is a vacuum line that I can find .. .I really haven't looked very hard ... Just know there is the port where the white Silicone line ran from that thermo-modulator to the front carb.

Dave - see the pic at the top of the page .. I believe that is the correct cam plate for the distributor without the smog components? I think it might be worth buying some new springs, however .. they looked old and .. and the distributor looked like it could use a bit of cleaning inside. If you have some springs, (or you think it requires a new cam plate let me know and I'll get them ordered.

Thanks again for the reply and help!

[david premo]

Hi Greg,
That is the correct cam, the heavy spring goes on the weight that runs for the short slot and the light spring goes on the weight for the long slot. Not sure if you have the correct non-smog springs, but likely they are the correct ones. Be sure to lube all the pivot points and the slots in the advance cam. Set the timing at 16 degrees before TDC and run the vacuum straight off the carburetor. The thermal valve is not necessary for the way your ignition advance is setup so don’t bother with it.
So the way the thermal valve works is it moves the vacuum from either manifold or carburetor depending on temperature of the water in the water outlet. When the engine is below I believe 205 degrees F it runs on carburetor vacuum. When it gets over 205 degrees F the wax inside expands and switches the vacuum to manifold vacuum and as a result advances the timing and cools the combustion temperature. At the same time roughly the fan clutch kicks in and pulls substantially more air through the radiator and adds to the cooling. Once the water temperature drops down to about 180 degrees F everything goes back to normal. What they were trying to do was raise the temperature at idle for more complete combustion to clean up tailpipe emissions and as long as everything was working properly no problem, if something failed it frequently would damage the engine.
Dave

[Stick]

Fantastic info. I may order some springs just be sure and when I get some time just go through the distributor one more time to get things cleaned up and ensure proper parts and lubrication.

For the immediate time, I'll switch out the vacuum source and re-check the timing

Thanks, Dave

[Gregs672000]

Thanks for the info Dave... I knew you knew! Greg, I'm guessing that the line to the carb is going to the barb I mentioned. I think it is usually on the rear carb for ease of installation and running the line to the dizzy, but either will work. The carbs may have been swapped around or replaced, or there may be a barb on the rear carb as well. It is just a tube that sticks down about 1/2 an inch.

[Stick]

I had a better look and do not see any additional vacuum ports on the carbs (unless I'm missing something). I rerouted a new vac line from distributor to a port on the front carb for now (1st pic below). Is it possible that who ever assembled the carbs mistakenly added the hardware for the rear carb onto the front carb or vice versa? Other than routing, would it make a difference?

New Vacuum routing.jpg

below are pics of the rear carb - I don't see any vac ports ...

rear carb.jpeg

underside rear carb.jpeg

[MattC]

Mine is in the same spot. You are fine.

[Stick]

Great to know - Thanks, Matt!

[JT68]

On the U20 the port is on the front carb. On the R16 it is under the rear carb.