I know the difference between static timing and total timing, and I do know that static timing is done with the vacuum advance disconnected. What I don't know is weather I need to plug the vacuum port on the carb while I set the static timing? I have read that on an early 302 (68) static timing should be around 12 at idle and total timing about 46 at 3500 RPM. with vacuum reconnected Any input would be very helpful.

 

You cannot have a vacuum leak while setting timing. Either plug the end of the disconnected hose or plug it at the carb. 46 degrees total at 3500 seems way too aggressive. 36 would be more reasonable.

 

Jim, the "timed" carburetor port should not have any vacuum at the factory idle RPM but, the directions always specify to disconnect and plug the vacuum advance port just to be sure. If the idle RPM you're checking the timing at is too high, (and vac advance connected) the butterflies have started to open and the vacuum advance will start tipping in skewing the timing results on the damper.

For that matter the centrifugal timing inside the distributor will start to advance as well if the idle RPM is high enough. Always use a low factory idle RPM to set initial to avoid this. Don't need to do anything to the distributor hose end, it's not going to suck any air.

46° of timing with vaccum advance connected would not be unreasonable somewhere around 3000RPM. More if you can get it, so long as its without spark knock at part throttle cruise conditions on the highway.

Back up a bit though. You'll want to see something like 34° to 36° BTDC, just initial and mechanical, probably before 3000 RPM or so, again - without vacuum advance connected. Actually as much as she'll stand really, so long as there's no spark knock under heavy load, full throttle conditions, allowing for fuel variance, compression ratio and other factors.

Vacuum advance is only doing its thing at lightly loaded, level ground steady cruising, part throttle situations. The engine wants/needs lots of extra advance under those conditions, the fuel mixture is very lean and consequently needs the fire lit way early. Many V8 run around 52° BTDC at steady highway cruise.

 

Jimmy, keep a couple golf tees handy, they work great for plugging the vac line while you set the static.

 

Thank you guys. I got those #s off the internet. I always try to do as much research as I can using our forum search and the internet, but I know just how unreliable the internet can be so, If I have any doubt at all, FTE answers are the law. Now armed with reliable information I can once again proceed with confidence