For checking your timing curve, you should have an underhood dwell / tach meter; and a timing light.
Disconnect the vacuum line from your distributor and plug it. Check your timing at idle. This is intial advance, and is what is adjusted by loosening the distributor hold down bolt and rotating the distributor by hand. 10 deg is a good starting point.
Rev the motor up 200 rpm or so at a time, and watch the advance. You get more advance as engine RPM increases -- This increase is called "mechanical advance", and is controlled by weights and springs inside the distributor. When the advance quits moving ahead, it's "all in". The final reading where advance stops increasing is called "Total Advance". You may need to put some extra marks on your balancer to read total advance, unless you have one of those fancy "dial back" timing lights. To figure how much mechanical advance you have, subtract Initial from Total.
The difference between "Full" and "Ported" vacuum is whether the opening is above or below the throttle plates in the carb. Remember that vacuum line you plugged when checking your timing? Put your finger over the end at idle. Got Vacuum? Then it's a "Full" vacuum line, and means your vacuum advance will be active at idle. No Vacuum? Then your line is hooked to a "Ported" vacuum source, and your vacuum advance will not be active at idle. Try it the other way, and see if your idle smooths out a little. Look around -- the other vacuum source should be close by, and have a rubber cap on it.
Are you running points or HEI? Points should have a "ballast wire", which is basically a resistance to drop voltage to the coil to keep from burning the points. This is sometimes lost, or the wrong size, when these old trucks are converted to 12V. HEI distributors should NOT have a ballast wire -- they need a full 12V. The points ballasts are sometimes left in when these old trucks are converted to HEI.
Now that you've got the ignition tuned in, use a tee to connect your vacuum gage to the vacuum advance hose going to your distributor. What? You don't have a vacuum gage? Need one, and they're cheap. Most FLAPs (Friendly Local Auto Parts stores) have them. Let us know how much vacuum you have at idle.
The Edelbrock book is VERY good, and includes a simple procedure for adjusting your idle mix by watching vacuum levels.
The rods and springs on your Edelbrock are hiding under two little flaps on top held down by small screws. Loosen a screw, slide the flap over, and tell us what color the springs are painted. Like Darby said, they're color coded -- If you've got the wrong spring color for your vacuum level, you'll be idling with the part of the metering rod intended for feeding much gas at high throttle. The "kits" are expensive, but they end up being cheaper than buying a set or two of springs, and a set or two of jets, and a pair of rods, while you tune it in.
And remember -- you're having fun!
Cheers,
mark.
'51 3100
