I use the all knowing Lars procedure - it works for me:

How to Set the Timing
When you think about it, setting the timing at idle speed makes no sense at all: You don’t operate your car at idle, and timing changes as the rpm changes. Fact is, the timing spec at idle speed is provided as a simple way for most people to set the timing, and is not a good procedure for optimum performance.
Small block Chevys (and most other GM performance V8 engines) perform best when the total timing (full centrifugal advance plus the initial timing setting with vacuum advance disconnected) is all in by 2,500 – 2,800 rpm and is set to 36 – 38 degrees. If you have an adjustable timing light, this is very easy to check. If you don’t, you need to scribe a 36-degree mark on your harmonic balancer. Here’s how:
Measure the circumference of your harmonic balancer using a sewing tape measure (or other flexible tape measure). Get it as accurate as you can. Take this measurement and divide by 10. The number you get is the distance to 36 degrees. Measure this distance CLOCKWISE from your existing harmonic balancer timing mark and place a clear mark on the balancer.
Remove your distributor cap and rotor. Remove the 2 centrifugal advance springs. Install the rotor and the cap (without the springs). Disconnect the vacuum advance.

NOTE: This procedure cannot be used on the HEI ignition systems. Removal of the springs will cause an artificially over-advanced condition that will never be achieved with the springs in place. You can use the basic technique described in this paper with the HEI units (setting timing up to 36 degrees), but to check total timing, you must install a set of soft springs. You cannot remove the springs altogether. With the soft springs in place, rev the engine until the centrifugal advance is pegged out. Adjust for 36 degrees total. Then re-install your original springs.

Start the engine. It may kick back a little due to the advance coming in immediately without the springs. If you’re using an adjustable timing light, set the light to 36 degrees advanced. Now rev the engine just a little while observing the timing marks with the light. It shouldn’t take much rpm to peg out the advance without the springs installed. With an adjustable light set at 36 degrees, align the stock timing marks with “0” when the timing is “pegged out.” With the non-adjustable light, align your new 36-degree mark with “0.” Rev the engine a little to make sure the timing will not advance any further. Shut it down.
Pop the cap and rotor and re-install the springs. Put everything back together, but leave the vacuum disconnected. Start it up. For future reference, make a note of the timing setting at idle. This is your new curb idle timing spec. Now give the engine a few quick rev’s past 3,000 rpm and verify that the full timing (36 degrees) is coming in. If it’s not, you need to change to a softer set of springs until you get full 36-degree advance before 3000 rpm. (NOTE: A stock set of springs will usually not allow full centrifugal advance to come in before redline rpm. If you have stock springs installed, don’t rev the engine beyond its limits to try to force full advance in.)
Shut it down and hook up the vacuum. Now do a road test.
The 36-degree 2500 rpm advance curve is optimum for performance, but may require premium fuel. Lug the car around, and punch the throttle at low rpm while listening for detonation (“engine knock”). If you’re getting any audible knock, you MUST retard the timing. Retard the timing in 2-degree increments until engine knock stops. Engine knock will seriously damage engine components if not corrected. If you get no knock, you may see slightly improved performance at 38 degrees total timing. This is particularly true if you’re running at high altitude.
If you have no engine knock under acceleration, but the car “chugs” or “jerks” at cruising speed (light throttle application), you are getting too much vacuum advance on top of the mechanical advance. You may need to change out the vacuum advance diaphragm with an adjustable unit available from aftermarket sources. Adjust these units so that you get the most vacuum advance possible without any “chugging” or “jerking” at cruise speed.
Your timing is now set for best possible performance. Make note of the new setting, and use this for your future tune-up work.

 

Yes I came across this artical, but stopped reading when I saw teh "non-HEI" disclamer. Looks like a good source of information regardless!

It just kills me that when I set the car to factory specs, it runs terrible, setting the timing to where the engine purrs results in a scary high advance. I think I'll start by checking the tape on the ballancer and go from there. But not today, already in trouble for spending the better part of Sat. down in the garage!

 

Another country heard from.

As I understand it, with vac line off and plugged, idle speed advance should be about 10*?? And with vac advance off and plugged, total advance should be at 36* when at 2200 to 3000 rpm? If not at 36* or so, the springs in the mechanical advance mechanism need to be changed?

So set at idle and hope the rest follows and is OK?

I just received a rebuit dist. for my 1965 327 c.i. and will install it soon. The old one had the vac advance mechanism bent. How I have no clue. I replaced that, but it still seems to have iginition problems which hopefully will be corrected with the new dist. The old one has pointless Crane Cam conversion which I plan to move to the new one.

 

Thanks to JohnZ's articles on timing, it's all begining to make sence. Thanks John and everyone else who chimed in to help out!!


steve

 

If after following all of these recommendations your car still doesn't idle and runs better at higher advances (above 40 degrees), check your firing order. I've had this happen before when a kid I was helping out insisted that he had the plug wires on correctly on his 302 until I found 2 different firing orders for Ford 302's and he had used the wrong order. After correcting the order, the timing fell into place by the book.

 

I have to agree with Jerry on the "normal" procedure to set timing - at idle; followed by a total timing check - and preceeded always by checking and seeting the dwell properly (I am starting to sound like my old auto mechanic teacher from high school). That's how I always set the timing on my pos '76 Plymouth Arrow (my HS car), my friend's AMC Hornet (his HS car, I was his wrench) and my dad's 1970 Opel GT (his car which I was only allowed to tune up, but not drive, in HS - it was a weak Corvette wannabe anyway)

However, for me and those other owners of L76s and perhaps L79s, setting the initial timing at idle is next to impossible, because at L76 "idle" [something like 900 rpm is usually required, although mine is now able to idle at 800] there is some advance already coming in, and taking it down to an idle where the advance is not yet started is next to impossible. That's where "total" or "all in" methods to set timing such as Lars' (and as JohnZ and Duke have advised consistently) come in quite handy, followed by checks down the rpm range (a map, if you will).

 

Hi Jerry,

I just wanted to let you know that you are not alone driving without the “petal to the floor” I like driving at a nice normal pace, I figure all those guys going fast are afraid someone might see the imperfections in their cars if they slowed down.

I treat my cars imperfections as badges of honor, all earned from experience.

Robert

 

Many centrifugal curves start at 700 (or maybe even a little below), which is below the speed that some engines will idle with any stability.

However, on most pre-emission engines ('63 FI being a possible exception) removing and plugging the vacuum can signal line will loose several hundred RPM, and often the engine will just barely be running, so you can set the initial timing.

This should always be followed by increasing engine revs until the the timing advances to be sure the centrifugal has not started. If the advance increases immediately you probably have not set a true initial timing. In this case you can use the following methods:

1. Install a stiff set of springs that you know don't allow the centrifugal to start below the lowest convenient and practical speed to set initial timing.

2. Set the total WOT timing (vacuum can disconnected) at some point above where the timing stops advancing.

3. Set the timing at cranking speed - engine cold without setting the choke so it will not start. This can be tedious because the flashes are so infrequent, it's tough to read the data.

4. Set the timing statically - set the balancer notch on the proper initial timing mark on the timing tab. Using an ohmeter between the negative coil terminal and ground, rotate the distributor until you are right at the transition between zero and infinite resistance. If you are careful this will be accurate within one degree of your target number.

As a check you can back the engine off a few degrees CCW, then rotate it CW until the ohmeter jumps and read where the notch is on the tab.

Duke

 

SWDuke,

If you set it at WOT( no more advance) would that be at 36 degree's??

/joe

 

Joe, Duke was referring to rpms in his "at some point above where the timing stops advancing" - like 2500 rpm - at this point, the advance is "all in" so you set the timing at 36 deg when the engine is at 2500 rpms, easy to do with a dial back timing light or an indexed flywheel.

 

36-38 degrees. On many engines the centrifugal is not all in until as high as 5000. Check your CSM and AMA specs for your engine and verify by increasing revs until the advance stops.

The only engines that can be checked at 2500 are 365 and 375 HP 327s since their OE curve toped out at 2350.

Duke

 

well you can guess what engine I have, and it ain't the fuelie

 

Duke,

Ok, I THINK I got it now... IF I'm correct the guy I bought the car from said the the advance is not in until 5000. I have a 327/350 but I will 2x check when the advance stops and then do the timing at that point.. I wonder if that's why I have a slight hestitation when I stomp on it in 2nd gear.. If I do it gradually its fine.. I guess it could be a secondary float adjustment also..

Many Thanks

/joe

 

if, after driving it for a few days, an engine likes more base timing
DON'T ARGUE WITH IT
just make sure the weights don't go into the ping zone (make it hit the stop earlier)
********mine like 14 base 35 total on 87 w/9.7