This is a new topic to continue my troubles with my distributor problems (failed attempts at installing Pertronix and starting/running/idling issues after re-installing the points and original distributor). At this current point the engine will not even start.

I had an Auto Parts Store rebuilt distributor in the attic so I got it down and got it ready to install. I bumped the engine around to near TDC and removed my original distributor. I installed the rebuilt one and started the engine. Set the dwell to 30 and set the timing to 4 deg Before (by the way, how is the timing mark graduated?). Adjusted the idle to around 1000. I tried screwing around with the idle mixture screws but could not get more than 4 -5 in of vacuum.

Good news : The engine will start and run with this distributor but I may not have the engine tuned exactly right.

Bad news: I guess I need to send my original distributor off for a Restore/Rebuild.

Finally made some progress.
Thanks for all of the help along the way.

Timing marks are graduated is 2* increments. If the engine is OE and so is the carb, 4-5 in/Hg is alittle low, IMO.

I would probably advance the dist timing using the vacuum gauge to say 7-8 in/Hg., then the idle speed can be turned down so the idle mixture screws can be used. Adjust mixture screws for best vacuum reading. Curb idle book suggests 950, but, 1K works for me. You're not going to get alot of vacuum because of the camshaft specs.

See where the timing marks are at. Shut the engine off, let it set for 10-15 minutes and restart. If the engine kicks back against the starter or cranks really slow, retard the timing by 2* and reattempt to start. Keep retarding timing until it does start to your likening, then turn up the curb idle to keep engine running.

All the above is a continual tinkering to get the best of both worlds, starting and running smoothly after starting.

Thanks for the tips. I have a few "rookie" questions since I have never been good at tuning.

When you say advance the dist to get 7-8 in vacuum, do you mean Before or After?
When I get it to 7-8 in of vacuum and if it kicks back upon restart, you say to retard the timing by 2*. Which is retard (besides myself), Before or After?

Thanks for the tips. I have a few "rookie" questions since I have never been good at tuning.

When you say advance the dist to get 7-8 in vacuum, do you mean Before or After?
When I get it to 7-8 in of vacuum and if it kicks back upon restart, you say to retard the timing by 2*. Which is retard (besides myself), Before or After?
Vacuum gauge reading is not relating to timing, its a measured condition and its units of measure are inches of Mercury (in/Hg). As you advance the distributor, CCW direction, you move the initial timing from 4* Before TDC to say, ie, 8* BTDC, the vacuum gauge will hopefully indicate more vacuum, ie, go from 4-5 in/Hg. to say, 6-8 in/Hg. or whatever it may read. As you do this event, you hear and read on the tach, the engine rpm go up. Now, you can turn down the curb idle and hopefully get some more adjustment from the mixture screws, the vacuum gauge, reading the amount of vacuum, will peak out and drop. Adjust for the peak, both screws, or how many there ever are.

Retarding and advancing are the actions of movement against the motion they are referenced against. Remove the dist cap, observe the rotor, crank the engine, the rotor spins clockwise when viewed from the top. Loosening the dist holddown clamp and turning the dist body (CCW) opposite of rotor direction (CW) is advancing. Turning the dist body (CW) with the rotor direction (CW) is retarding.

You will hear/read/feel the rpm change as you rotate the dist body.

Adjust all conditions for the best vacuum reading, the highest reading.

Wow - Thanks Dr. Everett. :-)

Even I can understand your lesson.

Your welcome, drdave. But I ain't no doctor, so yas don't have to call me a Dr., I haven't cured anybody.

Wait until you adjust the valves.........

I'm no doctor either (although that is my screen name reference) but I did stay at a Holiday Inn once.

I've done the valve adjustment a few times. That is a lot easier that tuning the distributor and carb.

I was thinking about the low vacuum reading, 4-5 in./Hg. If idle vacuum is low enough, this will open the power valve in the front metering plate.

The general rule of thumb, the power valve opening point is usally half the idle vacuum. I don't know what value is installed, there are two numbers stamped on the hex flat, indicating the point of opening.

If it is a 4.5, then it could be opening and introducing more fuel than needed to run at idle. This is why I suggest in getting the vacuum reading at it highest value, this will prevent the valve from opening prematurally.

Make sure there are no vacuum leaks, as this will give a low reading.

Sometimes more air is needed. This can be done two ways. One way is to drill a hole is each front throttle plate, starting with a .093 inch diameter. Then one slowly works their way up in hole size, use a 0-60 drill index, to allow more air to come through. This allows the throttle plates to close further thus allowing the idle circuit to do its intended job.

The other method I use is a setscrew on the throttle base on the passenger side and it interfaces with secondary linkage. I insert feeler gauge to slightly open the sec's. This allows me to close the primaries more. Its a trial and error method, increase feeler gauge thickness, retune primary mixtures.

Once I'm satisfied with the set-up, I add the feeler gauge thickness. I then remove the carb from the intake, measure the height of the setscrew, remove the screw from the bottom, the screwdriver slot is always on the bottom, and replace the screw from the top. I then add the existing height of the setscrew plus the feeler gauge thickness, and set the setscrew to this new height.

Now, you have adjustability of the secondary opening in using for the curb idle adjustment. Some times, drilling holes in the primary throttle plates is still needed.

Some more food for thought..........the vacuum gauge is an invaluable tool for tune-up.

An original DZ 302 will pull 9"-10" Hg. at 900 rpm idle; something else is wrong if all you're showing is 4"-5"; where do you have the vacuum gauge connected? It has to be connected to a full manifold vacuum source, not to the "ported" vacuum source on the side of the carb that the stock vacuum advance line is connected to. :)

An original DZ 302 will pull 9"-10" Hg. at 900 rpm idle; something else is wrong if all you're showing is 4"-5"; where do you have the vacuum gauge connected? It has to be connected to a full manifold vacuum source, not to the "ported" vacuum source on the side of the carb that the stock vacuum advance line is connected to. :)

John, I had the vacuum guage tee'd into the choke pull-off line at the front base of the carb. I am assuming that is manifold vacuum. In some of the photos of your engine I noticed that you have a T fitting for the brake booster line and the other line capped off. Is that where you attach a vacuum guage line?

You should tap off below the throttle plates to be sure. Choke pull-off should be full time vacuum, but not always. JohnZ is correct, 9-10" vacuum at idle of 900 rpm.

Crack open the throttle and see what the vacuum reads, higher rpm, it will register more.

Sorry I haven't been here lately. I'm working in Santa Barbara CA for the company and will be here a month. Had to take and get setup with internet access here at work.

I adjusted everything a couple of days ago. Set the timing to increase vacuum. It ended up being way too advanced. The timing mark was at the 12 o'clock position. I left it there and adjusted the screws on the carb to get the highest reading. Ended up being around 8.
Upon driving it around the block it is obvious that it is too advanced. It knocks when accellerating.
I plan to replace the vacuum fitting on the manifold from a 1 port to a 2 port so that I can tap into that point with my guage. After that I will tinker with it some more.
I also sent Jerry M. my original distributor for a rebuild. I'll have to do this all over again when I get it back.

Is this a stock Z/28 cam-equipped engine? It reads like it is not, an aftermarket cam?

The timing mark should still be on the scale, I would think. Decrease the timing by 2*, test drive. If it still pings, decrease another 2* and retest. Keep doing this until it doesn't ping. Obviously, you'll have to increase idle.

Have you done the feeler gauge trick to the secondaries as I described above? This would help the vacuum reading to increase.

How did this car run before?

To the best of my knowledge, the engine is completely stock. Before I removed the distributor to install the Pertronix the engine ran great with points.

I haven't tried your feeler guage suggestion. It seemed a little more involved for me to tackle that.

Before I removed the distributor to install the Pertronix the engine ran great with points.

Unlees you checked the timing before you pulled it, I think it's just gonna be a matter of trial and error (as was suggested) to find it's "happy spot" again. Can pretty much guarantee that it'll be more than the book 4 degree's. If it ran good before there shlouldn't be a need to poke around the carb...

I actually marked the timing mark with a black marker before I ever started this adventure. It was originally at 5 deg advanced.