ZZ4 timing?? [Archive] - Chevy Nova Forum

: ZZ4 timing??


slickman
8th-August-2007, 08:50 PM
I know GM says it should have an initial timing of 10 deg at 800 RPM. But, they say it should be 37 deg at 4,000 rpm total with the vac disconnected, Now, there is no way I'm going to set my timing up and bring it up to 4,000 rpm.

Anyone know what I should set it for at say 2,000 rpm? I was thinking on setting it up at 36 deg total with the vac disconnected..

ajs
8th-August-2007, 09:13 PM
I would say 10-12* inital and 36-38 total all in by 3000. If you have a HEI you can get a curve kit to set it up this way.

Paul Wright
8th-August-2007, 10:01 PM
The reason for checking the timing at 4,000 rpm is probably because this is the most likely point of detonation. If it doesn't exceed 37 degrees then they are happy warranty wise. The ZZ4 distributor already has the proper advance curve built in.

Is your concern a safety issue? I'd stay away from the fan blades, but 4,000 isn't like 7,000 rpm.

slickman
8th-August-2007, 10:15 PM
Is this a safety issue? I'd stay away from the fan blades, but 4,000 isn't like 7,000 rpm.

Thanks ajs, I'm using an Accel dizzy.

DriveWFO
8th-August-2007, 10:17 PM
Thanks Paul, I'm using an Accel dizzy.

Remember not grab the distributor cap w/ in-cap coil when retarding/advancing the timing...it can be a shocking experience.

ajs
8th-August-2007, 10:19 PM
Thanks ajs, I'm using an Accel dizzy.
You should be able to get a recurve kit for those as well. Personally I feel that 4000 is too late to get total timing.

Paul Wright
8th-August-2007, 11:47 PM
I updated my post, see above.
What is the reason for not using the ZZ4 distributor? It has the proper advance curve. GM spent a lot of money optimizing the package.

ajs
9th-August-2007, 12:23 AM
I updated my post, see above.
What is the reason for not using the ZZ4 distributor? It has the proper advance curve. GM spent a lot of money optimizing the package.


duh, I didn`t even catch that. Yeah, why don`t you just run the one that comes with it?

slickman
9th-August-2007, 06:28 AM
I used my Accel because the GM dizzy hits the firewall and I'm not going to butcher it to make it fit. I can change the dizzy springs to get the advance I need.

This Accel from the fact is set to get the total timing by 1600 with the stock springs. I have a set to push it to 32 deg total by 2800 RPM and one set to push it to 32 deg total by 4000.. Ya think I should install the springs to achieve the 32 deg advance at 4,000 RPM as per the GM spec?

Paul Wright
9th-August-2007, 09:27 AM
I believe the instructions say to check the advance at 4,000 rpm, not set the total advance at 4,000. They give a 10 degree base timing spec and the advance curve is built into the ZZ4 distributor so don't misinterpret the instructions as setting the total at 4,000 rpm. All they are asking is to double check the total at the rpm point of peak VE for warranty reasons.


You'll need to recurve the aftermarket distributor to match the curve of the ZZ4 HEI.
Since you can't run the distributor in the car to check it, what you need next is the ZZ4 advance curve spec.
I seem to recall seeing that somewhere but I can't remember exactly where.

GMPP must have a hotline to call. I'd get this distributor change verified for warranty purposes anyway.

When I was at Roush, we had people buy a well engineered, clean room built, dyno tested crate engine and then go monkey with it.
Then it would have problems and then they'd want it warranted.
A phone call can save a lot of grief.

slickman
9th-August-2007, 09:31 AM
I believe the instructions say to check the advance at 4,000 rpm, not set the total advance at 4,000. They give a base timing spec and the advance curve is built into the ZZ4 distributor so don't misinterpret the instructions as setting the total at 4,000 rpm.

You'll need to recurve the aftermarket distributor to match the curve of the ZZ4 HEI.
Since you can't run the distributor in the car to check it, what you need next is the ZZ4 advance curve spec.

Here's what the spec states;
Ignition Timing:
10° BTDC @ 800 RPM
32° total @ 4000 RPM with vacuum advance disconnected

That tells me, 32 deg total at 4,000rpm

Good idea about calling GMPP, I'll do that today....