Yo dudes. Got the beast running (woot) now help me make it mean.

The GM balancer is a bit hard to read compared to the old motor. The notch in the balancer IS the TDC mark, right? That'd be peachy ;)

What's a decent baseline RPM + advance?
600rpm and 14 btdc?


th200-4r w/ 24-2600 stall behind the motor.

Rather than trying to set a baseline, set timing at ~ 34* (w/o vacuum advance) at 3,000 rpm and and let the base set where it is. You will need a dial back light or a marked harmonic balancer of some type.

i set my ZZ4 to about 750-800 RPM. To make your timing 34* @3000, you have to change the distributor springs right? Because the mechanical advance adds 25* on the stock HEI I think. So your initial would have to be 9* to get 34* total. 9* is a little low isn't it? Am I looking at this right?

The springs on the dist do not affect the amount of advance, they determine how fast (or slowly) the advance comes in. Too light and the (mechanical) advance will all bee in too soon, and too heavy and the advance may not be in completely even at red line. You want your advance (initial + mechanical) to be around 36* and all in somewhere between 2500 and 2800 rpm. You will probably have to experiment with different springs and weights to get it to where it needs to be. Most stock distributors have somewhere between 20* and 24* of mechanical advance (at the crank). Check out the following link to see some useful information on setting timing. Good luck.

http://www.hotrodders.com/forum/distributor-tuning-theory-part-1-a-59033.html

Here is another link that is less theory and gives more specific instructions on setting timing.

http://www.vettefinders.com/index.cfm/fuseaction/Vette101Story/ID/19

Good reply. got a question then. *IF* the stock HEI had 25*. That is unchangeable and he would have no other choice but to have 10* intial if he wanted 36* total... Correct? And he'd buy different springs to get that all in sooner. I have to do this very soon and just want to make sure I'm reading things correctly.

Skaa-tel 79,
If you ever want to change heads on that ZZ4, give me a shout. I did 3 months worth of research to find the best cylinder head for the price that will keep 10:1 compression with no milling, have excellent quench, fits great, flows nice, and comes with nice valve springs to handle bigger cams hydraulic roller cams. I may be able to help with all I've learned. And I'm sure you can help my ass too! What size carb are you using. I got a 600 for now. I had a 750 but it seemed less responsive around town.

Thanks for the info shawn!

In regards to YOUR questions, you can measure how much your HEI advances with a dial back timing light very easily.

As far as the hypothetical 25deg advance being set in stone, well.. not so much. It's possible to alter the plate that the spring+weight assembly rotates in to allow more or less advance. Basically, just lengthening or shortening the grooves. On my old 305 I would only get 36 total with 10 or 12 initial I think.

I'm not planning on changing the heads just yet!!! But it's good to know someone's gone before me :) I chose a holley street avenger 670 based mostly on the boards recommendation. Seems right for my needs, IE street, so vacuum secondaries, electric choke, pretty good out of the box.

[edit] oh yeah, and the springs - go lighter if you want a quicker advance, heavier if you want a slower advance. If you're already on the lightest or heaviest springs, you can lighten or add material to the weights as well. I tried to get a slower curve on my old dist and ended up with the heaviest springs and ground a bunch of material off the weights. The dist in question was a proform and never really worked right.

If you're looking for GM's ZZ4 timing specs, according to the 2007 GMPP catalogue it is 10° initial, 32° total.

If you're looking for GM's ZZ4 timing specs, according to the 2007 GMPP catalogue it is 10° initial, 32° total.
That brings up a point. The only thing "ZZ4" on my ZZ4 is the block, crank, rods, pistons. Everything else: cam, heads, rockers, intake....etc... has been changed. So would I still follow the 10*/32* total? I have it at 14*/36 total.

Your timing is usually based upon your dynamic compression ratio and the efficiency of your heads. If you have an efficient combustion chamber head, you don't need as much timing. Likewise with higher a dynamic compression ratio, you don't want as much timing.