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'72 521


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Hey all, I'm new to this forum but not new to Datsun/Nissan.  I cut my teeth on Z's and Skyline's back in the Navy in the early '90's.


Well, I found a 521 that I could not pass up a few years ago.  The engine has been rebuilt and I'm working to get it road worthy right now with the last fix of the brake cylinders.  


I have a couple problems and requests for parts info.


1. Auto choke: I've bought a relay from Napa and want to put it in as the replacement.  The question is where should the choke tension be on the spring when the engine      is cool and never started up yet?

2. The carb is running a little rough. How many turns for the idle mixture screw be set to? 1 1/2 to 2 turns out??

3. The PCV hose from the intake (where the PCV valve is) to the block is make shift right now. Is this hose still able to be procured?  


Thanks for the help.

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1/ That is set as needed. On a cold engine if you take the top off the air filter and look the choke plate is open but spring loaded and trying to close. Step on the gas and it should snap closed and be ready to start. If you find it's hard starting you loosen the three screws and adjust richer. I nice cold day is best for this.




2/ Again it's an adjust as needed. To properly set the idle mixture warm the engine for at least 15 minutes. Lower the idle speed with the idle speed screw to about 700 rpms. If no tach just low enough so the engine isn't shaking too much. Now turn the idle mix screw in and out looking for the fastest smoothest idle. There is about a full half turn where not much happens so set roughly in the middle. The idle probably has increased and become smoother so turn down to 700 again. Repeat the in and out adjustment of the mixture screw looking for the sweet spot of improved idle quality. May take over half a dozen tries. You are done when you can't make any improvement in quality and the idle is 700 (plus or minus) If you have a vacuum gauge try for the highest vacuum reading you can get at your preferred idle speed.


3/ I would doubt it's available. The hose is larger on the engine side and smaller at the PCV vale end. I once had one with a piece of garden hose in the small end. It worked. As long as somewhat air tight it might have to do.

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