I just took my old 71 240Z distributor apart completely for the first time in 41 years for a thorough cleaning and inspection. I've replaced the consumables (points, condensor, etc.) many times over the years but never took the distributor completely apart, exposing the mechanical advance.

I was surprised to find out that this original distributor had only one mechanical advance spring installed in it. The illustrations show two and there is mouting points for two but my original maintenance manual actually refers to "spring" not "springs". I'm easily confused, Sooooo, I have two questions:
1) Were these distributors ever furnished with only one spring?
2) Can I get advance springs anywhere?

Back in the day (late 60's early 70's) one common tuning trick was to replace the mechanical advance springs with ones that would provide a more agressive advance in ignition timing. It's kind of funny... I have about 4 years of old Motor Trend magazines from that pre-electroinc distributor era with an article in almost every one of them that includes the spring swap-out to improve performance, no mater what car they were writing about.

It look like I will need someone familiar with the old school distributors to probably answer this one.

Vinny?

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John Kish
1971 240Z - original owner

You should send it into http://www.advanceddistributors.com/.

They rebuild vintage distributors and will recurve them for better performance/driveability. I've had them do two with great success. After 40 years the spring(s) on yours likely aren't controlling the advance very well.

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Bryan Little
Datsunzgarage.com

1970 240Z - enhanced F54 L28 w/P90, Weber DCOEs, 4:11 R200, Nissan T5 5-speed

Or replace it with a 280zx dizzy.

The whole idea is to get the spark to the hole at the optimum time i.e. more power or better economy. There is some wiggle room based on your need. The springs just hold off the spark a wee bit i.e. light springs-advance quicker heavy springs-adv. slower(centripital force of the weight acting on the cam post). What I have seen that mucks up the whole works is the disintegration of the "micro" ball bearings between the breaker plates which in turn jams it up tight. They will keep the vac. adv. from doing its job and saving you a buck or two in fuel economy. You can replace them as a set with............non OEM Part #....I strongly reccomend glass beeding / vibro bathing ALL parts. Reassemble with light grease and make sure everything moves freely and you didn't put it back together 180 deg off(ez to do-one slot is longer than the other on the "breaker cam post"). Then of course, pat it on the cap and tell it I'll see you in another 40 years. Hope the pics help

*New members: Dave Russell is a years-long CTZCC member from the Hartford area who has restored several old Datsuns, including an outstanding 1970 240Z. Dave loves to pull apart complicated electrical devices, refurbish them, then reinstall them in better-than-factory condition. Among his accomplishments during his idle time, Dave has completely rebuilt his own SUs, distributors, light switches, windshield wiper motors and linkage, electric radio antennas, and has fabricated his own TRIPLE SU MANIFOLD for the 240z cars.
No, he's not for hire. But he's a wealth of knowledge. A good guy to know.

Frank

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1970 240Z

If you are gonna rebuild a dizzy, rebuild an electronic one and kiss points goodby forever. You also get a much hotter spark using the 12-volt coil that you can use with the newer dizzy.
Another problem you can have with a missing spring or otherwise improperly curved dizzy (that advances too easily) is overheating the combustion chambers while cruising. This was a major problem with datsun roadsters and recurving their dizzies was a ncessity.

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71 on a rotisserie, two more in pieces in my shed...and a 69 1600 waiting for me to get to it