My Distributor Timing Is Horrible

[madkaw]

Best I can tell that dizzy has 24 degrees of mechanical advance. So lot's of initial timing is out. I would think it would handle 8 degrees initial without pinging-that's 32 all in. 

Vacuum advance is disconnected? If so, do you know it's locked out?

The ZX dizzy was made for a ZX engine-which you have:) Maybe you need to  give it a shot.

[Chickenman]

My plugs are gapped at .080. Msd ignition blaster coil pertromix. Otherwise runs great I just know I can get a few more ponies up high with less curve

As others have stated. .080" plug gap is too large. While it may run better at idle, the big issue is crossfire in the dizzy cap. All of the High Energy systems made by Ford, GM and MSD etc, utilizing a gap over .050", are designed to be used with a  large diameter distributor cap. This does two things:

 

1: It spaces the wire terminals farther apart so that you do not get cross firing. Depending on distributor rotor phasing, you could run into a situation at high RPM where the mechanical advance is locating the rotor tip close enough to the adjacent terminal, that cross firing can occur. That can cause massive pinging or detonation. On small diameter caps, keep the plug gap below .045" or better yet  .040".

 

2: High energy systems, like an MSD, Crane or even GM HEI, create a lot of Ionization in the distributor cap. This increases the risk of cross fire. Later model  Nissan Electronic distributors ( and Toyota and Honda etc ) had special distributor caps with vents to allow fresh air in and ionized air out. They also had special rotors with air vanes on the bottom to create a fan style venting system to get rid of the ionized gases inside the cap. Early distributor caps and rotors did not have these features. Running too large of a spark gap ( over .040" ) , with a CD Ignition and a small cap creates even MORE ionization.

 

Large plug gaps ( over .040" or .045" )  stress ALL of the ignition components a greater amount and greatly increase the chances of cross fire or spark leakage. There is absolutely no need to run over .040" plug gap with any Z motor, IMHO.

[siteunseen]

If you have a ZX dizzy the cap is larger as well as the plug gap. Does it utilize the E12-80?

Okay I see you have the OE dizzy.

Sorry.

[71Nissan240Z]

No it runs better to 7,000 rpms. Not just idle. I understand ionization etc....There's no real way to tell if it's stressing my ignition system without using a scope and looking as the signal differences the wires are creating. From what I can see the cap looks fine and there's no issues as of now. This has all been done by our forefathers and z home recommends it so I'm going to do it as long as someone with way more experience than me did it. The issue I'm having is my total timing sucks. My ignition system is great and brand new. However I really do accept all of your guys input. Thanks a bunch!

Edited March 26, 2015 by 71Nissan240Z

[madkaw]

I guess I don't understand what you mean by "my total timing sucks".  Earlier in the thread you wanted better initial timing , but you aren't happy with your total timing, but your car runs fine at 7000rpm?

Didn't answer about your vacuum advance.  

I still think .080 is too much gap which does effect timing.

[Zed Head]

I read a really interesting thread from long ago by a guy who tuned his car by butt-dyno and advancing timing until pinging started.  Then he got it on a real dyno and found at that he was actually leaving power behind because the ping zone was not the max power zone.  He had too much advance.  You might be spending time on something that won't get you much.  And as madkaw notes, "total timing sucks" really isn't accurate enough to act on.

[71Nissan240Z]

. All I'm asking is how I can modify my distributor to run more initial timing without going too far over on my total timing. I heard about jb welding weights and other things...what I want is someone who races these cars to share with me how to do this mod. That's all I'm really asking for. For example...I want to run 15 degrees at idle...but I can't because my total timing would be way over 40 degrees. There is a mod to reduce the amount of total advance so u can run more intial. I'm not talking about recurving the distributor which involves changing how fast full advance approaches at any given rpm.

Spark plug gap

http://www.zhome.com/ZCMnL/tech/ignition.html

I followed his advice. Argue with him not me .

Edited March 28, 2015 by 71Nissan240Z

[Zed Head]

Oh.  So you do want to pull timing.  In that case, the easiest thing to do might be to find a set of weights (and springs maybe) that have smaller numbers on them, and swap them for what you have.  The numbers stamped on the weights are the max. distributor timing, which is doubled to give crankshaft timing.  So if you have 24 degrees advance, the weights should be stamped with 12's.  The notches in weights determine how far they move.  

 

The springs determine when things start to happen and how fast it finishes.  I'd get some 1978 280Z parts, they typically have 9 or 9.5 weights.  18 or 19 total, so 33 or 34 with 15 initial.  Somebody would probably mail you a set for a few dollars from an old toasted distributor.  Specs. are in the FSM's, pick what you want and put some feelers out.

[Zed Head]

Here are a couple of shots of what I mean.  The 9.5 is a 1978 Dist. I have and the 11's are 1976.

[siteunseen]

After reading through this, http://atlanticz.ca/zclub/techtips/distributorrebuild/index.html, I spent $100 for a newly remanufactored one.

[71Nissan240Z]

Excellent. Thank you zed head!! I'll keep an update to what I do.

[Zed Head]

Just realized that it may not be the weights that set maximum centrifugal timing, but the the slotted plate instead, which seems to be part of the rotor shaft assembly.  The numbers are stamped on the plate.  It might be a matched set with the weights.