Just swapped out the computer controlled quadrabog on the old olds motor (1982) and fitted a used stock HEI vacuum advance distributor from ebay and a new factory reman edelbrock. I'm just curious as to what base timing you guys are setting these motors at and at what RPM? The sticker says 18* at 1100 RPM..but I've heard that with vac advance you need to step it down a little...I'm at 16* @1100 RPM right now. Thanks.
So you want the answers without doing any research, eh?
Ok here you go. Throw out what the book says.
The ideal curve would be:
At idle, vac + initial = 22 to 24 total
Vacuum advance connected to manifold vacuum port, not ported port.
Centrifugal advance curve only:
initial 10 to 12
plus 10 @1300/1400rpm (equals 20 to 22)
plus 20 @2200rpm (equals 30 to 32)
plus 22/24 @ 2500/2600 (equals 32 to 36)
If it pings under load with the above setup then your gas is bad or you'll
have to slow up the curve with different springs. Don't mess with the
initial curve at 10 to 12. And don't mess with the maximum vacuum
advance of 12. Make SURE you use manifold vacuum.
An adjustable vacuum advance is a must, as is a spring kit.
If this is not understandable, then find a speed shop to do it for you.
Do yourself a favor, and play with the timing. Give it the most advance it can take, without pinging.
Pick up a set of performance advance springs, and recurve your distributor. Pull the vacuum, throw in 10-12 degrees base. Then, with the vacuum still unplugged, check your timing at 2500 RPM. You should have your advance, "all in" by then. The maximum amount will be determined by your advance springs. Play with the springs until you find the sweet spot. I'm not sure what it is for a 307. But for a 350, you want 34-36 degrees. Of course this can be affected by vehicle weight, gearing, etc. I'd say for the 307, you'd want to run a little less.
Once you have the above figured out, you'll need to adjust your vacuum advance. You'll also want to decide if you want to run it off the timed port or the full manifold vacuum port. Which is another subject, altogether. I usually go with full manifold.
Once your vacuum is connected, you should not feel any shuddering at freeway speeds, low throttle. If you do, your ignition is too far advanced. Just take an hour or two, and play with it. You'll learn a lot. And buy yourself an advance timing light. It makes life easier. Or degree your balancer.
I too, am here in Ohio. So I know what you mean about the weather. I'm waiting for the weather to break, later in the week, to finish my cam swap.
