Can anyone give me some help with setting the timing for my 85 z-28?
I have a 305 stock with a Holley 650 4BBL and an Edelbrock performer nitrous kit. I know I'm supposed to retard it 2 degrees per 50 hp of nitrous, but I can't even get my timing as is. I tried unplugging the vac. advance on my dist. and pinching the line and the mark on the balancer is so far counterclockwise from the timing tab I don't know how much it's going to change it if I DO adjust it. The car runs fine so I thought the only thing wrong was something I'm doing.
I have a plain (non vac. advance) light, is that a problem? Or is there something else I'm not doing?
And excuse me for being an idiot, but how do I read the timing tab? Some people said the deep groove was 0* and someone else said that the tube on the right is 0*... and each little groove is 2*? It seems there isn't much room for adjustment because there's only 2 grooves on there, or do I need an aftermarket tab or tape?

 

Have you attempted to adjust the timing by rotating the distributor? If so, have you set the timing to the OEM spec just to see how it runs?

It wouldn't be a bad idea to verify that at #1 TDC, your timing marks are lining up (balancer & timing tab) at zero degrees. Not the easiest thing to do with the the motor together and in the car, but you can pull the #1 plug (by the way, when checking the timing, be sure you have the timing light connected to #1 cylinder as it's easy to connect the inductive pick-up to the wrong plug wire unless you are connecting it right at the plug), turn the motor over by hand using a ratchet, extention and socket on the balancer bolt. Spinning the motor clockwise (normal running rotation), get the timing marks close (20* BTDC approx.) and then put something like a stiff rubber hose into the #1 plug hole so that it makes contact with the top of the piston. Then continue to rotate the motor until the hose and piston stop coming up in the cylinder (this is best accomplished with the help of a friend). This will get you real close to knowing that #1 is at TDC. You'll want to pull off the driver's side valve cover and make sure the #1 intake and exhaust pushrods can spin freely as well, that way you know #1 cylinder is at the top of the compression stroke. Look for the balancer mark and see where it is on the timing tab...should be real close to the zero mark. Sort of a long drawn out process, but this way you know for sure.

If the mark on the balancer is counter-clockwise of the timing tab when you are checking the timing, the timing is advanced on the motor. How do you plan on retarding the timing when running the nitrous? If you are off the scale when checking the timing, yet the timing marks line up when the motor is at #1 TDC (as described above), you might want to install some timing tape on the balancer, so you can actually get a number when checking/setting the timing. Hope this helps some!

 

The engine catalyst says to set at 0*, but I'm no longer CC, so that's out of the question. Rotating the distributor DOES change it, but it all goes back to needing to know how much.
"Sort of a long drawn out process, but this way you know for sure. "-- I think I'm going to HAVE TO do it to figure out whats going on.