280ZX Distributor Advance Curve Reference

[Walter Moore]

Lately there have been several threads that all seem to be discussing timing advance problems related to the E12-80 electronic distributor conversion on older engines. For example:

http://www.classiczcars.com/forums/showthread.php?t=34031&highlight=E12-80

http://www.classiczcars.com/forums/showthread.php?t=34073&highlight=E12-80

http://www.classiczcars.com/forums/showthread.php?t=34126&highlight=E12-80

In at least one of them I ask if there was any way to know which distributors might be good candidates, and which ones to avoid, but never really got an answer. So I took it upon myself to download the factory service manuals for all five years of the 280ZX (1979 - 1983), dredge through them, and gather the information myself.

The attached Excel file summarizes what I found. It is an interesting document, and it clears up much of the confusion on the subject. For example I now believe that I can explain some of the vexing questions I had on this subject. For example:

Q: Why do so many sources recommend using only the 1979 model distributors?

A: Because that is the only year where you can be reasonably sure that the vacuum advance will not cause spark knock at part throttle without having to re-curve the distributor.

Q: Why does the E12-92 ignition module retard the timing by more than 8 degrees unless a 12V signal is applied to one of the extra pins?

A: Because starting with 1981 the vacuum advance produces 30 degrees of advance, and the ignition computer needed a way to retard the timing in the event of spark knock.

Remember that 1981 is about the beginning of the era when cars sold in the U.S. had to meet the dreaded and evil C.A.F.E. standards which made fuel mileage more important than anything else. I do not remember if it was in effect in 1981, but the car companies were all scrambling to meet the standards about that time.

Take a look at the file and many mysteries on this subject become self evident.

Distributor advance curves.xls

[=Enigma=]

This is great info. Very useful. Thanks for taking the time to do this? Now I have to go out and see what I've got.

[Zak's Z]

Walter, how do you know if you've got a 79 model distributor? Any specific markings to identify it?

[doradox]

Awesome info, thanks. Only an engineer would have done the min, max, and median.

Steve

[sblake01]

Walter, how do you know if you've got a 79 model distributor? Any specific markings to identify it?

The six digit numbers he listed will be on the side of the dist. above the Nissan part number, i.e. D6K8-02xxxx, D6K8-03xxxx, etc.

Edited April 23, 2009 by sblake01

[Zak's Z]

Thanks, I'll check mine.

[Weasel73240Z]

Walter...that is awesome info, and I think I just confirmed that I'm not getting enough total advance with my dizzy. That may explain my hesitation. According to your info, I should get about 37 degrees of advance (17 mech and 20 vac.), and I'm only getting about 23 - 25 total.

I think the answer is a lighter spring in my advance mechanism. I bought the new advance unit from a local Nissan dealer, along with the new breaker plate, but its not a Nissan part (I think its a Beck/Arnley). Is it easy (and possible) to change the spring in the advance unit?

[Walter Moore]

... Is it easy (and possible) to change the spring in the advance unit?

I am sure that it is possible, but I am an electrical engineer, not a mechanic or race technician. I am not an expert on modifying distributors, just gathering and applying information.

[Walter Moore]

Awesome info, thanks. Only an engineer would have done the min, max, and median.

Steve

So, you are in Colfax now? Didn't you used to list your location in Richmond? (Or do I have you confused with someone else?) I may see you around sometime. I don't live very far from Colfax, in fact I drive past it on the way to Lafayette once in a while.

[doradox]

So, you are in Colfax now? Didn't you used to list your location in Richmond? (Or do I have you confused with someone else?) I may see you around sometime. I don't live very far from Colfax, in fact I drive past it on the way to Lafayette once in a while.

Still Colfax, although I just listed Indiana until recently. Not actually in town though. Very far from Colfax? Lebanon? My son has seen a Z matching your avatar a couple time there. BTW your pin on the map is in Bowling Green KY.

Steve

[Walter Moore]

Thanks for pointing out the pin. I don't know how that happened.

Yes I live in Lebanon. I drive the Z around once in a while on nice days. This weekend the Indy Z car club is going to have an area reserved at a car show in Muncie at the Delaware county fairgrounds. I plan to be there Saturday. There might be one or two other S30's present. The Indy club is mostly late model cars... But it is still sort of fun.

[doradox]

Thanks for pointing out the pin. I don't know how that happened.

Yes I live in Lebanon. I drive the Z around once in a while on nice days. This weekend the Indy Z car club is going to have an area reserved at a car show in Muncie at the Delaware county fairgrounds. I plan to be there Saturday. There might be one or two other S30's present. The Indy club is mostly late model cars... But it is still sort of fun.

I've been meaning to get hooked up with the Indy club but life always seems to get in the way. I lived in Lebanon for 8 years before moving out to the sticks about 3 years ago. I'm surprised I never saw your Z.

Steve